netdev - Re: [PATCH manpages v2 1/2] udp.7: add UDP

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Date:   Mon, 6 Mar 2023 14:31:58 +0100
From:   Alejandro Colomar <alx.manpages@...il.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        linux-man@...r.kernel.org
Cc:     pabeni@...hat.com, netdev@...r.kernel.org,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH manpages v2 1/2] udp.7: add UDP_SEGMENT



On 3/6/23 14:30, Alejandro Colomar wrote:
> Hi Willem,
> 
> On 3/2/23 16:48, Willem de Bruijn wrote:
>> From: Willem de Bruijn <willemb@...gle.com>
>>
>> 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@...gle.com>
>>
> 
> It doesn't apply.  Can you please rebase on top of master?

Oops, sorry, I tried to apply 1/2 twice, instead of 1/2 and 2/2 :-)
Ignore that.

Cheers,

Alex
> 
> Thanks,
> 
> 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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