netdev - Re: [PATCH] udp: compute_score and sk_bound_dev

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Message-ID: <CA+FuTSf7WbEN_yhf_LR9RxZzgxHUcdb-OeMEA2--rci+HN2dqw@mail.gmail.com>
Date:   Wed, 9 Jun 2021 15:44:45 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Peter Kosyh <p.kosyh@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Mikhail Smirnov <smirnov@...tor-ts.ru>,
        "David S. Miller" <davem@...emloft.net>,
        mmanning@...tta.att-mail.com
Subject: Re: [PATCH] udp: compute_score and sk_bound_dev_if regression

On Wed, Jun 9, 2021 at 11:50 AM Peter Kosyh <p.kosyh@...il.com> wrote:
>
>
> udp: commit 6da5b0f027a825df2aebc1927a27bda185dc03d4

For completeness, this is commit 6da5b0f027a8 ("net: ensure unbound
datagram socket to be chosen when not in a VRF"). Adding the author.

> introduced regression in compute_score() Previously for addr_any sockets an
> interface bound socket had a higher priority than an unbound socket that
> seems right. For example, this feature is used in dhcprelay daemon and now it
> is broken.
> So, this patch returns the old behavior and gives higher score for sk_bound_dev_if sockets.
>
> Signed-off-by: Peter Kosyh <p.kosyh@...il.com>
> ---
>  net/ipv4/udp.c | 3 ++-
>  net/ipv6/udp.c | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 15f5504adf5b..4239ffa93c6f 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -390,7 +390,8 @@ static int compute_score(struct sock *sk, struct net *net,
>                                         dif, sdif);
>         if (!dev_match)
>                 return -1;
> -       score += 4;
> +       if (sk->sk_bound_dev_if)
> +               score += 4;
>
>         if (READ_ONCE(sk->sk_incoming_cpu) == raw_smp_processor_id())
>                 score++;
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index 199b080d418a..c2f88b5def25 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -133,7 +133,8 @@ static int compute_score(struct sock *sk, struct net *net,
>         dev_match = udp_sk_bound_dev_eq(net, sk->sk_bound_dev_if, dif, sdif);
>         if (!dev_match)
>                 return -1;
> -       score++;
> +       if (sk->sk_bound_dev_if)
> +               score++;
>
>         if (READ_ONCE(sk->sk_incoming_cpu) == raw_smp_processor_id())
>                 score++;
> --
> 2.31.1