[XFRM]: Netfilter IPsec output hooks

Call netfilter hooks before IPsec transforms. Packets visit the
FORWARD/LOCAL_OUT and POST_ROUTING hook before the first encapsulation
and the LOCAL_OUT and POST_ROUTING hook before each following tunnel mode
transform.

Patch from Herbert Xu <herbert@gondor.apana.org.au>:

Move the loop from dst_output into xfrm4_output/xfrm6_output since they're
the only ones who need to it. xfrm{4,6}_output_one() processes the first SA
all subsequent transport mode SAs and is called in a loop that calls the
netfilter hooks between each two calls.

In order to avoid the tail call issue, I've added the inline function
nf_hook which is nf_hook_slow plus the empty list check.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 54 insertions, 17 deletions

diff --git a/net/ipv4/xfrm4_output.c b/net/ipv4/xfrm4_output.c
index 66620a95942..51fabb8f7c5 100644
--- a/net/ipv4/xfrm4_output.c
+++ b/net/ipv4/xfrm4_output.c
@@ -8,8 +8,10 @@
  * 2 of the License, or (at your option) any later version.
  */
 
+#include <linux/compiler.h>
 #include <linux/skbuff.h>
 #include <linux/spinlock.h>
+#include <linux/netfilter_ipv4.h>
 #include <net/inet_ecn.h>
 #include <net/ip.h>
 #include <net/xfrm.h>
@@ -95,7 +97,7 @@ out:
         return ret;
 }
 
-int xfrm4_output(struct sk_buff *skb)
+static int xfrm4_output_one(struct sk_buff *skb)
 {
         struct dst_entry *dst = skb->dst;
         struct xfrm_state *x = dst->xfrm;
@@ -113,27 +115,32 @@ int xfrm4_output(struct sk_buff *skb)
                         goto error_nolock;
         }
 
-        spin_lock_bh(&x->lock);
-        err = xfrm_state_check(x, skb);
-        if (err)
-                goto error;
+        do {
+                spin_lock_bh(&x->lock);
+                err = xfrm_state_check(x, skb);
+                if (err)
+                        goto error;
 
-        xfrm4_encap(skb);
+                xfrm4_encap(skb);
 
-        err = x->type->output(x, skb);
-        if (err)
-                goto error;
+                err = x->type->output(x, skb);
+                if (err)
+                        goto error;
 
-        x->curlft.bytes += skb->len;
-        x->curlft.packets++;
+                x->curlft.bytes += skb->len;
+                x->curlft.packets++;
 
-        spin_unlock_bh(&x->lock);
+                spin_unlock_bh(&x->lock);
         
-        if (!(skb->dst = dst_pop(dst))) {
-                err = -EHOSTUNREACH;
-                goto error_nolock;
-        }
-        err = NET_XMIT_BYPASS;
+                if (!(skb->dst = dst_pop(dst))) {
+                        err = -EHOSTUNREACH;
+                        goto error_nolock;
+                }
+                dst = skb->dst;
+                x = dst->xfrm;
+        } while (x && !x->props.mode);
+
+        err = 0;
 
 out_exit:
         return err;
@@ -143,3 +150,33 @@ error_nolock:
         kfree_skb(skb);
         goto out_exit;
 }
+
+static int xfrm4_output_finish(struct sk_buff *skb)
+{
+        int err;
+
+        while (likely((err = xfrm4_output_one(skb)) == 0)) {
+                nf_reset(skb);
+
+                err = nf_hook(PF_INET, NF_IP_LOCAL_OUT, &skb, NULL,
+                              skb->dst->dev, dst_output);
+                if (unlikely(err != 1))
+                        break;
+
+                if (!skb->dst->xfrm)
+                        return dst_output(skb);
+
+                err = nf_hook(PF_INET, NF_IP_POST_ROUTING, &skb, NULL,
+                              skb->dst->dev, xfrm4_output_finish);
+                if (unlikely(err != 1))
+                        break;
+        }
+
+        return err;
+}
+
+int xfrm4_output(struct sk_buff *skb)
+{
+        return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dst->dev,
+                       xfrm4_output_finish);
+}