netdev - Re: [PATCHv3 net-next 1/2] udp: call udp_encap_enable for v6 sockets when enabling encap

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Message-ID: <CAKgT0Ud+mjksk1HWpLUSWziGUq9ZQLO33GiVHQtJhoCOpM0zUQ@mail.gmail.com>
Date:   Tue, 19 Jan 2021 14:17:46 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Martin Varghese <martin.varghese@...ia.com>
Subject: Re: [PATCHv3 net-next 1/2] udp: call udp_encap_enable for v6 sockets
 when enabling encap

On Fri, Jan 15, 2021 at 8:34 PM Xin Long <lucien.xin@...il.com> wrote:
>
> When enabling encap for a ipv6 socket without udp_encap_needed_key
> increased, UDP GRO won't work for v4 mapped v6 address packets as
> sk will be NULL in udp4_gro_receive().
>
> This patch is to enable it by increasing udp_encap_needed_key for
> v6 sockets in udp_tunnel_encap_enable(), and correspondingly
> decrease udp_encap_needed_key in udpv6_destroy_sock().
>
> v1->v2:
>   - add udp_encap_disable() and export it.
>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  include/net/udp.h        | 1 +
>  include/net/udp_tunnel.h | 3 +--
>  net/ipv4/udp.c           | 6 ++++++
>  net/ipv6/udp.c           | 4 +++-
>  4 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/include/net/udp.h b/include/net/udp.h
> index 877832b..1e7b6cd 100644
> --- a/include/net/udp.h
> +++ b/include/net/udp.h
> @@ -467,6 +467,7 @@ void udp_init(void);
>
>  DECLARE_STATIC_KEY_FALSE(udp_encap_needed_key);
>  void udp_encap_enable(void);
> +void udp_encap_disable(void);
>  #if IS_ENABLED(CONFIG_IPV6)
>  DECLARE_STATIC_KEY_FALSE(udpv6_encap_needed_key);
>  void udpv6_encap_enable(void);
> diff --git a/include/net/udp_tunnel.h b/include/net/udp_tunnel.h
> index 282d10e..afc7ce7 100644
> --- a/include/net/udp_tunnel.h
> +++ b/include/net/udp_tunnel.h
> @@ -181,9 +181,8 @@ static inline void udp_tunnel_encap_enable(struct socket *sock)
>  #if IS_ENABLED(CONFIG_IPV6)
>         if (sock->sk->sk_family == PF_INET6)
>                 ipv6_stub->udpv6_encap_enable();
> -       else
>  #endif
> -               udp_encap_enable();
> +       udp_encap_enable();
>  }
>
>  #define UDP_TUNNEL_NIC_MAX_TABLES      4
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 7103b0a..28bfe60 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -596,6 +596,12 @@ void udp_encap_enable(void)
>  }
>  EXPORT_SYMBOL(udp_encap_enable);
>
> +void udp_encap_disable(void)
> +{
> +       static_branch_dec(&udp_encap_needed_key);
> +}
> +EXPORT_SYMBOL(udp_encap_disable);
> +
>  /* Handler for tunnels with arbitrary destination ports: no socket lookup, go
>   * through error handlers in encapsulations looking for a match.
>   */

So this seems unbalanced to me. We are adding/modifying one spot where
we are calling the enable function, but the other callers don't call
the disable function? Specifically I am curious about how to deal with
the rxrpc_open_socket usage.

If we don't balance out all the callers I am not sure adding the
udp_encap_disable makes much sense.

> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index b9f3dfd..d754292 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -1608,8 +1608,10 @@ void udpv6_destroy_sock(struct sock *sk)
>                         if (encap_destroy)
>                                 encap_destroy(sk);
>                 }
> -               if (up->encap_enabled)
> +               if (up->encap_enabled) {
>                         static_branch_dec(&udpv6_encap_needed_key);
> +                       udp_encap_disable();
> +               }
>         }
>
>         inet6_destroy_sock(sk);
> --
> 2.1.0
>