[PATCH net-next] docs: networking: timestamping: mention MSG_EOR flag

[PATCH net-next] docs: networking: timestamping: mention MSG_EOR flag

[Eric Dumazet]

TCP got MSG_EOR support in linux-4.7.

This is a canonical way of making sure no coalescing
will be performed on the skb, even if it could not be
immediately sent.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Martin KaFai Lau <kafai@fb.com
Cc: Willem de Bruijn <willemb@google.com>
---
 Documentation/networking/timestamping.rst | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/timestamping.rst b/Documentation/networking/timestamping.rst
index f17c01834a1230d31957112bb7f9c207e9178ecc..5e93cd71f99f1b17169b31f2ff93e8bd5220e5cd 100644
--- a/Documentation/networking/timestamping.rst
+++ b/Documentation/networking/timestamping.rst
@@ -357,7 +357,8 @@ enabling SOF_TIMESTAMPING_OPT_ID and comparing the byte offset at
 send time with the value returned for each timestamp. It can prevent
 the situation by always flushing the TCP stack in between requests,
 for instance by enabling TCP_NODELAY and disabling TCP_CORK and
-autocork.
+autocork. After linux-4.7, a better way to prevent coalescing is
+to use MSG_EOR flag at sendmsg() time.
 
 These precautions ensure that the timestamp is generated only when all
 bytes have passed a timestamp point, assuming that the network stack
-- 
2.43.0.472.g3155946c3a-goog

Re: [PATCH net-next] docs: networking: timestamping: mention MSG_EOR flag

[Willem de Bruijn]

Eric Dumazet wrote:
> TCP got MSG_EOR support in linux-4.7.
> 
> This is a canonical way of making sure no coalescing
> will be performed on the skb, even if it could not be
> immediately sent.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Martin KaFai Lau <kafai@fb.com
> Cc: Willem de Bruijn <willemb@google.com>

Acked-by: Willem de Bruijn <willemb@google.com>

> ---
>  Documentation/networking/timestamping.rst | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/networking/timestamping.rst b/Documentation/networking/timestamping.rst
> index f17c01834a1230d31957112bb7f9c207e9178ecc..5e93cd71f99f1b17169b31f2ff93e8bd5220e5cd 100644
> --- a/Documentation/networking/timestamping.rst
> +++ b/Documentation/networking/timestamping.rst
> @@ -357,7 +357,8 @@ enabling SOF_TIMESTAMPING_OPT_ID and comparing the byte offset at
>  send time with the value returned for each timestamp. It can prevent
>  the situation by always flushing the TCP stack in between requests,
>  for instance by enabling TCP_NODELAY and disabling TCP_CORK and
> -autocork.
> +autocork. After linux-4.7, a better way to prevent coalescing is
> +to use MSG_EOR flag at sendmsg() time.

Good catch. We could even remove the old deprecated suggestion, and
drop the versioning, as this Documentation ships with the kernel to
which it applies.

Re: [PATCH net-next] docs: networking: timestamping: mention MSG_EOR flag

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 12 Dec 2023 11:06:08 +0000 you wrote:
> TCP got MSG_EOR support in linux-4.7.
> 
> This is a canonical way of making sure no coalescing
> will be performed on the skb, even if it could not be
> immediately sent.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Martin KaFai Lau <kafai@fb.com
> Cc: Willem de Bruijn <willemb@google.com>
> 
> [...]

Here is the summary with links:
  - [net-next] docs: networking: timestamping: mention MSG_EOR flag
    https://git.kernel.org/netdev/net-next/c/173b6d1cdf58

You are awesome, thank you!
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