netfilter: xt_TEE: have cloned packet travel through Xtables too
Jan Engelhardt [Mon, 19 Apr 2010 14:06:52 +0000 (16:06 +0200)]
Since Xtables is now reentrant/nestable, the cloned packet can also go
through Xtables and be subject to rules itself.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/ipv4/ip_output.c
net/ipv6/ip6_output.c
net/netfilter/xt_TEE.c

index 0abfdde..f09135e 100644 (file)
@@ -309,7 +309,6 @@ int ip_output(struct sk_buff *skb)
                            ip_finish_output,
                            !(IPCB(skb)->flags & IPSKB_REROUTED));
 }
-EXPORT_SYMBOL_GPL(ip_output);
 
 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
 {
index d09be7f..c10a38a 100644 (file)
@@ -176,7 +176,6 @@ int ip6_output(struct sk_buff *skb)
                            ip6_finish_output,
                            !(IP6CB(skb)->flags & IP6SKB_REROUTED));
 }
-EXPORT_SYMBOL_GPL(ip6_output);
 
 /*
  *     xmit an sk_buff (used by TCP)
index b3d7301..842e701 100644 (file)
@@ -12,6 +12,7 @@
  */
 #include <linux/ip.h>
 #include <linux/module.h>
+#include <linux/percpu.h>
 #include <linux/route.h>
 #include <linux/skbuff.h>
 #include <net/checksum.h>
@@ -32,6 +33,7 @@
 #endif
 
 static const union nf_inet_addr tee_zero_address;
+static DEFINE_PER_CPU(bool, tee_active);
 
 static struct net *pick_net(struct sk_buff *skb)
 {
@@ -91,6 +93,8 @@ tee_tg4(struct sk_buff *skb, const struct xt_target_param *par)
        const struct xt_tee_tginfo *info = par->targinfo;
        struct iphdr *iph;
 
+       if (percpu_read(tee_active))
+               return XT_CONTINUE;
        /*
         * Copy the skb, and route the copy. Will later return %XT_CONTINUE for
         * the original skb, which should continue on its way as if nothing has
@@ -125,24 +129,13 @@ tee_tg4(struct sk_buff *skb, const struct xt_target_param *par)
                --iph->ttl;
        ip_send_check(iph);
 
-       /*
-        * Xtables is not reentrant currently, so a choice has to be made:
-        * 1. return absolute verdict for the original and let the cloned
-        *    packet travel through the chains
-        * 2. let the original continue travelling and not pass the clone
-        *    to Xtables.
-        * #2 is chosen. Normally, we would use ip_local_out for the clone.
-        * Because iph->check is already correct and we don't pass it to
-        * Xtables anyway, a shortcut to dst_output [forwards to ip_output] can
-        * be taken. %IPSKB_REROUTED needs to be set so that ip_output does not
-        * invoke POSTROUTING on the cloned packet.
-        */
-       IPCB(skb)->flags |= IPSKB_REROUTED;
-       if (tee_tg_route4(skb, info))
-               ip_output(skb);
-       else
+       if (tee_tg_route4(skb, info)) {
+               percpu_write(tee_active, true);
+               ip_local_out(skb);
+               percpu_write(tee_active, false);
+       } else {
                kfree_skb(skb);
-
+       }
        return XT_CONTINUE;
 }
 
@@ -177,6 +170,8 @@ tee_tg6(struct sk_buff *skb, const struct xt_target_param *par)
 {
        const struct xt_tee_tginfo *info = par->targinfo;
 
+       if (percpu_read(tee_active))
+               return XT_CONTINUE;
        skb = pskb_copy(skb, GFP_ATOMIC);
        if (skb == NULL)
                return XT_CONTINUE;
@@ -192,12 +187,13 @@ tee_tg6(struct sk_buff *skb, const struct xt_target_param *par)
                struct ipv6hdr *iph = ipv6_hdr(skb);
                --iph->hop_limit;
        }
-       IP6CB(skb)->flags |= IP6SKB_REROUTED;
-       if (tee_tg_route6(skb, info))
-               ip6_output(skb);
-       else
+       if (tee_tg_route6(skb, info)) {
+               percpu_write(tee_active, true);
+               ip6_local_out(skb);
+               percpu_write(tee_active, false);
+       } else {
                kfree_skb(skb);
-
+       }
        return XT_CONTINUE;
 }
 #endif /* WITH_IPV6 */