Re: [PATCH net-next 5/5] selftests: mptcp: convert iptables to nftables for mptcp_join.sh

[Jakub Kicinski]

On Mon, 28 Sep 2026 23:17:59 +0200 Matthieu Baerts wrote:
> > Indeed, the RM_ADDR will be added in a second MPTCP option. It looks
> > like Netfilter doesn't handle that case. But that seems to be an issue
> > on the Netfilter side, rather than with the command that should work. I
> > will follow up with Netfilter devs. If a fix cannot be added on their
> > side, I will change the nft command to look at a specific offset.
> > 
> > Note that the command here is just to check there is no RM_ADDR sent on
> > the wrong side: it shouldn't catch any packets here anyway.  
> 
> After a discussion with Netfilter devs, it looks like a fix will not be
> easy to have. Yet, I wonder if it wouldn't be better to apply this patch
> like that (it doesn't break things), and have an explicit follow-up/fix
> to document this issue somehow.
> 
> @Hangbin: do you plan to look at a fix for that? I guess a raw payload
> looking at the same fields as what the previous cBPF rule was doing
> would be enough.
> 
> Don't hesitate to fix the "low" priority comments as well.
> 
> https://lore.kernel.org/all/20260926-net-next-mptcp-misc-feat-7-4-v1-0-67af4ab37406@xxxxxxxxxx/T/#u

-110, let me take the kernel patches for now, repost the selftests
please, in whatever form you decide to have them.