The TPROXY target implements redirection of non-local TCP/UDP traffic to local
sockets. Additionally, it's possible to manipulate the packet mark if and only
if a socket has been found. (We need this because we cannot use multiple
targets in the same iptables rule.)
Signed-off-by: Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx>
Signed-off-by: KOVACS Krisztian <hidden@xxxxxxxxxx>
---
include/linux/netfilter/xt_TPROXY.h | 14 +++++
net/netfilter/Kconfig | 13 +++++
net/netfilter/Makefile | 1
net/netfilter/xt_TPROXY.c | 97 +++++++++++++++++++++++++++++++++++
4 files changed, 125 insertions(+), 0 deletions(-)
diff --git a/include/linux/netfilter/xt_TPROXY.h b/include/linux/netfilter/xt_TPROXY.h
new file mode 100644
index 0000000..152e8f9
--- /dev/null
+++ b/include/linux/netfilter/xt_TPROXY.h
@@ -0,0 +1,14 @@
+#ifndef _XT_TPROXY_H_target
+#define _XT_TPROXY_H_target
+
+/* TPROXY target is capable of marking the packet to perform
+ * redirection. We can get rid of that whenever we get support for
+ * mutliple targets in the same rule. */
+struct xt_tproxy_target_info {
+ u_int32_t mark_mask;
+ u_int32_t mark_value;
+ __be32 laddr;
+ __be16 lport;
+};
+
+#endif /* _XT_TPROXY_H_target */
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 899fdde..441e46f 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -363,6 +363,19 @@ config NETFILTER_XT_TARGET_NOTRACK
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_TARGET_TPROXY
+ tristate '"TPROXY" target support'
+ depends on NETFILTER_TPROXY
+ depends on NETFILTER_XTABLES
+ select NF_DEFRAG_IPV4
+ help
+ This option adds a `TPROXY' target, which is somewhat similar to
+ REDIRECT. It can only be used in the mangle table and is useful
+ to redirect traffic to a transparent proxy. It does _not_ depend
+ on Netfilter connection tracking and NAT, unlike REDIRECT.
+
+ To compile it as a module, choose M here. If unsure, say N.
+
config NETFILTER_XT_TARGET_TRACE
tristate '"TRACE" target support'
depends on NETFILTER_XTABLES
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 7d7dbd6..0684e2b 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_NFLOG) += xt_NFLOG.o
obj-$(CONFIG_NETFILTER_XT_TARGET_NOTRACK) += xt_NOTRACK.o
obj-$(CONFIG_NETFILTER_XT_TARGET_TRACE) += xt_TRACE.o
obj-$(CONFIG_NETFILTER_XT_TARGET_SECMARK) += xt_SECMARK.o
+obj-$(CONFIG_NETFILTER_XT_TARGET_TPROXY) += xt_TPROXY.o
obj-$(CONFIG_NETFILTER_XT_TARGET_TCPMSS) += xt_TCPMSS.o
obj-$(CONFIG_NETFILTER_XT_TARGET_CONNSECMARK) += xt_CONNSECMARK.o
diff --git a/net/netfilter/xt_TPROXY.c b/net/netfilter/xt_TPROXY.c
new file mode 100644
index 0000000..395dad3
--- /dev/null
+++ b/net/netfilter/xt_TPROXY.c
@@ -0,0 +1,97 @@
+/*
+ * Transparent proxy support for Linux/iptables
+ *
+ * Copyright (c) 2006-2007 BalaBit IT Ltd.
+ * Author: Balazs Scheidler, Krisztian Kovacs
+ *
+ * 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/ip.h>
+#include <net/checksum.h>
+#include <net/udp.h>
+#include <net/inet_sock.h>
+
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_TPROXY.h>
+
+#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
+#include <net/netfilter/nf_tproxy_core.h>
+
+static unsigned int
+tproxy_target(struct sk_buff **pskb,
+ const struct net_device *in,
+ const struct net_device *out,
+ unsigned int hooknum,
+ const struct xt_target *target,
+ const void *targinfo)
+{
+ const struct iphdr *iph = ip_hdr(*pskb);
+ const struct xt_tproxy_target_info *tgi = targinfo;
+ struct sk_buff *skb = *pskb;
+ struct udphdr _hdr, *hp;
+ struct sock *sk;
+
+ /* TCP/UDP only */
+ if (iph->protocol != IPPROTO_TCP && iph->protocol != IPPROTO_UDP)
+ return NF_ACCEPT;
+
+ hp = skb_header_pointer(*pskb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
+ if (hp == NULL)
+ return NF_DROP;
+
+ sk = nf_tproxy_get_sock_v4(iph->protocol,
+ iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr,
+ hp->source, tgi->lport ? tgi->lport : hp->dest,
+ in, true);
+
+ /* NOTE: assign_sock consumes our sk reference */
+ if (sk && nf_tproxy_assign_sock(skb, sk)) {
+ /* This should be in a separate target, but we don't do multiple
+ targets on the same rule yet */
+ skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
+
+ pr_debug("redirecting: proto %u %08x:%u -> %08x:%u, mark: %x\n",
+ iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),
+ ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);
+ return NF_ACCEPT;
+ }
+
+ pr_debug("no socket, dropping: proto %u %08x:%u -> %08x:%u, mark: %x\n",
+ iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),
+ ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);
+ return NF_DROP;
+}
+
+static struct xt_target xt_tproxy_reg __read_mostly = {
+ .name = "TPROXY",
+ .family = AF_INET,
+ .table = "mangle",
+ .target = tproxy_target,
+ .targetsize = sizeof(struct xt_tproxy_target_info),
+ .hooks = 1 << NF_IP_PRE_ROUTING,
+ .me = THIS_MODULE,
+};
+
+static int __init xt_tproxy_init(void)
+{
+ nf_defrag_ipv4_enable();
+ return xt_register_target(&xt_tproxy_reg);
+}
+
+static void __exit xt_tproxy_fini(void)
+{
+ xt_unregister_target(&xt_tproxy_reg);
+}
+
+module_init(xt_tproxy_init);
+module_exit(xt_tproxy_fini);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Krisztian Kovacs");
+MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
+MODULE_ALIAS("ipt_TPROXY");
-
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