Re: [PATCH net-next v2 2/3] vxlan: honor per-nexthop fdb destination port

[Ido Schimmel <idosch@nvidia.com>]

On Fri, Jul 17, 2026 at 06:45:17AM +0000, Jack Ma wrote:
> 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)

Alignment is off

>  {
>  	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)

Remove the check given 'fdb_port' is never NULL?

> +		*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
>