[SRU][Trusty][PATCH v2 2/4] netfilter: bridge: restore vlan tag when refragmenting

[Jay Vosburgh]

From: Florian Westphal <fw at strlen.de>

BugLink: https://bugs.launchpad.net/nova/+bug/1463911

If bridge netfilter is used with both
bridge-nf-call-iptables and bridge-nf-filter-vlan-tagged enabled
then ip fragments in VLAN frames are sent without the vlan header.

This has never worked reliably.  Turns out this relied on pre-3.5
behaviour where skb frag_list was used to store ip fragments;
ip_fragment() then re-used these skbs.

But since commit 3cc4949269e01f39443d0fcfffb5bc6b47878d45
("ipv4: use skb coalescing in defragmentation") this is no longer
the case.  ip_do_fragment now needs to allocate new skbs, but these
don't contain the vlan tag information anymore.

Fix it by storing vlan information of the ressembled skb in the
br netfilter percpu frag area, and restore them for each of the
fragments.

Fixes: 3cc4949269e01f3 ("ipv4: use skb coalescing in defragmentation")
Signed-off-by: Florian Westphal <fw at strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
(backported from commit d7b597421519d6f680eb8e152a0d8447466ee2d6)
Signed-off-by: Jay Vosburgh <jay.vosburgh at canonical.com>
---
 net/bridge/br_netfilter.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index 6143a6f37c0e..247b5584d39a 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -179,6 +179,8 @@ struct brnf_frag_data {
 	char mac[NF_BRIDGE_MAX_MAC_HEADER_LENGTH];
 	u8 encap_size;
 	u8 size;
+	u16 vlan_tci;
+	__be16 vlan_proto;
 };
 
 static DEFINE_PER_CPU(struct brnf_frag_data, brnf_frag_data_storage);
@@ -886,6 +888,11 @@ static int br_nf_push_frag_xmit(struct sk_buff *skb)
 		return 0;
 	}
 
+	if (data->vlan_tci) {
+		skb->vlan_tci = data->vlan_tci;
+		skb->vlan_proto = data->vlan_proto;
+	}
+
 	skb_copy_to_linear_data_offset(skb, -data->size, data->mac, data->size);
 	__skb_push(skb, data->encap_size);
 
@@ -908,6 +915,9 @@ static int br_nf_dev_queue_xmit(struct sk_buff *skb)
 		nf_bridge_update_protocol(skb);
 
 		data = this_cpu_ptr(&brnf_frag_data_storage);
+
+		data->vlan_tci = skb->vlan_tci;
+		data->vlan_proto = skb->vlan_proto;
 		data->encap_size = nf_bridge_encap_header_len(skb);
 		data->size = ETH_HLEN + data->encap_size;
 
-- 
1.9.1