On Fri, 31 Jan 2020 07:01:21 -0800 Eric Dumazet edumazet@google.com wrote:
On Fri, Jan 31, 2020 at 4:25 AM sjpark@amazon.com wrote:
Signed-off-by: SeongJae Park sjpark@amazon.de
net/ipv4/tcp_input.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 2a976f57f7e7..b168e29e1ad1 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5893,8 +5893,12 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, * the segment and return)" */ if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||
after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt))
after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {/* Previous FIN/ACK or RST/ACK might be ignore. */inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,TCP_ATO_MIN, TCP_RTO_MAX);This is not what I suggested.
I suggested implementing a strategy where only the _first_ retransmit would be done earlier.
So you need to look at the current counter of retransmit attempts, then reset the timer if this SYN_SENT socket never resent a SYN.
We do not want to trigger packet storms, if for some reason the remote peer constantly sends us the same packet.
You're right, I missed the important point, thank you for pointing it. Among retransmission related fields of 'tcp_sock', I think '->total_retrans' would fit for this check. How about below change?
``` diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 2a976f57f7e7..29fc0e4da931 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5893,8 +5893,14 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, * the segment and return)" */ if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) || - after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) + after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { + /* Previous FIN/ACK or RST/ACK might be ignored. */ + if (tp->total_retrans == 0) + inet_csk_reset_xmit_timer(sk, + ICSK_TIME_RETRANS, TCP_ATO_MIN, + TCP_RTO_MAX); goto reset_and_undo; + }
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, ```
Thanks, SeongJae Park
Thanks.
goto reset_and_undo;
} if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,-- 2.17.1