A corner-case for the 3rd-ack after a data-on-synack is for only
the SYN to be acked. Handle this by, in ack processing, when in
SYN_RECV state (the state is not yet updated to ESTABLISHED)
marking the retransmit-queue sk_buff as having been lost.
Signed-off-by: Jeremy Harris <jgh@xxxxxxxx>
---
net/ipv4/tcp_input.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 345a08baaf02..a53021edddd5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4069,6 +4069,18 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
&rexmit);
}
+ /* On receiving a 3rd-ack, if we never sent a packet via
+ * the normal means (which counts them), yet there is data
+ * remaining for retransmit, it was data-on-synack not acked;
+ * mark the skb for retransmission.
+ */
+ if (sk->sk_state == TCP_SYN_RECV && tp->segs_out == 0) {
+ struct sk_buff *skb = tcp_rtx_queue_head(sk);
+
+ if (skb)
+ tcp_mark_skb_lost(sk, skb);
+ }
+
/* If needed, reset TLP/RTO timer when RACK doesn't set. */
if (flag & FLAG_SET_XMIT_TIMER)
tcp_set_xmit_timer(sk);
--
2.49.0
