[3.8.y.z extended stable] Patch "vti: get rid of nf mark rule in prerouting" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    vti: get rid of nf mark rule in prerouting

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.13.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 44bdc4a2f8d3a25c81f768c7b92d5165e42dfd2d Mon Sep 17 00:00:00 2001
From: Christophe Gouault <christophe.gouault at 6wind.com>
Date: Tue, 8 Oct 2013 17:21:22 +0200
Subject: vti: get rid of nf mark rule in prerouting

[ Upstream commit 7263a5187f9e9de45fcb51349cf0e031142c19a1 ]

This patch fixes and improves the use of vti interfaces (while
lightly changing the way of configuring them).

Currently:

- it is necessary to identify and mark inbound IPsec
  packets destined to each vti interface, via netfilter rules in
  the mangle table at prerouting hook.

- the vti module cannot retrieve the right tunnel in input since
  commit b9959fd3: vti tunnels all have an i_key, but the tunnel lookup
  is done with flag TUNNEL_NO_KEY, so there no chance to retrieve them.

- the i_key is used by the outbound processing as a mark to lookup
  for the right SP and SA bundle.

This patch uses the o_key to store the vti mark (instead of i_key) and
enables:

- to avoid the need for previously marking the inbound skbuffs via a
  netfilter rule.
- to properly retrieve the right tunnel in input, only based on the IPsec
  packet outer addresses.
- to properly perform an inbound policy check (using the tunnel o_key
  as a mark).
- to properly perform an outbound SPD and SAD lookup (using the tunnel
  o_key as a mark).
- to keep the current mark of the skbuff. The skbuff mark is neither
  used nor changed by the vti interface. Only the vti interface o_key
  is used.

SAs have a wildcard mark.
SPs have a mark equal to the vti interface o_key.

The vti interface must be created as follows (i_key = 0, o_key = mark):

   ip link add vti1 mode vti local 1.1.1.1 remote 2.2.2.2 okey 1

The SPs attached to vti1 must be created as follows (mark = vti1 o_key):

   ip xfrm policy add dir out mark 1 tmpl src 1.1.1.1 dst 2.2.2.2 \
      proto esp mode tunnel
   ip xfrm policy add dir in  mark 1 tmpl src 2.2.2.2 dst 1.1.1.1 \
      proto esp mode tunnel

The SAs are created with the default wildcard mark. There is no
distinction between global vs. vti SAs. Just their addresses will
possibly link them to a vti interface:

   ip xfrm state add src 1.1.1.1 dst 2.2.2.2 proto esp spi 1000 mode tunnel \
                 enc "cbc(aes)" "azertyuiopqsdfgh"

   ip xfrm state add src 2.2.2.2 dst 1.1.1.1 proto esp spi 2000 mode tunnel \
                 enc "cbc(aes)" "sqbdhgqsdjqjsdfh"

To avoid matching "global" (not vti) SPs in vti interfaces, global SPs
should no use the default wildcard mark, but explicitly match mark 0.

To avoid a double SPD lookup in input and output (in global and vti SPDs),
the NOPOLICY and NOXFRM options should be set on the vti interfaces:

   echo 1 > /proc/sys/net/ipv4/conf/vti1/disable_policy
   echo 1 > /proc/sys/net/ipv4/conf/vti1/disable_xfrm

The outgoing traffic is steered to vti1 by a route via the vti interface:

   ip route add 192.168.0.0/16 dev vti1

The incoming IPsec traffic is steered to vti1 because its outer addresses
match the vti1 tunnel configuration.

Signed-off-by: Christophe Gouault <christophe.gouault at 6wind.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/ipv4/ip_vti.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
index 5ccf343..d011525 100644
--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -323,8 +323,17 @@ static int vti_rcv(struct sk_buff *skb)
 	tunnel = vti_tunnel_lookup(dev_net(skb->dev), iph->saddr, iph->daddr);
 	if (tunnel != NULL) {
 		struct pcpu_tstats *tstats;
+		u32 oldmark = skb->mark;
+		int ret;

-		if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
+
+		/* temporarily mark the skb with the tunnel o_key, to
+		 * only match policies with this mark.
+		 */
+		skb->mark = be32_to_cpu(tunnel->parms.o_key);
+		ret = xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb);
+		skb->mark = oldmark;
+		if (!ret)
 			return -1;

 		tstats = this_cpu_ptr(tunnel->dev->tstats);
@@ -333,7 +342,6 @@ static int vti_rcv(struct sk_buff *skb)
 		tstats->rx_bytes += skb->len;
 		u64_stats_update_end(&tstats->syncp);

-		skb->mark = 0;
 		secpath_reset(skb);
 		skb->dev = tunnel->dev;
 		return 1;
@@ -365,7 +373,7 @@ static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)

 	memset(&fl4, 0, sizeof(fl4));
 	flowi4_init_output(&fl4, tunnel->parms.link,
-			   be32_to_cpu(tunnel->parms.i_key), RT_TOS(tos),
+			   be32_to_cpu(tunnel->parms.o_key), RT_TOS(tos),
 			   RT_SCOPE_UNIVERSE,
 			   IPPROTO_IPIP, 0,
 			   dst, tiph->saddr, 0, 0);
--
1.8.1.2