v4.19.13 snapshot.
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
new file mode 100644
index 0000000..018a484
--- /dev/null
+++ b/net/ipv4/tcp_fastopen.c
@@ -0,0 +1,536 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/crypto.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/tcp.h>
+#include <linux/rcupdate.h>
+#include <linux/rculist.h>
+#include <net/inetpeer.h>
+#include <net/tcp.h>
+
+void tcp_fastopen_init_key_once(struct net *net)
+{
+ u8 key[TCP_FASTOPEN_KEY_LENGTH];
+ struct tcp_fastopen_context *ctxt;
+
+ rcu_read_lock();
+ ctxt = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
+ if (ctxt) {
+ rcu_read_unlock();
+ return;
+ }
+ rcu_read_unlock();
+
+ /* tcp_fastopen_reset_cipher publishes the new context
+ * atomically, so we allow this race happening here.
+ *
+ * All call sites of tcp_fastopen_cookie_gen also check
+ * for a valid cookie, so this is an acceptable risk.
+ */
+ get_random_bytes(key, sizeof(key));
+ tcp_fastopen_reset_cipher(net, NULL, key, sizeof(key));
+}
+
+static void tcp_fastopen_ctx_free(struct rcu_head *head)
+{
+ struct tcp_fastopen_context *ctx =
+ container_of(head, struct tcp_fastopen_context, rcu);
+ crypto_free_cipher(ctx->tfm);
+ kfree(ctx);
+}
+
+void tcp_fastopen_destroy_cipher(struct sock *sk)
+{
+ struct tcp_fastopen_context *ctx;
+
+ ctx = rcu_dereference_protected(
+ inet_csk(sk)->icsk_accept_queue.fastopenq.ctx, 1);
+ if (ctx)
+ call_rcu(&ctx->rcu, tcp_fastopen_ctx_free);
+}
+
+void tcp_fastopen_ctx_destroy(struct net *net)
+{
+ struct tcp_fastopen_context *ctxt;
+
+ spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
+
+ ctxt = rcu_dereference_protected(net->ipv4.tcp_fastopen_ctx,
+ lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
+ rcu_assign_pointer(net->ipv4.tcp_fastopen_ctx, NULL);
+ spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
+
+ if (ctxt)
+ call_rcu(&ctxt->rcu, tcp_fastopen_ctx_free);
+}
+
+int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
+ void *key, unsigned int len)
+{
+ struct tcp_fastopen_context *ctx, *octx;
+ struct fastopen_queue *q;
+ int err;
+
+ ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+ ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
+
+ if (IS_ERR(ctx->tfm)) {
+ err = PTR_ERR(ctx->tfm);
+error: kfree(ctx);
+ pr_err("TCP: TFO aes cipher alloc error: %d\n", err);
+ return err;
+ }
+ err = crypto_cipher_setkey(ctx->tfm, key, len);
+ if (err) {
+ pr_err("TCP: TFO cipher key error: %d\n", err);
+ crypto_free_cipher(ctx->tfm);
+ goto error;
+ }
+ memcpy(ctx->key, key, len);
+
+
+ spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
+ if (sk) {
+ q = &inet_csk(sk)->icsk_accept_queue.fastopenq;
+ octx = rcu_dereference_protected(q->ctx,
+ lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
+ rcu_assign_pointer(q->ctx, ctx);
+ } else {
+ octx = rcu_dereference_protected(net->ipv4.tcp_fastopen_ctx,
+ lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
+ rcu_assign_pointer(net->ipv4.tcp_fastopen_ctx, ctx);
+ }
+ spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
+
+ if (octx)
+ call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
+ return err;
+}
+
+static bool __tcp_fastopen_cookie_gen(struct sock *sk, const void *path,
+ struct tcp_fastopen_cookie *foc)
+{
+ struct tcp_fastopen_context *ctx;
+ bool ok = false;
+
+ rcu_read_lock();
+
+ ctx = rcu_dereference(inet_csk(sk)->icsk_accept_queue.fastopenq.ctx);
+ if (!ctx)
+ ctx = rcu_dereference(sock_net(sk)->ipv4.tcp_fastopen_ctx);
+
+ if (ctx) {
+ crypto_cipher_encrypt_one(ctx->tfm, foc->val, path);
+ foc->len = TCP_FASTOPEN_COOKIE_SIZE;
+ ok = true;
+ }
+ rcu_read_unlock();
+ return ok;
+}
+
+/* Generate the fastopen cookie by doing aes128 encryption on both
+ * the source and destination addresses. Pad 0s for IPv4 or IPv4-mapped-IPv6
+ * addresses. For the longer IPv6 addresses use CBC-MAC.
+ *
+ * XXX (TFO) - refactor when TCP_FASTOPEN_COOKIE_SIZE != AES_BLOCK_SIZE.
+ */
+static bool tcp_fastopen_cookie_gen(struct sock *sk,
+ struct request_sock *req,
+ struct sk_buff *syn,
+ struct tcp_fastopen_cookie *foc)
+{
+ if (req->rsk_ops->family == AF_INET) {
+ const struct iphdr *iph = ip_hdr(syn);
+
+ __be32 path[4] = { iph->saddr, iph->daddr, 0, 0 };
+ return __tcp_fastopen_cookie_gen(sk, path, foc);
+ }
+
+#if IS_ENABLED(CONFIG_IPV6)
+ if (req->rsk_ops->family == AF_INET6) {
+ const struct ipv6hdr *ip6h = ipv6_hdr(syn);
+ struct tcp_fastopen_cookie tmp;
+
+ if (__tcp_fastopen_cookie_gen(sk, &ip6h->saddr, &tmp)) {
+ struct in6_addr *buf = &tmp.addr;
+ int i;
+
+ for (i = 0; i < 4; i++)
+ buf->s6_addr32[i] ^= ip6h->daddr.s6_addr32[i];
+ return __tcp_fastopen_cookie_gen(sk, buf, foc);
+ }
+ }
+#endif
+ return false;
+}
+
+
+/* If an incoming SYN or SYNACK frame contains a payload and/or FIN,
+ * queue this additional data / FIN.
+ */
+void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt)
+ return;
+
+ skb = skb_clone(skb, GFP_ATOMIC);
+ if (!skb)
+ return;
+
+ skb_dst_drop(skb);
+ /* segs_in has been initialized to 1 in tcp_create_openreq_child().
+ * Hence, reset segs_in to 0 before calling tcp_segs_in()
+ * to avoid double counting. Also, tcp_segs_in() expects
+ * skb->len to include the tcp_hdrlen. Hence, it should
+ * be called before __skb_pull().
+ */
+ tp->segs_in = 0;
+ tcp_segs_in(tp, skb);
+ __skb_pull(skb, tcp_hdrlen(skb));
+ sk_forced_mem_schedule(sk, skb->truesize);
+ skb_set_owner_r(skb, sk);
+
+ TCP_SKB_CB(skb)->seq++;
+ TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
+
+ tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+ __skb_queue_tail(&sk->sk_receive_queue, skb);
+ tp->syn_data_acked = 1;
+
+ /* u64_stats_update_begin(&tp->syncp) not needed here,
+ * as we certainly are not changing upper 32bit value (0)
+ */
+ tp->bytes_received = skb->len;
+
+ if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
+ tcp_fin(sk);
+}
+
+static struct sock *tcp_fastopen_create_child(struct sock *sk,
+ struct sk_buff *skb,
+ struct request_sock *req)
+{
+ struct tcp_sock *tp;
+ struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
+ struct sock *child;
+ bool own_req;
+
+ req->num_retrans = 0;
+ req->num_timeout = 0;
+ req->sk = NULL;
+
+ child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
+ NULL, &own_req);
+ if (!child)
+ return NULL;
+
+ spin_lock(&queue->fastopenq.lock);
+ queue->fastopenq.qlen++;
+ spin_unlock(&queue->fastopenq.lock);
+
+ /* Initialize the child socket. Have to fix some values to take
+ * into account the child is a Fast Open socket and is created
+ * only out of the bits carried in the SYN packet.
+ */
+ tp = tcp_sk(child);
+
+ tp->fastopen_rsk = req;
+ tcp_rsk(req)->tfo_listener = true;
+
+ /* RFC1323: The window in SYN & SYN/ACK segments is never
+ * scaled. So correct it appropriately.
+ */
+ tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
+ tp->max_window = tp->snd_wnd;
+
+ /* Activate the retrans timer so that SYNACK can be retransmitted.
+ * The request socket is not added to the ehash
+ * because it's been added to the accept queue directly.
+ */
+ inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
+ TCP_TIMEOUT_INIT, TCP_RTO_MAX);
+
+ refcount_set(&req->rsk_refcnt, 2);
+
+ /* Now finish processing the fastopen child socket. */
+ tcp_init_transfer(child, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB);
+
+ tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
+
+ tcp_fastopen_add_skb(child, skb);
+
+ tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
+ tp->rcv_wup = tp->rcv_nxt;
+ /* tcp_conn_request() is sending the SYNACK,
+ * and queues the child into listener accept queue.
+ */
+ return child;
+}
+
+static bool tcp_fastopen_queue_check(struct sock *sk)
+{
+ struct fastopen_queue *fastopenq;
+
+ /* Make sure the listener has enabled fastopen, and we don't
+ * exceed the max # of pending TFO requests allowed before trying
+ * to validating the cookie in order to avoid burning CPU cycles
+ * unnecessarily.
+ *
+ * XXX (TFO) - The implication of checking the max_qlen before
+ * processing a cookie request is that clients can't differentiate
+ * between qlen overflow causing Fast Open to be disabled
+ * temporarily vs a server not supporting Fast Open at all.
+ */
+ fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
+ if (fastopenq->max_qlen == 0)
+ return false;
+
+ if (fastopenq->qlen >= fastopenq->max_qlen) {
+ struct request_sock *req1;
+ spin_lock(&fastopenq->lock);
+ req1 = fastopenq->rskq_rst_head;
+ if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
+ __NET_INC_STATS(sock_net(sk),
+ LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
+ spin_unlock(&fastopenq->lock);
+ return false;
+ }
+ fastopenq->rskq_rst_head = req1->dl_next;
+ fastopenq->qlen--;
+ spin_unlock(&fastopenq->lock);
+ reqsk_put(req1);
+ }
+ return true;
+}
+
+static bool tcp_fastopen_no_cookie(const struct sock *sk,
+ const struct dst_entry *dst,
+ int flag)
+{
+ return (sock_net(sk)->ipv4.sysctl_tcp_fastopen & flag) ||
+ tcp_sk(sk)->fastopen_no_cookie ||
+ (dst && dst_metric(dst, RTAX_FASTOPEN_NO_COOKIE));
+}
+
+/* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
+ * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
+ * cookie request (foc->len == 0).
+ */
+struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
+ struct request_sock *req,
+ struct tcp_fastopen_cookie *foc,
+ const struct dst_entry *dst)
+{
+ bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
+ int tcp_fastopen = sock_net(sk)->ipv4.sysctl_tcp_fastopen;
+ struct tcp_fastopen_cookie valid_foc = { .len = -1 };
+ struct sock *child;
+
+ if (foc->len == 0) /* Client requests a cookie */
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
+
+ if (!((tcp_fastopen & TFO_SERVER_ENABLE) &&
+ (syn_data || foc->len >= 0) &&
+ tcp_fastopen_queue_check(sk))) {
+ foc->len = -1;
+ return NULL;
+ }
+
+ if (syn_data &&
+ tcp_fastopen_no_cookie(sk, dst, TFO_SERVER_COOKIE_NOT_REQD))
+ goto fastopen;
+
+ if (foc->len >= 0 && /* Client presents or requests a cookie */
+ tcp_fastopen_cookie_gen(sk, req, skb, &valid_foc) &&
+ foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
+ foc->len == valid_foc.len &&
+ !memcmp(foc->val, valid_foc.val, foc->len)) {
+ /* Cookie is valid. Create a (full) child socket to accept
+ * the data in SYN before returning a SYN-ACK to ack the
+ * data. If we fail to create the socket, fall back and
+ * ack the ISN only but includes the same cookie.
+ *
+ * Note: Data-less SYN with valid cookie is allowed to send
+ * data in SYN_RECV state.
+ */
+fastopen:
+ child = tcp_fastopen_create_child(sk, skb, req);
+ if (child) {
+ foc->len = -1;
+ NET_INC_STATS(sock_net(sk),
+ LINUX_MIB_TCPFASTOPENPASSIVE);
+ return child;
+ }
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
+ } else if (foc->len > 0) /* Client presents an invalid cookie */
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
+
+ valid_foc.exp = foc->exp;
+ *foc = valid_foc;
+ return NULL;
+}
+
+bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
+ struct tcp_fastopen_cookie *cookie)
+{
+ const struct dst_entry *dst;
+
+ tcp_fastopen_cache_get(sk, mss, cookie);
+
+ /* Firewall blackhole issue check */
+ if (tcp_fastopen_active_should_disable(sk)) {
+ cookie->len = -1;
+ return false;
+ }
+
+ dst = __sk_dst_get(sk);
+
+ if (tcp_fastopen_no_cookie(sk, dst, TFO_CLIENT_NO_COOKIE)) {
+ cookie->len = -1;
+ return true;
+ }
+ return cookie->len > 0;
+}
+
+/* This function checks if we want to defer sending SYN until the first
+ * write(). We defer under the following conditions:
+ * 1. fastopen_connect sockopt is set
+ * 2. we have a valid cookie
+ * Return value: return true if we want to defer until application writes data
+ * return false if we want to send out SYN immediately
+ */
+bool tcp_fastopen_defer_connect(struct sock *sk, int *err)
+{
+ struct tcp_fastopen_cookie cookie = { .len = 0 };
+ struct tcp_sock *tp = tcp_sk(sk);
+ u16 mss;
+
+ if (tp->fastopen_connect && !tp->fastopen_req) {
+ if (tcp_fastopen_cookie_check(sk, &mss, &cookie)) {
+ inet_sk(sk)->defer_connect = 1;
+ return true;
+ }
+
+ /* Alloc fastopen_req in order for FO option to be included
+ * in SYN
+ */
+ tp->fastopen_req = kzalloc(sizeof(*tp->fastopen_req),
+ sk->sk_allocation);
+ if (tp->fastopen_req)
+ tp->fastopen_req->cookie = cookie;
+ else
+ *err = -ENOBUFS;
+ }
+ return false;
+}
+EXPORT_SYMBOL(tcp_fastopen_defer_connect);
+
+/*
+ * The following code block is to deal with middle box issues with TFO:
+ * Middlebox firewall issues can potentially cause server's data being
+ * blackholed after a successful 3WHS using TFO.
+ * The proposed solution is to disable active TFO globally under the
+ * following circumstances:
+ * 1. client side TFO socket receives out of order FIN
+ * 2. client side TFO socket receives out of order RST
+ * 3. client side TFO socket has timed out three times consecutively during
+ * or after handshake
+ * We disable active side TFO globally for 1hr at first. Then if it
+ * happens again, we disable it for 2h, then 4h, 8h, ...
+ * And we reset the timeout back to 1hr when we see a successful active
+ * TFO connection with data exchanges.
+ */
+
+/* Disable active TFO and record current jiffies and
+ * tfo_active_disable_times
+ */
+void tcp_fastopen_active_disable(struct sock *sk)
+{
+ struct net *net = sock_net(sk);
+
+ atomic_inc(&net->ipv4.tfo_active_disable_times);
+ net->ipv4.tfo_active_disable_stamp = jiffies;
+ NET_INC_STATS(net, LINUX_MIB_TCPFASTOPENBLACKHOLE);
+}
+
+/* Calculate timeout for tfo active disable
+ * Return true if we are still in the active TFO disable period
+ * Return false if timeout already expired and we should use active TFO
+ */
+bool tcp_fastopen_active_should_disable(struct sock *sk)
+{
+ unsigned int tfo_bh_timeout = sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout;
+ int tfo_da_times = atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times);
+ unsigned long timeout;
+ int multiplier;
+
+ if (!tfo_da_times)
+ return false;
+
+ /* Limit timout to max: 2^6 * initial timeout */
+ multiplier = 1 << min(tfo_da_times - 1, 6);
+ timeout = multiplier * tfo_bh_timeout * HZ;
+ if (time_before(jiffies, sock_net(sk)->ipv4.tfo_active_disable_stamp + timeout))
+ return true;
+
+ /* Mark check bit so we can check for successful active TFO
+ * condition and reset tfo_active_disable_times
+ */
+ tcp_sk(sk)->syn_fastopen_ch = 1;
+ return false;
+}
+
+/* Disable active TFO if FIN is the only packet in the ofo queue
+ * and no data is received.
+ * Also check if we can reset tfo_active_disable_times if data is
+ * received successfully on a marked active TFO sockets opened on
+ * a non-loopback interface
+ */
+void tcp_fastopen_active_disable_ofo_check(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct dst_entry *dst;
+ struct sk_buff *skb;
+
+ if (!tp->syn_fastopen)
+ return;
+
+ if (!tp->data_segs_in) {
+ skb = skb_rb_first(&tp->out_of_order_queue);
+ if (skb && !skb_rb_next(skb)) {
+ if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
+ tcp_fastopen_active_disable(sk);
+ return;
+ }
+ }
+ } else if (tp->syn_fastopen_ch &&
+ atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times)) {
+ dst = sk_dst_get(sk);
+ if (!(dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK)))
+ atomic_set(&sock_net(sk)->ipv4.tfo_active_disable_times, 0);
+ dst_release(dst);
+ }
+}
+
+void tcp_fastopen_active_detect_blackhole(struct sock *sk, bool expired)
+{
+ u32 timeouts = inet_csk(sk)->icsk_retransmits;
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /* Broken middle-boxes may black-hole Fast Open connection during or
+ * even after the handshake. Be extremely conservative and pause
+ * Fast Open globally after hitting the third consecutive timeout or
+ * exceeding the configured timeout limit.
+ */
+ if ((tp->syn_fastopen || tp->syn_data || tp->syn_data_acked) &&
+ (timeouts == 2 || (timeouts < 2 && expired))) {
+ tcp_fastopen_active_disable(sk);
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL);
+ }
+}