v4.19.13 snapshot.
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
new file mode 100644
index 0000000..3470155
--- /dev/null
+++ b/include/net/request_sock.h
@@ -0,0 +1,230 @@
+/*
+ * NET Generic infrastructure for Network protocols.
+ *
+ * Definitions for request_sock
+ *
+ * Authors: Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ *
+ * From code originally in include/net/tcp.h
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#ifndef _REQUEST_SOCK_H
+#define _REQUEST_SOCK_H
+
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include <linux/bug.h>
+#include <linux/refcount.h>
+
+#include <net/sock.h>
+
+struct request_sock;
+struct sk_buff;
+struct dst_entry;
+struct proto;
+
+struct request_sock_ops {
+ int family;
+ unsigned int obj_size;
+ struct kmem_cache *slab;
+ char *slab_name;
+ int (*rtx_syn_ack)(const struct sock *sk,
+ struct request_sock *req);
+ void (*send_ack)(const struct sock *sk, struct sk_buff *skb,
+ struct request_sock *req);
+ void (*send_reset)(const struct sock *sk,
+ struct sk_buff *skb);
+ void (*destructor)(struct request_sock *req);
+ void (*syn_ack_timeout)(const struct request_sock *req);
+};
+
+int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
+
+/* struct request_sock - mini sock to represent a connection request
+ */
+struct request_sock {
+ struct sock_common __req_common;
+#define rsk_refcnt __req_common.skc_refcnt
+#define rsk_hash __req_common.skc_hash
+#define rsk_listener __req_common.skc_listener
+#define rsk_window_clamp __req_common.skc_window_clamp
+#define rsk_rcv_wnd __req_common.skc_rcv_wnd
+
+ struct request_sock *dl_next;
+ u16 mss;
+ u8 num_retrans; /* number of retransmits */
+ u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
+ u8 num_timeout:7; /* number of timeouts */
+ u32 ts_recent;
+ struct timer_list rsk_timer;
+ const struct request_sock_ops *rsk_ops;
+ struct sock *sk;
+ u32 *saved_syn;
+ u32 secid;
+ u32 peer_secid;
+};
+
+static inline struct request_sock *inet_reqsk(const struct sock *sk)
+{
+ return (struct request_sock *)sk;
+}
+
+static inline struct sock *req_to_sk(struct request_sock *req)
+{
+ return (struct sock *)req;
+}
+
+static inline struct request_sock *
+reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
+ bool attach_listener)
+{
+ struct request_sock *req;
+
+ req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
+ if (!req)
+ return NULL;
+ req->rsk_listener = NULL;
+ if (attach_listener) {
+ if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
+ kmem_cache_free(ops->slab, req);
+ return NULL;
+ }
+ req->rsk_listener = sk_listener;
+ }
+ req->rsk_ops = ops;
+ req_to_sk(req)->sk_prot = sk_listener->sk_prot;
+ sk_node_init(&req_to_sk(req)->sk_node);
+ sk_tx_queue_clear(req_to_sk(req));
+ req->saved_syn = NULL;
+ refcount_set(&req->rsk_refcnt, 0);
+
+ return req;
+}
+
+static inline void reqsk_free(struct request_sock *req)
+{
+ /* temporary debugging */
+ WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
+
+ req->rsk_ops->destructor(req);
+ if (req->rsk_listener)
+ sock_put(req->rsk_listener);
+ kfree(req->saved_syn);
+ kmem_cache_free(req->rsk_ops->slab, req);
+}
+
+static inline void reqsk_put(struct request_sock *req)
+{
+ if (refcount_dec_and_test(&req->rsk_refcnt))
+ reqsk_free(req);
+}
+
+/*
+ * For a TCP Fast Open listener -
+ * lock - protects the access to all the reqsk, which is co-owned by
+ * the listener and the child socket.
+ * qlen - pending TFO requests (still in TCP_SYN_RECV).
+ * max_qlen - max TFO reqs allowed before TFO is disabled.
+ *
+ * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
+ * structure above. But there is some implementation difficulty due to
+ * listen_sock being part of request_sock_queue hence will be freed when
+ * a listener is stopped. But TFO related fields may continue to be
+ * accessed even after a listener is closed, until its sk_refcnt drops
+ * to 0 implying no more outstanding TFO reqs. One solution is to keep
+ * listen_opt around until sk_refcnt drops to 0. But there is some other
+ * complexity that needs to be resolved. E.g., a listener can be disabled
+ * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
+ */
+struct fastopen_queue {
+ struct request_sock *rskq_rst_head; /* Keep track of past TFO */
+ struct request_sock *rskq_rst_tail; /* requests that caused RST.
+ * This is part of the defense
+ * against spoofing attack.
+ */
+ spinlock_t lock;
+ int qlen; /* # of pending (TCP_SYN_RECV) reqs */
+ int max_qlen; /* != 0 iff TFO is currently enabled */
+
+ struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */
+};
+
+/** struct request_sock_queue - queue of request_socks
+ *
+ * @rskq_accept_head - FIFO head of established children
+ * @rskq_accept_tail - FIFO tail of established children
+ * @rskq_defer_accept - User waits for some data after accept()
+ *
+ */
+struct request_sock_queue {
+ spinlock_t rskq_lock;
+ u8 rskq_defer_accept;
+
+ u32 synflood_warned;
+ atomic_t qlen;
+ atomic_t young;
+
+ struct request_sock *rskq_accept_head;
+ struct request_sock *rskq_accept_tail;
+ struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine
+ * if TFO is enabled.
+ */
+};
+
+void reqsk_queue_alloc(struct request_sock_queue *queue);
+
+void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
+ bool reset);
+
+static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
+{
+ return queue->rskq_accept_head == NULL;
+}
+
+static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
+ struct sock *parent)
+{
+ struct request_sock *req;
+
+ spin_lock_bh(&queue->rskq_lock);
+ req = queue->rskq_accept_head;
+ if (req) {
+ sk_acceptq_removed(parent);
+ queue->rskq_accept_head = req->dl_next;
+ if (queue->rskq_accept_head == NULL)
+ queue->rskq_accept_tail = NULL;
+ }
+ spin_unlock_bh(&queue->rskq_lock);
+ return req;
+}
+
+static inline void reqsk_queue_removed(struct request_sock_queue *queue,
+ const struct request_sock *req)
+{
+ if (req->num_timeout == 0)
+ atomic_dec(&queue->young);
+ atomic_dec(&queue->qlen);
+}
+
+static inline void reqsk_queue_added(struct request_sock_queue *queue)
+{
+ atomic_inc(&queue->young);
+ atomic_inc(&queue->qlen);
+}
+
+static inline int reqsk_queue_len(const struct request_sock_queue *queue)
+{
+ return atomic_read(&queue->qlen);
+}
+
+static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
+{
+ return atomic_read(&queue->young);
+}
+
+#endif /* _REQUEST_SOCK_H */