Merge branch 'tcp_fast_open_synack_fin'

Eric Dumazet says:

====================
tcp: fastopen: accept data/FIN present in SYNACK

Implements RFC 7413 (TCP Fast Open) 4.2.2, accepting payload and/or FIN
in SYNACK messages, and prepare removal of SYN flag in tcp_recvmsg()
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -1437,6 +1437,7 @@ void tcp_free_fastopen_req(struct tcp_sock *tp);
 
 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
+void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
 			      struct request_sock *req,
 			      struct tcp_fastopen_cookie *foc,

net/ipv4/tcp.c

@@ -1466,8 +1466,10 @@ static struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
 
 	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
 		offset = seq - TCP_SKB_CB(skb)->seq;
-		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
+		if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
+			pr_err_once("%s: found a SYN, please report !\n", __func__);
 			offset--;
+		}
 		if (offset < skb->len || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)) {
 			*off = offset;
 			return skb;
@@ -1657,8 +1659,10 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
 				break;
 
 			offset = *seq - TCP_SKB_CB(skb)->seq;
-			if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
+			if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
+				pr_err_once("%s: found a SYN, please report !\n", __func__);
 				offset--;
+			}
 			if (offset < skb->len)
 				goto found_ok_skb;
 			if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)

net/ipv4/tcp_fastopen.c

@@ -124,6 +124,38 @@ static bool tcp_fastopen_cookie_gen(struct request_sock *req,
 	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);
+	__skb_pull(skb, tcp_hdrlen(skb));
+	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;
+}
+
 static struct sock *tcp_fastopen_create_child(struct sock *sk,
 					      struct sk_buff *skb,
 					      struct dst_entry *dst,
@@ -132,7 +164,6 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
 	struct tcp_sock *tp;
 	struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 	struct sock *child;
-	u32 end_seq;
 	bool own_req;
 
 	req->num_retrans = 0;
@@ -178,35 +209,11 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
 	tcp_init_metrics(child);
 	tcp_init_buffer_space(child);
 
-	/* Queue the data carried in the SYN packet.
-	 * We used to play tricky games with skb_get().
-	 * With lockless listener, it is a dead end.
-	 * Do not think about it.
-	 *
-	 * XXX (TFO) - we honor a zero-payload TFO request for now,
-	 * (any reason not to?) but no need to queue the skb since
-	 * there is no data. How about SYN+FIN?
-	 */
-	end_seq = TCP_SKB_CB(skb)->end_seq;
-	if (end_seq != TCP_SKB_CB(skb)->seq + 1) {
-		struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
-
-		if (likely(skb2)) {
-			skb_dst_drop(skb2);
-			__skb_pull(skb2, tcp_hdrlen(skb));
-			skb_set_owner_r(skb2, child);
-			__skb_queue_tail(&child->sk_receive_queue, skb2);
-			tp->syn_data_acked = 1;
+	tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
 
-			/* u64_stats_update_begin(&tp->syncp) not needed here,
-			 * as we certainly are not changing upper 32bit value (0)
-			 */
-			tp->bytes_received = end_seq - TCP_SKB_CB(skb)->seq - 1;
-		} else {
-			end_seq = TCP_SKB_CB(skb)->seq + 1;
-		}
-	}
-	tcp_rsk(req)->rcv_nxt = tp->rcv_nxt = end_seq;
+	tcp_fastopen_add_skb(child, skb);
+
+	tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
 	/* tcp_conn_request() is sending the SYNACK,
 	 * and queues the child into listener accept queue.
 	 */

net/ipv4/tcp_input.c

@@ -5509,6 +5509,9 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
 	tp->syn_data_acked = tp->syn_data;
 	if (tp->syn_data_acked)
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
+
+	tcp_fastopen_add_skb(sk, synack);
+
 	return false;
 }