Re: [PATCH net-next v4 1/3] net: nexthop: add NHA_DST_PORT for fdb nexthops

On 7/22/26 7:17 PM, Jack Ma wrote:

Commit 1274e1cc4226 ("vxlan: ecmp support for mac fdb entries") lets a
single inner MAC be reached through a group of remote VTEPs, with the
kernel flow-hashing across the group members.  Each member carries its
own remote IP, but the UDP destination port is always taken from the
VXLAN device (vxlan->cfg.dst_port) and cannot be set per member.

Some deployments pack several receivers behind one underlay IP and tell
them apart by UDP port, so they need a per-nexthop destination port to
spread flows across (IP, port) tuples rather than IP alone.

Add a netlink attribute NHA_DST_PORT (__be16, mirroring NDA_PORT) that
carries an optional UDP destination port on an fdb nexthop.  It is only
accepted together with NHA_FDB and NHA_GATEWAY; it is stored in struct
nh_info and echoed back on dump.  The attribute is named generically
rather than fdb-specific so it can be reused should another nexthop type
ever need a destination port.  This patch is control-plane plumbing
only; the VXLAN datapath is wired up in a follow-up patch, so behaviour
is unchanged for now.

Signed-off-by: Jack Ma <redacted>
---
 include/net/nexthop.h        |  2 ++
 include/uapi/linux/nexthop.h |  3 +++
 net/ipv4/nexthop.c           | 20 +++++++++++++++++++-
 3 files changed, 24 insertions(+), 1 deletion(-)

Reviewed-by: David Ahern <dsahern@kernel.org>