[NETFILTER]: nf_conntrack: support for layer 3 protocol load on demand

x_tables matches and targets that require nf_conntrack_ipv[4|6] to work
don't have enough information to load on demand these modules. This
patch introduces the following changes to solve this issue:

o nf_ct_l3proto_try_module_get: try to load the layer 3 connection
tracker module and increases the refcount.
o nf_ct_l3proto_module put: drop the refcount of the module.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 124 insertions, 0 deletions

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index c2884065645..0ae281d9bfc 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -23,6 +23,8 @@
  * 26 Jan 2006: Harald Welte <laforge@netfilter.org>
  *      - restructure nf_conn (introduce nf_conn_help)
  *      - redesign 'features' how they were originally intended
+ * 26 Feb 2006: Pablo Neira Ayuso <pablo@eurodev.net>
+ *      - add support for L3 protocol module load on demand.
  *
  * Derived from net/ipv4/netfilter/ip_conntrack_core.c
  */
@@ -241,6 +243,35 @@ void nf_ct_l3proto_put(struct nf_conntrack_l3proto *p)
         module_put(p->me);
 }
 
+int
+nf_ct_l3proto_try_module_get(unsigned short l3proto)
+{
+        int ret;
+        struct nf_conntrack_l3proto *p;
+
+retry:  p = nf_ct_l3proto_find_get(l3proto);
+        if (p == &nf_conntrack_generic_l3proto) {
+                ret = request_module("nf_conntrack-%d", l3proto);
+                if (!ret)
+                        goto retry;
+
+                return -EPROTOTYPE;
+        }
+
+        return 0;
+}
+
+void nf_ct_l3proto_module_put(unsigned short l3proto)
+{
+        struct nf_conntrack_l3proto *p;
+
+        preempt_disable();
+        p = __nf_ct_l3proto_find(l3proto);
+        preempt_enable();
+
+        module_put(p->me);
+}
+
 static int nf_conntrack_hash_rnd_initted;
 static unsigned int nf_conntrack_hash_rnd;
 
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 290d5a0c559..75577e175b3 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -834,6 +834,8 @@ EXPORT_SYMBOL_GPL(__nf_ct_event_cache_init);
 EXPORT_PER_CPU_SYMBOL_GPL(nf_conntrack_ecache);
 EXPORT_SYMBOL_GPL(nf_ct_deliver_cached_events);
 #endif
+EXPORT_SYMBOL(nf_ct_l3proto_try_module_get);
+EXPORT_SYMBOL(nf_ct_l3proto_module_put);
 EXPORT_SYMBOL(nf_conntrack_l3proto_register);
 EXPORT_SYMBOL(nf_conntrack_l3proto_unregister);
 EXPORT_SYMBOL(nf_conntrack_protocol_register);
diff --git a/net/netfilter/xt_connmark.c b/net/netfilter/xt_connmark.c
index e810600345e..7b16f1ee16b 100644
--- a/net/netfilter/xt_connmark.c
+++ b/net/netfilter/xt_connmark.c
@@ -64,14 +64,30 @@ checkentry(const char *tablename,
                 printk(KERN_WARNING "connmark: only support 32bit mark\n");
                 return 0;
         }
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+        if (nf_ct_l3proto_try_module_get(match->family) < 0) {
+                printk(KERN_WARNING "can't load nf_conntrack support for "
+                                    "proto=%d\n", match->family);
+                return 0;
+        }
+#endif
         return 1;
 }
 
+static void
+destroy(const struct xt_match *match, void *matchinfo, unsigned int matchsize)
+{
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+        nf_ct_l3proto_module_put(match->family);
+#endif
+}
+
 static struct xt_match connmark_match = {
         .name           = "connmark",
         .match          = match,
         .matchsize      = sizeof(struct xt_connmark_info),
         .checkentry     = checkentry,
+        .destroy        = destroy,
         .family         = AF_INET,
         .me             = THIS_MODULE
 };
@@ -81,6 +97,7 @@ static struct xt_match connmark6_match = {
         .match          = match,
         .matchsize      = sizeof(struct xt_connmark_info),
         .checkentry     = checkentry,
+        .destroy        = destroy,
         .family         = AF_INET6,
         .me             = THIS_MODULE
 };
diff --git a/net/netfilter/xt_conntrack.c b/net/netfilter/xt_conntrack.c
index 7d20caa0d60..65a84809fd3 100644
--- a/net/netfilter/xt_conntrack.c
+++ b/net/netfilter/xt_conntrack.c
@@ -203,9 +203,37 @@ match(const struct sk_buff *skb,
 
 #endif /* CONFIG_NF_IP_CONNTRACK */
 
+static int
+checkentry(const char *tablename,
+           const void *ip,
+           const struct xt_match *match,
+           void *matchinfo,
+           unsigned int matchsize,
+           unsigned int hook_mask)
+{
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+        if (nf_ct_l3proto_try_module_get(match->family) < 0) {
+                printk(KERN_WARNING "can't load nf_conntrack support for "
+                                    "proto=%d\n", match->family);
+                return 0;
+        }
+#endif
+        return 1;
+}
+
+static void
+destroy(const struct xt_match *match, void *matchinfo, unsigned int matchsize)
+{
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+        nf_ct_l3proto_module_put(match->family);
+#endif
+}
+
 static struct xt_match conntrack_match = {
         .name           = "conntrack",
         .match          = match,
+        .checkentry     = checkentry,
+        .destroy        = destroy,
         .matchsize      = sizeof(struct xt_conntrack_info),
         .family         = AF_INET,
         .me             = THIS_MODULE,
diff --git a/net/netfilter/xt_helper.c b/net/netfilter/xt_helper.c
index 7d2d68b9155..101f0005e98 100644
--- a/net/netfilter/xt_helper.c
+++ b/net/netfilter/xt_helper.c
@@ -144,15 +144,31 @@ static int check(const char *tablename,
 {
         struct xt_helper_info *info = matchinfo;
 
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+        if (nf_ct_l3proto_try_module_get(match->family) < 0) {
+                printk(KERN_WARNING "can't load nf_conntrack support for "
+                                    "proto=%d\n", match->family);
+                return 0;
+        }
+#endif
         info->name[29] = '\0';
         return 1;
 }
 
+static void
+destroy(const struct xt_match *match, void *matchinfo, unsigned int matchsize)
+{
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+        nf_ct_l3proto_module_put(match->family);
+#endif
+}
+
 static struct xt_match helper_match = {
         .name           = "helper",
         .match          = match,
         .matchsize      = sizeof(struct xt_helper_info),
         .checkentry     = check,
+        .destroy        = destroy,
         .family         = AF_INET,
         .me             = THIS_MODULE,
 };
@@ -161,6 +177,7 @@ static struct xt_match helper6_match = {
         .match          = match,
         .matchsize      = sizeof(struct xt_helper_info),
         .checkentry     = check,
+        .destroy        = destroy,
         .family         = AF_INET6,
         .me             = THIS_MODULE,
 };
diff --git a/net/netfilter/xt_state.c b/net/netfilter/xt_state.c
index 7cd557c932b..e6c0be9d94d 100644
--- a/net/netfilter/xt_state.c
+++ b/net/netfilter/xt_state.c
@@ -44,9 +44,36 @@ match(const struct sk_buff *skb,
         return (sinfo->statemask & statebit);
 }
 
+static int check(const char *tablename,
+                 const void *inf,
+                 const struct xt_match *match,
+                 void *matchinfo,
+                 unsigned int matchsize,
+                 unsigned int hook_mask)
+{
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+        if (nf_ct_l3proto_try_module_get(match->family) < 0) {
+                printk(KERN_WARNING "can't load nf_conntrack support for "
+                                    "proto=%d\n", match->family);
+                return 0;
+        }
+#endif
+        return 1;
+}
+
+static void
+destroy(const struct xt_match *match, void *matchinfo, unsigned int matchsize)
+{
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+        nf_ct_l3proto_module_put(match->family);
+#endif
+}
+
 static struct xt_match state_match = {
         .name           = "state",
         .match          = match,
+        .checkentry     = check,
+        .destroy        = destroy,
         .matchsize      = sizeof(struct xt_state_info),
         .family         = AF_INET,
         .me             = THIS_MODULE,
@@ -55,6 +82,8 @@ static struct xt_match state_match = {
 static struct xt_match state6_match = {
         .name           = "state",
         .match          = match,
+        .checkentry     = check,
+        .destroy        = destroy,
         .matchsize      = sizeof(struct xt_state_info),
         .family         = AF_INET6,
         .me             = THIS_MODULE,