Re: ppp mru/mtu and ip masquerading

Andi Kleen (ak@muc.de)
28 Feb 1999 20:10:00 +0100

alan@lxorguk.ukuu.org.uk (Alan Cox) writes:
>
> With 2.2.x it is entirely possible given the changes to the masquerading
> code that a bug has crept in. But I've yet to see a trace for that and it
> would be suprising
>
> (If you think about it masquerading doesnt kick in on a download problem
> error case. The errored tcp frame bounces off the start of the low MTU
> PPP link before it is masqueraded)

There is a known bug with masquerading and path mtu discovery in 2.2. Icmp
forgets to unmasquerade an already masqueraded packet, so the ICMP payload
header contains the wrong address and the other end drops it.

For NAT it is handled in icmp.c, but not for Masquerading
currently. Fix is a bit more complex though because unlike NAT the
masquerading rule is not easily accessable from the skb.

-Andi

-- 
This is like TV. I don't like TV.


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