ofproto-dpif-upcall: Echo HASH attribute back to datapath.

The kernel datapath may sent upcall with hash info,
ovs-vswitchd should get it from upcall and then send
it back.

The reason is that:
| 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.
|
| 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.

Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2019-October/364062.html
Link: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/?id=bd1903b7c4596ba6f7677d0dfefd05ba5876707d
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/datapath/linux/compat/include/linux/openvswitch.h b/datapath/linux/compat/include/linux/openvswitch.h
index 7b16b1d5b..778827f8b 100644
--- a/datapath/linux/compat/include/linux/openvswitch.h
+++ b/datapath/linux/compat/include/linux/openvswitch.h
@@ -210,6 +210,7 @@ enum ovs_packet_attr {
 				       error logging should be suppressed. */
 	OVS_PACKET_ATTR_MRU,	    /* Maximum received IP fragment size. */
 	OVS_PACKET_ATTR_LEN,		/* Packet size before truncation. */
+	OVS_PACKET_ATTR_HASH,		/* Packet hash. */
 	__OVS_PACKET_ATTR_MAX
 };