netdev - Re: [PATCH v4 net-next 1/2] udp_tunnel: create a fastpath GRO lookup.

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Message-ID: <67d1c87fa3783_38d99f29416@willemb.c.googlers.com.notmuch>
Date: Wed, 12 Mar 2025 13:46:39 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Paolo Abeni <pabeni@...hat.com>, 
 netdev@...r.kernel.org
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Simon Horman <horms@...nel.org>, 
 David Ahern <dsahern@...nel.org>, 
 kuniyu@...zon.com
Subject: Re: [PATCH v4 net-next 1/2] udp_tunnel: create a fastpath GRO lookup.

Paolo Abeni wrote:
> Most UDP tunnels bind a socket to a local port, with ANY address, no
> peer and no interface index specified.
> Additionally it's quite common to have a single tunnel device per
> namespace.
> 
> Track in each namespace the UDP tunnel socket respecting the above.
> When only a single one is present, store a reference in the netns.
> 
> When such reference is not NULL, UDP tunnel GRO lookup just need to
> match the incoming packet destination port vs the socket local port.
> 
> The tunnel socket never sets the reuse[port] flag[s]. When bound to no
> address and interface, no other socket can exist in the same netns
> matching the specified local port.
> 
> Matching packets with non-local destination addresses will be
> aggregated, and eventually segmented as needed - no behavior changes
> intended.
> 
> Note that the UDP tunnel socket reference is stored into struct
> netns_ipv4 for both IPv4 and IPv6 tunnels. That is intentional to keep
> all the fastpath-related netns fields in the same struct and allow
> cacheline-based optimization. Currently both the IPv4 and IPv6 socket
> pointer share the same cacheline as the `udp_table` field.
> 
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Reviewed-by: Willem de Bruijn <willemb@...gle.com>