Hi Willem,
On 3/2/23 16:48, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@xxxxxxxxxx>
>
> UDP_SEGMENT was added in commit bec1f6f69736
> ("udp: generate gso with UDP_SEGMENT")
>
> $ git describe --contains bec1f6f69736
> linux/v4.18-rc1~114^2~377^2~8
>
> Kernel source has example code in tools/testing/selftests/net/udpgso*
>
> Per https://www.kernel.org/doc/man-pages/patches.html,
> "Describe how you obtained the information in your patch":
> I am the author of the above commit and follow-ons.
>
> Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Patch applied, with some minor tweaks and Simon's review tag.
Cheers,
Alex
>
> ---
>
> Changes v1->v2
> - semantic newlines: also break on comma and colon
> - remove bold: section number following function name
> - add bold: special macro USHRT_MAX
> ---
> man7/udp.7 | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/man7/udp.7 b/man7/udp.7
> index 5822bc551fdf..6646c1e96bb0 100644
> --- a/man7/udp.7
> +++ b/man7/udp.7
> @@ -204,6 +204,34 @@ portable.
> .\" UDP_ENCAP_ESPINUDP draft-ietf-ipsec-udp-encaps-06
> .\" UDP_ENCAP_L2TPINUDP rfc2661
> .\" FIXME Document UDP_NO_CHECK6_TX and UDP_NO_CHECK6_RX, added in Linux 3.16
> +.TP
> +.BR UDP_SEGMENT " (since Linux 4.18)"
> +Enables UDP segmentation offload.
> +Segmentation offload reduces
> +.BR send (2)
> +cost by transferring multiple datagrams worth of data as a single large
> +packet through the kernel transmit path,
> +even when that exceeds MTU.
> +As late as possible,
> +the large packet is split by segment size into a series of datagrams.
> +This segmentation offload step is deferred to hardware if supported,
> +else performed in software.
> +This option takes a value between 0 and
> +.BR USHRT_MAX
> +that sets the segment size:
> +the size of datagram payload,
> +excluding the UDP header.
> +The segment size must be chosen such that at most 64 datagrams are sent in
> +a single call and that the datagrams after segmentation meet the same MTU
> +rules that apply to datagrams sent without this option.
> +Segmentation offload depends on checksum offload,
> +as datagram checksums are computed after segmentation.
> +The option may also be set for individual
> +.BR sendmsg (2)
> +calls by passing it as a
> +.BR cmsg (7).
> +A value of zero disables the feature.
> +This option should not be used in code intended to be portable.
> .SS Ioctls
> These ioctls can be accessed using
> .BR ioctl (2).
--
<http://www.alejandro-colomar.es/>
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