[PATCH 10/12] xfrm: Honor original L3 slave device in xfrmi policy lookup

[Steffen Klassert]

From: Martin Willi <mar...@strongswan.org>

If an xfrmi is associated to a vrf layer 3 master device,
xfrm_policy_check() fails after traffic decapsulation. The input
interface is replaced by the layer 3 master device, and hence
xfrmi_decode_session() can't match the xfrmi anymore to satisfy
policy checking.

Extend ingress xfrmi lookup to honor the original layer 3 slave
device, allowing xfrm interfaces to operate within a vrf domain.

Fixes: f203b76d7809 ("xfrm: Add virtual xfrm interfaces")
Signed-off-by: Martin Willi <mar...@strongswan.org>
Signed-off-by: Steffen Klassert <steffen.klass...@secunet.com>
---
 include/net/xfrm.h        |  3 ++-
 net/xfrm/xfrm_interface.c | 17 ++++++++++++++---
 net/xfrm/xfrm_policy.c    |  2 +-
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 902437dfbce7..c9b0b2b5d672 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -295,7 +295,8 @@ struct xfrm_replay {
 };
 
 struct xfrm_if_cb {
-       struct xfrm_if  *(*decode_session)(struct sk_buff *skb);
+       struct xfrm_if  *(*decode_session)(struct sk_buff *skb,
+                                          unsigned short family);
 };
 
 void xfrm_if_register_cb(const struct xfrm_if_cb *ifcb);
diff --git a/net/xfrm/xfrm_interface.c b/net/xfrm/xfrm_interface.c
index dbb3c1945b5c..85fec98676d3 100644
--- a/net/xfrm/xfrm_interface.c
+++ b/net/xfrm/xfrm_interface.c
@@ -70,17 +70,28 @@ static struct xfrm_if *xfrmi_lookup(struct net *net, struct 
xfrm_state *x)
        return NULL;
 }
 
-static struct xfrm_if *xfrmi_decode_session(struct sk_buff *skb)
+static struct xfrm_if *xfrmi_decode_session(struct sk_buff *skb,
+                                           unsigned short family)
 {
        struct xfrmi_net *xfrmn;
-       int ifindex;
        struct xfrm_if *xi;
+       int ifindex = 0;
 
        if (!secpath_exists(skb) || !skb->dev)
                return NULL;
 
+       switch (family) {
+       case AF_INET6:
+               ifindex = inet6_sdif(skb);
+               break;
+       case AF_INET:
+               ifindex = inet_sdif(skb);
+               break;
+       }
+       if (!ifindex)
+               ifindex = skb->dev->ifindex;
+
        xfrmn = net_generic(xs_net(xfrm_input_state(skb)), xfrmi_net_id);
-       ifindex = skb->dev->ifindex;
 
        for_each_xfrmi_rcu(xfrmn->xfrmi[0], xi) {
                if (ifindex == xi->dev->ifindex &&
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 8d1a898d0ba5..a6b58df7a70f 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -3313,7 +3313,7 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct 
sk_buff *skb,
        ifcb = xfrm_if_get_cb();
 
        if (ifcb) {
-               xi = ifcb->decode_session(skb);
+               xi = ifcb->decode_session(skb, family);
                if (xi) {
                        if_id = xi->p.if_id;
                        net = xi->net;
-- 
2.17.1