netdev - Re: [PATCH v2 net] tcp: fix retrans timestamp on passive Fast Open

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Date:   Mon, 13 May 2019 12:43:40 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Yuchung Cheng <ycheng@...gle.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org, ncardwell@...gle.com
Subject: Re: [PATCH v2 net] tcp: fix retrans timestamp on passive Fast Open



On 5/13/19 10:32 AM, Yuchung Cheng wrote:
> Commit c7d13c8faa74 ("tcp: properly track retry time on
> passive Fast Open") sets the start of SYNACK retransmission
> time on passive Fast Open in "retrans_stamp". However the
> timestamp is not reset upon the handshake has completed. As a
> result, future data packet retransmission may not update it in
> tcp_retransmit_skb(). This may lead to socket aborting earlier
> unexpectedly by retransmits_timed_out() since retrans_stamp remains
> the SYNACK rtx time.
> 
> This bug only manifests on passive TFO sender that a) suffered
> SYNACK timeout and then b) stalls on very first loss recovery. Any
> successful loss recovery would reset the timestamp to avoid this
> issue.
> 
> Fixes: c7d13c8faa74 ("tcp: properly track retry time on passive Fast Open")
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
> ---

Signed-off-by: Eric Dumazet <edumazet@...gle.com>