[PATCH net-next 2/3] vxlan: honor per-nexthop fdb destination port

[Jack Ma <jack4it@gmail.com>]

When an fdb entry points at a nexthop group, vxlan_fdb_nh_path_select()
resolves the selected leg's remote IP but leaves the UDP destination port
at the device default (vxlan->cfg.dst_port).

Extend nexthop_path_fdb_result() to also return the selected nexthop's
NHA_FDB_PORT (0 when unset) and have vxlan_fdb_nh_path_select() store it
in rdst->remote_port.  vxlan_xmit_one() already prefers rdst->remote_port
when non-zero and falls back to the device port otherwise, so nexthops
without a port are unaffected.

This lets one fdb nexthop group load-balance a flow across legs that
share an underlay IP but differ in UDP destination port.

Signed-off-by: Jack Ma <jack4it@gmail.com>
---
 include/net/nexthop.h | 5 ++++-
 include/net/vxlan.h   | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/net/nexthop.h b/include/net/nexthop.h
index 9c8227996..7fb612a73 100644
--- a/include/net/nexthop.h
+++ b/include/net/nexthop.h
@@ -576,7 +576,8 @@ struct fib_nh_common *nexthop_fdb_nhc(struct nexthop *nh)
 }
 
 static inline struct fib_nh_common *nexthop_path_fdb_result(struct nexthop *nh,
-							    int hash)
+						    int hash,
+						    __be16 *fdb_port)
 {
 	struct nh_info *nhi;
 	struct nexthop *nhp;
@@ -585,6 +586,8 @@ static inline struct fib_nh_common *nexthop_path_fdb_result(struct nexthop *nh,
 	if (unlikely(!nhp))
 		return NULL;
 	nhi = rcu_dereference(nhp->nh_info);
+	if (fdb_port)
+		*fdb_port = nhi->fdb_port;
 	return &nhi->fib_nhc;
 }
 #endif
diff --git a/include/net/vxlan.h b/include/net/vxlan.h
index dfba89695..de41b3746 100644
--- a/include/net/vxlan.h
+++ b/include/net/vxlan.h
@@ -567,8 +567,9 @@ static inline bool vxlan_fdb_nh_path_select(struct nexthop *nh,
 					    struct vxlan_rdst *rdst)
 {
 	struct fib_nh_common *nhc;
+	__be16 fdb_port = 0;
 
-	nhc = nexthop_path_fdb_result(nh, hash >> 1);
+	nhc = nexthop_path_fdb_result(nh, hash >> 1, &fdb_port);
 	if (unlikely(!nhc))
 		return false;
 
@@ -583,6 +584,8 @@ static inline bool vxlan_fdb_nh_path_select(struct nexthop *nh,
 		break;
 	}
 
+	rdst->remote_port = fdb_port;
+
 	return true;
 }
 
-- 
2.43.0