On Wed, Nov 13, 2019 at 7:05 AM <xiangxia.m....@gmail.com> wrote: > > From: Tonghao Zhang <xiangxia.m....@gmail.com> > > When using the kernel datapath, the upcall don't > include skb hash info relatived. That will introduce > some problem, because the hash of skb is important > in kernel stack. For example, VXLAN module uses > it to select UDP src port. The tx queue selection > may also use the hash in stack. > > Hash is computed in different ways. Hash is random > for a TCP socket, and hash may be computed in hardware, > or software stack. Recalculation hash is not easy. > > Hash of TCP socket is computed: > tcp_v4_connect > -> sk_set_txhash (is random) > > __tcp_transmit_skb > -> skb_set_hash_from_sk > > There will be one upcall, without information of skb > hash, to ovs-vswitchd, for the first packet of a TCP > session. The rest packets will be processed in Open vSwitch > modules, hash kept. If this tcp session is forward to > VXLAN module, then the UDP src port of first tcp packet > is different from rest packets. > > TCP packets may come from the host or dockers, to Open vSwitch. > To fix it, we store the hash info to upcall, and restore hash > when packets sent back. > > +---------------+ +-------------------------+ > | Docker/VMs | | ovs-vswitchd | > +----+----------+ +-+--------------------+--+ > | ^ | > | | | > | | upcall v restore packet hash (not > recalculate) > | +-+--------------------+--+ > | tap netdev | | vxlan module > +---------------> +--> Open vSwitch ko +--> > or internal type | | > +-------------------------+ > > Reported-at: > https://mail.openvswitch.org/pipermail/ovs-dev/2019-October/364062.html > Signed-off-by: Tonghao Zhang <xiangxia.m....@gmail.com>
Acked-by: Pravin B Shelar <pshe...@ovn.org> Thanks. _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
