IPv6 BFD interop with Huawei, checksum 0 UDP

[Alexander Zubkov]

Hi all,

Slightly modified the patch (names & description) in spite of the
checksum verify semantics.

On Wed, Jun 26, 2024 at 9:03 AM Ville O <vojamo at gmail.com> wrote:
>
> Hello All,
>
> On Tue, Jun 25, 2024 at 9:05 PM Alexander Zubkov via Bird-users
> <bird-users at network.cz> wrote:
> > On Tue, Jun 25, 2024 at 3:04 PM Ondrej Zajicek <santiago at crfreenet.org> wrote:
> > > Seems to me (from cursory look at the kernel code, as it seems to be an
> > > undocumented option) that the socket option UDP_NO_CHECK6_RX does not
> > > disable UDP checksum verification in general, just allows to accept UDP
> > > packets with zero checksum, while UDP packets with invalid non-zero
> > > checksums would still be rejected. Which fits better to what we need for
> > > this.
> >
> > I've grepped the kernel source and I agree, it seems to only accept
> > zero checksums. Then maybe some phrases need to be reworded and the
> > configuration option to be renamed?
> >
>
> This is the impression I, too, got while doing research into this matter
> and looking at the patches [1] that implemented this feature.
> The commit message is very clear: only a checksum of 0 is
> special-case accepted.
>
> By the way it seems the patch has been backported by RH at least
> as far back as EL7 kernel version 3.10.0.
>
> And I have an update on my problem that started all this:
>
> The peer managed to update their devices to the latest Huawei OS
> version and this fixed IPv6 BFD checksums.
> Unfortunately the peer could not give me the old/current versions so I
> cannot give information on which versions are broken and which are
> fixed. I tried to get more detailed information but it just was not
> possible; I can only say "latest version".
>
> Since the problem was fixed with the Huawei update I then regret
> that I am unable to usefully test the diff.
> I tested the new UDP socket option simply with scapy and maybe
> something similar could work for functional testing if required.
>
> A big thank you to everyone!
>
>
> Regards,
>
> V O
>
> [1]: https://github.com/torvalds/linux/commit/1c19448c9ba6545b80ded18488a64a7f3d8e6998
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: bfd-udp6-no-csum-2.patch
Type: text/x-patch
Size: 5855 bytes
Desc: not available
URL: <http://trubka.network.cz/pipermail/bird-users/attachments/20240627/7188baf3/attachment.bin>