Subject: kern/18850: pppoe agrees remote MRU but does not set interface MTU
To: None <>
From: None <>
List: netbsd-bugs
Date: 10/29/2002 08:42:18
>Number:         18850
>Category:       kern
>Synopsis:       pppoe agrees remote MRU but does not set interface MTU
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Oct 29 00:43:00 PST 2002
>Originator:     Curt Sampson
>Release:        NetBSD 1.6
System: NetBSD 1.6 NetBSD 1.6 (VTGENERIC-$Revision: 1.3 $) #1: Wed Oct 16 16:43:49 JST 2002 i386
Architecture: i386
Machine: i386
    When I bring up a pppoe interface, and the remote end sends an MRU
    negotiation request during LCP, the in-kernel pppoe agrees with that
    MRU request. However, it does not set the MTU on the interface afterwards
    to ensure that that it will not send packets larger than that.
    Connection to my PPPoE provider. :-) Watch the negotiation:

	(from remote)        PPPoE  [ses 0xb5d6] Conf-Req(1), MRU=1454, ...
	(from my NetBSD box) PPPoE  [ses 0xb5d6] Conf-Ack(1), MRU=1454, ...

    Use ifconfig to look at the interface afterwards, and confirm that
    the MTU is still 1490.

    I'm happy to repeat this test if given kernel patches against 1.6.
    (Or something close enough that I can hack it into 1.6 without too much