Re: [PATCH mptcp-next] Squash to "selftests: mptcp: convert iptables to nftables for mptcp_join.sh"

[Hangbin Liu <hangbin.liu@linux.dev>]

On Fri, Oct 09, 2026 at 11:03:07AM +0200, Matthieu Baerts wrote:
> Hi Hangbin,
> 
> On 09/10/2026 09:26, Hangbin Liu wrote:
> > From: Hangbin Liu <liuhangbin@kylinos.cn>
> > 
> > After squash, the new commit description could be:
> 
> Thank you for the new version!
> 
> > diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
> > index b16e24418e73..cf079c18af12 100755
> > --- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
> > +++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
> > @@ -97,6 +97,20 @@ unset add_addr_tx_nr
> >  unset add_addr_echo_tx_nr
> >  unset add_addr_drop_tx_nr
> >  
> > +# A tcpdump capture of the RM_ADDR message looks like:
> > +#
> > +#   [TCP header: 20 bytes] [nop] [nop] [timestamp: 10 bytes] \
> > +#         [MPTCP DSS: 12 bytes] [MPTCP RM_ADDR: 4 bytes]
> > +#
> > +# nft cannot process the RM_ADDR option because it stops parsing after
> > +# matching the first DSS option. Use hard-coded byte offsets to match
> > +# RM_ADDR messages. We verify:
> > +#
> > +# TCP Data Offset (12 x 4 = 48 bytes), DSS (TCP[32] x 8) kind (MPTCP 0x1e)
> > +# and length (0x0c). RM_ADDR (TCP[44] x 8) kind (MPTCP 0x1e) and subtype (4)
> > +
> > +RM_ADDR_OFFSETS="tcp doff 12 @th,256,16 == 0x1e0c @th,352,8 == 0x1e @th,368,4 == 4"
> 
> The subtype is on 4 bits. For the moment, the rest are not used, but
> would it not be better to compare the 20 first bits of this offset?
> 
> So using this: (not tested)
> 
>   "tcp doff 12 @th,256,20 == 0x1e0c2 @th,352,12 == 0x1e044"

Here it should be @th,352,20 == 0x1e044
> 
> Or maybe we prefer not to be strict for the RM_ADDR size to match
> options with multiple IDs? Then having:
> 
>   "tcp doff 12 @th,256,20 == 0x1e0c2 @th,352,8 == 0x1e @th,368,4 == 4"
> 
> and for the comment:
> 
> # TCP Data Offset (12 x 4 = 48 bytes).
> # DSS (TCP[32] x 8) kind (MPTCP 0x1e), length (0x0c), subtype (2).
> # RM_ADDR (TCP[44] x 8) kind (MPTCP 0x1e), variable length, subtype (4).
> 
> I can modify this when applying if that's OK for you (and validated).

And both works for me. I tested these 2 rules, all are able to capture the
RM_ADDR messages.

        chain OUTPUT {
                type filter hook output priority filter; policy accept;
                ip saddr 10.0.2.1 tcp doff 12 @th,256,24 & 0xfffff0 == 0x1e0c20 @th,352,24 & 0xfffff0 == 0x1e0440 counter packets 1 bytes 68 accept
                ip saddr 10.0.1.1 tcp doff 12 @th,256,24 & 0xfffff0 == 0x1e0c20 @th,352,24 & 0xfffff0 == 0x1e0440 drop
        }

        chain OUTPUT {
                type filter hook output priority filter; policy accept;
                ip saddr 10.0.2.2 tcp doff 12 @th,256,24 & 0xfffff0 == 0x1e0c20 @th,352,8 0x1e @th,368,8 & 0xf0 == 0x40 counter packets 3 bytes 204 accept
                ip saddr 10.0.1.2 tcp doff 12 @th,256,24 & 0xfffff0 == 0x1e0c20 @th,352,8 0x1e @th,368,8 & 0xf0 == 0x40 drop
        }

Thanks
Hangbin