v4.19.13 snapshot.
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
new file mode 100644
index 0000000..bd134e3
--- /dev/null
+++ b/net/ipv4/tcp_output.c
@@ -0,0 +1,3778 @@
+/*
+ * INET An implementation of the TCP/IP protocol suite for the LINUX
+ * operating system. INET is implemented using the BSD Socket
+ * interface as the means of communication with the user level.
+ *
+ * Implementation of the Transmission Control Protocol(TCP).
+ *
+ * Authors: Ross Biro
+ * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
+ * Mark Evans, <evansmp@uhura.aston.ac.uk>
+ * Corey Minyard <wf-rch!minyard@relay.EU.net>
+ * Florian La Roche, <flla@stud.uni-sb.de>
+ * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
+ * Linus Torvalds, <torvalds@cs.helsinki.fi>
+ * Alan Cox, <gw4pts@gw4pts.ampr.org>
+ * Matthew Dillon, <dillon@apollo.west.oic.com>
+ * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
+ * Jorge Cwik, <jorge@laser.satlink.net>
+ */
+
+/*
+ * Changes: Pedro Roque : Retransmit queue handled by TCP.
+ * : Fragmentation on mtu decrease
+ * : Segment collapse on retransmit
+ * : AF independence
+ *
+ * Linus Torvalds : send_delayed_ack
+ * David S. Miller : Charge memory using the right skb
+ * during syn/ack processing.
+ * David S. Miller : Output engine completely rewritten.
+ * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
+ * Cacophonix Gaul : draft-minshall-nagle-01
+ * J Hadi Salim : ECN support
+ *
+ */
+
+#define pr_fmt(fmt) "TCP: " fmt
+
+#include <net/tcp.h>
+
+#include <linux/compiler.h>
+#include <linux/gfp.h>
+#include <linux/module.h>
+#include <linux/static_key.h>
+
+#include <trace/events/tcp.h>
+
+static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
+ int push_one, gfp_t gfp);
+
+/* Account for new data that has been sent to the network. */
+static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ unsigned int prior_packets = tp->packets_out;
+
+ tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
+
+ __skb_unlink(skb, &sk->sk_write_queue);
+ tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
+
+ tp->packets_out += tcp_skb_pcount(skb);
+ if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
+ tcp_rearm_rto(sk);
+
+ NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
+ tcp_skb_pcount(skb));
+}
+
+/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
+ * window scaling factor due to loss of precision.
+ * If window has been shrunk, what should we make? It is not clear at all.
+ * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
+ * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
+ * invalid. OK, let's make this for now:
+ */
+static inline __u32 tcp_acceptable_seq(const struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+
+ if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
+ (tp->rx_opt.wscale_ok &&
+ ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
+ return tp->snd_nxt;
+ else
+ return tcp_wnd_end(tp);
+}
+
+/* Calculate mss to advertise in SYN segment.
+ * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
+ *
+ * 1. It is independent of path mtu.
+ * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
+ * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
+ * attached devices, because some buggy hosts are confused by
+ * large MSS.
+ * 4. We do not make 3, we advertise MSS, calculated from first
+ * hop device mtu, but allow to raise it to ip_rt_min_advmss.
+ * This may be overridden via information stored in routing table.
+ * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
+ * probably even Jumbo".
+ */
+static __u16 tcp_advertise_mss(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ const struct dst_entry *dst = __sk_dst_get(sk);
+ int mss = tp->advmss;
+
+ if (dst) {
+ unsigned int metric = dst_metric_advmss(dst);
+
+ if (metric < mss) {
+ mss = metric;
+ tp->advmss = mss;
+ }
+ }
+
+ return (__u16)mss;
+}
+
+/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
+ * This is the first part of cwnd validation mechanism.
+ */
+void tcp_cwnd_restart(struct sock *sk, s32 delta)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
+ u32 cwnd = tp->snd_cwnd;
+
+ tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
+
+ tp->snd_ssthresh = tcp_current_ssthresh(sk);
+ restart_cwnd = min(restart_cwnd, cwnd);
+
+ while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
+ cwnd >>= 1;
+ tp->snd_cwnd = max(cwnd, restart_cwnd);
+ tp->snd_cwnd_stamp = tcp_jiffies32;
+ tp->snd_cwnd_used = 0;
+}
+
+/* Congestion state accounting after a packet has been sent. */
+static void tcp_event_data_sent(struct tcp_sock *tp,
+ struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ const u32 now = tcp_jiffies32;
+
+ if (tcp_packets_in_flight(tp) == 0)
+ tcp_ca_event(sk, CA_EVENT_TX_START);
+
+ tp->lsndtime = now;
+
+ /* If it is a reply for ato after last received
+ * packet, enter pingpong mode.
+ */
+ if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
+ icsk->icsk_ack.pingpong = 1;
+}
+
+/* Account for an ACK we sent. */
+static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts,
+ u32 rcv_nxt)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (unlikely(tp->compressed_ack > TCP_FASTRETRANS_THRESH)) {
+ NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
+ tp->compressed_ack - TCP_FASTRETRANS_THRESH);
+ tp->compressed_ack = TCP_FASTRETRANS_THRESH;
+ if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
+ __sock_put(sk);
+ }
+
+ if (unlikely(rcv_nxt != tp->rcv_nxt))
+ return; /* Special ACK sent by DCTCP to reflect ECN */
+ tcp_dec_quickack_mode(sk, pkts);
+ inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
+}
+
+
+u32 tcp_default_init_rwnd(u32 mss)
+{
+ /* Initial receive window should be twice of TCP_INIT_CWND to
+ * enable proper sending of new unsent data during fast recovery
+ * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
+ * limit when mss is larger than 1460.
+ */
+ u32 init_rwnd = TCP_INIT_CWND * 2;
+
+ if (mss > 1460)
+ init_rwnd = max((1460 * init_rwnd) / mss, 2U);
+ return init_rwnd;
+}
+
+/* Determine a window scaling and initial window to offer.
+ * Based on the assumption that the given amount of space
+ * will be offered. Store the results in the tp structure.
+ * NOTE: for smooth operation initial space offering should
+ * be a multiple of mss if possible. We assume here that mss >= 1.
+ * This MUST be enforced by all callers.
+ */
+void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
+ __u32 *rcv_wnd, __u32 *window_clamp,
+ int wscale_ok, __u8 *rcv_wscale,
+ __u32 init_rcv_wnd)
+{
+ unsigned int space = (__space < 0 ? 0 : __space);
+
+ /* If no clamp set the clamp to the max possible scaled window */
+ if (*window_clamp == 0)
+ (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);
+ space = min(*window_clamp, space);
+
+ /* Quantize space offering to a multiple of mss if possible. */
+ if (space > mss)
+ space = rounddown(space, mss);
+
+ /* NOTE: offering an initial window larger than 32767
+ * will break some buggy TCP stacks. If the admin tells us
+ * it is likely we could be speaking with such a buggy stack
+ * we will truncate our initial window offering to 32K-1
+ * unless the remote has sent us a window scaling option,
+ * which we interpret as a sign the remote TCP is not
+ * misinterpreting the window field as a signed quantity.
+ */
+ if (sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
+ (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
+ else
+ (*rcv_wnd) = space;
+
+ (*rcv_wscale) = 0;
+ if (wscale_ok) {
+ /* Set window scaling on max possible window */
+ space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
+ space = max_t(u32, space, sysctl_rmem_max);
+ space = min_t(u32, space, *window_clamp);
+ while (space > U16_MAX && (*rcv_wscale) < TCP_MAX_WSCALE) {
+ space >>= 1;
+ (*rcv_wscale)++;
+ }
+ }
+
+ if (!init_rcv_wnd) /* Use default unless specified otherwise */
+ init_rcv_wnd = tcp_default_init_rwnd(mss);
+ *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
+
+ /* Set the clamp no higher than max representable value */
+ (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
+}
+EXPORT_SYMBOL(tcp_select_initial_window);
+
+/* Chose a new window to advertise, update state in tcp_sock for the
+ * socket, and return result with RFC1323 scaling applied. The return
+ * value can be stuffed directly into th->window for an outgoing
+ * frame.
+ */
+static u16 tcp_select_window(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ u32 old_win = tp->rcv_wnd;
+ u32 cur_win = tcp_receive_window(tp);
+ u32 new_win = __tcp_select_window(sk);
+
+ /* Never shrink the offered window */
+ if (new_win < cur_win) {
+ /* Danger Will Robinson!
+ * Don't update rcv_wup/rcv_wnd here or else
+ * we will not be able to advertise a zero
+ * window in time. --DaveM
+ *
+ * Relax Will Robinson.
+ */
+ if (new_win == 0)
+ NET_INC_STATS(sock_net(sk),
+ LINUX_MIB_TCPWANTZEROWINDOWADV);
+ new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
+ }
+ tp->rcv_wnd = new_win;
+ tp->rcv_wup = tp->rcv_nxt;
+
+ /* Make sure we do not exceed the maximum possible
+ * scaled window.
+ */
+ if (!tp->rx_opt.rcv_wscale &&
+ sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
+ new_win = min(new_win, MAX_TCP_WINDOW);
+ else
+ new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
+
+ /* RFC1323 scaling applied */
+ new_win >>= tp->rx_opt.rcv_wscale;
+
+ /* If we advertise zero window, disable fast path. */
+ if (new_win == 0) {
+ tp->pred_flags = 0;
+ if (old_win)
+ NET_INC_STATS(sock_net(sk),
+ LINUX_MIB_TCPTOZEROWINDOWADV);
+ } else if (old_win == 0) {
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
+ }
+
+ return new_win;
+}
+
+/* Packet ECN state for a SYN-ACK */
+static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+
+ TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
+ if (!(tp->ecn_flags & TCP_ECN_OK))
+ TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
+ else if (tcp_ca_needs_ecn(sk) ||
+ tcp_bpf_ca_needs_ecn(sk))
+ INET_ECN_xmit(sk);
+}
+
+/* Packet ECN state for a SYN. */
+static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
+ bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
+ tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
+
+ if (!use_ecn) {
+ const struct dst_entry *dst = __sk_dst_get(sk);
+
+ if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
+ use_ecn = true;
+ }
+
+ tp->ecn_flags = 0;
+
+ if (use_ecn) {
+ TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
+ tp->ecn_flags = TCP_ECN_OK;
+ if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
+ INET_ECN_xmit(sk);
+ }
+}
+
+static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
+{
+ if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)
+ /* tp->ecn_flags are cleared at a later point in time when
+ * SYN ACK is ultimatively being received.
+ */
+ TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
+}
+
+static void
+tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
+{
+ if (inet_rsk(req)->ecn_ok)
+ th->ece = 1;
+}
+
+/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
+ * be sent.
+ */
+static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
+ struct tcphdr *th, int tcp_header_len)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (tp->ecn_flags & TCP_ECN_OK) {
+ /* Not-retransmitted data segment: set ECT and inject CWR. */
+ if (skb->len != tcp_header_len &&
+ !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
+ INET_ECN_xmit(sk);
+ if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
+ tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
+ th->cwr = 1;
+ skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
+ }
+ } else if (!tcp_ca_needs_ecn(sk)) {
+ /* ACK or retransmitted segment: clear ECT|CE */
+ INET_ECN_dontxmit(sk);
+ }
+ if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
+ th->ece = 1;
+ }
+}
+
+/* Constructs common control bits of non-data skb. If SYN/FIN is present,
+ * auto increment end seqno.
+ */
+static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
+{
+ skb->ip_summed = CHECKSUM_PARTIAL;
+
+ TCP_SKB_CB(skb)->tcp_flags = flags;
+ TCP_SKB_CB(skb)->sacked = 0;
+
+ tcp_skb_pcount_set(skb, 1);
+
+ TCP_SKB_CB(skb)->seq = seq;
+ if (flags & (TCPHDR_SYN | TCPHDR_FIN))
+ seq++;
+ TCP_SKB_CB(skb)->end_seq = seq;
+}
+
+static inline bool tcp_urg_mode(const struct tcp_sock *tp)
+{
+ return tp->snd_una != tp->snd_up;
+}
+
+#define OPTION_SACK_ADVERTISE (1 << 0)
+#define OPTION_TS (1 << 1)
+#define OPTION_MD5 (1 << 2)
+#define OPTION_WSCALE (1 << 3)
+#define OPTION_FAST_OPEN_COOKIE (1 << 8)
+#define OPTION_SMC (1 << 9)
+
+static void smc_options_write(__be32 *ptr, u16 *options)
+{
+#if IS_ENABLED(CONFIG_SMC)
+ if (static_branch_unlikely(&tcp_have_smc)) {
+ if (unlikely(OPTION_SMC & *options)) {
+ *ptr++ = htonl((TCPOPT_NOP << 24) |
+ (TCPOPT_NOP << 16) |
+ (TCPOPT_EXP << 8) |
+ (TCPOLEN_EXP_SMC_BASE));
+ *ptr++ = htonl(TCPOPT_SMC_MAGIC);
+ }
+ }
+#endif
+}
+
+struct tcp_out_options {
+ u16 options; /* bit field of OPTION_* */
+ u16 mss; /* 0 to disable */
+ u8 ws; /* window scale, 0 to disable */
+ u8 num_sack_blocks; /* number of SACK blocks to include */
+ u8 hash_size; /* bytes in hash_location */
+ __u8 *hash_location; /* temporary pointer, overloaded */
+ __u32 tsval, tsecr; /* need to include OPTION_TS */
+ struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
+};
+
+/* Write previously computed TCP options to the packet.
+ *
+ * Beware: Something in the Internet is very sensitive to the ordering of
+ * TCP options, we learned this through the hard way, so be careful here.
+ * Luckily we can at least blame others for their non-compliance but from
+ * inter-operability perspective it seems that we're somewhat stuck with
+ * the ordering which we have been using if we want to keep working with
+ * those broken things (not that it currently hurts anybody as there isn't
+ * particular reason why the ordering would need to be changed).
+ *
+ * At least SACK_PERM as the first option is known to lead to a disaster
+ * (but it may well be that other scenarios fail similarly).
+ */
+static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
+ struct tcp_out_options *opts)
+{
+ u16 options = opts->options; /* mungable copy */
+
+ if (unlikely(OPTION_MD5 & options)) {
+ *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
+ (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
+ /* overload cookie hash location */
+ opts->hash_location = (__u8 *)ptr;
+ ptr += 4;
+ }
+
+ if (unlikely(opts->mss)) {
+ *ptr++ = htonl((TCPOPT_MSS << 24) |
+ (TCPOLEN_MSS << 16) |
+ opts->mss);
+ }
+
+ if (likely(OPTION_TS & options)) {
+ if (unlikely(OPTION_SACK_ADVERTISE & options)) {
+ *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
+ (TCPOLEN_SACK_PERM << 16) |
+ (TCPOPT_TIMESTAMP << 8) |
+ TCPOLEN_TIMESTAMP);
+ options &= ~OPTION_SACK_ADVERTISE;
+ } else {
+ *ptr++ = htonl((TCPOPT_NOP << 24) |
+ (TCPOPT_NOP << 16) |
+ (TCPOPT_TIMESTAMP << 8) |
+ TCPOLEN_TIMESTAMP);
+ }
+ *ptr++ = htonl(opts->tsval);
+ *ptr++ = htonl(opts->tsecr);
+ }
+
+ if (unlikely(OPTION_SACK_ADVERTISE & options)) {
+ *ptr++ = htonl((TCPOPT_NOP << 24) |
+ (TCPOPT_NOP << 16) |
+ (TCPOPT_SACK_PERM << 8) |
+ TCPOLEN_SACK_PERM);
+ }
+
+ if (unlikely(OPTION_WSCALE & options)) {
+ *ptr++ = htonl((TCPOPT_NOP << 24) |
+ (TCPOPT_WINDOW << 16) |
+ (TCPOLEN_WINDOW << 8) |
+ opts->ws);
+ }
+
+ if (unlikely(opts->num_sack_blocks)) {
+ struct tcp_sack_block *sp = tp->rx_opt.dsack ?
+ tp->duplicate_sack : tp->selective_acks;
+ int this_sack;
+
+ *ptr++ = htonl((TCPOPT_NOP << 24) |
+ (TCPOPT_NOP << 16) |
+ (TCPOPT_SACK << 8) |
+ (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
+ TCPOLEN_SACK_PERBLOCK)));
+
+ for (this_sack = 0; this_sack < opts->num_sack_blocks;
+ ++this_sack) {
+ *ptr++ = htonl(sp[this_sack].start_seq);
+ *ptr++ = htonl(sp[this_sack].end_seq);
+ }
+
+ tp->rx_opt.dsack = 0;
+ }
+
+ if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
+ struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
+ u8 *p = (u8 *)ptr;
+ u32 len; /* Fast Open option length */
+
+ if (foc->exp) {
+ len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
+ *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
+ TCPOPT_FASTOPEN_MAGIC);
+ p += TCPOLEN_EXP_FASTOPEN_BASE;
+ } else {
+ len = TCPOLEN_FASTOPEN_BASE + foc->len;
+ *p++ = TCPOPT_FASTOPEN;
+ *p++ = len;
+ }
+
+ memcpy(p, foc->val, foc->len);
+ if ((len & 3) == 2) {
+ p[foc->len] = TCPOPT_NOP;
+ p[foc->len + 1] = TCPOPT_NOP;
+ }
+ ptr += (len + 3) >> 2;
+ }
+
+ smc_options_write(ptr, &options);
+}
+
+static void smc_set_option(const struct tcp_sock *tp,
+ struct tcp_out_options *opts,
+ unsigned int *remaining)
+{
+#if IS_ENABLED(CONFIG_SMC)
+ if (static_branch_unlikely(&tcp_have_smc)) {
+ if (tp->syn_smc) {
+ if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
+ opts->options |= OPTION_SMC;
+ *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
+ }
+ }
+ }
+#endif
+}
+
+static void smc_set_option_cond(const struct tcp_sock *tp,
+ const struct inet_request_sock *ireq,
+ struct tcp_out_options *opts,
+ unsigned int *remaining)
+{
+#if IS_ENABLED(CONFIG_SMC)
+ if (static_branch_unlikely(&tcp_have_smc)) {
+ if (tp->syn_smc && ireq->smc_ok) {
+ if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
+ opts->options |= OPTION_SMC;
+ *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
+ }
+ }
+ }
+#endif
+}
+
+/* Compute TCP options for SYN packets. This is not the final
+ * network wire format yet.
+ */
+static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
+ struct tcp_out_options *opts,
+ struct tcp_md5sig_key **md5)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ unsigned int remaining = MAX_TCP_OPTION_SPACE;
+ struct tcp_fastopen_request *fastopen = tp->fastopen_req;
+
+ *md5 = NULL;
+#ifdef CONFIG_TCP_MD5SIG
+ if (unlikely(rcu_access_pointer(tp->md5sig_info))) {
+ *md5 = tp->af_specific->md5_lookup(sk, sk);
+ if (*md5) {
+ opts->options |= OPTION_MD5;
+ remaining -= TCPOLEN_MD5SIG_ALIGNED;
+ }
+ }
+#endif
+
+ /* We always get an MSS option. The option bytes which will be seen in
+ * normal data packets should timestamps be used, must be in the MSS
+ * advertised. But we subtract them from tp->mss_cache so that
+ * calculations in tcp_sendmsg are simpler etc. So account for this
+ * fact here if necessary. If we don't do this correctly, as a
+ * receiver we won't recognize data packets as being full sized when we
+ * should, and thus we won't abide by the delayed ACK rules correctly.
+ * SACKs don't matter, we never delay an ACK when we have any of those
+ * going out. */
+ opts->mss = tcp_advertise_mss(sk);
+ remaining -= TCPOLEN_MSS_ALIGNED;
+
+ if (likely(sock_net(sk)->ipv4.sysctl_tcp_timestamps && !*md5)) {
+ opts->options |= OPTION_TS;
+ opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
+ opts->tsecr = tp->rx_opt.ts_recent;
+ remaining -= TCPOLEN_TSTAMP_ALIGNED;
+ }
+ if (likely(sock_net(sk)->ipv4.sysctl_tcp_window_scaling)) {
+ opts->ws = tp->rx_opt.rcv_wscale;
+ opts->options |= OPTION_WSCALE;
+ remaining -= TCPOLEN_WSCALE_ALIGNED;
+ }
+ if (likely(sock_net(sk)->ipv4.sysctl_tcp_sack)) {
+ opts->options |= OPTION_SACK_ADVERTISE;
+ if (unlikely(!(OPTION_TS & opts->options)))
+ remaining -= TCPOLEN_SACKPERM_ALIGNED;
+ }
+
+ if (fastopen && fastopen->cookie.len >= 0) {
+ u32 need = fastopen->cookie.len;
+
+ need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
+ TCPOLEN_FASTOPEN_BASE;
+ need = (need + 3) & ~3U; /* Align to 32 bits */
+ if (remaining >= need) {
+ opts->options |= OPTION_FAST_OPEN_COOKIE;
+ opts->fastopen_cookie = &fastopen->cookie;
+ remaining -= need;
+ tp->syn_fastopen = 1;
+ tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
+ }
+ }
+
+ smc_set_option(tp, opts, &remaining);
+
+ return MAX_TCP_OPTION_SPACE - remaining;
+}
+
+/* Set up TCP options for SYN-ACKs. */
+static unsigned int tcp_synack_options(const struct sock *sk,
+ struct request_sock *req,
+ unsigned int mss, struct sk_buff *skb,
+ struct tcp_out_options *opts,
+ const struct tcp_md5sig_key *md5,
+ struct tcp_fastopen_cookie *foc)
+{
+ struct inet_request_sock *ireq = inet_rsk(req);
+ unsigned int remaining = MAX_TCP_OPTION_SPACE;
+
+#ifdef CONFIG_TCP_MD5SIG
+ if (md5) {
+ opts->options |= OPTION_MD5;
+ remaining -= TCPOLEN_MD5SIG_ALIGNED;
+
+ /* We can't fit any SACK blocks in a packet with MD5 + TS
+ * options. There was discussion about disabling SACK
+ * rather than TS in order to fit in better with old,
+ * buggy kernels, but that was deemed to be unnecessary.
+ */
+ ireq->tstamp_ok &= !ireq->sack_ok;
+ }
+#endif
+
+ /* We always send an MSS option. */
+ opts->mss = mss;
+ remaining -= TCPOLEN_MSS_ALIGNED;
+
+ if (likely(ireq->wscale_ok)) {
+ opts->ws = ireq->rcv_wscale;
+ opts->options |= OPTION_WSCALE;
+ remaining -= TCPOLEN_WSCALE_ALIGNED;
+ }
+ if (likely(ireq->tstamp_ok)) {
+ opts->options |= OPTION_TS;
+ opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
+ opts->tsecr = req->ts_recent;
+ remaining -= TCPOLEN_TSTAMP_ALIGNED;
+ }
+ if (likely(ireq->sack_ok)) {
+ opts->options |= OPTION_SACK_ADVERTISE;
+ if (unlikely(!ireq->tstamp_ok))
+ remaining -= TCPOLEN_SACKPERM_ALIGNED;
+ }
+ if (foc != NULL && foc->len >= 0) {
+ u32 need = foc->len;
+
+ need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
+ TCPOLEN_FASTOPEN_BASE;
+ need = (need + 3) & ~3U; /* Align to 32 bits */
+ if (remaining >= need) {
+ opts->options |= OPTION_FAST_OPEN_COOKIE;
+ opts->fastopen_cookie = foc;
+ remaining -= need;
+ }
+ }
+
+ smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
+
+ return MAX_TCP_OPTION_SPACE - remaining;
+}
+
+/* Compute TCP options for ESTABLISHED sockets. This is not the
+ * final wire format yet.
+ */
+static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
+ struct tcp_out_options *opts,
+ struct tcp_md5sig_key **md5)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ unsigned int size = 0;
+ unsigned int eff_sacks;
+
+ opts->options = 0;
+
+ *md5 = NULL;
+#ifdef CONFIG_TCP_MD5SIG
+ if (unlikely(rcu_access_pointer(tp->md5sig_info))) {
+ *md5 = tp->af_specific->md5_lookup(sk, sk);
+ if (*md5) {
+ opts->options |= OPTION_MD5;
+ size += TCPOLEN_MD5SIG_ALIGNED;
+ }
+ }
+#endif
+
+ if (likely(tp->rx_opt.tstamp_ok)) {
+ opts->options |= OPTION_TS;
+ opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
+ opts->tsecr = tp->rx_opt.ts_recent;
+ size += TCPOLEN_TSTAMP_ALIGNED;
+ }
+
+ eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
+ if (unlikely(eff_sacks)) {
+ const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
+ opts->num_sack_blocks =
+ min_t(unsigned int, eff_sacks,
+ (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
+ TCPOLEN_SACK_PERBLOCK);
+ size += TCPOLEN_SACK_BASE_ALIGNED +
+ opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
+ }
+
+ return size;
+}
+
+
+/* TCP SMALL QUEUES (TSQ)
+ *
+ * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
+ * to reduce RTT and bufferbloat.
+ * We do this using a special skb destructor (tcp_wfree).
+ *
+ * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
+ * needs to be reallocated in a driver.
+ * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
+ *
+ * Since transmit from skb destructor is forbidden, we use a tasklet
+ * to process all sockets that eventually need to send more skbs.
+ * We use one tasklet per cpu, with its own queue of sockets.
+ */
+struct tsq_tasklet {
+ struct tasklet_struct tasklet;
+ struct list_head head; /* queue of tcp sockets */
+};
+static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
+
+static void tcp_tsq_write(struct sock *sk)
+{
+ if ((1 << sk->sk_state) &
+ (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
+ TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) {
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (tp->lost_out > tp->retrans_out &&
+ tp->snd_cwnd > tcp_packets_in_flight(tp)) {
+ tcp_mstamp_refresh(tp);
+ tcp_xmit_retransmit_queue(sk);
+ }
+
+ tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
+ 0, GFP_ATOMIC);
+ }
+}
+
+static void tcp_tsq_handler(struct sock *sk)
+{
+ bh_lock_sock(sk);
+ if (!sock_owned_by_user(sk))
+ tcp_tsq_write(sk);
+ else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
+ sock_hold(sk);
+ bh_unlock_sock(sk);
+}
+/*
+ * One tasklet per cpu tries to send more skbs.
+ * We run in tasklet context but need to disable irqs when
+ * transferring tsq->head because tcp_wfree() might
+ * interrupt us (non NAPI drivers)
+ */
+static void tcp_tasklet_func(unsigned long data)
+{
+ struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
+ LIST_HEAD(list);
+ unsigned long flags;
+ struct list_head *q, *n;
+ struct tcp_sock *tp;
+ struct sock *sk;
+
+ local_irq_save(flags);
+ list_splice_init(&tsq->head, &list);
+ local_irq_restore(flags);
+
+ list_for_each_safe(q, n, &list) {
+ tp = list_entry(q, struct tcp_sock, tsq_node);
+ list_del(&tp->tsq_node);
+
+ sk = (struct sock *)tp;
+ smp_mb__before_atomic();
+ clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
+
+ tcp_tsq_handler(sk);
+ sk_free(sk);
+ }
+}
+
+#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
+ TCPF_WRITE_TIMER_DEFERRED | \
+ TCPF_DELACK_TIMER_DEFERRED | \
+ TCPF_MTU_REDUCED_DEFERRED)
+/**
+ * tcp_release_cb - tcp release_sock() callback
+ * @sk: socket
+ *
+ * called from release_sock() to perform protocol dependent
+ * actions before socket release.
+ */
+void tcp_release_cb(struct sock *sk)
+{
+ unsigned long flags, nflags;
+
+ /* perform an atomic operation only if at least one flag is set */
+ do {
+ flags = sk->sk_tsq_flags;
+ if (!(flags & TCP_DEFERRED_ALL))
+ return;
+ nflags = flags & ~TCP_DEFERRED_ALL;
+ } while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
+
+ if (flags & TCPF_TSQ_DEFERRED) {
+ tcp_tsq_write(sk);
+ __sock_put(sk);
+ }
+ /* Here begins the tricky part :
+ * We are called from release_sock() with :
+ * 1) BH disabled
+ * 2) sk_lock.slock spinlock held
+ * 3) socket owned by us (sk->sk_lock.owned == 1)
+ *
+ * But following code is meant to be called from BH handlers,
+ * so we should keep BH disabled, but early release socket ownership
+ */
+ sock_release_ownership(sk);
+
+ if (flags & TCPF_WRITE_TIMER_DEFERRED) {
+ tcp_write_timer_handler(sk);
+ __sock_put(sk);
+ }
+ if (flags & TCPF_DELACK_TIMER_DEFERRED) {
+ tcp_delack_timer_handler(sk);
+ __sock_put(sk);
+ }
+ if (flags & TCPF_MTU_REDUCED_DEFERRED) {
+ inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
+ __sock_put(sk);
+ }
+}
+EXPORT_SYMBOL(tcp_release_cb);
+
+void __init tcp_tasklet_init(void)
+{
+ int i;
+
+ for_each_possible_cpu(i) {
+ struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
+
+ INIT_LIST_HEAD(&tsq->head);
+ tasklet_init(&tsq->tasklet,
+ tcp_tasklet_func,
+ (unsigned long)tsq);
+ }
+}
+
+/*
+ * Write buffer destructor automatically called from kfree_skb.
+ * We can't xmit new skbs from this context, as we might already
+ * hold qdisc lock.
+ */
+void tcp_wfree(struct sk_buff *skb)
+{
+ struct sock *sk = skb->sk;
+ struct tcp_sock *tp = tcp_sk(sk);
+ unsigned long flags, nval, oval;
+
+ /* Keep one reference on sk_wmem_alloc.
+ * Will be released by sk_free() from here or tcp_tasklet_func()
+ */
+ WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
+
+ /* If this softirq is serviced by ksoftirqd, we are likely under stress.
+ * Wait until our queues (qdisc + devices) are drained.
+ * This gives :
+ * - less callbacks to tcp_write_xmit(), reducing stress (batches)
+ * - chance for incoming ACK (processed by another cpu maybe)
+ * to migrate this flow (skb->ooo_okay will be eventually set)
+ */
+ if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
+ goto out;
+
+ for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
+ struct tsq_tasklet *tsq;
+ bool empty;
+
+ if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
+ goto out;
+
+ nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
+ nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
+ if (nval != oval)
+ continue;
+
+ /* queue this socket to tasklet queue */
+ local_irq_save(flags);
+ tsq = this_cpu_ptr(&tsq_tasklet);
+ empty = list_empty(&tsq->head);
+ list_add(&tp->tsq_node, &tsq->head);
+ if (empty)
+ tasklet_schedule(&tsq->tasklet);
+ local_irq_restore(flags);
+ return;
+ }
+out:
+ sk_free(sk);
+}
+
+/* Note: Called under soft irq.
+ * We can call TCP stack right away, unless socket is owned by user.
+ */
+enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
+{
+ struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
+ struct sock *sk = (struct sock *)tp;
+
+ tcp_tsq_handler(sk);
+ sock_put(sk);
+
+ return HRTIMER_NORESTART;
+}
+
+static void tcp_internal_pacing(struct sock *sk, const struct sk_buff *skb)
+{
+ u64 len_ns;
+ u32 rate;
+
+ if (!tcp_needs_internal_pacing(sk))
+ return;
+ rate = sk->sk_pacing_rate;
+ if (!rate || rate == ~0U)
+ return;
+
+ len_ns = (u64)skb->len * NSEC_PER_SEC;
+ do_div(len_ns, rate);
+ hrtimer_start(&tcp_sk(sk)->pacing_timer,
+ ktime_add_ns(ktime_get(), len_ns),
+ HRTIMER_MODE_ABS_PINNED_SOFT);
+ sock_hold(sk);
+}
+
+static void tcp_update_skb_after_send(struct tcp_sock *tp, struct sk_buff *skb)
+{
+ skb->skb_mstamp = tp->tcp_mstamp;
+ list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
+}
+
+/* This routine actually transmits TCP packets queued in by
+ * tcp_do_sendmsg(). This is used by both the initial
+ * transmission and possible later retransmissions.
+ * All SKB's seen here are completely headerless. It is our
+ * job to build the TCP header, and pass the packet down to
+ * IP so it can do the same plus pass the packet off to the
+ * device.
+ *
+ * We are working here with either a clone of the original
+ * SKB, or a fresh unique copy made by the retransmit engine.
+ */
+static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
+ int clone_it, gfp_t gfp_mask, u32 rcv_nxt)
+{
+ const struct inet_connection_sock *icsk = inet_csk(sk);
+ struct inet_sock *inet;
+ struct tcp_sock *tp;
+ struct tcp_skb_cb *tcb;
+ struct tcp_out_options opts;
+ unsigned int tcp_options_size, tcp_header_size;
+ struct sk_buff *oskb = NULL;
+ struct tcp_md5sig_key *md5;
+ struct tcphdr *th;
+ int err;
+
+ BUG_ON(!skb || !tcp_skb_pcount(skb));
+ tp = tcp_sk(sk);
+
+ if (clone_it) {
+ TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
+ - tp->snd_una;
+ oskb = skb;
+
+ tcp_skb_tsorted_save(oskb) {
+ if (unlikely(skb_cloned(oskb)))
+ skb = pskb_copy(oskb, gfp_mask);
+ else
+ skb = skb_clone(oskb, gfp_mask);
+ } tcp_skb_tsorted_restore(oskb);
+
+ if (unlikely(!skb))
+ return -ENOBUFS;
+ }
+ skb->skb_mstamp = tp->tcp_mstamp;
+
+ inet = inet_sk(sk);
+ tcb = TCP_SKB_CB(skb);
+ memset(&opts, 0, sizeof(opts));
+
+ if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
+ tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
+ else
+ tcp_options_size = tcp_established_options(sk, skb, &opts,
+ &md5);
+ tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
+
+ /* if no packet is in qdisc/device queue, then allow XPS to select
+ * another queue. We can be called from tcp_tsq_handler()
+ * which holds one reference to sk.
+ *
+ * TODO: Ideally, in-flight pure ACK packets should not matter here.
+ * One way to get this would be to set skb->truesize = 2 on them.
+ */
+ skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
+
+ /* If we had to use memory reserve to allocate this skb,
+ * this might cause drops if packet is looped back :
+ * Other socket might not have SOCK_MEMALLOC.
+ * Packets not looped back do not care about pfmemalloc.
+ */
+ skb->pfmemalloc = 0;
+
+ skb_push(skb, tcp_header_size);
+ skb_reset_transport_header(skb);
+
+ skb_orphan(skb);
+ skb->sk = sk;
+ skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
+ skb_set_hash_from_sk(skb, sk);
+ refcount_add(skb->truesize, &sk->sk_wmem_alloc);
+
+ skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);
+
+ /* Build TCP header and checksum it. */
+ th = (struct tcphdr *)skb->data;
+ th->source = inet->inet_sport;
+ th->dest = inet->inet_dport;
+ th->seq = htonl(tcb->seq);
+ th->ack_seq = htonl(rcv_nxt);
+ *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
+ tcb->tcp_flags);
+
+ th->check = 0;
+ th->urg_ptr = 0;
+
+ /* The urg_mode check is necessary during a below snd_una win probe */
+ if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
+ if (before(tp->snd_up, tcb->seq + 0x10000)) {
+ th->urg_ptr = htons(tp->snd_up - tcb->seq);
+ th->urg = 1;
+ } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
+ th->urg_ptr = htons(0xFFFF);
+ th->urg = 1;
+ }
+ }
+
+ tcp_options_write((__be32 *)(th + 1), tp, &opts);
+ skb_shinfo(skb)->gso_type = sk->sk_gso_type;
+ if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
+ th->window = htons(tcp_select_window(sk));
+ tcp_ecn_send(sk, skb, th, tcp_header_size);
+ } else {
+ /* RFC1323: The window in SYN & SYN/ACK segments
+ * is never scaled.
+ */
+ th->window = htons(min(tp->rcv_wnd, 65535U));
+ }
+#ifdef CONFIG_TCP_MD5SIG
+ /* Calculate the MD5 hash, as we have all we need now */
+ if (md5) {
+ sk_nocaps_add(sk, NETIF_F_GSO_MASK);
+ tp->af_specific->calc_md5_hash(opts.hash_location,
+ md5, sk, skb);
+ }
+#endif
+
+ icsk->icsk_af_ops->send_check(sk, skb);
+
+ if (likely(tcb->tcp_flags & TCPHDR_ACK))
+ tcp_event_ack_sent(sk, tcp_skb_pcount(skb), rcv_nxt);
+
+ if (skb->len != tcp_header_size) {
+ tcp_event_data_sent(tp, sk);
+ tp->data_segs_out += tcp_skb_pcount(skb);
+ tp->bytes_sent += skb->len - tcp_header_size;
+ tcp_internal_pacing(sk, skb);
+ }
+
+ if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
+ TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
+ tcp_skb_pcount(skb));
+
+ tp->segs_out += tcp_skb_pcount(skb);
+ /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
+ skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
+ skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
+
+ /* Our usage of tstamp should remain private */
+ skb->tstamp = 0;
+
+ /* Cleanup our debris for IP stacks */
+ memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
+ sizeof(struct inet6_skb_parm)));
+
+ err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
+
+ if (unlikely(err > 0)) {
+ tcp_enter_cwr(sk);
+ err = net_xmit_eval(err);
+ }
+ if (!err && oskb) {
+ tcp_update_skb_after_send(tp, oskb);
+ tcp_rate_skb_sent(sk, oskb);
+ }
+ return err;
+}
+
+static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
+ gfp_t gfp_mask)
+{
+ return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask,
+ tcp_sk(sk)->rcv_nxt);
+}
+
+/* This routine just queues the buffer for sending.
+ *
+ * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
+ * otherwise socket can stall.
+ */
+static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /* Advance write_seq and place onto the write_queue. */
+ tp->write_seq = TCP_SKB_CB(skb)->end_seq;
+ __skb_header_release(skb);
+ tcp_add_write_queue_tail(sk, skb);
+ sk->sk_wmem_queued += skb->truesize;
+ sk_mem_charge(sk, skb->truesize);
+}
+
+/* Initialize TSO segments for a packet. */
+static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
+{
+ if (skb->len <= mss_now) {
+ /* Avoid the costly divide in the normal
+ * non-TSO case.
+ */
+ tcp_skb_pcount_set(skb, 1);
+ TCP_SKB_CB(skb)->tcp_gso_size = 0;
+ } else {
+ tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
+ TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
+ }
+}
+
+/* Pcount in the middle of the write queue got changed, we need to do various
+ * tweaks to fix counters
+ */
+static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ tp->packets_out -= decr;
+
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
+ tp->sacked_out -= decr;
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
+ tp->retrans_out -= decr;
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
+ tp->lost_out -= decr;
+
+ /* Reno case is special. Sigh... */
+ if (tcp_is_reno(tp) && decr > 0)
+ tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
+
+ if (tp->lost_skb_hint &&
+ before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
+ (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
+ tp->lost_cnt_hint -= decr;
+
+ tcp_verify_left_out(tp);
+}
+
+static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
+{
+ return TCP_SKB_CB(skb)->txstamp_ack ||
+ (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
+}
+
+static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
+{
+ struct skb_shared_info *shinfo = skb_shinfo(skb);
+
+ if (unlikely(tcp_has_tx_tstamp(skb)) &&
+ !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
+ struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
+ u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
+
+ shinfo->tx_flags &= ~tsflags;
+ shinfo2->tx_flags |= tsflags;
+ swap(shinfo->tskey, shinfo2->tskey);
+ TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
+ TCP_SKB_CB(skb)->txstamp_ack = 0;
+ }
+}
+
+static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
+{
+ TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
+ TCP_SKB_CB(skb)->eor = 0;
+}
+
+/* Insert buff after skb on the write or rtx queue of sk. */
+static void tcp_insert_write_queue_after(struct sk_buff *skb,
+ struct sk_buff *buff,
+ struct sock *sk,
+ enum tcp_queue tcp_queue)
+{
+ if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
+ __skb_queue_after(&sk->sk_write_queue, skb, buff);
+ else
+ tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
+}
+
+/* Function to create two new TCP segments. Shrinks the given segment
+ * to the specified size and appends a new segment with the rest of the
+ * packet to the list. This won't be called frequently, I hope.
+ * Remember, these are still headerless SKBs at this point.
+ */
+int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
+ struct sk_buff *skb, u32 len,
+ unsigned int mss_now, gfp_t gfp)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *buff;
+ int nsize, old_factor;
+ int nlen;
+ u8 flags;
+
+ if (WARN_ON(len > skb->len))
+ return -EINVAL;
+
+ nsize = skb_headlen(skb) - len;
+ if (nsize < 0)
+ nsize = 0;
+
+ if (skb_unclone(skb, gfp))
+ return -ENOMEM;
+
+ /* Get a new skb... force flag on. */
+ buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
+ if (!buff)
+ return -ENOMEM; /* We'll just try again later. */
+
+ sk->sk_wmem_queued += buff->truesize;
+ sk_mem_charge(sk, buff->truesize);
+ nlen = skb->len - len - nsize;
+ buff->truesize += nlen;
+ skb->truesize -= nlen;
+
+ /* Correct the sequence numbers. */
+ TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
+ TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
+ TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
+
+ /* PSH and FIN should only be set in the second packet. */
+ flags = TCP_SKB_CB(skb)->tcp_flags;
+ TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
+ TCP_SKB_CB(buff)->tcp_flags = flags;
+ TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
+ tcp_skb_fragment_eor(skb, buff);
+
+ skb_split(skb, buff, len);
+
+ buff->ip_summed = CHECKSUM_PARTIAL;
+
+ buff->tstamp = skb->tstamp;
+ tcp_fragment_tstamp(skb, buff);
+
+ old_factor = tcp_skb_pcount(skb);
+
+ /* Fix up tso_factor for both original and new SKB. */
+ tcp_set_skb_tso_segs(skb, mss_now);
+ tcp_set_skb_tso_segs(buff, mss_now);
+
+ /* Update delivered info for the new segment */
+ TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;
+
+ /* If this packet has been sent out already, we must
+ * adjust the various packet counters.
+ */
+ if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
+ int diff = old_factor - tcp_skb_pcount(skb) -
+ tcp_skb_pcount(buff);
+
+ if (diff)
+ tcp_adjust_pcount(sk, skb, diff);
+ }
+
+ /* Link BUFF into the send queue. */
+ __skb_header_release(buff);
+ tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
+ if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
+ list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
+
+ return 0;
+}
+
+/* This is similar to __pskb_pull_tail(). The difference is that pulled
+ * data is not copied, but immediately discarded.
+ */
+static int __pskb_trim_head(struct sk_buff *skb, int len)
+{
+ struct skb_shared_info *shinfo;
+ int i, k, eat;
+
+ eat = min_t(int, len, skb_headlen(skb));
+ if (eat) {
+ __skb_pull(skb, eat);
+ len -= eat;
+ if (!len)
+ return 0;
+ }
+ eat = len;
+ k = 0;
+ shinfo = skb_shinfo(skb);
+ for (i = 0; i < shinfo->nr_frags; i++) {
+ int size = skb_frag_size(&shinfo->frags[i]);
+
+ if (size <= eat) {
+ skb_frag_unref(skb, i);
+ eat -= size;
+ } else {
+ shinfo->frags[k] = shinfo->frags[i];
+ if (eat) {
+ shinfo->frags[k].page_offset += eat;
+ skb_frag_size_sub(&shinfo->frags[k], eat);
+ eat = 0;
+ }
+ k++;
+ }
+ }
+ shinfo->nr_frags = k;
+
+ skb->data_len -= len;
+ skb->len = skb->data_len;
+ return len;
+}
+
+/* Remove acked data from a packet in the transmit queue. */
+int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
+{
+ u32 delta_truesize;
+
+ if (skb_unclone(skb, GFP_ATOMIC))
+ return -ENOMEM;
+
+ delta_truesize = __pskb_trim_head(skb, len);
+
+ TCP_SKB_CB(skb)->seq += len;
+ skb->ip_summed = CHECKSUM_PARTIAL;
+
+ if (delta_truesize) {
+ skb->truesize -= delta_truesize;
+ sk->sk_wmem_queued -= delta_truesize;
+ sk_mem_uncharge(sk, delta_truesize);
+ sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
+ }
+
+ /* Any change of skb->len requires recalculation of tso factor. */
+ if (tcp_skb_pcount(skb) > 1)
+ tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
+
+ return 0;
+}
+
+/* Calculate MSS not accounting any TCP options. */
+static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ const struct inet_connection_sock *icsk = inet_csk(sk);
+ int mss_now;
+
+ /* Calculate base mss without TCP options:
+ It is MMS_S - sizeof(tcphdr) of rfc1122
+ */
+ mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
+
+ /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
+ if (icsk->icsk_af_ops->net_frag_header_len) {
+ const struct dst_entry *dst = __sk_dst_get(sk);
+
+ if (dst && dst_allfrag(dst))
+ mss_now -= icsk->icsk_af_ops->net_frag_header_len;
+ }
+
+ /* Clamp it (mss_clamp does not include tcp options) */
+ if (mss_now > tp->rx_opt.mss_clamp)
+ mss_now = tp->rx_opt.mss_clamp;
+
+ /* Now subtract optional transport overhead */
+ mss_now -= icsk->icsk_ext_hdr_len;
+
+ /* Then reserve room for full set of TCP options and 8 bytes of data */
+ if (mss_now < 48)
+ mss_now = 48;
+ return mss_now;
+}
+
+/* Calculate MSS. Not accounting for SACKs here. */
+int tcp_mtu_to_mss(struct sock *sk, int pmtu)
+{
+ /* Subtract TCP options size, not including SACKs */
+ return __tcp_mtu_to_mss(sk, pmtu) -
+ (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
+}
+
+/* Inverse of above */
+int tcp_mss_to_mtu(struct sock *sk, int mss)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ const struct inet_connection_sock *icsk = inet_csk(sk);
+ int mtu;
+
+ mtu = mss +
+ tp->tcp_header_len +
+ icsk->icsk_ext_hdr_len +
+ icsk->icsk_af_ops->net_header_len;
+
+ /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
+ if (icsk->icsk_af_ops->net_frag_header_len) {
+ const struct dst_entry *dst = __sk_dst_get(sk);
+
+ if (dst && dst_allfrag(dst))
+ mtu += icsk->icsk_af_ops->net_frag_header_len;
+ }
+ return mtu;
+}
+EXPORT_SYMBOL(tcp_mss_to_mtu);
+
+/* MTU probing init per socket */
+void tcp_mtup_init(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct net *net = sock_net(sk);
+
+ icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
+ icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
+ icsk->icsk_af_ops->net_header_len;
+ icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
+ icsk->icsk_mtup.probe_size = 0;
+ if (icsk->icsk_mtup.enabled)
+ icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
+}
+EXPORT_SYMBOL(tcp_mtup_init);
+
+/* This function synchronize snd mss to current pmtu/exthdr set.
+
+ tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
+ for TCP options, but includes only bare TCP header.
+
+ tp->rx_opt.mss_clamp is mss negotiated at connection setup.
+ It is minimum of user_mss and mss received with SYN.
+ It also does not include TCP options.
+
+ inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
+
+ tp->mss_cache is current effective sending mss, including
+ all tcp options except for SACKs. It is evaluated,
+ taking into account current pmtu, but never exceeds
+ tp->rx_opt.mss_clamp.
+
+ NOTE1. rfc1122 clearly states that advertised MSS
+ DOES NOT include either tcp or ip options.
+
+ NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
+ are READ ONLY outside this function. --ANK (980731)
+ */
+unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ int mss_now;
+
+ if (icsk->icsk_mtup.search_high > pmtu)
+ icsk->icsk_mtup.search_high = pmtu;
+
+ mss_now = tcp_mtu_to_mss(sk, pmtu);
+ mss_now = tcp_bound_to_half_wnd(tp, mss_now);
+
+ /* And store cached results */
+ icsk->icsk_pmtu_cookie = pmtu;
+ if (icsk->icsk_mtup.enabled)
+ mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
+ tp->mss_cache = mss_now;
+
+ return mss_now;
+}
+EXPORT_SYMBOL(tcp_sync_mss);
+
+/* Compute the current effective MSS, taking SACKs and IP options,
+ * and even PMTU discovery events into account.
+ */
+unsigned int tcp_current_mss(struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ const struct dst_entry *dst = __sk_dst_get(sk);
+ u32 mss_now;
+ unsigned int header_len;
+ struct tcp_out_options opts;
+ struct tcp_md5sig_key *md5;
+
+ mss_now = tp->mss_cache;
+
+ if (dst) {
+ u32 mtu = dst_mtu(dst);
+ if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
+ mss_now = tcp_sync_mss(sk, mtu);
+ }
+
+ header_len = tcp_established_options(sk, NULL, &opts, &md5) +
+ sizeof(struct tcphdr);
+ /* The mss_cache is sized based on tp->tcp_header_len, which assumes
+ * some common options. If this is an odd packet (because we have SACK
+ * blocks etc) then our calculated header_len will be different, and
+ * we have to adjust mss_now correspondingly */
+ if (header_len != tp->tcp_header_len) {
+ int delta = (int) header_len - tp->tcp_header_len;
+ mss_now -= delta;
+ }
+
+ return mss_now;
+}
+
+/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
+ * As additional protections, we do not touch cwnd in retransmission phases,
+ * and if application hit its sndbuf limit recently.
+ */
+static void tcp_cwnd_application_limited(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
+ sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
+ /* Limited by application or receiver window. */
+ u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
+ u32 win_used = max(tp->snd_cwnd_used, init_win);
+ if (win_used < tp->snd_cwnd) {
+ tp->snd_ssthresh = tcp_current_ssthresh(sk);
+ tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
+ }
+ tp->snd_cwnd_used = 0;
+ }
+ tp->snd_cwnd_stamp = tcp_jiffies32;
+}
+
+static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
+{
+ const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /* Track the maximum number of outstanding packets in each
+ * window, and remember whether we were cwnd-limited then.
+ */
+ if (!before(tp->snd_una, tp->max_packets_seq) ||
+ tp->packets_out > tp->max_packets_out) {
+ tp->max_packets_out = tp->packets_out;
+ tp->max_packets_seq = tp->snd_nxt;
+ tp->is_cwnd_limited = is_cwnd_limited;
+ }
+
+ if (tcp_is_cwnd_limited(sk)) {
+ /* Network is feed fully. */
+ tp->snd_cwnd_used = 0;
+ tp->snd_cwnd_stamp = tcp_jiffies32;
+ } else {
+ /* Network starves. */
+ if (tp->packets_out > tp->snd_cwnd_used)
+ tp->snd_cwnd_used = tp->packets_out;
+
+ if (sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle &&
+ (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
+ !ca_ops->cong_control)
+ tcp_cwnd_application_limited(sk);
+
+ /* The following conditions together indicate the starvation
+ * is caused by insufficient sender buffer:
+ * 1) just sent some data (see tcp_write_xmit)
+ * 2) not cwnd limited (this else condition)
+ * 3) no more data to send (tcp_write_queue_empty())
+ * 4) application is hitting buffer limit (SOCK_NOSPACE)
+ */
+ if (tcp_write_queue_empty(sk) && sk->sk_socket &&
+ test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
+ (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
+ tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
+ }
+}
+
+/* Minshall's variant of the Nagle send check. */
+static bool tcp_minshall_check(const struct tcp_sock *tp)
+{
+ return after(tp->snd_sml, tp->snd_una) &&
+ !after(tp->snd_sml, tp->snd_nxt);
+}
+
+/* Update snd_sml if this skb is under mss
+ * Note that a TSO packet might end with a sub-mss segment
+ * The test is really :
+ * if ((skb->len % mss) != 0)
+ * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
+ * But we can avoid doing the divide again given we already have
+ * skb_pcount = skb->len / mss_now
+ */
+static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
+ const struct sk_buff *skb)
+{
+ if (skb->len < tcp_skb_pcount(skb) * mss_now)
+ tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
+}
+
+/* Return false, if packet can be sent now without violation Nagle's rules:
+ * 1. It is full sized. (provided by caller in %partial bool)
+ * 2. Or it contains FIN. (already checked by caller)
+ * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
+ * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
+ * With Minshall's modification: all sent small packets are ACKed.
+ */
+static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
+ int nonagle)
+{
+ return partial &&
+ ((nonagle & TCP_NAGLE_CORK) ||
+ (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
+}
+
+/* Return how many segs we'd like on a TSO packet,
+ * to send one TSO packet per ms
+ */
+static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
+ int min_tso_segs)
+{
+ u32 bytes, segs;
+
+ bytes = min(sk->sk_pacing_rate >> sk->sk_pacing_shift,
+ sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);
+
+ /* Goal is to send at least one packet per ms,
+ * not one big TSO packet every 100 ms.
+ * This preserves ACK clocking and is consistent
+ * with tcp_tso_should_defer() heuristic.
+ */
+ segs = max_t(u32, bytes / mss_now, min_tso_segs);
+
+ return segs;
+}
+
+/* Return the number of segments we want in the skb we are transmitting.
+ * See if congestion control module wants to decide; otherwise, autosize.
+ */
+static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
+{
+ const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
+ u32 min_tso, tso_segs;
+
+ min_tso = ca_ops->min_tso_segs ?
+ ca_ops->min_tso_segs(sk) :
+ sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs;
+
+ tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
+ return min_t(u32, tso_segs, sk->sk_gso_max_segs);
+}
+
+/* Returns the portion of skb which can be sent right away */
+static unsigned int tcp_mss_split_point(const struct sock *sk,
+ const struct sk_buff *skb,
+ unsigned int mss_now,
+ unsigned int max_segs,
+ int nonagle)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ u32 partial, needed, window, max_len;
+
+ window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
+ max_len = mss_now * max_segs;
+
+ if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
+ return max_len;
+
+ needed = min(skb->len, window);
+
+ if (max_len <= needed)
+ return max_len;
+
+ partial = needed % mss_now;
+ /* If last segment is not a full MSS, check if Nagle rules allow us
+ * to include this last segment in this skb.
+ * Otherwise, we'll split the skb at last MSS boundary
+ */
+ if (tcp_nagle_check(partial != 0, tp, nonagle))
+ return needed - partial;
+
+ return needed;
+}
+
+/* Can at least one segment of SKB be sent right now, according to the
+ * congestion window rules? If so, return how many segments are allowed.
+ */
+static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
+ const struct sk_buff *skb)
+{
+ u32 in_flight, cwnd, halfcwnd;
+
+ /* Don't be strict about the congestion window for the final FIN. */
+ if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
+ tcp_skb_pcount(skb) == 1)
+ return 1;
+
+ in_flight = tcp_packets_in_flight(tp);
+ cwnd = tp->snd_cwnd;
+ if (in_flight >= cwnd)
+ return 0;
+
+ /* For better scheduling, ensure we have at least
+ * 2 GSO packets in flight.
+ */
+ halfcwnd = max(cwnd >> 1, 1U);
+ return min(halfcwnd, cwnd - in_flight);
+}
+
+/* Initialize TSO state of a skb.
+ * This must be invoked the first time we consider transmitting
+ * SKB onto the wire.
+ */
+static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
+{
+ int tso_segs = tcp_skb_pcount(skb);
+
+ if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
+ tcp_set_skb_tso_segs(skb, mss_now);
+ tso_segs = tcp_skb_pcount(skb);
+ }
+ return tso_segs;
+}
+
+
+/* Return true if the Nagle test allows this packet to be
+ * sent now.
+ */
+static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
+ unsigned int cur_mss, int nonagle)
+{
+ /* Nagle rule does not apply to frames, which sit in the middle of the
+ * write_queue (they have no chances to get new data).
+ *
+ * This is implemented in the callers, where they modify the 'nonagle'
+ * argument based upon the location of SKB in the send queue.
+ */
+ if (nonagle & TCP_NAGLE_PUSH)
+ return true;
+
+ /* Don't use the nagle rule for urgent data (or for the final FIN). */
+ if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
+ return true;
+
+ if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
+ return true;
+
+ return false;
+}
+
+/* Does at least the first segment of SKB fit into the send window? */
+static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
+ const struct sk_buff *skb,
+ unsigned int cur_mss)
+{
+ u32 end_seq = TCP_SKB_CB(skb)->end_seq;
+
+ if (skb->len > cur_mss)
+ end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
+
+ return !after(end_seq, tcp_wnd_end(tp));
+}
+
+/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
+ * which is put after SKB on the list. It is very much like
+ * tcp_fragment() except that it may make several kinds of assumptions
+ * in order to speed up the splitting operation. In particular, we
+ * know that all the data is in scatter-gather pages, and that the
+ * packet has never been sent out before (and thus is not cloned).
+ */
+static int tso_fragment(struct sock *sk, enum tcp_queue tcp_queue,
+ struct sk_buff *skb, unsigned int len,
+ unsigned int mss_now, gfp_t gfp)
+{
+ struct sk_buff *buff;
+ int nlen = skb->len - len;
+ u8 flags;
+
+ /* All of a TSO frame must be composed of paged data. */
+ if (skb->len != skb->data_len)
+ return tcp_fragment(sk, tcp_queue, skb, len, mss_now, gfp);
+
+ buff = sk_stream_alloc_skb(sk, 0, gfp, true);
+ if (unlikely(!buff))
+ return -ENOMEM;
+
+ sk->sk_wmem_queued += buff->truesize;
+ sk_mem_charge(sk, buff->truesize);
+ buff->truesize += nlen;
+ skb->truesize -= nlen;
+
+ /* Correct the sequence numbers. */
+ TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
+ TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
+ TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
+
+ /* PSH and FIN should only be set in the second packet. */
+ flags = TCP_SKB_CB(skb)->tcp_flags;
+ TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
+ TCP_SKB_CB(buff)->tcp_flags = flags;
+
+ /* This packet was never sent out yet, so no SACK bits. */
+ TCP_SKB_CB(buff)->sacked = 0;
+
+ tcp_skb_fragment_eor(skb, buff);
+
+ buff->ip_summed = CHECKSUM_PARTIAL;
+ skb_split(skb, buff, len);
+ tcp_fragment_tstamp(skb, buff);
+
+ /* Fix up tso_factor for both original and new SKB. */
+ tcp_set_skb_tso_segs(skb, mss_now);
+ tcp_set_skb_tso_segs(buff, mss_now);
+
+ /* Link BUFF into the send queue. */
+ __skb_header_release(buff);
+ tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
+
+ return 0;
+}
+
+/* Try to defer sending, if possible, in order to minimize the amount
+ * of TSO splitting we do. View it as a kind of TSO Nagle test.
+ *
+ * This algorithm is from John Heffner.
+ */
+static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
+ bool *is_cwnd_limited,
+ bool *is_rwnd_limited,
+ u32 max_segs)
+{
+ const struct inet_connection_sock *icsk = inet_csk(sk);
+ u32 age, send_win, cong_win, limit, in_flight;
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *head;
+ int win_divisor;
+
+ if (icsk->icsk_ca_state >= TCP_CA_Recovery)
+ goto send_now;
+
+ /* Avoid bursty behavior by allowing defer
+ * only if the last write was recent.
+ */
+ if ((s32)(tcp_jiffies32 - tp->lsndtime) > 0)
+ goto send_now;
+
+ in_flight = tcp_packets_in_flight(tp);
+
+ BUG_ON(tcp_skb_pcount(skb) <= 1);
+ BUG_ON(tp->snd_cwnd <= in_flight);
+
+ send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
+
+ /* From in_flight test above, we know that cwnd > in_flight. */
+ cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
+
+ limit = min(send_win, cong_win);
+
+ /* If a full-sized TSO skb can be sent, do it. */
+ if (limit >= max_segs * tp->mss_cache)
+ goto send_now;
+
+ /* Middle in queue won't get any more data, full sendable already? */
+ if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
+ goto send_now;
+
+ win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
+ if (win_divisor) {
+ u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
+
+ /* If at least some fraction of a window is available,
+ * just use it.
+ */
+ chunk /= win_divisor;
+ if (limit >= chunk)
+ goto send_now;
+ } else {
+ /* Different approach, try not to defer past a single
+ * ACK. Receiver should ACK every other full sized
+ * frame, so if we have space for more than 3 frames
+ * then send now.
+ */
+ if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
+ goto send_now;
+ }
+
+ /* TODO : use tsorted_sent_queue ? */
+ head = tcp_rtx_queue_head(sk);
+ if (!head)
+ goto send_now;
+ age = tcp_stamp_us_delta(tp->tcp_mstamp, head->skb_mstamp);
+ /* If next ACK is likely to come too late (half srtt), do not defer */
+ if (age < (tp->srtt_us >> 4))
+ goto send_now;
+
+ /* Ok, it looks like it is advisable to defer.
+ * Three cases are tracked :
+ * 1) We are cwnd-limited
+ * 2) We are rwnd-limited
+ * 3) We are application limited.
+ */
+ if (cong_win < send_win) {
+ if (cong_win <= skb->len) {
+ *is_cwnd_limited = true;
+ return true;
+ }
+ } else {
+ if (send_win <= skb->len) {
+ *is_rwnd_limited = true;
+ return true;
+ }
+ }
+
+ /* If this packet won't get more data, do not wait. */
+ if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
+ goto send_now;
+
+ return true;
+
+send_now:
+ return false;
+}
+
+static inline void tcp_mtu_check_reprobe(struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct net *net = sock_net(sk);
+ u32 interval;
+ s32 delta;
+
+ interval = net->ipv4.sysctl_tcp_probe_interval;
+ delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
+ if (unlikely(delta >= interval * HZ)) {
+ int mss = tcp_current_mss(sk);
+
+ /* Update current search range */
+ icsk->icsk_mtup.probe_size = 0;
+ icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
+ sizeof(struct tcphdr) +
+ icsk->icsk_af_ops->net_header_len;
+ icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
+
+ /* Update probe time stamp */
+ icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
+ }
+}
+
+static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
+{
+ struct sk_buff *skb, *next;
+
+ skb = tcp_send_head(sk);
+ tcp_for_write_queue_from_safe(skb, next, sk) {
+ if (len <= skb->len)
+ break;
+
+ if (unlikely(TCP_SKB_CB(skb)->eor))
+ return false;
+
+ len -= skb->len;
+ }
+
+ return true;
+}
+
+/* Create a new MTU probe if we are ready.
+ * MTU probe is regularly attempting to increase the path MTU by
+ * deliberately sending larger packets. This discovers routing
+ * changes resulting in larger path MTUs.
+ *
+ * Returns 0 if we should wait to probe (no cwnd available),
+ * 1 if a probe was sent,
+ * -1 otherwise
+ */
+static int tcp_mtu_probe(struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb, *nskb, *next;
+ struct net *net = sock_net(sk);
+ int probe_size;
+ int size_needed;
+ int copy, len;
+ int mss_now;
+ int interval;
+
+ /* Not currently probing/verifying,
+ * not in recovery,
+ * have enough cwnd, and
+ * not SACKing (the variable headers throw things off)
+ */
+ if (likely(!icsk->icsk_mtup.enabled ||
+ icsk->icsk_mtup.probe_size ||
+ inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
+ tp->snd_cwnd < 11 ||
+ tp->rx_opt.num_sacks || tp->rx_opt.dsack))
+ return -1;
+
+ /* Use binary search for probe_size between tcp_mss_base,
+ * and current mss_clamp. if (search_high - search_low)
+ * smaller than a threshold, backoff from probing.
+ */
+ mss_now = tcp_current_mss(sk);
+ probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
+ icsk->icsk_mtup.search_low) >> 1);
+ size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
+ interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
+ /* When misfortune happens, we are reprobing actively,
+ * and then reprobe timer has expired. We stick with current
+ * probing process by not resetting search range to its orignal.
+ */
+ if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
+ interval < net->ipv4.sysctl_tcp_probe_threshold) {
+ /* Check whether enough time has elaplased for
+ * another round of probing.
+ */
+ tcp_mtu_check_reprobe(sk);
+ return -1;
+ }
+
+ /* Have enough data in the send queue to probe? */
+ if (tp->write_seq - tp->snd_nxt < size_needed)
+ return -1;
+
+ if (tp->snd_wnd < size_needed)
+ return -1;
+ if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
+ return 0;
+
+ /* Do we need to wait to drain cwnd? With none in flight, don't stall */
+ if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
+ if (!tcp_packets_in_flight(tp))
+ return -1;
+ else
+ return 0;
+ }
+
+ if (!tcp_can_coalesce_send_queue_head(sk, probe_size))
+ return -1;
+
+ /* We're allowed to probe. Build it now. */
+ nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
+ if (!nskb)
+ return -1;
+ sk->sk_wmem_queued += nskb->truesize;
+ sk_mem_charge(sk, nskb->truesize);
+
+ skb = tcp_send_head(sk);
+
+ TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
+ TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
+ TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
+ TCP_SKB_CB(nskb)->sacked = 0;
+ nskb->csum = 0;
+ nskb->ip_summed = CHECKSUM_PARTIAL;
+
+ tcp_insert_write_queue_before(nskb, skb, sk);
+ tcp_highest_sack_replace(sk, skb, nskb);
+
+ len = 0;
+ tcp_for_write_queue_from_safe(skb, next, sk) {
+ copy = min_t(int, skb->len, probe_size - len);
+ skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
+
+ if (skb->len <= copy) {
+ /* We've eaten all the data from this skb.
+ * Throw it away. */
+ TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
+ /* If this is the last SKB we copy and eor is set
+ * we need to propagate it to the new skb.
+ */
+ TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;
+ tcp_unlink_write_queue(skb, sk);
+ sk_wmem_free_skb(sk, skb);
+ } else {
+ TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
+ ~(TCPHDR_FIN|TCPHDR_PSH);
+ if (!skb_shinfo(skb)->nr_frags) {
+ skb_pull(skb, copy);
+ } else {
+ __pskb_trim_head(skb, copy);
+ tcp_set_skb_tso_segs(skb, mss_now);
+ }
+ TCP_SKB_CB(skb)->seq += copy;
+ }
+
+ len += copy;
+
+ if (len >= probe_size)
+ break;
+ }
+ tcp_init_tso_segs(nskb, nskb->len);
+
+ /* We're ready to send. If this fails, the probe will
+ * be resegmented into mss-sized pieces by tcp_write_xmit().
+ */
+ if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
+ /* Decrement cwnd here because we are sending
+ * effectively two packets. */
+ tp->snd_cwnd--;
+ tcp_event_new_data_sent(sk, nskb);
+
+ icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
+ tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
+ tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
+
+ return 1;
+ }
+
+ return -1;
+}
+
+static bool tcp_pacing_check(const struct sock *sk)
+{
+ return tcp_needs_internal_pacing(sk) &&
+ hrtimer_is_queued(&tcp_sk(sk)->pacing_timer);
+}
+
+/* TCP Small Queues :
+ * Control number of packets in qdisc/devices to two packets / or ~1 ms.
+ * (These limits are doubled for retransmits)
+ * This allows for :
+ * - better RTT estimation and ACK scheduling
+ * - faster recovery
+ * - high rates
+ * Alas, some drivers / subsystems require a fair amount
+ * of queued bytes to ensure line rate.
+ * One example is wifi aggregation (802.11 AMPDU)
+ */
+static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
+ unsigned int factor)
+{
+ unsigned int limit;
+
+ limit = max(2 * skb->truesize, sk->sk_pacing_rate >> sk->sk_pacing_shift);
+ limit = min_t(u32, limit,
+ sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);
+ limit <<= factor;
+
+ if (refcount_read(&sk->sk_wmem_alloc) > limit) {
+ /* Always send skb if rtx queue is empty.
+ * No need to wait for TX completion to call us back,
+ * after softirq/tasklet schedule.
+ * This helps when TX completions are delayed too much.
+ */
+ if (tcp_rtx_queue_empty(sk))
+ return false;
+
+ set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
+ /* It is possible TX completion already happened
+ * before we set TSQ_THROTTLED, so we must
+ * test again the condition.
+ */
+ smp_mb__after_atomic();
+ if (refcount_read(&sk->sk_wmem_alloc) > limit)
+ return true;
+ }
+ return false;
+}
+
+static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
+{
+ const u32 now = tcp_jiffies32;
+ enum tcp_chrono old = tp->chrono_type;
+
+ if (old > TCP_CHRONO_UNSPEC)
+ tp->chrono_stat[old - 1] += now - tp->chrono_start;
+ tp->chrono_start = now;
+ tp->chrono_type = new;
+}
+
+void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /* If there are multiple conditions worthy of tracking in a
+ * chronograph then the highest priority enum takes precedence
+ * over the other conditions. So that if something "more interesting"
+ * starts happening, stop the previous chrono and start a new one.
+ */
+ if (type > tp->chrono_type)
+ tcp_chrono_set(tp, type);
+}
+
+void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+
+ /* There are multiple conditions worthy of tracking in a
+ * chronograph, so that the highest priority enum takes
+ * precedence over the other conditions (see tcp_chrono_start).
+ * If a condition stops, we only stop chrono tracking if
+ * it's the "most interesting" or current chrono we are
+ * tracking and starts busy chrono if we have pending data.
+ */
+ if (tcp_rtx_and_write_queues_empty(sk))
+ tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
+ else if (type == tp->chrono_type)
+ tcp_chrono_set(tp, TCP_CHRONO_BUSY);
+}
+
+/* This routine writes packets to the network. It advances the
+ * send_head. This happens as incoming acks open up the remote
+ * window for us.
+ *
+ * LARGESEND note: !tcp_urg_mode is overkill, only frames between
+ * snd_up-64k-mss .. snd_up cannot be large. However, taking into
+ * account rare use of URG, this is not a big flaw.
+ *
+ * Send at most one packet when push_one > 0. Temporarily ignore
+ * cwnd limit to force at most one packet out when push_one == 2.
+
+ * Returns true, if no segments are in flight and we have queued segments,
+ * but cannot send anything now because of SWS or another problem.
+ */
+static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
+ int push_one, gfp_t gfp)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+ unsigned int tso_segs, sent_pkts;
+ int cwnd_quota;
+ int result;
+ bool is_cwnd_limited = false, is_rwnd_limited = false;
+ u32 max_segs;
+
+ sent_pkts = 0;
+
+ tcp_mstamp_refresh(tp);
+ if (!push_one) {
+ /* Do MTU probing. */
+ result = tcp_mtu_probe(sk);
+ if (!result) {
+ return false;
+ } else if (result > 0) {
+ sent_pkts = 1;
+ }
+ }
+
+ max_segs = tcp_tso_segs(sk, mss_now);
+ while ((skb = tcp_send_head(sk))) {
+ unsigned int limit;
+
+ if (tcp_pacing_check(sk))
+ break;
+
+ tso_segs = tcp_init_tso_segs(skb, mss_now);
+ BUG_ON(!tso_segs);
+
+ if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
+ /* "skb_mstamp" is used as a start point for the retransmit timer */
+ tcp_update_skb_after_send(tp, skb);
+ goto repair; /* Skip network transmission */
+ }
+
+ cwnd_quota = tcp_cwnd_test(tp, skb);
+ if (!cwnd_quota) {
+ if (push_one == 2)
+ /* Force out a loss probe pkt. */
+ cwnd_quota = 1;
+ else
+ break;
+ }
+
+ if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
+ is_rwnd_limited = true;
+ break;
+ }
+
+ if (tso_segs == 1) {
+ if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
+ (tcp_skb_is_last(sk, skb) ?
+ nonagle : TCP_NAGLE_PUSH))))
+ break;
+ } else {
+ if (!push_one &&
+ tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
+ &is_rwnd_limited, max_segs))
+ break;
+ }
+
+ limit = mss_now;
+ if (tso_segs > 1 && !tcp_urg_mode(tp))
+ limit = tcp_mss_split_point(sk, skb, mss_now,
+ min_t(unsigned int,
+ cwnd_quota,
+ max_segs),
+ nonagle);
+
+ if (skb->len > limit &&
+ unlikely(tso_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
+ skb, limit, mss_now, gfp)))
+ break;
+
+ if (tcp_small_queue_check(sk, skb, 0))
+ break;
+
+ if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
+ break;
+
+repair:
+ /* Advance the send_head. This one is sent out.
+ * This call will increment packets_out.
+ */
+ tcp_event_new_data_sent(sk, skb);
+
+ tcp_minshall_update(tp, mss_now, skb);
+ sent_pkts += tcp_skb_pcount(skb);
+
+ if (push_one)
+ break;
+ }
+
+ if (is_rwnd_limited)
+ tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
+ else
+ tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
+
+ if (likely(sent_pkts)) {
+ if (tcp_in_cwnd_reduction(sk))
+ tp->prr_out += sent_pkts;
+
+ /* Send one loss probe per tail loss episode. */
+ if (push_one != 2)
+ tcp_schedule_loss_probe(sk, false);
+ is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
+ tcp_cwnd_validate(sk, is_cwnd_limited);
+ return false;
+ }
+ return !tp->packets_out && !tcp_write_queue_empty(sk);
+}
+
+bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ u32 timeout, rto_delta_us;
+ int early_retrans;
+
+ /* Don't do any loss probe on a Fast Open connection before 3WHS
+ * finishes.
+ */
+ if (tp->fastopen_rsk)
+ return false;
+
+ early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
+ /* Schedule a loss probe in 2*RTT for SACK capable connections
+ * not in loss recovery, that are either limited by cwnd or application.
+ */
+ if ((early_retrans != 3 && early_retrans != 4) ||
+ !tp->packets_out || !tcp_is_sack(tp) ||
+ (icsk->icsk_ca_state != TCP_CA_Open &&
+ icsk->icsk_ca_state != TCP_CA_CWR))
+ return false;
+
+ /* Probe timeout is 2*rtt. Add minimum RTO to account
+ * for delayed ack when there's one outstanding packet. If no RTT
+ * sample is available then probe after TCP_TIMEOUT_INIT.
+ */
+ if (tp->srtt_us) {
+ timeout = usecs_to_jiffies(tp->srtt_us >> 2);
+ if (tp->packets_out == 1)
+ timeout += TCP_RTO_MIN;
+ else
+ timeout += TCP_TIMEOUT_MIN;
+ } else {
+ timeout = TCP_TIMEOUT_INIT;
+ }
+
+ /* If the RTO formula yields an earlier time, then use that time. */
+ rto_delta_us = advancing_rto ?
+ jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
+ tcp_rto_delta_us(sk); /* How far in future is RTO? */
+ if (rto_delta_us > 0)
+ timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
+
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
+ TCP_RTO_MAX);
+ return true;
+}
+
+/* Thanks to skb fast clones, we can detect if a prior transmit of
+ * a packet is still in a qdisc or driver queue.
+ * In this case, there is very little point doing a retransmit !
+ */
+static bool skb_still_in_host_queue(const struct sock *sk,
+ const struct sk_buff *skb)
+{
+ if (unlikely(skb_fclone_busy(sk, skb))) {
+ NET_INC_STATS(sock_net(sk),
+ LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
+ return true;
+ }
+ return false;
+}
+
+/* When probe timeout (PTO) fires, try send a new segment if possible, else
+ * retransmit the last segment.
+ */
+void tcp_send_loss_probe(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+ int pcount;
+ int mss = tcp_current_mss(sk);
+
+ skb = tcp_send_head(sk);
+ if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
+ pcount = tp->packets_out;
+ tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
+ if (tp->packets_out > pcount)
+ goto probe_sent;
+ goto rearm_timer;
+ }
+ skb = skb_rb_last(&sk->tcp_rtx_queue);
+ if (unlikely(!skb)) {
+ WARN_ONCE(tp->packets_out,
+ "invalid inflight: %u state %u cwnd %u mss %d\n",
+ tp->packets_out, sk->sk_state, tp->snd_cwnd, mss);
+ inet_csk(sk)->icsk_pending = 0;
+ return;
+ }
+
+ /* At most one outstanding TLP retransmission. */
+ if (tp->tlp_high_seq)
+ goto rearm_timer;
+
+ if (skb_still_in_host_queue(sk, skb))
+ goto rearm_timer;
+
+ pcount = tcp_skb_pcount(skb);
+ if (WARN_ON(!pcount))
+ goto rearm_timer;
+
+ if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
+ if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
+ (pcount - 1) * mss, mss,
+ GFP_ATOMIC)))
+ goto rearm_timer;
+ skb = skb_rb_next(skb);
+ }
+
+ if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
+ goto rearm_timer;
+
+ if (__tcp_retransmit_skb(sk, skb, 1))
+ goto rearm_timer;
+
+ /* Record snd_nxt for loss detection. */
+ tp->tlp_high_seq = tp->snd_nxt;
+
+probe_sent:
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
+ /* Reset s.t. tcp_rearm_rto will restart timer from now */
+ inet_csk(sk)->icsk_pending = 0;
+rearm_timer:
+ tcp_rearm_rto(sk);
+}
+
+/* Push out any pending frames which were held back due to
+ * TCP_CORK or attempt at coalescing tiny packets.
+ * The socket must be locked by the caller.
+ */
+void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
+ int nonagle)
+{
+ /* If we are closed, the bytes will have to remain here.
+ * In time closedown will finish, we empty the write queue and
+ * all will be happy.
+ */
+ if (unlikely(sk->sk_state == TCP_CLOSE))
+ return;
+
+ if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
+ sk_gfp_mask(sk, GFP_ATOMIC)))
+ tcp_check_probe_timer(sk);
+}
+
+/* Send _single_ skb sitting at the send head. This function requires
+ * true push pending frames to setup probe timer etc.
+ */
+void tcp_push_one(struct sock *sk, unsigned int mss_now)
+{
+ struct sk_buff *skb = tcp_send_head(sk);
+
+ BUG_ON(!skb || skb->len < mss_now);
+
+ tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
+}
+
+/* This function returns the amount that we can raise the
+ * usable window based on the following constraints
+ *
+ * 1. The window can never be shrunk once it is offered (RFC 793)
+ * 2. We limit memory per socket
+ *
+ * RFC 1122:
+ * "the suggested [SWS] avoidance algorithm for the receiver is to keep
+ * RECV.NEXT + RCV.WIN fixed until:
+ * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
+ *
+ * i.e. don't raise the right edge of the window until you can raise
+ * it at least MSS bytes.
+ *
+ * Unfortunately, the recommended algorithm breaks header prediction,
+ * since header prediction assumes th->window stays fixed.
+ *
+ * Strictly speaking, keeping th->window fixed violates the receiver
+ * side SWS prevention criteria. The problem is that under this rule
+ * a stream of single byte packets will cause the right side of the
+ * window to always advance by a single byte.
+ *
+ * Of course, if the sender implements sender side SWS prevention
+ * then this will not be a problem.
+ *
+ * BSD seems to make the following compromise:
+ *
+ * If the free space is less than the 1/4 of the maximum
+ * space available and the free space is less than 1/2 mss,
+ * then set the window to 0.
+ * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
+ * Otherwise, just prevent the window from shrinking
+ * and from being larger than the largest representable value.
+ *
+ * This prevents incremental opening of the window in the regime
+ * where TCP is limited by the speed of the reader side taking
+ * data out of the TCP receive queue. It does nothing about
+ * those cases where the window is constrained on the sender side
+ * because the pipeline is full.
+ *
+ * BSD also seems to "accidentally" limit itself to windows that are a
+ * multiple of MSS, at least until the free space gets quite small.
+ * This would appear to be a side effect of the mbuf implementation.
+ * Combining these two algorithms results in the observed behavior
+ * of having a fixed window size at almost all times.
+ *
+ * Below we obtain similar behavior by forcing the offered window to
+ * a multiple of the mss when it is feasible to do so.
+ *
+ * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
+ * Regular options like TIMESTAMP are taken into account.
+ */
+u32 __tcp_select_window(struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ /* MSS for the peer's data. Previous versions used mss_clamp
+ * here. I don't know if the value based on our guesses
+ * of peer's MSS is better for the performance. It's more correct
+ * but may be worse for the performance because of rcv_mss
+ * fluctuations. --SAW 1998/11/1
+ */
+ int mss = icsk->icsk_ack.rcv_mss;
+ int free_space = tcp_space(sk);
+ int allowed_space = tcp_full_space(sk);
+ int full_space = min_t(int, tp->window_clamp, allowed_space);
+ int window;
+
+ if (unlikely(mss > full_space)) {
+ mss = full_space;
+ if (mss <= 0)
+ return 0;
+ }
+ if (free_space < (full_space >> 1)) {
+ icsk->icsk_ack.quick = 0;
+
+ if (tcp_under_memory_pressure(sk))
+ tp->rcv_ssthresh = min(tp->rcv_ssthresh,
+ 4U * tp->advmss);
+
+ /* free_space might become our new window, make sure we don't
+ * increase it due to wscale.
+ */
+ free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
+
+ /* if free space is less than mss estimate, or is below 1/16th
+ * of the maximum allowed, try to move to zero-window, else
+ * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
+ * new incoming data is dropped due to memory limits.
+ * With large window, mss test triggers way too late in order
+ * to announce zero window in time before rmem limit kicks in.
+ */
+ if (free_space < (allowed_space >> 4) || free_space < mss)
+ return 0;
+ }
+
+ if (free_space > tp->rcv_ssthresh)
+ free_space = tp->rcv_ssthresh;
+
+ /* Don't do rounding if we are using window scaling, since the
+ * scaled window will not line up with the MSS boundary anyway.
+ */
+ if (tp->rx_opt.rcv_wscale) {
+ window = free_space;
+
+ /* Advertise enough space so that it won't get scaled away.
+ * Import case: prevent zero window announcement if
+ * 1<<rcv_wscale > mss.
+ */
+ window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
+ } else {
+ window = tp->rcv_wnd;
+ /* Get the largest window that is a nice multiple of mss.
+ * Window clamp already applied above.
+ * If our current window offering is within 1 mss of the
+ * free space we just keep it. This prevents the divide
+ * and multiply from happening most of the time.
+ * We also don't do any window rounding when the free space
+ * is too small.
+ */
+ if (window <= free_space - mss || window > free_space)
+ window = rounddown(free_space, mss);
+ else if (mss == full_space &&
+ free_space > window + (full_space >> 1))
+ window = free_space;
+ }
+
+ return window;
+}
+
+void tcp_skb_collapse_tstamp(struct sk_buff *skb,
+ const struct sk_buff *next_skb)
+{
+ if (unlikely(tcp_has_tx_tstamp(next_skb))) {
+ const struct skb_shared_info *next_shinfo =
+ skb_shinfo(next_skb);
+ struct skb_shared_info *shinfo = skb_shinfo(skb);
+
+ shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
+ shinfo->tskey = next_shinfo->tskey;
+ TCP_SKB_CB(skb)->txstamp_ack |=
+ TCP_SKB_CB(next_skb)->txstamp_ack;
+ }
+}
+
+/* Collapses two adjacent SKB's during retransmission. */
+static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *next_skb = skb_rb_next(skb);
+ int next_skb_size;
+
+ next_skb_size = next_skb->len;
+
+ BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
+
+ if (next_skb_size) {
+ if (next_skb_size <= skb_availroom(skb))
+ skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
+ next_skb_size);
+ else if (!skb_shift(skb, next_skb, next_skb_size))
+ return false;
+ }
+ tcp_highest_sack_replace(sk, next_skb, skb);
+
+ /* Update sequence range on original skb. */
+ TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
+
+ /* Merge over control information. This moves PSH/FIN etc. over */
+ TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
+
+ /* All done, get rid of second SKB and account for it so
+ * packet counting does not break.
+ */
+ TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
+ TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
+
+ /* changed transmit queue under us so clear hints */
+ tcp_clear_retrans_hints_partial(tp);
+ if (next_skb == tp->retransmit_skb_hint)
+ tp->retransmit_skb_hint = skb;
+
+ tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
+
+ tcp_skb_collapse_tstamp(skb, next_skb);
+
+ tcp_rtx_queue_unlink_and_free(next_skb, sk);
+ return true;
+}
+
+/* Check if coalescing SKBs is legal. */
+static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
+{
+ if (tcp_skb_pcount(skb) > 1)
+ return false;
+ if (skb_cloned(skb))
+ return false;
+ /* Some heuristics for collapsing over SACK'd could be invented */
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
+ return false;
+
+ return true;
+}
+
+/* Collapse packets in the retransmit queue to make to create
+ * less packets on the wire. This is only done on retransmission.
+ */
+static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
+ int space)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb = to, *tmp;
+ bool first = true;
+
+ if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)
+ return;
+ if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
+ return;
+
+ skb_rbtree_walk_from_safe(skb, tmp) {
+ if (!tcp_can_collapse(sk, skb))
+ break;
+
+ if (!tcp_skb_can_collapse_to(to))
+ break;
+
+ space -= skb->len;
+
+ if (first) {
+ first = false;
+ continue;
+ }
+
+ if (space < 0)
+ break;
+
+ if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
+ break;
+
+ if (!tcp_collapse_retrans(sk, to))
+ break;
+ }
+}
+
+/* This retransmits one SKB. Policy decisions and retransmit queue
+ * state updates are done by the caller. Returns non-zero if an
+ * error occurred which prevented the send.
+ */
+int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ unsigned int cur_mss;
+ int diff, len, err;
+
+
+ /* Inconclusive MTU probe */
+ if (icsk->icsk_mtup.probe_size)
+ icsk->icsk_mtup.probe_size = 0;
+
+ /* Do not sent more than we queued. 1/4 is reserved for possible
+ * copying overhead: fragmentation, tunneling, mangling etc.
+ */
+ if (refcount_read(&sk->sk_wmem_alloc) >
+ min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
+ sk->sk_sndbuf))
+ return -EAGAIN;
+
+ if (skb_still_in_host_queue(sk, skb))
+ return -EBUSY;
+
+ if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
+ if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) {
+ WARN_ON_ONCE(1);
+ return -EINVAL;
+ }
+ if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
+ return -ENOMEM;
+ }
+
+ if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
+ return -EHOSTUNREACH; /* Routing failure or similar. */
+
+ cur_mss = tcp_current_mss(sk);
+
+ /* If receiver has shrunk his window, and skb is out of
+ * new window, do not retransmit it. The exception is the
+ * case, when window is shrunk to zero. In this case
+ * our retransmit serves as a zero window probe.
+ */
+ if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
+ TCP_SKB_CB(skb)->seq != tp->snd_una)
+ return -EAGAIN;
+
+ len = cur_mss * segs;
+ if (skb->len > len) {
+ if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
+ cur_mss, GFP_ATOMIC))
+ return -ENOMEM; /* We'll try again later. */
+ } else {
+ if (skb_unclone(skb, GFP_ATOMIC))
+ return -ENOMEM;
+
+ diff = tcp_skb_pcount(skb);
+ tcp_set_skb_tso_segs(skb, cur_mss);
+ diff -= tcp_skb_pcount(skb);
+ if (diff)
+ tcp_adjust_pcount(sk, skb, diff);
+ if (skb->len < cur_mss)
+ tcp_retrans_try_collapse(sk, skb, cur_mss);
+ }
+
+ /* RFC3168, section 6.1.1.1. ECN fallback */
+ if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
+ tcp_ecn_clear_syn(sk, skb);
+
+ /* Update global and local TCP statistics. */
+ segs = tcp_skb_pcount(skb);
+ TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
+ if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
+ __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
+ tp->total_retrans += segs;
+ tp->bytes_retrans += skb->len;
+
+ /* make sure skb->data is aligned on arches that require it
+ * and check if ack-trimming & collapsing extended the headroom
+ * beyond what csum_start can cover.
+ */
+ if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
+ skb_headroom(skb) >= 0xFFFF)) {
+ struct sk_buff *nskb;
+
+ tcp_skb_tsorted_save(skb) {
+ nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
+ err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
+ -ENOBUFS;
+ } tcp_skb_tsorted_restore(skb);
+
+ if (!err) {
+ tcp_update_skb_after_send(tp, skb);
+ tcp_rate_skb_sent(sk, skb);
+ }
+ } else {
+ err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
+ }
+
+ if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
+ tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
+ TCP_SKB_CB(skb)->seq, segs, err);
+
+ if (likely(!err)) {
+ TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
+ trace_tcp_retransmit_skb(sk, skb);
+ } else if (err != -EBUSY) {
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
+ }
+ return err;
+}
+
+int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int err = __tcp_retransmit_skb(sk, skb, segs);
+
+ if (err == 0) {
+#if FASTRETRANS_DEBUG > 0
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
+ net_dbg_ratelimited("retrans_out leaked\n");
+ }
+#endif
+ TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
+ tp->retrans_out += tcp_skb_pcount(skb);
+
+ /* Save stamp of the first retransmit. */
+ if (!tp->retrans_stamp)
+ tp->retrans_stamp = tcp_skb_timestamp(skb);
+
+ }
+
+ if (tp->undo_retrans < 0)
+ tp->undo_retrans = 0;
+ tp->undo_retrans += tcp_skb_pcount(skb);
+ return err;
+}
+
+/* This gets called after a retransmit timeout, and the initially
+ * retransmitted data is acknowledged. It tries to continue
+ * resending the rest of the retransmit queue, until either
+ * we've sent it all or the congestion window limit is reached.
+ */
+void tcp_xmit_retransmit_queue(struct sock *sk)
+{
+ const struct inet_connection_sock *icsk = inet_csk(sk);
+ struct sk_buff *skb, *rtx_head, *hole = NULL;
+ struct tcp_sock *tp = tcp_sk(sk);
+ u32 max_segs;
+ int mib_idx;
+
+ if (!tp->packets_out)
+ return;
+
+ rtx_head = tcp_rtx_queue_head(sk);
+ skb = tp->retransmit_skb_hint ?: rtx_head;
+ max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
+ skb_rbtree_walk_from(skb) {
+ __u8 sacked;
+ int segs;
+
+ if (tcp_pacing_check(sk))
+ break;
+
+ /* we could do better than to assign each time */
+ if (!hole)
+ tp->retransmit_skb_hint = skb;
+
+ segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
+ if (segs <= 0)
+ return;
+ sacked = TCP_SKB_CB(skb)->sacked;
+ /* In case tcp_shift_skb_data() have aggregated large skbs,
+ * we need to make sure not sending too bigs TSO packets
+ */
+ segs = min_t(int, segs, max_segs);
+
+ if (tp->retrans_out >= tp->lost_out) {
+ break;
+ } else if (!(sacked & TCPCB_LOST)) {
+ if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
+ hole = skb;
+ continue;
+
+ } else {
+ if (icsk->icsk_ca_state != TCP_CA_Loss)
+ mib_idx = LINUX_MIB_TCPFASTRETRANS;
+ else
+ mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
+ }
+
+ if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
+ continue;
+
+ if (tcp_small_queue_check(sk, skb, 1))
+ return;
+
+ if (tcp_retransmit_skb(sk, skb, segs))
+ return;
+
+ NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
+
+ if (tcp_in_cwnd_reduction(sk))
+ tp->prr_out += tcp_skb_pcount(skb);
+
+ if (skb == rtx_head &&
+ icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+ inet_csk(sk)->icsk_rto,
+ TCP_RTO_MAX);
+ }
+}
+
+/* We allow to exceed memory limits for FIN packets to expedite
+ * connection tear down and (memory) recovery.
+ * Otherwise tcp_send_fin() could be tempted to either delay FIN
+ * or even be forced to close flow without any FIN.
+ * In general, we want to allow one skb per socket to avoid hangs
+ * with edge trigger epoll()
+ */
+void sk_forced_mem_schedule(struct sock *sk, int size)
+{
+ int amt;
+
+ if (size <= sk->sk_forward_alloc)
+ return;
+ amt = sk_mem_pages(size);
+ sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
+ sk_memory_allocated_add(sk, amt);
+
+ if (mem_cgroup_sockets_enabled && sk->sk_memcg)
+ mem_cgroup_charge_skmem(sk->sk_memcg, amt);
+}
+
+/* Send a FIN. The caller locks the socket for us.
+ * We should try to send a FIN packet really hard, but eventually give up.
+ */
+void tcp_send_fin(struct sock *sk)
+{
+ struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /* Optimization, tack on the FIN if we have one skb in write queue and
+ * this skb was not yet sent, or we are under memory pressure.
+ * Note: in the latter case, FIN packet will be sent after a timeout,
+ * as TCP stack thinks it has already been transmitted.
+ */
+ if (!tskb && tcp_under_memory_pressure(sk))
+ tskb = skb_rb_last(&sk->tcp_rtx_queue);
+
+ if (tskb) {
+coalesce:
+ TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
+ TCP_SKB_CB(tskb)->end_seq++;
+ tp->write_seq++;
+ if (tcp_write_queue_empty(sk)) {
+ /* This means tskb was already sent.
+ * Pretend we included the FIN on previous transmit.
+ * We need to set tp->snd_nxt to the value it would have
+ * if FIN had been sent. This is because retransmit path
+ * does not change tp->snd_nxt.
+ */
+ tp->snd_nxt++;
+ return;
+ }
+ } else {
+ skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
+ if (unlikely(!skb)) {
+ if (tskb)
+ goto coalesce;
+ return;
+ }
+ INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
+ skb_reserve(skb, MAX_TCP_HEADER);
+ sk_forced_mem_schedule(sk, skb->truesize);
+ /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
+ tcp_init_nondata_skb(skb, tp->write_seq,
+ TCPHDR_ACK | TCPHDR_FIN);
+ tcp_queue_skb(sk, skb);
+ }
+ __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
+}
+
+/* We get here when a process closes a file descriptor (either due to
+ * an explicit close() or as a byproduct of exit()'ing) and there
+ * was unread data in the receive queue. This behavior is recommended
+ * by RFC 2525, section 2.17. -DaveM
+ */
+void tcp_send_active_reset(struct sock *sk, gfp_t priority)
+{
+ struct sk_buff *skb;
+
+ TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
+
+ /* NOTE: No TCP options attached and we never retransmit this. */
+ skb = alloc_skb(MAX_TCP_HEADER, priority);
+ if (!skb) {
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
+ return;
+ }
+
+ /* Reserve space for headers and prepare control bits. */
+ skb_reserve(skb, MAX_TCP_HEADER);
+ tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
+ TCPHDR_ACK | TCPHDR_RST);
+ tcp_mstamp_refresh(tcp_sk(sk));
+ /* Send it off. */
+ if (tcp_transmit_skb(sk, skb, 0, priority))
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
+
+ /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
+ * skb here is different to the troublesome skb, so use NULL
+ */
+ trace_tcp_send_reset(sk, NULL);
+}
+
+/* Send a crossed SYN-ACK during socket establishment.
+ * WARNING: This routine must only be called when we have already sent
+ * a SYN packet that crossed the incoming SYN that caused this routine
+ * to get called. If this assumption fails then the initial rcv_wnd
+ * and rcv_wscale values will not be correct.
+ */
+int tcp_send_synack(struct sock *sk)
+{
+ struct sk_buff *skb;
+
+ skb = tcp_rtx_queue_head(sk);
+ if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
+ pr_err("%s: wrong queue state\n", __func__);
+ return -EFAULT;
+ }
+ if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
+ if (skb_cloned(skb)) {
+ struct sk_buff *nskb;
+
+ tcp_skb_tsorted_save(skb) {
+ nskb = skb_copy(skb, GFP_ATOMIC);
+ } tcp_skb_tsorted_restore(skb);
+ if (!nskb)
+ return -ENOMEM;
+ INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
+ tcp_rtx_queue_unlink_and_free(skb, sk);
+ __skb_header_release(nskb);
+ tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
+ sk->sk_wmem_queued += nskb->truesize;
+ sk_mem_charge(sk, nskb->truesize);
+ skb = nskb;
+ }
+
+ TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
+ tcp_ecn_send_synack(sk, skb);
+ }
+ return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
+}
+
+/**
+ * tcp_make_synack - Prepare a SYN-ACK.
+ * sk: listener socket
+ * dst: dst entry attached to the SYNACK
+ * req: request_sock pointer
+ *
+ * Allocate one skb and build a SYNACK packet.
+ * @dst is consumed : Caller should not use it again.
+ */
+struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
+ struct request_sock *req,
+ struct tcp_fastopen_cookie *foc,
+ enum tcp_synack_type synack_type)
+{
+ struct inet_request_sock *ireq = inet_rsk(req);
+ const struct tcp_sock *tp = tcp_sk(sk);
+ struct tcp_md5sig_key *md5 = NULL;
+ struct tcp_out_options opts;
+ struct sk_buff *skb;
+ int tcp_header_size;
+ struct tcphdr *th;
+ int mss;
+
+ skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
+ if (unlikely(!skb)) {
+ dst_release(dst);
+ return NULL;
+ }
+ /* Reserve space for headers. */
+ skb_reserve(skb, MAX_TCP_HEADER);
+
+ switch (synack_type) {
+ case TCP_SYNACK_NORMAL:
+ skb_set_owner_w(skb, req_to_sk(req));
+ break;
+ case TCP_SYNACK_COOKIE:
+ /* Under synflood, we do not attach skb to a socket,
+ * to avoid false sharing.
+ */
+ break;
+ case TCP_SYNACK_FASTOPEN:
+ /* sk is a const pointer, because we want to express multiple
+ * cpu might call us concurrently.
+ * sk->sk_wmem_alloc in an atomic, we can promote to rw.
+ */
+ skb_set_owner_w(skb, (struct sock *)sk);
+ break;
+ }
+ skb_dst_set(skb, dst);
+
+ mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
+
+ memset(&opts, 0, sizeof(opts));
+#ifdef CONFIG_SYN_COOKIES
+ if (unlikely(req->cookie_ts))
+ skb->skb_mstamp = cookie_init_timestamp(req);
+ else
+#endif
+ skb->skb_mstamp = tcp_clock_us();
+
+#ifdef CONFIG_TCP_MD5SIG
+ rcu_read_lock();
+ md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
+#endif
+ skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
+ tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
+ foc) + sizeof(*th);
+
+ skb_push(skb, tcp_header_size);
+ skb_reset_transport_header(skb);
+
+ th = (struct tcphdr *)skb->data;
+ memset(th, 0, sizeof(struct tcphdr));
+ th->syn = 1;
+ th->ack = 1;
+ tcp_ecn_make_synack(req, th);
+ th->source = htons(ireq->ir_num);
+ th->dest = ireq->ir_rmt_port;
+ skb->mark = ireq->ir_mark;
+ skb->ip_summed = CHECKSUM_PARTIAL;
+ th->seq = htonl(tcp_rsk(req)->snt_isn);
+ /* XXX data is queued and acked as is. No buffer/window check */
+ th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
+
+ /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
+ th->window = htons(min(req->rsk_rcv_wnd, 65535U));
+ tcp_options_write((__be32 *)(th + 1), NULL, &opts);
+ th->doff = (tcp_header_size >> 2);
+ __TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
+
+#ifdef CONFIG_TCP_MD5SIG
+ /* Okay, we have all we need - do the md5 hash if needed */
+ if (md5)
+ tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
+ md5, req_to_sk(req), skb);
+ rcu_read_unlock();
+#endif
+
+ /* Do not fool tcpdump (if any), clean our debris */
+ skb->tstamp = 0;
+ return skb;
+}
+EXPORT_SYMBOL(tcp_make_synack);
+
+static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ const struct tcp_congestion_ops *ca;
+ u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
+
+ if (ca_key == TCP_CA_UNSPEC)
+ return;
+
+ rcu_read_lock();
+ ca = tcp_ca_find_key(ca_key);
+ if (likely(ca && try_module_get(ca->owner))) {
+ module_put(icsk->icsk_ca_ops->owner);
+ icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
+ icsk->icsk_ca_ops = ca;
+ }
+ rcu_read_unlock();
+}
+
+/* Do all connect socket setups that can be done AF independent. */
+static void tcp_connect_init(struct sock *sk)
+{
+ const struct dst_entry *dst = __sk_dst_get(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ __u8 rcv_wscale;
+ u32 rcv_wnd;
+
+ /* We'll fix this up when we get a response from the other end.
+ * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
+ */
+ tp->tcp_header_len = sizeof(struct tcphdr);
+ if (sock_net(sk)->ipv4.sysctl_tcp_timestamps)
+ tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
+
+#ifdef CONFIG_TCP_MD5SIG
+ if (tp->af_specific->md5_lookup(sk, sk))
+ tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
+#endif
+
+ /* If user gave his TCP_MAXSEG, record it to clamp */
+ if (tp->rx_opt.user_mss)
+ tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
+ tp->max_window = 0;
+ tcp_mtup_init(sk);
+ tcp_sync_mss(sk, dst_mtu(dst));
+
+ tcp_ca_dst_init(sk, dst);
+
+ if (!tp->window_clamp)
+ tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
+ tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
+
+ tcp_initialize_rcv_mss(sk);
+
+ /* limit the window selection if the user enforce a smaller rx buffer */
+ if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
+ (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
+ tp->window_clamp = tcp_full_space(sk);
+
+ rcv_wnd = tcp_rwnd_init_bpf(sk);
+ if (rcv_wnd == 0)
+ rcv_wnd = dst_metric(dst, RTAX_INITRWND);
+
+ tcp_select_initial_window(sk, tcp_full_space(sk),
+ tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
+ &tp->rcv_wnd,
+ &tp->window_clamp,
+ sock_net(sk)->ipv4.sysctl_tcp_window_scaling,
+ &rcv_wscale,
+ rcv_wnd);
+
+ tp->rx_opt.rcv_wscale = rcv_wscale;
+ tp->rcv_ssthresh = tp->rcv_wnd;
+
+ sk->sk_err = 0;
+ sock_reset_flag(sk, SOCK_DONE);
+ tp->snd_wnd = 0;
+ tcp_init_wl(tp, 0);
+ tcp_write_queue_purge(sk);
+ tp->snd_una = tp->write_seq;
+ tp->snd_sml = tp->write_seq;
+ tp->snd_up = tp->write_seq;
+ tp->snd_nxt = tp->write_seq;
+
+ if (likely(!tp->repair))
+ tp->rcv_nxt = 0;
+ else
+ tp->rcv_tstamp = tcp_jiffies32;
+ tp->rcv_wup = tp->rcv_nxt;
+ tp->copied_seq = tp->rcv_nxt;
+
+ inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
+ inet_csk(sk)->icsk_retransmits = 0;
+ tcp_clear_retrans(tp);
+}
+
+static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
+
+ tcb->end_seq += skb->len;
+ __skb_header_release(skb);
+ sk->sk_wmem_queued += skb->truesize;
+ sk_mem_charge(sk, skb->truesize);
+ tp->write_seq = tcb->end_seq;
+ tp->packets_out += tcp_skb_pcount(skb);
+}
+
+/* Build and send a SYN with data and (cached) Fast Open cookie. However,
+ * queue a data-only packet after the regular SYN, such that regular SYNs
+ * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
+ * only the SYN sequence, the data are retransmitted in the first ACK.
+ * If cookie is not cached or other error occurs, falls back to send a
+ * regular SYN with Fast Open cookie request option.
+ */
+static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct tcp_fastopen_request *fo = tp->fastopen_req;
+ int space, err = 0;
+ struct sk_buff *syn_data;
+
+ tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
+ if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
+ goto fallback;
+
+ /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
+ * user-MSS. Reserve maximum option space for middleboxes that add
+ * private TCP options. The cost is reduced data space in SYN :(
+ */
+ tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
+
+ space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
+ MAX_TCP_OPTION_SPACE;
+
+ space = min_t(size_t, space, fo->size);
+
+ /* limit to order-0 allocations */
+ space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
+
+ syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
+ if (!syn_data)
+ goto fallback;
+ syn_data->ip_summed = CHECKSUM_PARTIAL;
+ memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
+ if (space) {
+ int copied = copy_from_iter(skb_put(syn_data, space), space,
+ &fo->data->msg_iter);
+ if (unlikely(!copied)) {
+ tcp_skb_tsorted_anchor_cleanup(syn_data);
+ kfree_skb(syn_data);
+ goto fallback;
+ }
+ if (copied != space) {
+ skb_trim(syn_data, copied);
+ space = copied;
+ }
+ }
+ /* No more data pending in inet_wait_for_connect() */
+ if (space == fo->size)
+ fo->data = NULL;
+ fo->copied = space;
+
+ tcp_connect_queue_skb(sk, syn_data);
+ if (syn_data->len)
+ tcp_chrono_start(sk, TCP_CHRONO_BUSY);
+
+ err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
+
+ syn->skb_mstamp = syn_data->skb_mstamp;
+
+ /* Now full SYN+DATA was cloned and sent (or not),
+ * remove the SYN from the original skb (syn_data)
+ * we keep in write queue in case of a retransmit, as we
+ * also have the SYN packet (with no data) in the same queue.
+ */
+ TCP_SKB_CB(syn_data)->seq++;
+ TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
+ if (!err) {
+ tp->syn_data = (fo->copied > 0);
+ tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
+ goto done;
+ }
+
+ /* data was not sent, put it in write_queue */
+ __skb_queue_tail(&sk->sk_write_queue, syn_data);
+ tp->packets_out -= tcp_skb_pcount(syn_data);
+
+fallback:
+ /* Send a regular SYN with Fast Open cookie request option */
+ if (fo->cookie.len > 0)
+ fo->cookie.len = 0;
+ err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
+ if (err)
+ tp->syn_fastopen = 0;
+done:
+ fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
+ return err;
+}
+
+/* Build a SYN and send it off. */
+int tcp_connect(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *buff;
+ int err;
+
+ tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
+
+ if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
+ return -EHOSTUNREACH; /* Routing failure or similar. */
+
+ tcp_connect_init(sk);
+
+ if (unlikely(tp->repair)) {
+ tcp_finish_connect(sk, NULL);
+ return 0;
+ }
+
+ buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
+ if (unlikely(!buff))
+ return -ENOBUFS;
+
+ tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
+ tcp_mstamp_refresh(tp);
+ tp->retrans_stamp = tcp_time_stamp(tp);
+ tcp_connect_queue_skb(sk, buff);
+ tcp_ecn_send_syn(sk, buff);
+ tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
+
+ /* Send off SYN; include data in Fast Open. */
+ err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
+ tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
+ if (err == -ECONNREFUSED)
+ return err;
+
+ /* We change tp->snd_nxt after the tcp_transmit_skb() call
+ * in order to make this packet get counted in tcpOutSegs.
+ */
+ tp->snd_nxt = tp->write_seq;
+ tp->pushed_seq = tp->write_seq;
+ buff = tcp_send_head(sk);
+ if (unlikely(buff)) {
+ tp->snd_nxt = TCP_SKB_CB(buff)->seq;
+ tp->pushed_seq = TCP_SKB_CB(buff)->seq;
+ }
+ TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
+
+ /* Timer for repeating the SYN until an answer. */
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+ inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
+ return 0;
+}
+EXPORT_SYMBOL(tcp_connect);
+
+/* Send out a delayed ack, the caller does the policy checking
+ * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
+ * for details.
+ */
+void tcp_send_delayed_ack(struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ int ato = icsk->icsk_ack.ato;
+ unsigned long timeout;
+
+ if (ato > TCP_DELACK_MIN) {
+ const struct tcp_sock *tp = tcp_sk(sk);
+ int max_ato = HZ / 2;
+
+ if (icsk->icsk_ack.pingpong ||
+ (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
+ max_ato = TCP_DELACK_MAX;
+
+ /* Slow path, intersegment interval is "high". */
+
+ /* If some rtt estimate is known, use it to bound delayed ack.
+ * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
+ * directly.
+ */
+ if (tp->srtt_us) {
+ int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
+ TCP_DELACK_MIN);
+
+ if (rtt < max_ato)
+ max_ato = rtt;
+ }
+
+ ato = min(ato, max_ato);
+ }
+
+ /* Stay within the limit we were given */
+ timeout = jiffies + ato;
+
+ /* Use new timeout only if there wasn't a older one earlier. */
+ if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
+ /* If delack timer was blocked or is about to expire,
+ * send ACK now.
+ */
+ if (icsk->icsk_ack.blocked ||
+ time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
+ tcp_send_ack(sk);
+ return;
+ }
+
+ if (!time_before(timeout, icsk->icsk_ack.timeout))
+ timeout = icsk->icsk_ack.timeout;
+ }
+ icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
+ icsk->icsk_ack.timeout = timeout;
+ sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
+}
+
+/* This routine sends an ack and also updates the window. */
+void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
+{
+ struct sk_buff *buff;
+
+ /* If we have been reset, we may not send again. */
+ if (sk->sk_state == TCP_CLOSE)
+ return;
+
+ /* We are not putting this on the write queue, so
+ * tcp_transmit_skb() will set the ownership to this
+ * sock.
+ */
+ buff = alloc_skb(MAX_TCP_HEADER,
+ sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
+ if (unlikely(!buff)) {
+ inet_csk_schedule_ack(sk);
+ inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
+ TCP_DELACK_MAX, TCP_RTO_MAX);
+ return;
+ }
+
+ /* Reserve space for headers and prepare control bits. */
+ skb_reserve(buff, MAX_TCP_HEADER);
+ tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
+
+ /* We do not want pure acks influencing TCP Small Queues or fq/pacing
+ * too much.
+ * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
+ */
+ skb_set_tcp_pure_ack(buff);
+
+ /* Send it off, this clears delayed acks for us. */
+ __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt);
+}
+EXPORT_SYMBOL_GPL(__tcp_send_ack);
+
+void tcp_send_ack(struct sock *sk)
+{
+ __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt);
+}
+
+/* This routine sends a packet with an out of date sequence
+ * number. It assumes the other end will try to ack it.
+ *
+ * Question: what should we make while urgent mode?
+ * 4.4BSD forces sending single byte of data. We cannot send
+ * out of window data, because we have SND.NXT==SND.MAX...
+ *
+ * Current solution: to send TWO zero-length segments in urgent mode:
+ * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
+ * out-of-date with SND.UNA-1 to probe window.
+ */
+static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+
+ /* We don't queue it, tcp_transmit_skb() sets ownership. */
+ skb = alloc_skb(MAX_TCP_HEADER,
+ sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
+ if (!skb)
+ return -1;
+
+ /* Reserve space for headers and set control bits. */
+ skb_reserve(skb, MAX_TCP_HEADER);
+ /* Use a previous sequence. This should cause the other
+ * end to send an ack. Don't queue or clone SKB, just
+ * send it.
+ */
+ tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
+ NET_INC_STATS(sock_net(sk), mib);
+ return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
+}
+
+/* Called from setsockopt( ... TCP_REPAIR ) */
+void tcp_send_window_probe(struct sock *sk)
+{
+ if (sk->sk_state == TCP_ESTABLISHED) {
+ tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
+ tcp_mstamp_refresh(tcp_sk(sk));
+ tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
+ }
+}
+
+/* Initiate keepalive or window probe from timer. */
+int tcp_write_wakeup(struct sock *sk, int mib)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+
+ if (sk->sk_state == TCP_CLOSE)
+ return -1;
+
+ skb = tcp_send_head(sk);
+ if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
+ int err;
+ unsigned int mss = tcp_current_mss(sk);
+ unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
+
+ if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
+ tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
+
+ /* We are probing the opening of a window
+ * but the window size is != 0
+ * must have been a result SWS avoidance ( sender )
+ */
+ if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
+ skb->len > mss) {
+ seg_size = min(seg_size, mss);
+ TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
+ if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
+ skb, seg_size, mss, GFP_ATOMIC))
+ return -1;
+ } else if (!tcp_skb_pcount(skb))
+ tcp_set_skb_tso_segs(skb, mss);
+
+ TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
+ err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
+ if (!err)
+ tcp_event_new_data_sent(sk, skb);
+ return err;
+ } else {
+ if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
+ tcp_xmit_probe_skb(sk, 1, mib);
+ return tcp_xmit_probe_skb(sk, 0, mib);
+ }
+}
+
+/* A window probe timeout has occurred. If window is not closed send
+ * a partial packet else a zero probe.
+ */
+void tcp_send_probe0(struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct net *net = sock_net(sk);
+ unsigned long probe_max;
+ int err;
+
+ err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
+
+ if (tp->packets_out || tcp_write_queue_empty(sk)) {
+ /* Cancel probe timer, if it is not required. */
+ icsk->icsk_probes_out = 0;
+ icsk->icsk_backoff = 0;
+ return;
+ }
+
+ if (err <= 0) {
+ if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
+ icsk->icsk_backoff++;
+ icsk->icsk_probes_out++;
+ probe_max = TCP_RTO_MAX;
+ } else {
+ /* If packet was not sent due to local congestion,
+ * do not backoff and do not remember icsk_probes_out.
+ * Let local senders to fight for local resources.
+ *
+ * Use accumulated backoff yet.
+ */
+ if (!icsk->icsk_probes_out)
+ icsk->icsk_probes_out = 1;
+ probe_max = TCP_RESOURCE_PROBE_INTERVAL;
+ }
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
+ tcp_probe0_when(sk, probe_max),
+ TCP_RTO_MAX);
+}
+
+int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
+{
+ const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
+ struct flowi fl;
+ int res;
+
+ tcp_rsk(req)->txhash = net_tx_rndhash();
+ res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
+ if (!res) {
+ __TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
+ __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
+ if (unlikely(tcp_passive_fastopen(sk)))
+ tcp_sk(sk)->total_retrans++;
+ trace_tcp_retransmit_synack(sk, req);
+ }
+ return res;
+}
+EXPORT_SYMBOL(tcp_rtx_synack);