1 files changed, 9 insertions, 1 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 38b6a811edfc..c49a4fc175bd 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5652,6 +5652,7 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
         struct tcp_sock *tp = tcp_sk(sk);
         struct sk_buff *data = tcp_write_queue_head(sk);
         u16 mss = tp->rx_opt.mss_clamp;
+        bool syn_drop;
 
         if (mss == tp->rx_opt.user_mss) {
                 struct tcp_options_received opt;
@@ -5664,7 +5665,14 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
                 mss = opt.mss_clamp;
         }
 
-        tcp_fastopen_cache_set(sk, mss, cookie);
+        /* The SYN-ACK neither has cookie nor acknowledges the data. Presumably
+         * the remote receives only the retransmitted (regular) SYNs: either
+         * the original SYN-data or the corresponding SYN-ACK is lost.
+         */
+        syn_drop = (cookie->len <= 0 && data &&
+                    inet_csk(sk)->icsk_retransmits);
+
+        tcp_fastopen_cache_set(sk, mss, cookie, syn_drop);
 
         if (data) { /* Retransmit unacked data in SYN */
                 tcp_retransmit_skb(sk, data);