Patchwork vlan: mask vlan prio bits

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Submitter Eric Dumazet
Date July 18, 2013, 2:19 p.m.
Message ID <1374157166.6097.28.camel@edumazet-glaptop>
Download mbox | patch
Permalink /patch/260072/
State Accepted
Delegated to: David Miller
Headers show

Comments

Eric Dumazet - July 18, 2013, 2:19 p.m.
From: Eric Dumazet <edumazet@google.com>

In commit 48cc32d38a52d0b68f91a171a8d00531edc6a46e
("vlan: don't deliver frames for unknown vlans to protocols")
Florian made sure we set pkt_type to PACKET_OTHERHOST
if the vlan id is set and we could find a vlan device for this
particular id.

But we also have a problem if prio bits are set.

Steinar reported an issue on a router receiving IPv6 frames with a
vlan tag of 4000 (id 0, prio 2), and tunneled into a sit device,
because skb->vlan_tci is set.

Forwarded frame is completely corrupted : We can see (8100:4000)
being inserted in the middle of IPv6 source address :

16:48:00.780413 IP6 2001:16d8:8100:4000:ee1c:0:9d9:bc87 >
9f94:4d95:2001:67c:29f4::: ICMP6, unknown icmp6 type (0), length 64
       0x0000:  0000 0029 8000 c7c3 7103 0001 a0ae e651
       0x0010:  0000 0000 ccce 0b00 0000 0000 1011 1213
       0x0020:  1415 1617 1819 1a1b 1c1d 1e1f 2021 2223
       0x0030:  2425 2627 2829 2a2b 2c2d 2e2f 3031 3233

It seems we are not really ready to properly cope with this right now.

We can probably do better in future kernels : 
vlan_get_ingress_priority() should be a netdev property instead of
a per vlan_dev one.

For stable kernels, lets clear vlan_tci to fix the bugs.

Reported-by: Steinar H. Gunderson <sesse@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/if_vlan.h |    3 +--
 net/8021q/vlan_core.c   |    2 +-
 net/core/dev.c          |   11 +++++++++--
 3 files changed, 11 insertions(+), 5 deletions(-)



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Eric Dumazet - July 18, 2013, 3:49 p.m.
On Thu, 2013-07-18 at 07:19 -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> In commit 48cc32d38a52d0b68f91a171a8d00531edc6a46e
> ("vlan: don't deliver frames for unknown vlans to protocols")
> Florian made sure we set pkt_type to PACKET_OTHERHOST
> if the vlan id is set and we could find a vlan device for this
> particular id.
> 
> But we also have a problem if prio bits are set.
> 
> Steinar reported an issue on a router receiving IPv6 frames with a
> vlan tag of 4000 (id 0, prio 2), and tunneled into a sit device,
> because skb->vlan_tci is set.
> 
> Forwarded frame is completely corrupted : We can see (8100:4000)
> being inserted in the middle of IPv6 source address :
> 
> 16:48:00.780413 IP6 2001:16d8:8100:4000:ee1c:0:9d9:bc87 >
> 9f94:4d95:2001:67c:29f4::: ICMP6, unknown icmp6 type (0), length 64
>        0x0000:  0000 0029 8000 c7c3 7103 0001 a0ae e651
>        0x0010:  0000 0000 ccce 0b00 0000 0000 1011 1213
>        0x0020:  1415 1617 1819 1a1b 1c1d 1e1f 2021 2223
>        0x0030:  2425 2627 2829 2a2b 2c2d 2e2f 3031 3233
> 
> It seems we are not really ready to properly cope with this right now.
> 
> We can probably do better in future kernels : 
> vlan_get_ingress_priority() should be a netdev property instead of
> a per vlan_dev one.
> 
> For stable kernels, lets clear vlan_tci to fix the bugs.
> 
> Reported-by: Steinar H. Gunderson <sesse@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---

While looking at the 'future' patches for net-next, I found
that vlan_dev_get_egress_qos_mask() uses no protection at all
while doing the lookup in hash table.

This is racy with concurrent insert/deletes, eventually.

This probably needs a bit of RCU care ;)


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David Miller - July 18, 2013, 8:05 p.m.
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 18 Jul 2013 07:19:26 -0700

> From: Eric Dumazet <edumazet@google.com>
> 
> In commit 48cc32d38a52d0b68f91a171a8d00531edc6a46e
> ("vlan: don't deliver frames for unknown vlans to protocols")
> Florian made sure we set pkt_type to PACKET_OTHERHOST
> if the vlan id is set and we could find a vlan device for this
> particular id.
> 
> But we also have a problem if prio bits are set.
> 
> Steinar reported an issue on a router receiving IPv6 frames with a
> vlan tag of 4000 (id 0, prio 2), and tunneled into a sit device,
> because skb->vlan_tci is set.
> 
> Forwarded frame is completely corrupted : We can see (8100:4000)
> being inserted in the middle of IPv6 source address :
> 
> 16:48:00.780413 IP6 2001:16d8:8100:4000:ee1c:0:9d9:bc87 >
> 9f94:4d95:2001:67c:29f4::: ICMP6, unknown icmp6 type (0), length 64
>        0x0000:  0000 0029 8000 c7c3 7103 0001 a0ae e651
>        0x0010:  0000 0000 ccce 0b00 0000 0000 1011 1213
>        0x0020:  1415 1617 1819 1a1b 1c1d 1e1f 2021 2223
>        0x0030:  2425 2627 2829 2a2b 2c2d 2e2f 3031 3233
> 
> It seems we are not really ready to properly cope with this right now.
> 
> We can probably do better in future kernels : 
> vlan_get_ingress_priority() should be a netdev property instead of
> a per vlan_dev one.
> 
> For stable kernels, lets clear vlan_tci to fix the bugs.
> 
> Reported-by: Steinar H. Gunderson <sesse@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied and queued up for -stable, thanks Eric.
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Patch

diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index cdcbafa..715c343 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -79,9 +79,8 @@  static inline int is_vlan_dev(struct net_device *dev)
 }
 
 #define vlan_tx_tag_present(__skb)	((__skb)->vlan_tci & VLAN_TAG_PRESENT)
-#define vlan_tx_nonzero_tag_present(__skb) \
-	(vlan_tx_tag_present(__skb) && ((__skb)->vlan_tci & VLAN_VID_MASK))
 #define vlan_tx_tag_get(__skb)		((__skb)->vlan_tci & ~VLAN_TAG_PRESENT)
+#define vlan_tx_tag_get_id(__skb)	((__skb)->vlan_tci & VLAN_VID_MASK)
 
 #if defined(CONFIG_VLAN_8021Q) || defined(CONFIG_VLAN_8021Q_MODULE)
 
diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index 8a15eaa..4a78c4d 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -9,7 +9,7 @@  bool vlan_do_receive(struct sk_buff **skbp)
 {
 	struct sk_buff *skb = *skbp;
 	__be16 vlan_proto = skb->vlan_proto;
-	u16 vlan_id = skb->vlan_tci & VLAN_VID_MASK;
+	u16 vlan_id = vlan_tx_tag_get_id(skb);
 	struct net_device *vlan_dev;
 	struct vlan_pcpu_stats *rx_stats;
 
diff --git a/net/core/dev.c b/net/core/dev.c
index a3d8d44..26755dd 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3580,8 +3580,15 @@  ncls:
 		}
 	}
 
-	if (vlan_tx_nonzero_tag_present(skb))
-		skb->pkt_type = PACKET_OTHERHOST;
+	if (unlikely(vlan_tx_tag_present(skb))) {
+		if (vlan_tx_tag_get_id(skb))
+			skb->pkt_type = PACKET_OTHERHOST;
+		/* Note: we might in the future use prio bits
+		 * and set skb->priority like in vlan_do_receive()
+		 * For the time being, just ignore Priority Code Point
+		 */
+		skb->vlan_tci = 0;
+	}
 
 	/* deliver only exact match when indicated */
 	null_or_dev = deliver_exact ? skb->dev : NULL;