netdev - Re: [PATCH net v2] net-timestamp: support TCP GSO case for a few missing flags

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Message-ID: <67c707ae56c92_257ad9294e6@willemb.c.googlers.com.notmuch>
Date: Tue, 04 Mar 2025 09:01:18 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jason Xing <kerneljasonxing@...il.com>, 
 davem@...emloft.net, 
 edumazet@...gle.com, 
 kuba@...nel.org, 
 pabeni@...hat.com, 
 ncardwell@...gle.com, 
 kuniyu@...zon.com, 
 dsahern@...nel.org, 
 willemb@...gle.com, 
 willemdebruijn.kernel@...il.com, 
 horms@...nel.org
Cc: netdev@...r.kernel.org, 
 Jason Xing <kerneljasonxing@...il.com>
Subject: Re: [PATCH net v2] net-timestamp: support TCP GSO case for a few
 missing flags

Jason Xing wrote:
> When I read through the TSO codes, I found out that we probably
> miss initializing the tx_flags of last seg when TSO is turned
> off, which means at the following points no more timestamp
> (for this last one) will be generated. There are three flags
> to be handled in this patch:
> 1. SKBTX_HW_TSTAMP
> 2. SKBTX_BPF
> 3. SKBTX_SCHED_TSTAMP
> Note that SKBTX_BPF[1] was added in 6.14.0-rc2 by commit
> 6b98ec7e882af ("bpf: Add BPF_SOCK_OPS_TSTAMP_SCHED_CB callback")
> and only belongs to net-next branch material for now. The common
> issue of the above three flags can be fixed by this single patch.
> 
> This patch initializes the tx_flags to SKBTX_ANY_TSTAMP like what
> the UDP GSO does to make the newly segmented last skb inherit the
> tx_flags so that requested timestamp will be generated in each
> certain layer, or else that last one has zero value of tx_flags
> which leads to no timestamp at all.
> 
> Fixes: 4ed2d765dfacc ("net-timestamp: TCP timestamping")
> Signed-off-by: Jason Xing <kerneljasonxing@...il.com>

Reviewed-by: Willem de Bruijn <willemb@...gle.com>