netdev - Re: [PATCH net] net/sched: act_mirred: Pull mac prior redir to non mac_header

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Message-Id: <20191227.163622.1874013727124631819.davem@davemloft.net>
Date:   Fri, 27 Dec 2019 16:36:22 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     shmulik@...anetworks.com
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        netdev@...r.kernel.org, shmulik.ladkani@...il.com,
        sladkani@...ofpoint.com
Subject: Re: [PATCH net] net/sched: act_mirred: Pull mac prior redir to non
 mac_header_xmit device

From: shmulik@...anetworks.com
Date: Wed, 25 Dec 2019 10:51:01 +0200

> From: Shmulik Ladkani <sladkani@...ofpoint.com>
> 
> There's no skb_pull performed when a mirred action is set at egress of a
> mac device, with a target device/action that expects skb->data to point
> at the network header.
> 
> As a result, either the target device is errornously given an skb with
> data pointing to the mac (egress case), or the net stack receives the
> skb with data pointing to the mac (ingress case).
> 
> E.g:
>  # tc qdisc add dev eth9 root handle 1: prio
>  # tc filter add dev eth9 parent 1: prio 9 protocol ip handle 9 basic \
>    action mirred egress redirect dev tun0
> 
>  (tun0 is a tun device. result: tun0 errornously gets the eth header
>   instead of the iph)
> 
> Revise the push/pull logic of tcf_mirred_act() to not rely on the
> skb_at_tc_ingress() vs tcf_mirred_act_wants_ingress() comparison, as it
> does not cover all "pull" cases.
> 
> Instead, calculate whether the required action on the target device
> requires the data to point at the network header, and compare this to
> whether skb->data points to network header - and make the push/pull
> adjustments as necessary.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Shmulik Ladkani <sladkani@...ofpoint.com>
> Tested-by: Jamal Hadi Salim <jhs@...atatu.com>
> Acked-by: Jamal Hadi Salim <jhs@...atatu.com>

Applied and queued up for -stable.