From: Ondrej Zajicek <santiago@crfreenet.org>
To: "Toke Høiland-Jørgensen" <toke@toke.dk>
Cc: bird-users@network.cz, wireguard@lists.zx2c4.com,
Stefan Haller <stefan.haller@stha.de>
Subject: Re: [PATCH] babel: Drop check for IF_MULTICAST interface flag
Date: Mon, 19 Apr 2021 18:32:59 +0200 [thread overview]
Message-ID: <YH2wux4jIJuD4RS2@feanor.crfreenet.org> (raw)
In-Reply-To: <87y2degz09.fsf@toke.dk>
On Mon, Apr 19, 2021 at 03:55:18PM +0200, Toke Høiland-Jørgensen wrote:
> Ondrej Zajicek <santiago@crfreenet.org> writes:
>
> > Is there a reason why to disregard the IF_MULTICAST flag? This seems to me
> > more like a bug in FreeBSD Wireguard implementation that should be fixed
> > there. Is this flag properly checked on Linux, or is there some reason why
> > the flag is missing?
>
> We did fix Wireguard - see:
> https://git.zx2c4.com/wireguard-freebsd/patch/?id=a7a84a17faf784857f076e37aa4818f6b6c12a95
>
> However, that didn't help, Babel still refused to use the interface.
> Looking at krt-sock.c, the IF_MULTICAST flag is only set on
> IFF_POINTOPOINT or IFF_BROADCAST on bsd. The Linux code (in netlink.c)
> has a further:
>
> if (fl & IFF_MULTICAST)
> f.flags |= IF_MULTICAST;
>
> beneath the other flag checks, so maybe that's really what's missing on
> the BSD side?
Yes, it is likely that it is an issue in sysdep/bsd code.
> > Routing protocols in BIRD generally follow this flag (and perhaps use
> > it to switch to unicast-only mode), so i do not see why Babel should
> > behave differently.
>
> Yeah, I do believe I originally copied that check from one of the other
> protocols. I can see how it makes sense to check the flag and change
> operation mode based on it, but given that Babel doesn't do that it just
> seems kinda redundant? If the interface *actually* is unable to send
> multicast packets, the subsequent socket operation is going to fail, and
> at least that produces an error message instead of just silently
> ignoring the interface like that flag check does :)
Well, i am OK with generating a warning in cases of non-matching interface
type, instead of ignoring it silently. (In contrast to iface down or missing
lladdr, which should be silent, as it may correct later.)
--
Elen sila lumenn' omentielvo
Ondrej 'Santiago' Zajicek (email: santiago@crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
next prev parent reply other threads:[~2021-04-20 4:52 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-15 13:44 Toke Høiland-Jørgensen
2021-04-19 13:03 ` Ondrej Zajicek
2021-04-19 13:55 ` Toke Høiland-Jørgensen
2021-04-19 16:32 ` Ondrej Zajicek [this message]
2021-04-19 18:24 ` Toke Høiland-Jørgensen
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