seg6: Extend seg6_lookup_any_nexthop() with an oif argument

seg6_lookup_any_nexthop() is called by the different endpoint behaviors
(e.g., End, End.X) to resolve an IPv6 route. Extend the function with an
output interface argument so that it could be used to resolve a route
with a certain output interface. This will be used by subsequent patches
that will extend the End.X behavior with an output interface as an
optional argument.

ip6_route_input_lookup() cannot be used when an output interface is
specified as it ignores this parameter. Similarly, calling
ip6_pol_route() when a table ID was not specified (e.g., End.X behavior)
is wrong.

Therefore, when an output interface is specified without a table ID,
resolve the route using ip6_route_output() which will take the output
interface into account.

Note that no endpoint behavior currently passes both a table ID and an
output interface, so the oif argument passed to ip6_pol_route() is
always zero and there are no functional changes in this regard.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Link: https://patch.msgid.link/20250612122323.584113-2-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 10 insertions, 7 deletions

diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index a11a02b4ba95..8bce7512df97 100644
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -270,7 +270,7 @@ static void advance_nextseg(struct ipv6_sr_hdr *srh, struct in6_addr *daddr)
 
 static int
 seg6_lookup_any_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
-			u32 tbl_id, bool local_delivery)
+			u32 tbl_id, bool local_delivery, int oif)
 {
 	struct net *net = dev_net(skb->dev);
 	struct ipv6hdr *hdr = ipv6_hdr(skb);
@@ -282,6 +282,7 @@ seg6_lookup_any_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
 
 	memset(&fl6, 0, sizeof(fl6));
 	fl6.flowi6_iif = skb->dev->ifindex;
+	fl6.flowi6_oif = oif;
 	fl6.daddr = nhaddr ? *nhaddr : hdr->daddr;
 	fl6.saddr = hdr->saddr;
 	fl6.flowlabel = ip6_flowinfo(hdr);
@@ -291,17 +292,19 @@ seg6_lookup_any_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
 	if (nhaddr)
 		fl6.flowi6_flags = FLOWI_FLAG_KNOWN_NH;
 
-	if (!tbl_id) {
+	if (!tbl_id && !oif) {
 		dst = ip6_route_input_lookup(net, skb->dev, &fl6, skb, flags);
-	} else {
+	} else if (tbl_id) {
 		struct fib6_table *table;
 
 		table = fib6_get_table(net, tbl_id);
 		if (!table)
 			goto out;
 
-		rt = ip6_pol_route(net, table, 0, &fl6, skb, flags);
+		rt = ip6_pol_route(net, table, oif, &fl6, skb, flags);
 		dst = &rt->dst;
+	} else {
+		dst = ip6_route_output(net, NULL, &fl6);
 	}
 
 	/* we want to discard traffic destined for local packet processing,
@@ -330,7 +333,7 @@ out:
 int seg6_lookup_nexthop(struct sk_buff *skb,
 			struct in6_addr *nhaddr, u32 tbl_id)
 {
-	return seg6_lookup_any_nexthop(skb, nhaddr, tbl_id, false);
+	return seg6_lookup_any_nexthop(skb, nhaddr, tbl_id, false, 0);
 }
 
 static __u8 seg6_flv_lcblock_octects(const struct seg6_flavors_info *finfo)
@@ -1277,7 +1280,7 @@ static int input_action_end_dt6(struct sk_buff *skb,
 	/* note: this time we do not need to specify the table because the VRF
 	 * takes care of selecting the correct table.
 	 */
-	seg6_lookup_any_nexthop(skb, NULL, 0, true);
+	seg6_lookup_any_nexthop(skb, NULL, 0, true, 0);
 
 	return dst_input(skb);
 
@@ -1285,7 +1288,7 @@ legacy_mode:
 #endif
 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
-	seg6_lookup_any_nexthop(skb, NULL, slwt->table, true);
+	seg6_lookup_any_nexthop(skb, NULL, slwt->table, true, 0);
 
 	return dst_input(skb);