netdev - Re: [PATCH net v2 2/4] selftests/net: add no ARP b/mcast,null poison test

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Message-ID: <CA+3n-TprC7Fs0HiBndR+OpYmy2vq=raiuSE=_R49LVxjax8Aug@mail.gmail.com>
Date: Thu, 29 Jan 2026 19:28:22 +0100
From: Marc Sune <marcdevel@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: willemdebruijn.kernel@...il.com, pabeni@...hat.com, netdev@...r.kernel.org, 
	dborkman@...nel.org, vadim.fedorenko@...ux.dev
Subject: Re: [PATCH net v2 2/4] selftests/net: add no ARP b/mcast,null poison test

Missatge de Jakub Kicinski <kuba@...nel.org> del dia dj., 29 de gen.
2026 a les 5:27:
>
> On Tue, 27 Jan 2026 00:53:03 +0100 Marc Suñé wrote:
> > Add a selftest to test that ARP bcast/mcast/null poisioning checks
> > are never bypassed.
>
> > diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
> > index 45c4ea381bc3..a765f1800752 100644
> > --- a/tools/testing/selftests/net/Makefile
> > +++ b/tools/testing/selftests/net/Makefile
> > @@ -9,6 +9,7 @@ CFLAGS += -I../
> >  TEST_PROGS := \
> >       altnames.sh \
> >       amt.sh \
> > +     arp_no_invalid_sha_poision.sh \
>
> alphabetical sort pls
>
> >       arp_ndisc_evict_nocarrier.sh \
> >       arp_ndisc_untracked_subnets.sh \
> >       bareudp.sh \
>
> > +readonly V4_ADDR0="10.0.10.1"
> > +readonly V4_ADDR1="10.0.10.2"
> > +readonly BCAST_MAC="ff:ff:ff:ff:ff:ff"
> > +readonly MCAST_MAC="01:00:5e:00:00:00"
> > +readonly NULL_MAC="00:00:00:00:00:00"
> > +readonly VALID_MAC="02:01:02:03:04:05"
> > +readonly ARP_REQ=1
> > +readonly ARP_REPLY=2
> > +nsid=100
>
> unused? (please run shellcheck)

Errors fixed in v3.

>
> > +ret=0
> > +veth0_ifindex=0
> > +veth1_mac=
>
> > diff --git a/tools/testing/selftests/net/arp_send.c b/tools/testing/selftests/net/arp_send.c
> > new file mode 100644
>
> Could you check if mausezahn from netsniff-ng can send these
> packets already? We already depend on mausezahn for other tests.
>
> Similar comments on patch 4, I'm not gonna repeat.

I can do that for ARP, but not for NDP apparently. Only basic ICMPv6
echo req/reply is supported. For NDP (ICMPv6), it needs to be
specified using -P (hex). Kind of ugly...

In RFC v1 I proposed to use a scapy
(https://lore.kernel.org/netdev/3cfd28edb2c2b055e74b975623a3d38ade0237f1.1766349632.git.marcdevel@gmail.com/),
which is substantially smaller than arp_send/ndisc_send.c. I dropped
it based on the v1 review I got. I see scapy is used in bpf/ and
tc-testing/ self-tests.

What's your preference?

a) use mausezahn only for ARP, use ndisc_send.c for NDP
b) use only .c progs for consistency
c) recover the scapy patch and squash it in patches 2/4

Thanks