[PATCH 3.11 24/66] vti: get rid of nf mark rule in prerouting

Greg Kroah-Hartman
2013-11-01T22:08:07Z

From: Christophe Gouault <christophe.gouault@6wind.com>

[ 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@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/ip_vti.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -285,8 +285,17 @@ 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);
@@ -295,7 +304,6 @@ 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;
@@ -327,7 +335,7 @@ static netdev_tx_t vti_tunnel_xmit(struc

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);