[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 66620a9..51fabb8 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);
+}