netdev - Re: [PATCH 1/2] tcp: setup random timestamp offset when write

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Date:   Sat, 18 Feb 2017 12:19:04 +0300
From:   Alexey Kodanev <alexey.kodanev@...cle.com>
To:     David Miller <davem@...emloft.net>,
        Florian Westphal <fw@...len.de>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH 1/2] tcp: setup random timestamp offset when write_seq
 already set

Hi,
On 18.02.2017 3:56, Alexey Kodanev wrote:
> Found that when random offset enabled (default) TCP client can
> still start new connections with and without random offsets. Later,
> if server does active close and re-use sockets in TIME-WAIT state,
> new SYN from client can be rejected on PAWS check inside
> tcp_timewait_state_process().
>

Actually, on second thoughts, we can just copy tsoffset from tw socket:

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 89a95da..f40a61d 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -126,6 +126,7 @@ int tcp_twsk_unique(struct sock *sk, struct sock
*sktw, void *twp)
                        tp->write_seq = 1;
                tp->rx_opt.ts_recent       = tcptw->tw_ts_recent;
                tp->rx_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
+               tp->tsoffset               = tcptw->tw_ts_offset;
                sock_hold(sktw);
                return 1;
        }

Will test this and send a new version.

Thanks,
Alexey