[PATCH net] openvswitch: Fix upcall OVS_TUNNEL_KEY_ATTR_GENEVE_OPTS

[Yi-Hung Wei <yihung.wei@gmail.com>]

TUNNEL_GENEVE_OPT is set on tun_flags in struct sw_flow_key when
a packet is coming from a geneve tunnel no matter the size of geneve
option is zero or not.  On the other hand, TUNNEL_VXLAN_OPT or
TUNNEL_ERSPAN_OPT is set when the VXLAN or ERSPAN option is available.
Currently, ovs kernel module only generates
OVS_TUNNEL_KEY_ATTR_GENEVE_OPTS when the tun_opts_len is non-zero.
As a result, for a geneve packet without tun_metadata, when the packet
is reinserted from userspace after upcall, we miss the TUNNEL_GENEVE_OPT
in the tun_flags on struct sw_flow_key, and that will further cause
megaflow matching issue.

This patch changes the way that we deal with the upcall netlink message
generation to make sure the geneve tun_flags is set consistently
as the packet is firstly received from the geneve tunnel in order to
avoid megaflow matching issue demonstrated by the following flows.
This issue is only observed on ovs kernel datapath.

Consider the following two flows, and the two cases.
* flow1: icmp traffic from gnv0 to gnv1, without any tun_metadata
* flow2: icmp traffic form gnv0 to gnv1 with tun_metadata0

Case 1)
Send flow2 first, and then send flow1.  When both flows are running,
both the following two flows are hit, which is expected.

table=2, priority=200, in_port=gnv0, icmp, ct_state=+trk+est, reg9=0x0/0xff action=output:gnv1
table=2, priority=200, in_port=gnv0, icmp, ct_state=+trk+est, reg9=0x1/0xff action=output:gnv1

Case 2)
Send flow1 first, then send flow2.  When both flows are running,
only the following flow is hit.
table=2, priority=200, in_port=gnv0, icmp, ct_state=+trk+est, reg9=0x0/0xff action=output:gnv1

Example flows)

table=0, arp, actions=NORMAL
table=0, in_port=gnv1, icmp, action=ct(table=1)
table=0, in_port=gnv0, icmp  action=move:NXM_NX_TUN_METADATA0[0..7]->NXM_NX_REG9[0..7], resubmit(,1)
table=1, in_port=gnv1, icmp, action=output:gnv0
table=1, in_port=gnv0, icmp  action=ct(table=2)
table=2, priority=300, in_port=gnv0, icmp, ct_state=+trk+new, action=ct(commit),output:gnv1
table=2, priority=200, in_port=gnv0, icmp, ct_state=+trk+est, reg9=0x0/0xff action=output:gnv1
table=2, priority=200, in_port=gnv0, icmp, ct_state=+trk+est, reg9=0x1/0xff action=output:gnv1

Fixes: fc4099f17240 ("openvswitch: Fix egress tunnel info.")
Signed-off-by: Yi-Hung Wei <yihung.wei@gmail.com>
---
 net/openvswitch/flow_netlink.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index 9d3e50c4d29f..b03ec6a1a1fa 100644
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -912,13 +912,13 @@ static int __ip_tun_to_nlattr(struct sk_buff *skb,
 	if ((output->tun_flags & TUNNEL_OAM) &&
 	    nla_put_flag(skb, OVS_TUNNEL_KEY_ATTR_OAM))
 		return -EMSGSIZE;
-	if (swkey_tun_opts_len) {
-		if (output->tun_flags & TUNNEL_GENEVE_OPT &&
-		    nla_put(skb, OVS_TUNNEL_KEY_ATTR_GENEVE_OPTS,
+	if (output->tun_flags & TUNNEL_GENEVE_OPT) {
+		if (nla_put(skb, OVS_TUNNEL_KEY_ATTR_GENEVE_OPTS,
 			    swkey_tun_opts_len, tun_opts))
 			return -EMSGSIZE;
-		else if (output->tun_flags & TUNNEL_VXLAN_OPT &&
-			 vxlan_opt_to_nlattr(skb, tun_opts, swkey_tun_opts_len))
+	} else if (swkey_tun_opts_len) {
+		if (output->tun_flags & TUNNEL_VXLAN_OPT &&
+		    vxlan_opt_to_nlattr(skb, tun_opts, swkey_tun_opts_len))
 			return -EMSGSIZE;
 		else if (output->tun_flags & TUNNEL_ERSPAN_OPT &&
 			 nla_put(skb, OVS_TUNNEL_KEY_ATTR_ERSPAN_OPTS,
-- 
2.7.4