Date: Tue, 08 Jul 2003 08:15:53 -0700 From: Sam Leffler <sam@errno.com> To: Bill Paul <wpaul@FreeBSD.org>, Garrett Wollman <wollman@lcs.mit.edu> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/net if_vlan.c Message-ID: <690626358.1057652153@melange.errno.com> In-Reply-To: <20030707234511.3B0FB37B401@hub.freebsd.org> References: <20030707234511.3B0FB37B401@hub.freebsd.org>
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>> <<On Sat, 5 Jul 2003 20:24:25 -0700 (PDT), Bill Paul <wpaul@FreeBSD.org>
>> said:
>>
>> > I'm not quite sure what the right thing is to do here. Neither the
>> > vlan(4) nor ifconfig(8) man pages suggest which way to go. For now,
>> > I've removed this use of EVL_VLANOFTAG() so that the tag will match
>> > correctly in all cases. I will not get upset if somebody makes a
>> > compelling argument for using EVL_VLANOFTAG() everywhere instead,
>> > as long as the use is consistent.
>>
>> VLAN tags have only 12 bits. Anything else is part of the 802.1p
>> encapsulation header (either the priority or the ``this packet was
>> translated from Token Ring'' bit).
>>
>> -GAWollman
>>
>
> Ok, based on this (and what others have said), it looks like the
> correct behavior is to mask off all but the VLAN ID bits in all cases
> in vlan_input(). This is easy enough to do. The only issue then is
> what to do about the fact that the user is currently allowed to set
> the non-VLAN ID bits with ifconfig(8). We can do one of two things:
>
> 1) Change vlan_input() to apply EVL_VLANOFTAG() to all incoming tags
> (in both hardware and non-hardware tagging cases) and change the
> vlan_ioctl() function to only accept vlan tags from 0 to 4095
> and return EINVAL if the caller tries to set any of the other
> bits. (Prevent user from shooting self in foot.)
>
> 2) Let the user set any bits, but always mask off the non-VLAN ID
> bits in vlan_input(), i.e.:
>
> --- if_vlan.c.orig Sat Jul 5 19:53:51 2003
> +++ if_vlan.c Mon Jul 7 10:44:07 2003
> @@ -429,7 +429,8 @@
>
> for (ifv = LIST_FIRST(&ifv_list); ifv != NULL;
> ifv = LIST_NEXT(ifv, ifv_list))
> - if (ifp == ifv->ifv_p && tag == ifv->ifv_tag)
> + if (ifp == ifv->ifv_p && EVL_VLANOFTAG(tag) ==
> + EVL_VLANOFTAG(ifv->ifv_tag))
> break;
>
> if (ifv == NULL || (ifv->ifv_if.if_flags & IFF_UP) == 0) {
>
> I am leaning towards option 1). Am I sane or not?
Go with 1). I agree that users should be dealing only with the 12-bit id,
not the priority bits. But this still leaves the issue of honoring the
priority bits on reception.
Sam
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