netfilter 30/62: xtables: add CT target

Patrick McHardy
2010-02-16T14:56:01Z

commit 84f3bb9ae9db90f7fb15d98b55279a58ab1b2363
Author: Patrick McHardy <kaber@trash.net>
Date: Wed Feb 3 17:17:06 2010 +0100

netfilter: xtables: add CT target

Add a new target for the raw table, which can be used to specify conntrack
parameters for specific connections, f.i. the conntrack helper.

The target attaches a "template" connection tracking entry to the skb, which
is used by the conntrack core when initializing a new conntrack.

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

diff --git a/include/linux/netfilter/Kbuild b/include/linux/netfilter/Kbuild
index 2aea503..a5a63e4 100644
--- a/include/linux/netfilter/Kbuild
+++ b/include/linux/netfilter/Kbuild
@@ -6,6 +6,7 @@ header-y += nfnetlink_queue.h
header-y += xt_CLASSIFY.h
header-y += xt_CONNMARK.h
header-y += xt_CONNSECMARK.h
+header-y += xt_CT.h
header-y += xt_DSCP.h
header-y += xt_LED.h
header-y += xt_MARK.h
diff --git a/include/linux/netfilter/xt_CT.h b/include/linux/netfilter/xt_CT.h
new file mode 100644
index 0000000..7fd0eff
--- /dev/null
+++ b/include/linux/netfilter/xt_CT.h
@@ -0,0 +1,17 @@
+#ifndef _XT_CT_H
+#define _XT_CT_H
+
+#define XT_CT_NOTRACK 0x1
+
+struct xt_ct_target_info {
+ u_int16_t flags;
+ u_int16_t __unused;
+ u_int32_t ct_events;
+ u_int32_t exp_events;
+ char helper[16];
+
+ /* Used internally by the kernel */
+ struct nf_conn *ct __attribute__((aligned(8)));
+};
+
+#endif /* _XT_CT_H */
diff --git a/include/net/netfilter/nf_conntrack_helper.h b/include/net/netfilter/nf_conntrack_helper.h
index e17aaa3..32c305d 100644
--- a/include/net/netfilter/nf_conntrack_helper.h
+++ b/include/net/netfilter/nf_conntrack_helper.h
@@ -42,6 +42,9 @@ struct nf_conntrack_helper {
extern struct nf_conntrack_helper *
__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum);

+extern struct nf_conntrack_helper *
+nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum);
+
extern int nf_conntrack_helper_register(struct nf_conntrack_helper *);
extern void nf_conntrack_helper_unregister(struct nf_conntrack_helper *);

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 634d14a..4469d45 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -341,6 +341,18 @@ config NETFILTER_XT_TARGET_CONNSECMARK

To compile it as a module, choose M here. If unsure, say N.

+config NETFILTER_XT_TARGET_CT
+ tristate '"CT" target support'
+ depends on NF_CONNTRACK
+ depends on IP_NF_RAW || IP6_NF_RAW
+ depends on NETFILTER_ADVANCED
+ help
+ This options adds a `CT' target, which allows to specify initial
+ connection tracking parameters like events to be delivered and
+ the helper to be used.
+
+ To compile it as a module, choose M here. If unsure, say N.
+
config NETFILTER_XT_TARGET_DSCP
tristate '"DSCP" and "TOS" target support'
depends on IP_NF_MANGLE || IP6_NF_MANGLE
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 49f62ee..f873644 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -44,6 +44,7 @@ obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o
obj-$(CONFIG_NETFILTER_XT_TARGET_CLASSIFY) += xt_CLASSIFY.o
obj-$(CONFIG_NETFILTER_XT_TARGET_CONNMARK) += xt_CONNMARK.o
obj-$(CONFIG_NETFILTER_XT_TARGET_CONNSECMARK) += xt_CONNSECMARK.o
+obj-$(CONFIG_NETFILTER_XT_TARGET_CT) += xt_CT.o
obj-$(CONFIG_NETFILTER_XT_TARGET_DSCP) += xt_DSCP.o
obj-$(CONFIG_NETFILTER_XT_TARGET_HL) += xt_HL.o
obj-$(CONFIG_NETFILTER_XT_TARGET_LED) += xt_LED.o
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index 8144b0d..a74a576 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -83,6 +83,25 @@ __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
}
EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);

+struct nf_conntrack_helper *
+nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
+{
+ struct nf_conntrack_helper *h;
+
+ h = __nf_conntrack_helper_find(name, l3num, protonum);
+#ifdef CONFIG_MODULES
+ if (h == NULL) {
+ if (request_module("nfct-helper-%s", name) == 0)
+ h = __nf_conntrack_helper_find(name, l3num, protonum);
+ }
+#endif
+ if (h != NULL && !try_module_get(h->me))
+ h = NULL;
+
+ return h;
+}
+EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
+
struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
{
struct nf_conn_help *help;
diff --git a/net/netfilter/xt_CT.c b/net/netfilter/xt_CT.c
new file mode 100644
index 0000000..8183a05
--- /dev/null
+++ b/net/netfilter/xt_CT.c
@@ -0,0 +1,158 @@
+/*
+ * Copyright (c) 2010 Patrick McHardy <kaber@trash.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/selinux.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_CT.h>
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_ecache.h>
+
+static unsigned int xt_ct_target(struct sk_buff *skb,
+ const struct xt_target_param *par)
+{
+ const struct xt_ct_target_info *info = par->targinfo;
+ struct nf_conn *ct = info->ct;
+
+ /* Previously seen (loopback)? Ignore. */
+ if (skb->nfct != NULL)
+ return XT_CONTINUE;
+
+ atomic_inc(&ct->ct_general.use);
+ skb->nfct = &ct->ct_general;
+ skb->nfctinfo = IP_CT_NEW;
+
+ return XT_CONTINUE;
+}
+
+static u8 xt_ct_find_proto(const struct xt_tgchk_param *par)
+{
+ if (par->family == AF_INET) {
+ const struct ipt_entry *e = par->entryinfo;
+
+ if (e->ip.invflags & IPT_INV_PROTO)
+ return 0;
+ return e->ip.proto;
+ } else if (par->family == AF_INET6) {
+ const struct ip6t_entry *e = par->entryinfo;
+
+ if (e->ipv6.invflags & IP6T_INV_PROTO)
+ return 0;
+ return e->ipv6.proto;
+ } else
+ return 0;
+}
+
+static bool xt_ct_tg_check(const struct xt_tgchk_param *par)
+{
+ struct xt_ct_target_info *info = par->targinfo;
+ struct nf_conntrack_tuple t;
+ struct nf_conn_help *help;
+ struct nf_conn *ct;
+ u8 proto;
+
+ if (info->flags & ~XT_CT_NOTRACK)
+ return false;
+
+ if (info->flags & XT_CT_NOTRACK) {
+ ct = &nf_conntrack_untracked;
+ atomic_inc(&ct->ct_general.use);
+ goto out;
+ }
+
+ if (nf_ct_l3proto_try_module_get(par->family) < 0)
+ goto err1;
+
+ memset(&t, 0, sizeof(t));
+ ct = nf_conntrack_alloc(par->net, &t, &t, GFP_KERNEL);
+ if (IS_ERR(ct))
+ goto err2;
+
+ if ((info->ct_events || info->exp_events) &&
+ !nf_ct_ecache_ext_add(ct, info->ct_events, info->exp_events,
+ GFP_KERNEL))
+ goto err3;
+
+ if (info->helper[0]) {
+ proto = xt_ct_find_proto(par);
+ if (!proto)
+ goto err3;
+
+ help = nf_ct_helper_ext_add(ct, GFP_KERNEL);
+ if (help == NULL)
+ goto err3;
+
+ help->helper = nf_conntrack_helper_try_module_get(info->helper,
+ par->family,
+ proto);
+ if (help->helper == NULL)
+ goto err3;
+ }
+
+ __set_bit(IPS_TEMPLATE_BIT, &ct->status);
+ __set_bit(IPS_CONFIRMED_BIT, &ct->status);
+out:
+ info->ct = ct;
+ return true;
+
+err3:
+ nf_conntrack_free(ct);
+err2:
+ nf_ct_l3proto_module_put(par->family);
+err1:
+ return false;
+}
+
+static void xt_ct_tg_destroy(const struct xt_tgdtor_param *par)
+{
+ struct xt_ct_target_info *info = par->targinfo;
+ struct nf_conn *ct = info->ct;
+ struct nf_conn_help *help;
+
+ if (ct != &nf_conntrack_untracked) {
+ help = nfct_help(ct);
+ if (help)
+ module_put(help->helper->me);
+
+ nf_ct_l3proto_module_put(par->family);
+ }
+ nf_ct_put(info->ct);
+}
+
+static struct xt_target xt_ct_tg __read_mostly = {
+ .name = "CT",
+ .family = NFPROTO_UNSPEC,
+ .targetsize = XT_ALIGN(sizeof(struct xt_ct_target_info)),
+ .checkentry = xt_ct_tg_check,
+ .destroy = xt_ct_tg_destroy,
+ .target = xt_ct_target,
+ .table = "raw",
+ .me = THIS_MODULE,
+};
+
+static int __init xt_ct_tg_init(void)
+{
+ return xt_register_target(&xt_ct_tg);
+}
+
+static void __exit xt_ct_tg_exit(void)
+{
+ xt_unregister_target(&xt_ct_tg);
+}
+
+module_init(xt_ct_tg_init);
+module_exit(xt_ct_tg_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Xtables: connection tracking target");
+MODULE_ALIAS("ipt_CT");
+MODULE_ALIAS("ip6t_CT");