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From: Xuanqiang Luo <xuanqiang.luo@linux.dev>
To: Jason Xing <kerneljasonxing@gmail.com>
Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
	kuba@kernel.org, pabeni@redhat.com, horms@kernel.org,
	willemb@google.com, kuniyu@google.com
Subject: Re: [PATCH net v2] tcp: preserve timestamps across receive queue collapse
Date: Thu, 17 Sep 2026 22:09:32 +0800	[thread overview]
Message-ID: <e70bcac1-7970-4d79-b210-bf31193aee3c@linux.dev> (raw)
In-Reply-To: <20260917132742.87117-1-kerneljasonxing@gmail.com>

在 2026/9/17 21:27, Jason Xing 写道:
> When tcp_collapse() rebuilds skbs under memory pressure, the copy
> process doesn't include the right tstamp and hwtstamp from the
> old skb. And memcpy(nskb->cb, skb->cb, ...) copies has_rxtstamp,
> but nskb->tstamp and hwtstamps are left at zero, so
> tcp_recv_timestamp() ends up emitting no cmsg at all.
> 
> In net timestamping case, if such an skb happens to be the last
> one consumed in a recvmsg() call, the application receives no RX
> timestamp for that call.
> 
> Fix this by copying both tstamp and hwtstamp to the new skb right
> after the initialization.
> 
> Fixes: 98aaa913b4ed ("tcp: Extend SOF_TIMESTAMPING_RX_SOFTWARE to TCP recvmsg")
> Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>

Thanks,
Xuanqiang

  reply	other threads:[~2026-09-17 14:09 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-17 13:27 [PATCH net v2] tcp: preserve timestamps across receive queue collapse Jason Xing
2026-09-17 14:09 ` Xuanqiang Luo [this message]
2026-09-21 15:34 ` netdev-bot+sashiko
2026-09-21 15:47   ` Eric Dumazet
2026-09-24 14:33     ` Jason Xing

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