I have discovered that on one machine, if I enable either GSO or GRO (with ethtool -K), and then change the interface MTU, the machine ceases to be IPv6 neighbour-discoverable. After the following commands: ethtool -K eth0 gro on gso on # doesn't matter which of them, or both ifconfig eth0 mtu 4082 the machine is no longer ping6'able from LAN by "new" hosts (which haven't seen it recently) -- until something ELSE is adjusted on the same interface of that machine, e.g. the following command helps (I don't know why, the PROMISC mode is already disabled when it runs): ifconfig eth0 -promisc The NIC (using the "skge" driver): 00:08.0 Ethernet controller: 3Com Corporation 3c940 10/100/1000Base-T [Marvell] (rev 10) The system is a Debian Squeeze with 2.6.33 kernel and ethtool 2.6.33. The issue is 100% reproducible.
(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface). On Tue, 13 Apr 2010 16:17:44 GMT bugzilla-daemon@bugzilla.kernel.org wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=15777 > > Summary: Changing MTU after enabling GSO/GRO breaks incoming > IPv6 neighbour discovery > Product: Networking > Version: 2.5 > Kernel Version: 2.6.33 > Platform: All > OS/Version: Linux > Tree: Mainline > Status: NEW > Severity: normal > Priority: P1 > Component: IPV6 > AssignedTo: yoshfuji@linux-ipv6.org > ReportedBy: roman@rm.pp.ru > Regression: No > > > I have discovered that on one machine, if I enable either GSO or GRO (with > ethtool -K), and then change the interface MTU, the machine ceases to be IPv6 > neighbour-discoverable. After the following commands: > > ethtool -K eth0 gro on gso on # doesn't matter which of them, or both > ifconfig eth0 mtu 4082 > > the machine is no longer ping6'able from LAN by "new" hosts (which haven't > seen > it recently) -- until something ELSE is adjusted on the same interface of > that > machine, e.g. the following command helps (I don't know why, the PROMISC mode > is already disabled when it runs): > > ifconfig eth0 -promisc > > The NIC (using the "skge" driver): > > 00:08.0 Ethernet controller: 3Com Corporation 3c940 10/100/1000Base-T > [Marvell] (rev 10) > > The system is a Debian Squeeze with 2.6.33 kernel and ethtool 2.6.33. > > The issue is 100% reproducible.
Closing as obsolete, if this is still seen with modern kernels please re-open and update