netdev - Re: [PATCH net] udp: prevent skbs lingering in tunnel socket queues

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Message-ID: <CAM_iQpXOxcT+P2mxF9okdeD2d-=mXXxba6c-AQk-hgv7qian2A@mail.gmail.com>
Date:	Thu, 19 May 2016 15:33:34 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net] udp: prevent skbs lingering in tunnel socket queues

On Thu, May 19, 2016 at 6:58 AM, Hannes Frederic Sowa
<hannes@...essinduktion.org> wrote:
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 2e3ebfe5549ef5..d56c0559b477cb 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1565,7 +1565,7 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
>
>                 /* if we're overly short, let UDP handle it */
>                 encap_rcv = ACCESS_ONCE(up->encap_rcv);
> -               if (skb->len > sizeof(struct udphdr) && encap_rcv) {
> +               if (encap_rcv) {


I don't think you can just remove it here, l2tp_udp_recv_core() still
relies on it:

        /* UDP has verifed checksum */

        /* UDP always verifies the packet length. */
        __skb_pull(skb, sizeof(struct udphdr));