Re: PF doc oddity

On 2010/12/17 23:18, Karl O. Pinc wrote:
> Hi,
> 
> I'm wondering why pf.conf(5) has an example
> scrub setting where the mtu is 1440 when
> 1460 would be the usual mtu for a 1500
> byte IP datagram.
> 
> From OpenBSD 4.8:
> -----------<snip>----------
>      For example:
> 
>            match in all scrub (no-df max-mss 1440)
> -----------<snip>----------
> 
> Is my brain just not clicking?

The normal use case for max-mss is when packets are forwarded via
a tunnel of some sort (pppoe, gif, gre, ipsec etc) where full-sized
packets can't be passed through.

So you would usually want to set it to a lower value than is
already in the packet.