linux-kernel - Re: Sending 802.1Q packets using AF_PACKET socket on filtered bridge forwards with wrong MAC addresses

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Message-ID: <CAPpVWGtgf1cLBq0fyXKbZnzAgzvoX2mm3sLYm5QS7us5H-0XKQ@mail.gmail.com>
Date:   Wed, 29 Nov 2017 14:01:11 -0800
From:   Brandon Carpenter <brandon.carpenter@...herpath.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Sending 802.1Q packets using AF_PACKET socket on filtered bridge
 forwards with wrong MAC addresses

I narrowed the search to a memmove() called from
skb_reorder_vlan_header() in net/core/skbuff.c.

>     memmove(skb->data - ETH_HLEN, skb->data - skb->mac_len - VLAN_HLEN,
>        2 * ETH_ALEN);

Calling skb_reset_mac_len() after skb_reset_mac_header() before
calling br_allowed_ingress() in net/bridge/br_device.c fixes the
problem.

diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index af5b8c87f590..e10131e2f68f 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -58,6 +58,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct
net_device *dev)
        BR_INPUT_SKB_CB(skb)->brdev = dev;

        skb_reset_mac_header(skb);
+       skb_reset_mac_len(skb);
        eth = eth_hdr(skb);
        skb_pull(skb, ETH_HLEN);

I'll put together an official patch  and submit it. Should I use
another email account? Are my emails being ignored because of that
stupid disclaimer my employer attaches to my messages (outside my
control)?

Brandon

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