[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>

3 files changed, 21 insertions, 16 deletions

diff --git a/net/ipv4/xfrm4_policy.c b/net/ipv4/xfrm4_policy.c
index 10b72d185bb9..5ccae3a463c2 100644
--- a/net/ipv4/xfrm4_policy.c
+++ b/net/ipv4/xfrm4_policy.c
@@ -115,7 +115,7 @@ static int xfrm4_fill_dst(struct xfrm_dst *xdst, struct net_device *dev)
 }
 
 static void
-_decode_session4(struct sk_buff *skb, struct flowi *fl)
+_decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
 {
         struct iphdr *iph = ip_hdr(skb);
         u8 *xprth = skb_network_header(skb) + iph->ihl * 4;
@@ -131,8 +131,8 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl)
                         if (pskb_may_pull(skb, xprth + 4 - skb->data)) {
                                 __be16 *ports = (__be16 *)xprth;
 
-                                fl->fl_ip_sport = ports[0];
-                                fl->fl_ip_dport = ports[1];
+                                fl->fl_ip_sport = ports[!!reverse];
+                                fl->fl_ip_dport = ports[!reverse];
                         }
                         break;
 
@@ -174,8 +174,8 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl)
                 }
         }
         fl->proto = iph->protocol;
-        fl->fl4_dst = iph->daddr;
-        fl->fl4_src = iph->saddr;
+        fl->fl4_dst = reverse ? iph->saddr : iph->daddr;
+        fl->fl4_src = reverse ? iph->daddr : iph->saddr;
         fl->fl4_tos = iph->tos;
 }
 
diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c
index 181cf91538f1..d26b7dc3f33b 100644
--- a/net/ipv6/xfrm6_policy.c
+++ b/net/ipv6/xfrm6_policy.c
@@ -123,7 +123,7 @@ static int xfrm6_fill_dst(struct xfrm_dst *xdst, struct net_device *dev)
 }
 
 static inline void
-_decode_session6(struct sk_buff *skb, struct flowi *fl)
+_decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
 {
         u16 offset = skb_network_header_len(skb);
         struct ipv6hdr *hdr = ipv6_hdr(skb);
@@ -132,8 +132,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl)
         u8 nexthdr = nh[IP6CB(skb)->nhoff];
 
         memset(fl, 0, sizeof(struct flowi));
-        ipv6_addr_copy(&fl->fl6_dst, &hdr->daddr);
-        ipv6_addr_copy(&fl->fl6_src, &hdr->saddr);
+        ipv6_addr_copy(&fl->fl6_dst, reverse ? &hdr->saddr : &hdr->daddr);
+        ipv6_addr_copy(&fl->fl6_src, reverse ? &hdr->daddr : &hdr->saddr);
 
         while (pskb_may_pull(skb, nh + offset + 1 - skb->data)) {
                 nh = skb_network_header(skb);
@@ -156,8 +156,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl)
                         if (pskb_may_pull(skb, nh + offset + 4 - skb->data)) {
                                 __be16 *ports = (__be16 *)exthdr;
 
-                                fl->fl_ip_sport = ports[0];
-                                fl->fl_ip_dport = ports[1];
+                                fl->fl_ip_sport = ports[!!reverse];
+                                fl->fl_ip_dport = ports[!reverse];
                         }
                         fl->proto = nexthdr;
                         return;
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);