From: Eric Dumazet <eduma...@google.com>
Jakub reported Data included in a Fastopen SYN that had to be
retransmit would have to wait for an RTO if TX completions are slow,
even with prior fix.
This is because tcp_rcv_fastopen_synack() does not use standard
rtx logic, meaning TSQ handler exits early in tcp_tsq_write()
because tp->lost_out == tp->retrans_out
Lets make tcp_rcv_fastopen_synack() use standard rtx logic,
by using tcp_mark_skb_lost() on the skb thats needs to be
sent again.
Not this raised a warning in tcp_fastretrans_alert() during my tests
since we consider the data not being aknowledged
by the receiver does not mean packet was lost on the network.
Signed-off-by: Eric Dumazet <eduma...@google.com>
Reported-by: Jakub Kicinski <k...@kernel.org>
Cc: Neal Cardwell <ncardw...@google.com>
Cc: Yuchung Cheng <ych...@google.com>
---
net/ipv4/tcp_input.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index
69a545db80d2ead47ffcf2f3819a6d066e95f35d..4cf4dd532d1c65bba417a66ba6b7783491b6380a
100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2914,7 +2914,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const
u32 prior_snd_una,
/* D. Check state exit conditions. State can be terminated
* when high_seq is ACKed. */
if (icsk->icsk_ca_state == TCP_CA_Open) {
- WARN_ON(tp->retrans_out != 0);
+ WARN_ON(tp->retrans_out != 0 && !tp->syn_data);
tp->retrans_stamp = 0;
} else if (!before(tp->snd_una, tp->high_seq)) {
switch (icsk->icsk_ca_state) {
@@ -5994,11 +5994,9 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk,
struct sk_buff *synack,
tp->fastopen_client_fail = TFO_SYN_RETRANSMITTED;
else
tp->fastopen_client_fail = TFO_DATA_NOT_ACKED;
- skb_rbtree_walk_from(data) {
- if (__tcp_retransmit_skb(sk, data, 1))
- break;
- }
- tcp_rearm_rto(sk);
+ skb_rbtree_walk_from(data)
+ tcp_mark_skb_lost(sk, data);
+ tcp_xmit_retransmit_queue(sk);
NET_INC_STATS(sock_net(sk),
LINUX_MIB_TCPFASTOPENACTIVEFAIL);
return true;
--
2.31.0.rc2.261.g7f71774620-goog
