netdev - Re: Bug#1106321: iproute2: "ip monitor" fails with current trixie's linux kernel / iproute2 combination

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Message-ID: <CAMw=ZnTLuVjisLhD2nA094gOE2wkTLyr90Do0QidF5nHG_0k9g@mail.gmail.com>
Date: Fri, 23 May 2025 02:10:41 +0100
From: Luca Boccassi <bluca@...ian.org>
To: Yuyang Huang <yuyanghuang@...gle.com>
Cc: David Ahern <dsahern@...nel.org>, Stephen Hemminger <stephen@...workplumber.org>, 
	1106321@...s.debian.org, Netdev <netdev@...r.kernel.org>, 
	Maciej Żenczykowski <maze@...gle.com>
Subject: Re: Bug#1106321: iproute2: "ip monitor" fails with current trixie's
 linux kernel / iproute2 combination

On Fri, 23 May 2025 at 01:58, Yuyang Huang <yuyanghuang@...gle.com> wrote:
>
> Backward compatibility is broken due to the exit(1) in the following changes.
>
> ```
> + if (lmask & IPMON_LMADDR) {
> + if ((!preferred_family || preferred_family == AF_INET) &&
> +     rtnl_add_nl_group(&rth, RTNLGRP_IPV4_MCADDR) < 0) {
> + fprintf(stderr,
> + "Failed to add ipv4 mcaddr group to list\n");
> + exit(1);
> + }
> + if ((!preferred_family || preferred_family == AF_INET6) &&
> +     rtnl_add_nl_group(&rth, RTNLGRP_IPV6_MCADDR) < 0) {
> + fprintf(stderr,
> + "Failed to add ipv6 mcaddr group to list\n");
> + exit(1);
> + }
> + }
> +
> + if (lmask & IPMON_LACADDR) {
> + if ((!preferred_family || preferred_family == AF_INET6) &&
> +     rtnl_add_nl_group(&rth, RTNLGRP_IPV6_ACADDR) < 0) {
> + fprintf(stderr,
> + "Failed to add ipv6 acaddr group to list\n");
> + exit(1);
> + }
> + }
> +
> ```
>
> My patches follow the existing code styles, so I also added exit(1).
>
> Link: https://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git/tree/ip/ipmonitor.c#n330
>
> I thought iproute2 was intentionally not backward compatible, but it
> sounds like that's not true.
>
> I can submit a fix patch to remove the exit(1), which should fix the
> backward compatibility issue.
>
> Shall we proceed with this proposal?

iproute2 is generally backward compatible with previous kernels yes,
so it would be great to have a fix for this. Thanks!