[NETFILTER]: nf_conntrack: automatic sysctl registation for conntrack protocols

Add helper functions for sysctl registration with optional instantiating
of common path elements (like net/netfilter) and use it for support for
automatic registation of conntrack protocol sysctls.

Signed-off-by: Patrick McHardy <kaber@trash.net>

3 files changed, 237 insertions, 0 deletions

diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 627105df1040..84d529ded952 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -4,6 +4,7 @@ nf_conntrack-y	:= nf_conntrack_core.o nf_conntrack_standalone.o nf_conntrack_exp
 nf_conntrack-$(CONFIG_NF_CONNTRACK_EVENTS) += nf_conntrack_ecache.o
 
 obj-$(CONFIG_NETFILTER) = netfilter.o
+obj-$(CONFIG_SYSCTL) += nf_sysctl.o
 
 obj-$(CONFIG_NETFILTER_NETLINK) += nfnetlink.o
 obj-$(CONFIG_NETFILTER_NETLINK_QUEUE) += nfnetlink_queue.o
diff --git a/net/netfilter/nf_conntrack_proto.c b/net/netfilter/nf_conntrack_proto.c
index a6a3b1ddd00d..941b5c3754af 100644
--- a/net/netfilter/nf_conntrack_proto.c
+++ b/net/netfilter/nf_conntrack_proto.c
@@ -12,6 +12,7 @@
 #include <linux/types.h>
 #include <linux/netfilter.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/skbuff.h>
 #include <linux/vmalloc.h>
 #include <linux/stddef.h>
@@ -30,6 +31,34 @@
 struct nf_conntrack_l4proto **nf_ct_protos[PF_MAX] __read_mostly;
 struct nf_conntrack_l3proto *nf_ct_l3protos[AF_MAX] __read_mostly;
 
+#ifdef CONFIG_SYSCTL
+static DEFINE_MUTEX(nf_ct_proto_sysctl_mutex);
+
+static int
+nf_ct_register_sysctl(struct ctl_table_header **header, struct ctl_table *path,
+                      struct ctl_table *table, unsigned int *users)
+{
+        if (*header == NULL) {
+                *header = nf_register_sysctl_table(path, table);
+                if (*header == NULL)
+                        return -ENOMEM;
+        }
+        if (users != NULL)
+                (*users)++;
+        return 0;
+}
+
+static void
+nf_ct_unregister_sysctl(struct ctl_table_header **header,
+                        struct ctl_table *table, unsigned int *users)
+{
+        if (users != NULL && --*users > 0)
+                return;
+        nf_unregister_sysctl_table(*header, table);
+        *header = NULL;
+}
+#endif
+
 struct nf_conntrack_l4proto *
 __nf_ct_l4proto_find(u_int16_t l3proto, u_int8_t l4proto)
 {
@@ -124,6 +153,33 @@ static int kill_l4proto(struct nf_conn *i, void *data)
                         l4proto->l3proto);
 }
 
+static int nf_ct_l3proto_register_sysctl(struct nf_conntrack_l3proto *l3proto)
+{
+        int err = 0;
+
+#ifdef CONFIG_SYSCTL
+        mutex_lock(&nf_ct_proto_sysctl_mutex);
+        if (l3proto->ctl_table != NULL) {
+                err = nf_ct_register_sysctl(&l3proto->ctl_table_header,
+                                            l3proto->ctl_table_path,
+                                            l3proto->ctl_table, NULL);
+        }
+        mutex_unlock(&nf_ct_proto_sysctl_mutex);
+#endif
+        return err;
+}
+
+static void nf_ct_l3proto_unregister_sysctl(struct nf_conntrack_l3proto *l3proto)
+{
+#ifdef CONFIG_SYSCTL
+        mutex_lock(&nf_ct_proto_sysctl_mutex);
+        if (l3proto->ctl_table_header != NULL)
+                nf_ct_unregister_sysctl(&l3proto->ctl_table_header,
+                                        l3proto->ctl_table, NULL);
+        mutex_unlock(&nf_ct_proto_sysctl_mutex);
+#endif
+}
+
 int nf_conntrack_l3proto_register(struct nf_conntrack_l3proto *proto)
 {
         int ret = 0;
@@ -139,6 +195,12 @@ int nf_conntrack_l3proto_register(struct nf_conntrack_l3proto *proto)
                 goto out_unlock;
         }
         nf_ct_l3protos[proto->l3proto] = proto;
+        write_unlock_bh(&nf_conntrack_lock);
+
+        ret = nf_ct_l3proto_register_sysctl(proto);
+        if (ret < 0)
+                nf_conntrack_l3proto_unregister(proto);
+        return ret;
 
 out_unlock:
         write_unlock_bh(&nf_conntrack_lock);
@@ -165,6 +227,8 @@ int nf_conntrack_l3proto_unregister(struct nf_conntrack_l3proto *proto)
         nf_ct_l3protos[proto->l3proto] = &nf_conntrack_l3proto_generic;
         write_unlock_bh(&nf_conntrack_lock);
 
+        nf_ct_l3proto_unregister_sysctl(proto);
+
         /* Somebody could be still looking at the proto in bh. */
         synchronize_net();
 
@@ -175,6 +239,36 @@ out:
         return ret;
 }
 
+static int nf_ct_l4proto_register_sysctl(struct nf_conntrack_l4proto *l4proto)
+{
+        int err = 0;
+
+#ifdef CONFIG_SYSCTL
+        mutex_lock(&nf_ct_proto_sysctl_mutex);
+        if (l4proto->ctl_table != NULL) {
+                err = nf_ct_register_sysctl(l4proto->ctl_table_header,
+                                            nf_net_netfilter_sysctl_path,
+                                            l4proto->ctl_table,
+                                            l4proto->ctl_table_users);
+        }
+        mutex_unlock(&nf_ct_proto_sysctl_mutex);
+#endif
+        return err;
+}
+
+static void nf_ct_l4proto_unregister_sysctl(struct nf_conntrack_l4proto *l4proto)
+{
+#ifdef CONFIG_SYSCTL
+        mutex_lock(&nf_ct_proto_sysctl_mutex);
+        if (l4proto->ctl_table_header != NULL &&
+            *l4proto->ctl_table_header != NULL)
+                nf_ct_unregister_sysctl(l4proto->ctl_table_header,
+                                        l4proto->ctl_table,
+                                        l4proto->ctl_table_users);
+        mutex_unlock(&nf_ct_proto_sysctl_mutex);
+#endif
+}
+
 /* FIXME: Allow NULL functions and sub in pointers to generic for
    them. --RR */
 int nf_conntrack_l4proto_register(struct nf_conntrack_l4proto *l4proto)
@@ -230,6 +324,12 @@ retry:
         }
 
         nf_ct_protos[l4proto->l3proto][l4proto->l4proto] = l4proto;
+        write_unlock_bh(&nf_conntrack_lock);
+
+        ret = nf_ct_l4proto_register_sysctl(l4proto);
+        if (ret < 0)
+                nf_conntrack_l4proto_unregister(l4proto);
+        return ret;
 
 out_unlock:
         write_unlock_bh(&nf_conntrack_lock);
@@ -257,6 +357,8 @@ int nf_conntrack_l4proto_unregister(struct nf_conntrack_l4proto *l4proto)
                 = &nf_conntrack_l4proto_generic;
         write_unlock_bh(&nf_conntrack_lock);
 
+        nf_ct_l4proto_unregister_sysctl(l4proto);
+
         /* Somebody could be still looking at the proto in bh. */
         synchronize_net();
 
diff --git a/net/netfilter/nf_sysctl.c b/net/netfilter/nf_sysctl.c
new file mode 100644
index 000000000000..06ddddb2911f
--- /dev/null
+++ b/net/netfilter/nf_sysctl.c
@@ -0,0 +1,134 @@
+/* nf_sysctl.c  netfilter sysctl registration/unregistation
+ *
+ * Copyright (c) 2006 Patrick McHardy <kaber@trash.net>
+ */
+#include <linux/module.h>
+#include <linux/sysctl.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+
+static void
+path_free(struct ctl_table *path, struct ctl_table *table)
+{
+        struct ctl_table *t, *next;
+
+        for (t = path; t != NULL && t != table; t = next) {
+                next = t->child;
+                kfree(t);
+        }
+}
+
+static struct ctl_table *
+path_dup(struct ctl_table *path, struct ctl_table *table)
+{
+        struct ctl_table *t, *last = NULL, *tmp;
+
+        for (t = path; t != NULL; t = t->child) {
+                /* twice the size since path elements are terminated by an
+                 * empty element */
+                tmp = kmemdup(t, 2 * sizeof(*t), GFP_KERNEL);
+                if (tmp == NULL) {
+                        if (last != NULL)
+                                path_free(path, table);
+                        return NULL;
+                }
+
+                if (last != NULL)
+                        last->child = tmp;
+                else
+                        path = tmp;
+                last = tmp;
+        }
+
+        if (last != NULL)
+                last->child = table;
+        else
+                path = table;
+
+        return path;
+}
+
+struct ctl_table_header *
+nf_register_sysctl_table(struct ctl_table *path, struct ctl_table *table)
+{
+        struct ctl_table_header *header;
+
+        path = path_dup(path, table);
+        if (path == NULL)
+                return NULL;
+        header = register_sysctl_table(path, 0);
+        if (header == NULL)
+                path_free(path, table);
+        return header;
+}
+EXPORT_SYMBOL_GPL(nf_register_sysctl_table);
+
+void
+nf_unregister_sysctl_table(struct ctl_table_header *header,
+                           struct ctl_table *table)
+{
+        struct ctl_table *path = header->ctl_table;
+
+        unregister_sysctl_table(header);
+        path_free(path, table);
+}
+EXPORT_SYMBOL_GPL(nf_unregister_sysctl_table);
+
+/* net/netfilter */
+static struct ctl_table nf_net_netfilter_table[] = {
+        {
+                .ctl_name       = NET_NETFILTER,
+                .procname       = "netfilter",
+                .mode           = 0555,
+        },
+        {
+                .ctl_name       = 0
+        }
+};
+struct ctl_table nf_net_netfilter_sysctl_path[] = {
+        {
+                .ctl_name       = CTL_NET,
+                .procname       = "net",
+                .mode           = 0555,
+                .child          = nf_net_netfilter_table,
+        },
+        {
+                .ctl_name       = 0
+        }
+};
+EXPORT_SYMBOL_GPL(nf_net_netfilter_sysctl_path);
+
+/* net/ipv4/netfilter */
+static struct ctl_table nf_net_ipv4_netfilter_table[] = {
+        {
+                .ctl_name       = NET_IPV4_NETFILTER,
+                .procname       = "netfilter",
+                .mode           = 0555,
+        },
+        {
+                .ctl_name       = 0
+        }
+};
+static struct ctl_table nf_net_ipv4_table[] = {
+        {
+                .ctl_name       = NET_IPV4,
+                .procname       = "ipv4",
+                .mode           = 0555,
+                .child          = nf_net_ipv4_netfilter_table,
+        },
+        {
+                .ctl_name       = 0
+        }
+};
+struct ctl_table nf_net_ipv4_netfilter_sysctl_path[] = {
+        {
+                .ctl_name       = CTL_NET,
+                .procname       = "net",
+                .mode           = 0555,
+                .child          = nf_net_ipv4_table,
+        },
+        {
+                .ctl_name       = 0
+        }
+};
+EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path);