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

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Message-Id: <20160910.231317.431318504608631938.davem@davemloft.net>
Date:   Sat, 10 Sep 2016 23:13:17 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dsa@...ulusnetworks.com
Cc:     netdev@...r.kernel.org, shm@...ulusnetworks.com
Subject: Re: [PATCH net-next v2 00/11] net: Convert vrf to tx hook

From: David Ahern <dsa@...ulusnetworks.com>
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.