1 files changed, 72 insertions, 27 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 97671bff597a..077d9abdfcf5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2252,7 +2252,7 @@ static bool tcp_skb_spurious_retrans(const struct tcp_sock *tp,
  */
 static inline bool tcp_packet_delayed(const struct tcp_sock *tp)
 {
-        return !tp->retrans_stamp ||
+        return tp->retrans_stamp &&
                tcp_tsopt_ecr_before(tp, tp->retrans_stamp);
 }
 
@@ -3521,7 +3521,7 @@ static void tcp_xmit_recovery(struct sock *sk, int rexmit)
 {
         struct tcp_sock *tp = tcp_sk(sk);
 
-        if (rexmit == REXMIT_NONE)
+        if (rexmit == REXMIT_NONE || sk->sk_state == TCP_SYN_SENT)
                 return;
 
         if (unlikely(rexmit == 2)) {
@@ -5647,6 +5647,32 @@ discard:
 }
 EXPORT_SYMBOL(tcp_rcv_established);
 
+void tcp_init_transfer(struct sock *sk, int bpf_op)
+{
+        struct inet_connection_sock *icsk = inet_csk(sk);
+        struct tcp_sock *tp = tcp_sk(sk);
+
+        tcp_mtup_init(sk);
+        icsk->icsk_af_ops->rebuild_header(sk);
+        tcp_init_metrics(sk);
+
+        /* Initialize the congestion window to start the transfer.
+         * Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
+         * retransmitted. In light of RFC6298 more aggressive 1sec
+         * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
+         * retransmission has occurred.
+         */
+        if (tp->total_retrans > 1 && tp->undo_marker)
+                tp->snd_cwnd = 1;
+        else
+                tp->snd_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
+        tp->snd_cwnd_stamp = tcp_jiffies32;
+
+        tcp_call_bpf(sk, bpf_op, 0, NULL);
+        tcp_init_congestion_control(sk);
+        tcp_init_buffer_space(sk);
+}
+
 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
 {
         struct tcp_sock *tp = tcp_sk(sk);
@@ -5748,6 +5774,21 @@ static void smc_check_reset_syn(struct tcp_sock *tp)
 #endif
 }
 
+static void tcp_try_undo_spurious_syn(struct sock *sk)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        u32 syn_stamp;
+
+        /* undo_marker is set when SYN or SYNACK times out. The timeout is
+         * spurious if the ACK's timestamp option echo value matches the
+         * original SYN timestamp.
+         */
+        syn_stamp = tp->retrans_stamp;
+        if (tp->undo_marker && syn_stamp && tp->rx_opt.saw_tstamp &&
+            syn_stamp == tp->rx_opt.rcv_tsecr)
+                tp->undo_marker = 0;
+}
+
 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
                                          const struct tcphdr *th)
 {
@@ -5815,6 +5856,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
                 tcp_ecn_rcv_synack(tp, th);
 
                 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
+                tcp_try_undo_spurious_syn(sk);
                 tcp_ack(sk, skb, FLAG_SLOWPATH);
 
                 /* Ok.. it's good. Set up sequence numbers and
@@ -5973,6 +6015,27 @@ reset_and_undo:
         return 1;
 }
 
+static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
+{
+        tcp_try_undo_loss(sk, false);
+        inet_csk(sk)->icsk_retransmits = 0;
+
+        /* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1,
+         * we no longer need req so release it.
+         */
+        reqsk_fastopen_remove(sk, tcp_sk(sk)->fastopen_rsk, false);
+
+        /* Re-arm the timer because data may have been sent out.
+         * This is similar to the regular data transmission case
+         * when new data has just been ack'ed.
+         *
+         * (TFO) - we could try to be more aggressive and
+         * retransmitting any data sooner based on when they
+         * are sent out.
+         */
+        tcp_rearm_rto(sk);
+}
+
 /*
  *      This function implements the receiving procedure of RFC 793 for
  *      all states except ESTABLISHED and TIME_WAIT.
@@ -6069,22 +6132,11 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
                 if (!tp->srtt_us)
                         tcp_synack_rtt_meas(sk, req);
 
-                /* Once we leave TCP_SYN_RECV, we no longer need req
-                 * so release it.
-                 */
                 if (req) {
-                        inet_csk(sk)->icsk_retransmits = 0;
-                        reqsk_fastopen_remove(sk, req, false);
-                        /* Re-arm the timer because data may have been sent out.
-                         * This is similar to the regular data transmission case
-                         * when new data has just been ack'ed.
-                         *
-                         * (TFO) - we could try to be more aggressive and
-                         * retransmitting any data sooner based on when they
-                         * are sent out.
-                         */
-                        tcp_rearm_rto(sk);
+                        tcp_rcv_synrecv_state_fastopen(sk);
                 } else {
+                        tcp_try_undo_spurious_syn(sk);
+                        tp->retrans_stamp = 0;
                         tcp_init_transfer(sk, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB);
                         tp->copied_seq = tp->rcv_nxt;
                 }
@@ -6119,16 +6171,9 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
         case TCP_FIN_WAIT1: {
                 int tmo;
 
-                /* If we enter the TCP_FIN_WAIT1 state and we are a
-                 * Fast Open socket and this is the first acceptable
-                 * ACK we have received, this would have acknowledged
-                 * our SYNACK so stop the SYNACK timer.
-                 */
-                if (req) {
-                        /* We no longer need the request sock. */
-                        reqsk_fastopen_remove(sk, req, false);
-                        tcp_rearm_rto(sk);
-                }
+                if (req)
+                        tcp_rcv_synrecv_state_fastopen(sk);
+
                 if (tp->snd_una != tp->write_seq)
                         break;
 
@@ -6303,7 +6348,7 @@ static void tcp_openreq_init(struct request_sock *req,
         req->cookie_ts = 0;
         tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
         tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
-        tcp_rsk(req)->snt_synack = tcp_clock_us();
+        tcp_rsk(req)->snt_synack = 0;
         tcp_rsk(req)->last_oow_ack_time = 0;
         req->mss = rx_opt->mss_clamp;
         req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;