Hello,
On Mon, Sep 02, 2024 at 11:44:24PM +0000, Jason Healy wrote:
</snip>
>
> Just to double-check, is the MTU in this case (1300) for an IPv6 link?
> If so, should the MTU be lowered when translated back to IPv4 (20
> bytes smaller) to account for the extra bloat of the headers? Or are
> we already back to IPv4 by the time we hit RT? I'm having a little
> trouble understanding the topology.
pf(4) does exactly that. it adjusts MTU for difference of
header sizes between IPv6 and IPv4. Snippet below comes
from pf_translate_icmp_af().
3061 break;
3062 case ICMP6_PACKET_TOO_BIG:
3063 type = ICMP_UNREACH;
3064 code = ICMP_UNREACH_NEEDFRAG;
3065 mtu -= 20;
3066 break;
firewall shrinks reported MTU by 20 bytes/octets when it
translates ICMPv6 too-big message to ICMPv4 need-frag.
>
> > I understand what are you trying to do. I'm afraid I will need
> > output of ifconfig and pf.conf. Taking a brief look into your source
> > code I can see icmp6_reflect() is aware of routing domains, so I would
> > assume things should work too.
>
> I will send this under separate cover as a direct message to you.
>
I will try to look at it sometimes later.
regards
sashan
