Hello,
On Mon, 8 Sept 2025 at 10:43, chenyongchang via discuss
<[email protected]> wrote:
>
> Hi all,
> I noticed an issue when recalculating UDP checksums in
> dp_packet_ol_send_prepare -> packet_udp_complete_csum -> csum_finish.
Avoid sending the same mail multiple times.
>
> If the packet is the first fragment of a UDP fragmented packet, the
> checksum can be wrong.
> Example:
> UDP payload 2000 bytes, fragmented with MTU 1500.
> First fragment payload 1480 bytes, but udp->udp_len = 2008.
> Checksum calculation cannot access later fragments, so it’s incorrect.
>
> Has anyone seen this before or have a recommended solution for handling UDP
> checksum on fragmented packets?
This report is a bit low on details.
I'll assume you are talking about the main branch.
There was a fix recently, you can have a look at: 3ffb1c4012b7 ("ipf:
Complete l4 checksum before frag out.").
If this does not help, does reverting e36793e11fe8 ("dp-packet:
Resolve unknown checksums.") fix your issue?
And we will need a reproducer.
--
David Marchand
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