Re: [PATCH] udp: Correctly look up outbound socket with port remappings

[Stefano Brivio <sbrivio@redhat.com>]

On Wed, 24 Apr 2024 11:05:34 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> Commit bb9bf0bb ("tcp, udp: Don't precompute port remappings in epoll
> references") changed the epoll reference for UDP sockets to include the
> bound port as seen by the socket itself, rather than the bound port it
> would be translated to on the guest side.  As a side effect, it also means
> that udp_tap_map[] is indexed by the bound port on the host side, rather
> than on the guest side.  This is consistent and a good idea, however we
> forgot to account for it when finding the correct outgoing socket for
> packets originating in the guest.  This means that if forwarding UDP
> inbound with a port number change, reply packets would be misdirected.
> 
> Fix this by applying the reverse mapping before looking up the socket in
> udp_tap_handler().  While we're at it, use 'port' directly instead of
> 'uref.port' in udp_sock_init().  Those now always have the same value -
> failing to realise that is the same error as above.
> 
> Link: https://bugs.passt.top/show_bug.cgi?id=87
> Fixes: bb9bf0bb ("tcp, udp: Don't precompute port remappings in epoll
>                   references")
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Applied.

-- 
Stefano