[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>

1 files changed, 11 insertions, 6 deletions

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 3d516d57b5b2..2e10d46c0e8c 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1732,8 +1732,8 @@ xfrm_policy_ok(struct xfrm_tmpl *tmpl, struct sec_path *sp, int start,
         return start;
 }
 
-int
-xfrm_decode_session(struct sk_buff *skb, struct flowi *fl, unsigned short family)
+int __xfrm_decode_session(struct sk_buff *skb, struct flowi *fl,
+                          unsigned int family, int reverse)
 {
         struct xfrm_policy_afinfo *afinfo = xfrm_policy_get_afinfo(family);
         int err;
@@ -1741,12 +1741,12 @@ xfrm_decode_session(struct sk_buff *skb, struct flowi *fl, unsigned short family
         if (unlikely(afinfo == NULL))
                 return -EAFNOSUPPORT;
 
-        afinfo->decode_session(skb, fl);
+        afinfo->decode_session(skb, fl, reverse);
         err = security_xfrm_decode_session(skb, &fl->secid);
         xfrm_policy_put_afinfo(afinfo);
         return err;
 }
-EXPORT_SYMBOL(xfrm_decode_session);
+EXPORT_SYMBOL(__xfrm_decode_session);
 
 static inline int secpath_has_nontransport(struct sec_path *sp, int k, int *idxp)
 {
@@ -1768,11 +1768,16 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
         int npols = 0;
         int xfrm_nr;
         int pi;
+        int reverse;
         struct flowi fl;
-        u8 fl_dir = policy_to_flow_dir(dir);
+        u8 fl_dir;
         int xerr_idx = -1;
 
-        if (xfrm_decode_session(skb, &fl, family) < 0)
+        reverse = dir & ~XFRM_POLICY_MASK;
+        dir &= XFRM_POLICY_MASK;
+        fl_dir = policy_to_flow_dir(dir);
+
+        if (__xfrm_decode_session(skb, &fl, family, reverse) < 0)
                 return 0;
         nf_nat_decode_session(skb, &fl, family);