[IPSEC]: Added xfrm_decode_session_reverse and xfrmX_policy_check_reverse

RFC 4301 requires us to relookup ICMP traffic that does not match any
policies using the reverse of its payload.  This patch adds the functions
xfrm_decode_session_reverse and xfrmX_policy_check_reverse so we can get
the reverse flow to perform such a lookup.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 59 insertions, 5 deletions

diff --git a/include/linux/xfrm.h b/include/linux/xfrm.h
index b58adc52448d..c0e41e02234f 100644
--- a/include/linux/xfrm.h
+++ b/include/linux/xfrm.h
@@ -114,6 +114,7 @@ enum
         XFRM_POLICY_IN  = 0,
         XFRM_POLICY_OUT = 1,
         XFRM_POLICY_FWD = 2,
+        XFRM_POLICY_MASK = 3,
         XFRM_POLICY_MAX = 3
 };
 
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index fe881b6e2bd0..d6dae5ae7abe 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -239,7 +239,8 @@ struct xfrm_policy_afinfo {
         int                     (*get_saddr)(xfrm_address_t *saddr, xfrm_address_t *daddr);
         struct dst_entry        *(*find_bundle)(struct flowi *fl, struct xfrm_policy *policy);
         void                    (*decode_session)(struct sk_buff *skb,
-                                                  struct flowi *fl);
+                                                  struct flowi *fl,
+                                                  int reverse);
         int                     (*get_tos)(struct flowi *fl);
         int                     (*fill_dst)(struct xfrm_dst *xdst,
                                             struct net_device *dev);
@@ -844,14 +845,23 @@ xfrm_state_addr_cmp(struct xfrm_tmpl *tmpl, struct xfrm_state *x, unsigned short
 #ifdef CONFIG_XFRM
 extern int __xfrm_policy_check(struct sock *, int dir, struct sk_buff *skb, unsigned short family);
 
-static inline int xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb, unsigned short family)
+static inline int __xfrm_policy_check2(struct sock *sk, int dir,
+                                       struct sk_buff *skb,
+                                       unsigned int family, int reverse)
 {
+        int ndir = dir | (reverse ? XFRM_POLICY_MASK + 1 : 0);
+
         if (sk && sk->sk_policy[XFRM_POLICY_IN])
-                return __xfrm_policy_check(sk, dir, skb, family);
+                return __xfrm_policy_check(sk, ndir, skb, family);
 
         return  (!xfrm_policy_count[dir] && !skb->sp) ||
                 (skb->dst->flags & DST_NOPOLICY) ||
-                __xfrm_policy_check(sk, dir, skb, family);
+                __xfrm_policy_check(sk, ndir, skb, family);
+}
+
+static inline int xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb, unsigned short family)
+{
+        return __xfrm_policy_check2(sk, dir, skb, family, 0);
 }
 
 static inline int xfrm4_policy_check(struct sock *sk, int dir, struct sk_buff *skb)
@@ -864,7 +874,34 @@ static inline int xfrm6_policy_check(struct sock *sk, int dir, struct sk_buff *s
         return xfrm_policy_check(sk, dir, skb, AF_INET6);
 }
 
-extern int xfrm_decode_session(struct sk_buff *skb, struct flowi *fl, unsigned short family);
+static inline int xfrm4_policy_check_reverse(struct sock *sk, int dir,
+                                             struct sk_buff *skb)
+{
+        return __xfrm_policy_check2(sk, dir, skb, AF_INET, 1);
+}
+
+static inline int xfrm6_policy_check_reverse(struct sock *sk, int dir,
+                                             struct sk_buff *skb)
+{
+        return __xfrm_policy_check2(sk, dir, skb, AF_INET6, 1);
+}
+
+extern int __xfrm_decode_session(struct sk_buff *skb, struct flowi *fl,
+                                 unsigned int family, int reverse);
+
+static inline int xfrm_decode_session(struct sk_buff *skb, struct flowi *fl,
+                                      unsigned int family)
+{
+        return __xfrm_decode_session(skb, fl, family, 0);
+}
+
+static inline int xfrm_decode_session_reverse(struct sk_buff *skb,
+                                              struct flowi *fl,
+                                              unsigned int family)
+{
+        return __xfrm_decode_session(skb, fl, family, 1);
+}
+
 extern int __xfrm_route_forward(struct sk_buff *skb, unsigned short family);
 
 static inline int xfrm_route_forward(struct sk_buff *skb, unsigned short family)
@@ -925,6 +962,22 @@ static inline int xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *sk
 {
         return 1;
 }
+static inline int xfrm_decode_session_reverse(struct sk_buff *skb,
+                                              struct flowi *fl,
+                                              unsigned int family)
+{
+        return -ENOSYS;
+}
+static inline int xfrm4_policy_check_reverse(struct sock *sk, int dir,
+                                             struct sk_buff *skb)
+{
+        return 1;
+}
+static inline int xfrm6_policy_check_reverse(struct sock *sk, int dir,
+                                             struct sk_buff *skb)
+{
+        return 1;
+}
 #endif
 
 static __inline__