compat: Backport ipv6_stub change

A patch backported to the Linux stable 4.14 tree and present in the
latest stable 4.14.181 kernel breaks ipv6_stub usage.

The commit is
8ab8786f78c3 ("net ipv6_stub: use ip6_dst_lookup_flow instead of ip6_dst_lookup").

Create the compat layer define to check for it and fixup usage in vxlan
and geneve modules.

Passes Travis here:
https://travis-ci.org/github/gvrose8192/ovs-experimental/builds/689798733

Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: William Tu <u9012063@gmail.com>

acinclude.m4

@@ -529,6 +529,8 @@ AC_DEFUN([OVS_CHECK_LINUX_COMPAT], [
   OVS_GREP_IFELSE([$KSRC/include/net/ip6_fib.h], [rt6_get_cookie],
                   [OVS_DEFINE([HAVE_RT6_GET_COOKIE])])
 
+  OVS_FIND_FIELD_IFELSE([$KSRC/include/net/addrconf.h], [ipv6_stub],
+                        [dst_entry])
   OVS_GREP_IFELSE([$KSRC/include/net/addrconf.h], [ipv6_dst_lookup.*net],
                   [OVS_DEFINE([HAVE_IPV6_DST_LOOKUP_NET])])
   OVS_GREP_IFELSE([$KSRC/include/net/addrconf.h], [ipv6_dst_lookup_flow.*net],

datapath/linux/compat/geneve.c

@@ -962,7 +962,16 @@ static struct dst_entry *geneve_get_v6_dst(struct sk_buff *skb,
 			return dst;
 	}
 
-#if defined(HAVE_IPV6_DST_LOOKUP_FLOW_NET)
+#if defined(HAVE_IPV6_STUB_WITH_DST_ENTRY) && defined(HAVE_IPV6_DST_LOOKUP_FLOW)
+#ifdef HAVE_IPV6_DST_LOOKUP_FLOW_NET
+	dst = ipv6_stub->ipv6_dst_lookup_flow(geneve->net, gs6->sock->sk, fl6,
+					      NULL);
+#else
+	dst = ipv6_stub->ipv6_dst_lookup_flow(gs6->sock->sk, fl6,
+					      NULL);
+#endif
+	if (IS_ERR(dst)) {
+#elif defined(HAVE_IPV6_DST_LOOKUP_FLOW_NET)
 	if (ipv6_stub->ipv6_dst_lookup_flow(geneve->net, gs6->sock->sk, &dst,
                                             fl6)) {
 #elif defined(HAVE_IPV6_DST_LOOKUP_FLOW)

datapath/linux/compat/vxlan.c

@@ -967,7 +967,10 @@ static struct dst_entry *vxlan6_get_route(struct vxlan_dev *vxlan,
 	bool use_cache = (dst_cache && ip_tunnel_dst_cache_usable(skb, info));
 	struct dst_entry *ndst;
 	struct flowi6 fl6;
+#if !defined(HAVE_IPV6_STUB_WITH_DST_ENTRY) || \
+    !defined(HAVE_IPV6_DST_LOOKUP_FLOW)
 	int err;
+#endif
 
 	if (!sock6)
 		return ERR_PTR(-EIO);
@@ -990,7 +993,15 @@ static struct dst_entry *vxlan6_get_route(struct vxlan_dev *vxlan,
 	fl6.fl6_dport = dport;
 	fl6.fl6_sport = sport;
 
-#if defined(HAVE_IPV6_DST_LOOKUP_FLOW_NET)
+#if defined(HAVE_IPV6_STUB_WITH_DST_ENTRY) && defined(HAVE_IPV6_DST_LOOKUP_FLOW)
+#ifdef HAVE_IPV6_DST_LOOKUP_FLOW_NET
+	ndst = ipv6_stub->ipv6_dst_lookup_flow(vxlan->net, sock6->sock->sk,
+					       &fl6, NULL);
+#else
+	ndst = ipv6_stub->ipv6_dst_lookup_flow(sock6->sock->sk, &fl6, NULL);
+#endif
+	if (unlikely(IS_ERR(ndst))) {
+#elif defined(HAVE_IPV6_DST_LOOKUP_FLOW_NET)
 	err = ipv6_stub->ipv6_dst_lookup_flow(vxlan->net, sock6->sock->sk,
 					      &ndst, &fl6);
 #elif defined(HAVE_IPV6_DST_LOOKUP_FLOW)
@@ -1004,8 +1015,13 @@ static struct dst_entry *vxlan6_get_route(struct vxlan_dev *vxlan,
 #else
 	err = ip6_dst_lookup(vxlan->vn6_sock->sock->sk, &ndst, &fl6);
 #endif
+#if defined(HAVE_IPV6_STUB_WITH_DST_ENTRY) && defined(HAVE_IPV6_DST_LOOKUP_FLOW)
+		return ERR_PTR(-ENETUNREACH);
+	}
+#else
 	if (err < 0)
 		return ERR_PTR(err);
+#endif
 
 	*saddr = fl6.saddr;
 	if (use_cache)