xt_condition can be used by userspace to influence decisions in rules
by means of togglable variables without having to reload the entire
ruleset.
Signed-off-by: Jan Engelhardt <jengelh@xxxxxxxxxx>
---
include/linux/netfilter/Kbuild | 1 +
include/linux/netfilter/xt_condition.h | 12 ++
net/netfilter/Kconfig | 8 +
net/netfilter/Makefile | 1 +
net/netfilter/xt_condition.c | 243 ++++++++++++++++++++++++++++++++
5 files changed, 265 insertions(+), 0 deletions(-)
create mode 100644 include/linux/netfilter/xt_condition.h
create mode 100644 net/netfilter/xt_condition.c
diff --git a/include/linux/netfilter/Kbuild b/include/linux/netfilter/Kbuild
index 48767cd..6b67603 100644
--- a/include/linux/netfilter/Kbuild
+++ b/include/linux/netfilter/Kbuild
@@ -19,6 +19,7 @@ header-y += xt_TCPOPTSTRIP.h
header-y += xt_TEE.h
header-y += xt_TPROXY.h
header-y += xt_comment.h
+header-y += xt_condition.h
header-y += xt_connbytes.h
header-y += xt_connlimit.h
header-y += xt_connmark.h
diff --git a/include/linux/netfilter/xt_condition.h b/include/linux/netfilter/xt_condition.h
new file mode 100644
index 0000000..0fd1b75
--- /dev/null
+++ b/include/linux/netfilter/xt_condition.h
@@ -0,0 +1,12 @@
+#ifndef _XT_CONDITION_H
+#define _XT_CONDITION_H
+
+struct xt_condition_mtinfo {
+ char name[31];
+ __u8 invert;
+
+ /* Used internally by the kernel */
+ void *condvar __attribute__((aligned(8)));
+};
+
+#endif /* _XT_CONDITION_H */
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index bfd9b6f..dd74e7d 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -624,6 +624,14 @@ config NETFILTER_XT_MATCH_COMMENT
If you want to compile it as a module, say M here and read
<file:Documentation/kbuild/modules.txt>. If unsure, say `N'.
+config NETFILTER_XT_MATCH_CONDITION
+ tristate '"condition" match support'
+ depends on NETFILTER_ADVANCED
+ depends on PROC_FS
+ ---help---
+ This option allows you to match firewall rules against condition
+ variables stored in the /proc/net/nf_condition directory.
+
config NETFILTER_XT_MATCH_CONNBYTES
tristate '"connbytes" per-connection counter match support'
depends on NF_CONNTRACK
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index f032195..e75d5fa 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -66,6 +66,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_TRACE) += xt_TRACE.o
# matches
obj-$(CONFIG_NETFILTER_XT_MATCH_CLUSTER) += xt_cluster.o
obj-$(CONFIG_NETFILTER_XT_MATCH_COMMENT) += xt_comment.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_CONDITION) += xt_condition.o
obj-$(CONFIG_NETFILTER_XT_MATCH_CONNBYTES) += xt_connbytes.o
obj-$(CONFIG_NETFILTER_XT_MATCH_CONNLIMIT) += xt_connlimit.o
obj-$(CONFIG_NETFILTER_XT_MATCH_CONNTRACK) += xt_conntrack.o
diff --git a/net/netfilter/xt_condition.c b/net/netfilter/xt_condition.c
new file mode 100644
index 0000000..f1ae67a
--- /dev/null
+++ b/net/netfilter/xt_condition.c
@@ -0,0 +1,243 @@
+/*
+ * "condition" match extension for Xtables
+ *
+ * Description: This module allows firewall rules to match using
+ * condition variables available through procfs.
+ *
+ * Authors:
+ * Stephane Ouellette <ouellettes [at] videotron ca>, 2002-10-22
+ * Massimiliano Hofer <max [at] nucleus it>, 2006-05-15
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License; either version 2
+ * or 3 of the License, as published by the Free Software Foundation.
+ */
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/version.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_condition.h>
+#include <asm/uaccess.h>
+
+/* Defaults, these can be overridden on the module command-line. */
+static unsigned int condition_list_perms = S_IRUSR | S_IWUSR;
+static unsigned int condition_uid_perms;
+static unsigned int condition_gid_perms;
+
+MODULE_AUTHOR("Stephane Ouellette <ouellettes@xxxxxxxxxxxx>");
+MODULE_AUTHOR("Massimiliano Hofer <max@xxxxxxxxxx>");
+MODULE_AUTHOR("Jan Engelhardt <jengelh@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Allows rules to match against condition variables");
+MODULE_LICENSE("GPL");
+module_param(condition_list_perms, uint, S_IRUSR | S_IWUSR);
+MODULE_PARM_DESC(condition_list_perms, "permissions on /proc/net/nf_condition/* files");
+module_param(condition_uid_perms, uint, S_IRUSR | S_IWUSR);
+MODULE_PARM_DESC(condition_uid_perms, "user owner of /proc/net/nf_condition/* files");
+module_param(condition_gid_perms, uint, S_IRUSR | S_IWUSR);
+MODULE_PARM_DESC(condition_gid_perms, "group owner of /proc/net/nf_condition/* files");
+MODULE_ALIAS("ipt_condition");
+MODULE_ALIAS("ip6t_condition");
+
+struct condition_variable {
+ struct list_head list;
+ struct proc_dir_entry *status_proc;
+ unsigned int refcount;
+ bool enabled;
+};
+
+/* proc_lock is a user context only semaphore used for write access */
+/* to the conditions' list. */
+static struct mutex proc_lock;
+
+static LIST_HEAD(conditions_list);
+static struct proc_dir_entry *proc_net_condition;
+
+static int condition_proc_read(char __user *buffer, char **start, off_t offset,
+ int length, int *eof, void *data)
+{
+ const struct condition_variable *var = data;
+
+ buffer[0] = var->enabled ? '1' : '0';
+ buffer[1] = '\n';
+ if (length >= 2)
+ *eof = true;
+ return 2;
+}
+
+static int condition_proc_write(struct file *file, const char __user *buffer,
+ unsigned long length, void *data)
+{
+ struct condition_variable *var = data;
+ char newval;
+
+ if (length > 0) {
+ if (get_user(newval, buffer) != 0)
+ return -EFAULT;
+ /* Match only on the first character */
+ switch (newval) {
+ case '0':
+ var->enabled = false;
+ break;
+ case '1':
+ var->enabled = true;
+ break;
+ }
+ }
+ return length;
+}
+
+static bool
+condition_mt(const struct sk_buff *skb, const struct xt_match_param *par)
+{
+ const struct xt_condition_mtinfo *info = par->matchinfo;
+ const struct condition_variable *var = info->condvar;
+ bool x;
+
+ rcu_read_lock();
+ x = rcu_dereference(var->enabled);
+ rcu_read_unlock();
+
+ return x ^ info->invert;
+}
+
+static int condition_mt_check(const struct xt_mtchk_param *par)
+{
+ struct xt_condition_mtinfo *info = par->matchinfo;
+ struct condition_variable *var;
+
+ /* Forbid certain names */
+ if (*info->name == '\0' || *info->name == '.' ||
+ info->name[sizeof(info->name)-1] != '\0' ||
+ memchr(info->name, '/', sizeof(info->name)) != NULL) {
+ printk(KERN_INFO KBUILD_MODNAME ": name not allowed or too "
+ "long: \"%.*s\"\n", (unsigned int)sizeof(info->name),
+ info->name);
+ return false;
+ }
+ /*
+ * Let's acquire the lock, check for the condition and add it
+ * or increase the reference counter.
+ */
+ if (mutex_lock_interruptible(&proc_lock) != 0)
+ return -EINTR;
+
+ list_for_each_entry(var, &conditions_list, list) {
+ if (strcmp(info->name, var->status_proc->name) == 0) {
+ ++var->refcount;
+ mutex_unlock(&proc_lock);
+ info->condvar = var;
+ return true;
+ }
+ }
+
+ /* At this point, we need to allocate a new condition variable. */
+ var = kmalloc(sizeof(struct condition_variable), GFP_KERNEL);
+ if (var == NULL) {
+ mutex_unlock(&proc_lock);
+ return -ENOMEM;
+ }
+
+ /* Create the condition variable's proc file entry. */
+ var->status_proc = create_proc_entry(info->name, condition_list_perms,
+ proc_net_condition);
+ if (var->status_proc == NULL) {
+ kfree(var);
+ mutex_unlock(&proc_lock);
+ return -ENOMEM;
+ }
+
+ var->refcount = 1;
+ var->enabled = false;
+ var->status_proc->data = var;
+ wmb();
+ var->status_proc->read_proc = condition_proc_read;
+ var->status_proc->write_proc = condition_proc_write;
+ list_add_rcu(&var->list, &conditions_list);
+ var->status_proc->uid = condition_uid_perms;
+ var->status_proc->gid = condition_gid_perms;
+ mutex_unlock(&proc_lock);
+ info->condvar = var;
+ return true;
+}
+
+static void condition_mt_destroy(const struct xt_mtdtor_param *par)
+{
+ const struct xt_condition_mtinfo *info = par->matchinfo;
+ struct condition_variable *var = info->condvar;
+
+ mutex_lock(&proc_lock);
+ if (--var->refcount == 0) {
+ list_del_rcu(&var->list);
+ remove_proc_entry(var->status_proc->name, proc_net_condition);
+ mutex_unlock(&proc_lock);
+ /*
+ * synchronize_rcu() would be good enough, but
+ * synchronize_net() guarantees that no packet
+ * will go out with the old rule after
+ * succesful removal.
+ */
+ synchronize_net();
+ kfree(var);
+ return;
+ }
+ mutex_unlock(&proc_lock);
+}
+
+static struct xt_match condition_mt_reg __read_mostly = {
+ .name = "condition",
+ .revision = 1,
+ .family = NFPROTO_UNSPEC,
+ .matchsize = sizeof(struct xt_condition_mtinfo),
+ .match = condition_mt,
+ .checkentry = condition_mt_check,
+ .destroy = condition_mt_destroy,
+ .me = THIS_MODULE,
+};
+
+static const char *const dir_name = "nf_condition";
+
+static int __net_init condnet_mt_init(struct net *net)
+{
+ int ret;
+
+ proc_net_condition = proc_mkdir(dir_name, net->proc_net);
+ if (proc_net_condition == NULL)
+ return -EACCES;
+
+ ret = xt_register_match(&condition_mt_reg);
+ if (ret < 0) {
+ remove_proc_entry(dir_name, net->proc_net);
+ return ret;
+ }
+
+ return 0;
+}
+
+static void __net_exit condnet_mt_exit(struct net *net)
+{
+ xt_unregister_match(&condition_mt_reg);
+ remove_proc_entry(dir_name, net->proc_net);
+}
+
+static struct pernet_operations condition_mt_netops = {
+ .init = condnet_mt_init,
+ .exit = condnet_mt_exit,
+};
+
+static int __init condition_mt_init(void)
+{
+ mutex_init(&proc_lock);
+ return register_pernet_subsys(&condition_mt_netops);
+}
+
+static void __exit condition_mt_exit(void)
+{
+ unregister_pernet_subsys(&condition_mt_netops);
+}
+
+module_init(condition_mt_init);
+module_exit(condition_mt_exit);
--
1.7.0.2
--
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