Hi Jesse, as part of our discussion on flow-based tunneling a few weeks ago you mentioned that you would like to see an implementation of MSS Clamping in user-space in order to eliminate the need for gre_err().
I made a start on implementing this, and I have a non-configurable version working. Its pretty crude and just adjust the MSS on all TCP SYN packets with no payload that are seen in handle_flow_miss_common(). That much seems to work. But I am unsure about a few things. * Should it be configurable per-output port? If so that may be problematic if there are multiple outputs as the packet data is mangled. * I am unsure how to automatically calculate the desired Clamp size. In particular, in for GRE it would be nice to allow it to be automatically clamped to the underlying MTU less the header size. But I'm unsure of a sane way to obtain the MTU. Perhaps I am on the wrong track? It does seem to me that this might be easier implemented in the datapath as ovs_tnl_send() already has access to skb, the MTU and could leverage the existing netfilter MMS clamp code. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
