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: Yuchung Cheng <ycheng@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -5646,6 +5646,34 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
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}
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}
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static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
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struct tcp_fastopen_cookie *cookie)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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struct sk_buff *data = tcp_write_queue_head(sk);
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u16 mss = tp->rx_opt.mss_clamp;
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if (mss == tp->rx_opt.user_mss) {
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struct tcp_options_received opt;
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const u8 *hash_location;
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/* Get original SYNACK MSS value if user MSS sets mss_clamp */
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tcp_clear_options(&opt);
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opt.user_mss = opt.mss_clamp = 0;
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tcp_parse_options(synack, &opt, &hash_location, 0, NULL);
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mss = opt.mss_clamp;
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}
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tcp_fastopen_cache_set(sk, mss, cookie);
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if (data) { /* Retransmit unacked data in SYN */
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tcp_retransmit_skb(sk, data);
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tcp_rearm_rto(sk);
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return true;
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}
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return false;
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}
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static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
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const struct tcphdr *th, unsigned int len)
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{
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@ -5653,9 +5681,10 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
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struct inet_connection_sock *icsk = inet_csk(sk);
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struct tcp_sock *tp = tcp_sk(sk);
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struct tcp_cookie_values *cvp = tp->cookie_values;
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struct tcp_fastopen_cookie foc = { .len = -1 };
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int saved_clamp = tp->rx_opt.mss_clamp;
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tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0, NULL);
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tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0, &foc);
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if (th->ack) {
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/* rfc793:
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@ -5665,11 +5694,9 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
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* If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
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* a reset (unless the RST bit is set, if so drop
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* the segment and return)"
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*
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* We do not send data with SYN, so that RFC-correct
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* test reduces to:
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*/
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if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
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if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||
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after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt))
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goto reset_and_undo;
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if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
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@ -5781,6 +5808,9 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
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tcp_finish_connect(sk, skb);
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if (tp->syn_fastopen && tcp_rcv_fastopen_synack(sk, skb, &foc))
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return -1;
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if (sk->sk_write_pending ||
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icsk->icsk_accept_queue.rskq_defer_accept ||
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icsk->icsk_ack.pingpong) {
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