[PATCH v2 0/2] netfilter: xtables: xt_condition inclusion and change to u32

[PATCH v2 0/2] netfilter: xtables: xt_condition inclusion and change to u32

[luciano.coelho]

From: Luciano Coelho <luciano.coelho@nokia.com>

Hello,

Here v2 of the xt_condition patch, it contains some changes suggested by Jan.

When these patches get accepted, I'll send the implementation of the condition
target, as discussed before.

In RFC v2 I've made a few changes as discussed in the review:

  * Removed per-netns module parameters
  * Use par->net instead of current->nsproxy->net_ns
  * Fix file-leak in procfs when exiting the netns

I didn't get any more comments in RFC v2, so I assume it is okay to send it for
inclusion.

>From [RFC v2] to [PATCH], I've only rebased and added a new patch to support
u32 instead of boolean as the value for the condition.

In PATCH v2:

  * Bumped up the revision to 2
  * Changed the buffer declaration to have the size of the biggest possible u32 string
  * Return -ERANGE instead of -EINVALID when the value passed is too big.

Cheers,
Luca.


Luciano Coelho (2):
  netfilter: xtables: inclusion of xt_condition
  netfilter: xt_condition: change the value from boolean to u32

 include/linux/netfilter/Kbuild         |    1 +
 include/linux/netfilter/xt_condition.h |   15 ++
 net/netfilter/Kconfig                  |    8 +
 net/netfilter/Makefile                 |    1 +
 net/netfilter/xt_condition.c           |  269 ++++++++++++++++++++++++++++++++
 5 files changed, 294 insertions(+), 0 deletions(-)
 create mode 100644 include/linux/netfilter/xt_condition.h
 create mode 100644 net/netfilter/xt_condition.c

[PATCH v2 1/2] netfilter: xtables: inclusion of xt_condition

[luciano.coelho]

From: Luciano Coelho <luciano.coelho@nokia.com>

xt_condition can be used by userspace to influence decisions in rules
by means of togglable variables without having to reload the entire
ruleset.

This is a respin of the module in Xtables-addons, with support for
multiple namespaces and other small improvements.  Some of the changes
were made by Jan Engelhardt.

Cc: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
---
 include/linux/netfilter/Kbuild         |    1 +
 include/linux/netfilter/xt_condition.h |   14 ++
 net/netfilter/Kconfig                  |    8 +
 net/netfilter/Makefile                 |    1 +
 net/netfilter/xt_condition.c           |  265 ++++++++++++++++++++++++++++++++
 5 files changed, 289 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 edeeabd..60363f5 100644
--- a/include/linux/netfilter/Kbuild
+++ b/include/linux/netfilter/Kbuild
@@ -22,6 +22,7 @@ header-y += xt_TEE.h
 header-y += xt_TPROXY.h
 header-y += xt_cluster.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..4faf3ca
--- /dev/null
+++ b/include/linux/netfilter/xt_condition.h
@@ -0,0 +1,14 @@
+#ifndef _XT_CONDITION_H
+#define _XT_CONDITION_H
+
+#include <linux/types.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 4328825..5044dd6 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -621,6 +621,14 @@ 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 441050f..bbf72bb 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -67,6 +67,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_IDLETIMER) += xt_IDLETIMER.o
 # matches
 obj-$(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..a78d832
--- /dev/null
+++ b/net/netfilter/xt_condition.c
@@ -0,0 +1,265 @@
+/*
+ *	"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.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#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 <net/netns/generic.h>
+#include <asm/uaccess.h>
+
+/* Defaults, these can be overridden on the module command-line. */
+static unsigned int condition_list_perms = S_IRUGO | S_IWUSR;
+static unsigned int condition_uid_perms = 0;
+static unsigned int condition_gid_perms = 0;
+
+MODULE_AUTHOR("Stephane Ouellette <ouellettes@videotron.ca>");
+MODULE_AUTHOR("Massimiliano Hofer <max@nucleus.it>");
+MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
+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, "default permissions on /proc/net/nf_condition/* files");
+module_param(condition_uid_perms, uint, S_IRUSR | S_IWUSR);
+MODULE_PARM_DESC(condition_uid_perms, "default user owner of /proc/net/nf_condition/* files");
+module_param(condition_gid_perms, uint, S_IRUSR | S_IWUSR);
+MODULE_PARM_DESC(condition_gid_perms, "default 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;
+};
+
+struct condition_net {
+	struct list_head list;
+	struct proc_dir_entry *proc_dir;
+};
+
+static int condition_net_id;
+static inline struct condition_net *condition_pernet(struct net *net)
+{
+	return net_generic(net, condition_net_id);
+}
+
+/* proc_lock is a user context only semaphore used for write access */
+/*           to the conditions' list.                               */
+static DEFINE_MUTEX(proc_lock);
+
+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, struct xt_action_param *par)
+{
+	const struct xt_condition_mtinfo *info = par->matchinfo;
+	const struct condition_variable *var   = info->condvar;
+
+	return var->enabled ^ info->invert;
+}
+
+static int condition_mt_check(const struct xt_mtchk_param *par)
+{
+	struct xt_condition_mtinfo *info = par->matchinfo;
+	struct condition_variable *var;
+	struct condition_net *cond_net = condition_pernet(par->net);
+
+	/* Forbid certain names */
+	if (*info->name == '\0' || *info->name == '.' ||
+	    info->name[sizeof(info->name)-1] != '\0' ||
+	    memchr(info->name, '/', sizeof(info->name)) != NULL) {
+		pr_info("name not allowed or too long: \"%.*s\"\n",
+			(unsigned int)sizeof(info->name), info->name);
+		return -EINVAL;
+	}
+
+	/*
+	 * Let's acquire the lock, check for the condition and add it
+	 * or increase the reference counter.
+	 */
+	mutex_lock(&proc_lock);
+	list_for_each_entry(var, &cond_net->list, list) {
+		if (strcmp(info->name, var->status_proc->name) == 0) {
+			++var->refcount;
+			mutex_unlock(&proc_lock);
+			info->condvar = var;
+			return 0;
+		}
+	}
+
+	/* 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,
+					     cond_net->proc_dir);
+	if (var->status_proc == NULL) {
+		kfree(var);
+		mutex_unlock(&proc_lock);
+		return -ENOMEM;
+	}
+
+	var->refcount = 1;
+	var->enabled  = false;
+	var->status_proc->data       = var;
+	var->status_proc->read_proc  = condition_proc_read;
+	var->status_proc->write_proc = condition_proc_write;
+	var->status_proc->uid        = condition_uid_perms;
+	var->status_proc->gid        = condition_gid_perms;
+	list_add(&var->list, &cond_net->list);
+	mutex_unlock(&proc_lock);
+	info->condvar = var;
+	return 0;
+}
+
+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;
+	struct condition_net *cond_net = condition_pernet(par->net);
+
+	mutex_lock(&proc_lock);
+	if (--var->refcount == 0) {
+		list_del(&var->list);
+		/* status_proc may be null in case of ns exit */
+		if (var->status_proc)
+			remove_proc_entry(var->status_proc->name,
+					  cond_net->proc_dir);
+		mutex_unlock(&proc_lock);
+		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)
+{
+	struct condition_net *cond_net = condition_pernet(net);
+
+	INIT_LIST_HEAD(&cond_net->list);
+
+	cond_net->proc_dir = proc_mkdir(dir_name, net->proc_net);
+
+	return (cond_net->proc_dir == NULL) ? -EACCES : 0;
+}
+
+static void __net_exit condnet_mt_exit(struct net *net)
+{
+	struct condition_net *cond_net = condition_pernet(net);
+	struct condition_variable *var, *tmp;
+
+	mutex_lock(&proc_lock);
+	list_for_each_entry_safe(var, tmp, &cond_net->list, list) {
+		remove_proc_entry(var->status_proc->name,
+				  cond_net->proc_dir);
+		/* set to null so we don't double remove in mt_destroy */
+		var->status_proc = NULL;
+	}
+
+	mutex_unlock(&proc_lock);
+
+	remove_proc_entry(dir_name, net->proc_net);
+}
+
+static struct pernet_operations condition_mt_netops = {
+	.init = condnet_mt_init,
+	.exit = condnet_mt_exit,
+	.id   = &condition_net_id,
+	.size = sizeof(struct condition_net),
+};
+
+static int __init condition_mt_init(void)
+{
+	int ret;
+
+	mutex_init(&proc_lock);
+	ret = xt_register_match(&condition_mt_reg);
+	if (ret < 0)
+		return ret;
+
+	ret = register_pernet_subsys(&condition_mt_netops);
+	if (ret < 0) {
+		xt_unregister_match(&condition_mt_reg);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __exit condition_mt_exit(void)
+{
+	unregister_pernet_subsys(&condition_mt_netops);
+	xt_unregister_match(&condition_mt_reg);
+}
+
+module_init(condition_mt_init);
+module_exit(condition_mt_exit);
-- 
1.7.0.4

[PATCH v2 2/2] netfilter: xt_condition: change the value from boolean to u32

[luciano.coelho]

From: Luciano Coelho <luciano.coelho@nokia.com>

Previously the condition match was using boolean values for the condition,
which is a bit limited, so this patch changes the value to a u32.

This is not a problem at the moment, since only userspace can set the
condition and it can do more advanced checks before setting the value.  But
when the condition target gets implemented, having a u32 value will make it
much more flexible.

Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
---
 include/linux/netfilter/xt_condition.h |    3 +-
 net/netfilter/xt_condition.c           |   54 +++++++++++++++++---------------
 2 files changed, 31 insertions(+), 26 deletions(-)

diff --git a/include/linux/netfilter/xt_condition.h b/include/linux/netfilter/xt_condition.h
index 4faf3ca..c4fe899 100644
--- a/include/linux/netfilter/xt_condition.h
+++ b/include/linux/netfilter/xt_condition.h
@@ -4,8 +4,9 @@
 #include <linux/types.h>
 
 struct xt_condition_mtinfo {
-	char name[31];
+	char name[27];
 	__u8 invert;
+	__u32 value;
 
 	/* Used internally by the kernel */
 	void *condvar __attribute__((aligned(8)));
diff --git a/net/netfilter/xt_condition.c b/net/netfilter/xt_condition.c
index a78d832..cc9ada9 100644
--- a/net/netfilter/xt_condition.c
+++ b/net/netfilter/xt_condition.c
@@ -48,7 +48,7 @@ struct condition_variable {
 	struct list_head list;
 	struct proc_dir_entry *status_proc;
 	unsigned int refcount;
-	bool enabled;
+	u32 value;
 };
 
 struct condition_net {
@@ -71,32 +71,36 @@ static int condition_proc_read(char __user *buffer, char **start, off_t offset,
 {
 	const struct condition_variable *var = data;
 
-	buffer[0] = var->enabled ? '1' : '0';
-	buffer[1] = '\n';
-	if (length >= 2)
-		*eof = true;
-	return 2;
+	return snprintf(buffer, length, "%u\n", var->value);
 }
 
-static int condition_proc_write(struct file *file, const char __user *buffer,
+static int condition_proc_write(struct file *file, const char __user *input,
 				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;
-		}
-	}
+	/* the longest possible string is MAX_UINT in octal */
+	char buf[sizeof("+037777777777")];
+	unsigned long long value;
+
+	if (length == 0)
+		return 0;
+
+	if (length > sizeof(buf))
+		return -EINVAL;
+
+	if (copy_from_user(buf, input, length) != 0)
+		return -EFAULT;
+
+	buf[length - 1] = '\0';
+
+	if (strict_strtoull(buf, 0, &value) != 0)
+		return -EINVAL;
+
+	if (value > (u32) value)
+		return -ERANGE;
+
+	var->value = value;
+
 	return length;
 }
 
@@ -106,7 +110,7 @@ condition_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	const struct xt_condition_mtinfo *info = par->matchinfo;
 	const struct condition_variable *var   = info->condvar;
 
-	return var->enabled ^ info->invert;
+	return (var->value == info->value) ^ info->invert;
 }
 
 static int condition_mt_check(const struct xt_mtchk_param *par)
@@ -156,7 +160,7 @@ static int condition_mt_check(const struct xt_mtchk_param *par)
 	}
 
 	var->refcount = 1;
-	var->enabled  = false;
+	var->value = 0;
 	var->status_proc->data       = var;
 	var->status_proc->read_proc  = condition_proc_read;
 	var->status_proc->write_proc = condition_proc_write;
@@ -190,7 +194,7 @@ static void condition_mt_destroy(const struct xt_mtdtor_param *par)
 
 static struct xt_match condition_mt_reg __read_mostly = {
 	.name       = "condition",
-	.revision   = 1,
+	.revision   = 2,
 	.family     = NFPROTO_UNSPEC,
 	.matchsize  = sizeof(struct xt_condition_mtinfo),
 	.match      = condition_mt,
-- 
1.7.0.4

Re: [PATCH v2 0/2] netfilter: xtables: xt_condition inclusion and change to u32

[Patrick McHardy]

Am 06.08.2010 14:21, schrieb luciano.coelho@nokia.com:
> From: Luciano Coelho <luciano.coelho@nokia.com>
> 
> Hello,
> 
> Here v2 of the xt_condition patch, it contains some changes suggested by Jan.
> 
> When these patches get accepted, I'll send the implementation of the condition
> target, as discussed before.
> 
> In RFC v2 I've made a few changes as discussed in the review:
> 
>   * Removed per-netns module parameters
>   * Use par->net instead of current->nsproxy->net_ns
>   * Fix file-leak in procfs when exiting the netns
> 
> I didn't get any more comments in RFC v2, so I assume it is okay to send it for
> inclusion.

The merge window for networking patches is closed, I'm only taking
bugfixes at this time. Please resend once net-next opens up again.

Re: [PATCH v2 0/2] netfilter: xtables: xt_condition inclusion and change to u32

[Luciano Coelho]

On Fri, 2010-08-06 at 15:54 +0200, ext Patrick McHardy wrote:
> Am 06.08.2010 14:21, schrieb luciano.coelho@nokia.com:
> > From: Luciano Coelho <luciano.coelho@nokia.com>
> > 
> > Hello,
> > 
> > Here v2 of the xt_condition patch, it contains some changes suggested by Jan.
> > 
> > When these patches get accepted, I'll send the implementation of the condition
> > target, as discussed before.
> > 
> > In RFC v2 I've made a few changes as discussed in the review:
> > 
> >   * Removed per-netns module parameters
> >   * Use par->net instead of current->nsproxy->net_ns
> >   * Fix file-leak in procfs when exiting the netns
> > 
> > I didn't get any more comments in RFC v2, so I assume it is okay to send it for
> > inclusion.
> 
> The merge window for networking patches is closed, I'm only taking
> bugfixes at this time. Please resend once net-next opens up again.

Ok, I'll resend once the trees are open again.

I'll probably include some more patches on top of this then.

-- 
Cheers,
Luca.