[PATCH v2] netfilter: x_tables: add xt_tunnel match

[PATCH v2] netfilter: x_tables: add xt_tunnel match

[wenxu]

From: wenxu <wenxu@ucloud.cn>

This patch allows us to match on the tunnel metadata that is available
of the packet. We can use this to validate if the packet comes from/goes
to tunnel and the corresponding tunnel ID in the iptables.

Signed-off-by: wenxu <wenxu@ucloud.cn>
---
 include/uapi/linux/netfilter/xt_tunnel.h | 12 +++++++
 net/netfilter/Kconfig                    | 10 ++++++
 net/netfilter/Makefile                   |  1 +
 net/netfilter/xt_tunnel.c                | 56 ++++++++++++++++++++++++++++++++
 4 files changed, 79 insertions(+)
 create mode 100644 include/uapi/linux/netfilter/xt_tunnel.h
 create mode 100644 net/netfilter/xt_tunnel.c

diff --git a/include/uapi/linux/netfilter/xt_tunnel.h b/include/uapi/linux/netfilter/xt_tunnel.h
new file mode 100644
index 0000000..5231afa
--- /dev/null
+++ b/include/uapi/linux/netfilter/xt_tunnel.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _XT_TUNNEL_H
+#define _XT_TUNNEL_H
+
+#include <linux/types.h>
+
+struct xt_tunnel_mtinfo {
+	__u32 key, mask;
+	__u8 invert;
+};
+
+#endif /*_XT_TUNNEL_H*/
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index beb3a69..ee52a75 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -1586,6 +1586,16 @@ config NETFILTER_XT_MATCH_U32
 
 	  Details and examples are in the kernel module source.
 
+config NETFILTER_XT_MATCH_TUNNEL
+	tristate '"tunnel" match support'
+	depends on NETFILTER_ADVANCED
+	help
+	  This option adds a "tunnel" match, which allows you to match based on
+	  the packet tunnel_id
+
+	  If you want to compile it as a module, say M here.
+	  If unsure, say N.
+
 endif # NETFILTER_XTABLES
 
 endmenu
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 1ae65a3..965541c 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -198,6 +198,7 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_STRING) += xt_string.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_TCPMSS) += xt_tcpmss.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_TIME) += xt_time.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_U32) += xt_u32.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_TUNNEL) += xt_tunnel.o
 
 # ipset
 obj-$(CONFIG_IP_SET) += ipset/
diff --git a/net/netfilter/xt_tunnel.c b/net/netfilter/xt_tunnel.c
new file mode 100644
index 0000000..0ca1dce
--- /dev/null
+++ b/net/netfilter/xt_tunnel.c
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <net/dst_metadata.h>
+#include <net/ip_tunnels.h>
+
+#include <linux/netfilter/xt_tunnel.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("wenxu <wenxu@ucloud.cn>");
+MODULE_DESCRIPTION("Xtables: packet tunnel match");
+MODULE_ALIAS("ipt_tunnel");
+MODULE_ALIAS("ip6t_tunnel");
+
+static bool
+tunnel_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+	const struct xt_tunnel_mtinfo *info = par->matchinfo;
+	struct ip_tunnel_info *tun_info;
+	u32 key;
+
+	tun_info = skb_tunnel_info(skb);
+	if (tun_info) {
+		key = ntohl(tunnel_id_to_key32(tun_info->key.tun_id));
+		return ((key & info->mask) == info->key) ^ info->invert;
+	}
+
+	return info->invert;
+}
+
+static struct xt_match tunnel_mt_reg __read_mostly = {
+	.name           = "tunnel",
+	.revision       = 0,
+	.family         = NFPROTO_UNSPEC,
+	.match          = tunnel_mt,
+	.matchsize      = sizeof(struct xt_tunnel_mtinfo),
+	.hooks          = ((1 << NF_INET_PRE_ROUTING) |
+					  (1 << NF_INET_POST_ROUTING) |
+					  (1 << NF_INET_LOCAL_OUT) |
+					  (1 << NF_INET_FORWARD)),
+	.me             = THIS_MODULE,
+};
+
+static int __init tunnel_mt_init(void)
+{
+	return xt_register_match(&tunnel_mt_reg);
+}
+
+static void __exit tunnel_mt_exit(void)
+{
+	xt_unregister_match(&tunnel_mt_reg);
+}
+
+module_init(tunnel_mt_init);
+module_exit(tunnel_mt_exit);
-- 
1.8.3.1

Re: [PATCH v2] netfilter: x_tables: add xt_tunnel match

[Pablo Neira Ayuso]

On Thu, Jan 10, 2019 at 01:16:08PM +0800, wenxu@ucloud.cn wrote:
[...]
> +static struct xt_match tunnel_mt_reg __read_mostly = {
> +	.name           = "tunnel",
> +	.revision       = 0,
> +	.family         = NFPROTO_UNSPEC,
> +	.match          = tunnel_mt,
> +	.matchsize      = sizeof(struct xt_tunnel_mtinfo),
> +	.hooks          = ((1 << NF_INET_PRE_ROUTING) |
> +					  (1 << NF_INET_POST_ROUTING) |
> +					  (1 << NF_INET_LOCAL_OUT) |
> +					  (1 << NF_INET_FORWARD)),

Are you sure this works from the forward chain? This template is
dropped after the route lookup.

Thanks.

Re: [PATCH v2] netfilter: x_tables: add xt_tunnel match

[wenxu]

On 1/11/2019 2:15 AM, Pablo Neira Ayuso wrote:
> On Thu, Jan 10, 2019 at 01:16:08PM +0800, wenxu@ucloud.cn wrote:
> [...]
>> +static struct xt_match tunnel_mt_reg __read_mostly = {
>> +	.name           = "tunnel",
>> +	.revision       = 0,
>> +	.family         = NFPROTO_UNSPEC,
>> +	.match          = tunnel_mt,
>> +	.matchsize      = sizeof(struct xt_tunnel_mtinfo),
>> +	.hooks          = ((1 << NF_INET_PRE_ROUTING) |
>> +					  (1 << NF_INET_POST_ROUTING) |
>> +					  (1 << NF_INET_LOCAL_OUT) |
>> +					  (1 << NF_INET_FORWARD)),
> Are you sure this works from the forward chain? This template is
> dropped after the route lookup.
>
> Thanks.

Yes.  NF_INET_FORWARD is also used to match the packet goes to tunnel(IP_TUNNEL_INFO_TX type), After route lookup, the packet send to tunnel through lwtunnel-route.

NF_INET_PRE_ROUTING can be used for 'from' tunnel match, The other three hooks can be used for 'to' tunnel match.

Re: [PATCH v2] netfilter: x_tables: add xt_tunnel match

[Pablo Neira Ayuso]

On Thu, Jan 10, 2019 at 01:16:08PM +0800, wenxu@ucloud.cn wrote:
> From: wenxu <wenxu@ucloud.cn>
> 
> This patch allows us to match on the tunnel metadata that is available
> of the packet. We can use this to validate if the packet comes from/goes
> to tunnel and the corresponding tunnel ID in the iptables.

One more question, we already have support for this in nft_tunnel.c,
would it be good if we just add the missing pieces to userspace there?
I have some patches here I need to push out for this...

Re: [PATCH v2] netfilter: x_tables: add xt_tunnel match

[wenxu]

On 2019/1/18 下午10:18, Pablo Neira Ayuso wrote:
> On Thu, Jan 10, 2019 at 01:16:08PM +0800, wenxu@ucloud.cn wrote:
>> From: wenxu <wenxu@ucloud.cn>
>>
>> This patch allows us to match on the tunnel metadata that is available
>> of the packet. We can use this to validate if the packet comes from/goes
>> to tunnel and the corresponding tunnel ID in the iptables.
> One more question, we already have support for this in nft_tunnel.c,
> would it be good if we just add the missing pieces to userspace there?
> I have some patches here I need to push out for this...
>
Yes, nftables can do this. I just want the people also can get it through iptables.

Anyway It's  fine for me.