Re: [PATCH net] tcp: initialize send sequence numbers before deferring TFO

[Kuniyuki Iwashima]

On Mon, 02 Nov 2026 11:59:43 +0800, Qingfang Deng wrote:
> TCP_FASTOPEN_CONNECT can return from connect() before tcp_connect_init()
> when a cached cookie or cookieless Fast Open allows deferring the SYN.
> At this point write_seq contains the initial sequence number, while
> snd_una and snd_nxt have not been initialized to that sequence number.
> 
> Consequently, inet_diag and /proc/net/tcp{,6} report the initial
> sequence number as the send queue length despite no SYN or payload being
> queued.
> 
> Initialize snd_una and snd_nxt to write_seq before marking the
> connection as deferred. Both sequence-based queue lengths then remain
> zero until the first write starts the connection and runs
> tcp_connect_init().
> 
> Fixes: 19f6d3f3c842 ("net/tcp-fastopen: Add new API support")
> Signed-off-by: Qingfang Deng <qingfang.deng@xxxxxxxxx>

Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>