Development discussion of WireGuard
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From: "Toke Høiland-Jørgensen" <toke@toke.dk>
To: Ondrej Zajicek <santiago@crfreenet.org>
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 20:24:38 +0200	[thread overview]
Message-ID: <87im4igmjd.fsf@toke.dk> (raw)
In-Reply-To: <YH2wux4jIJuD4RS2@feanor.crfreenet.org>

Ondrej Zajicek <santiago@crfreenet.org> writes:

> 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.

Alright, I'll send a patch for that then :)

>> > 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.)

OK, fine with me; I'll send an updated patch that adds a warning instead
of dropping the check...

-Toke

      reply	other threads:[~2021-04-19 18:27 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
2021-04-19 18:24       ` Toke Høiland-Jørgensen [this message]

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