From a7abf3cd76e1e190a2c22afe5ffd0f695c7641b0 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 11 Mar 2021 12:35:05 -0800 Subject: [PATCH] tcp: consider using standard rtx logic in tcp_rcv_fastopen_synack() 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 Reported-by: Jakub Kicinski Cc: Neal Cardwell Cc: Yuchung Cheng Signed-off-by: David S. Miller --- 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 69a545d..4cf4dd5 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; -- 2.7.4