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Commit 8e4178c1 authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller
Browse files

net-tcp: Fast Open client - receiving SYN-ACK 



On receiving the SYN-ACK after SYN-data, the client needs to
a) update the cached MSS and cookie (if included in SYN-ACK)
b) retransmit the data not yet acknowledged by the SYN-ACK in the final ACK of
   the handshake.

Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 783237e8

net/ipv4/tcp_input.c

+35 −5
Original line number Diff line number Diff line
@@ -5646,6 +5646,34 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb) 
	}

}



static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,

				    struct tcp_fastopen_cookie *cookie)

{

	struct tcp_sock *tp = tcp_sk(sk);

	struct sk_buff *data = tcp_write_queue_head(sk);

	u16 mss = tp->rx_opt.mss_clamp;



	if (mss == tp->rx_opt.user_mss) {

		struct tcp_options_received opt;

		const u8 *hash_location;



		/* Get original SYNACK MSS value if user MSS sets mss_clamp */

		tcp_clear_options(&opt);

		opt.user_mss = opt.mss_clamp = 0;

		tcp_parse_options(synack, &opt, &hash_location, 0, NULL);

		mss = opt.mss_clamp;

	}



	tcp_fastopen_cache_set(sk, mss, cookie);



	if (data) { /* Retransmit unacked data in SYN */

		tcp_retransmit_skb(sk, data);

		tcp_rearm_rto(sk);

		return true;

	}

	return false;

}



static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,

					 const struct tcphdr *th, unsigned int len)

{
@@ -5653,9 +5681,10 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 
	struct inet_connection_sock *icsk = inet_csk(sk);

	struct tcp_sock *tp = tcp_sk(sk);

	struct tcp_cookie_values *cvp = tp->cookie_values;

	struct tcp_fastopen_cookie foc = { .len = -1 };

	int saved_clamp = tp->rx_opt.mss_clamp;



	tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0, NULL);

	tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0, &foc);



	if (th->ack) {

		/* rfc793:
@@ -5665,11 +5694,9 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 
		 *	  If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send

		 *        a reset (unless the RST bit is set, if so drop

		 *        the segment and return)"

		 *

		 *  We do not send data with SYN, so that RFC-correct

		 *  test reduces to:

		 */

		if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)

		if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||

		    after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt))

			goto reset_and_undo;



		if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
@@ -5781,6 +5808,9 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 


		tcp_finish_connect(sk, skb);



		if (tp->syn_fastopen && tcp_rcv_fastopen_synack(sk, skb, &foc))

			return -1;



		if (sk->sk_write_pending ||

		    icsk->icsk_accept_queue.rskq_defer_accept ||

		    icsk->icsk_ack.pingpong) {