Re: [PATCH net-next v2 00/11] net: Convert vrf to tx hook

From: David Ahern <redacted>
Date: Sat, 10 Sep 2016 12:09:51 -0700

The motivation for this series is that ICMP Unreachable - Fragmentation
Needed packets are not handled properly for VRFs. Specifically, the
FIB lookup in __ip_rt_update_pmtu fails so no nexthop exception is
created with the reduced MTU. As a result connections stall if packets
larger than the smallest MTU in the path are generated.

While investigating that problem I also noticed that the MSS for all
connections in a VRF is based on the VRF device's MTU and not the
route the packets ultimately go through. VRF currently uses a dst
to direct packets to the device. The first FIB lookup returns this dst
and then the lookup in the VRF driver gets the actual output route. A
side effect of this design is that the VRF dst is cached on sockets
and then used for calculations like the MSS.

This series fixes this problem by removing the hook in the FIB lookups
that returns the dst pointing to the VRF device to the VRF and always
doing the actual FIB lookup. This allows the real dst to be used
throughout the stack (for example the MSS). Packets are diverted to
the VRF device on Tx using an l3mdev hook in the output path similar to
to what is done for Rx. The end result is a simpler implementation for
VRF with fewer intrusions into the network stack and symmetrical packet
handling for Rx and Tx paths.

 ...

Series applied, thanks David.