DF (Don't frag) issues

[David Malone]

On Mon, Apr 25, 2005 at 08:01:15PM +0200, Andre Oppermann wrote:
>  - Handling of received ICMP Needfrag messages.  The logic was broken
>    for the cases where the ICMP didn't contain a suggested value.  This
>    brokeness is in there since 5.2R and comes from my cleanup of the
>    routing table and introduction of TCP hostcache.  However there is
>    no way to fix it at all.  It was broken even before I broke it more.
>    The idea behind the old code was to step down the MTU when we got
>    a ICMP Needfrag by one step and try again.  Unfortunatly it is very
>    likely that the tcp window was open by a few segments already when
>    we hit this.  This gets us a number of those ICMP's in rapid succession
>    each stepping us one down.

I wonder if we could look into the quoted IP header and extract the
length of the IP packet that caused the needs-frag ICMP. That would
stop us getting in knots when there are a few packets in flight and
would give us a good idea about where we need to step down from.

	David.