Netfilter: Import xt_TEE
Originally from Sebastian Classen.
xt_TEE is the logical successor to ipt_ROUTE; routing based on packet
charactersitics is done using xt_MARK/iproute2/fwmark nowadays, so
what remains of ipt_ROUTE is the --tee option, which xt_TEE implements.
Signed-off-by: Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx>
Cc: Sebastian Classen <sebastian.classen@xxxxxxxxxx>
---
include/linux/netfilter/xt_TEE.h | 12 +
net/netfilter/Kconfig | 13 ++
net/netfilter/Makefile | 1
net/netfilter/xt_TEE.c | 240 +++++++++++++++++++++++++++++++++++++++
4 files changed, 266 insertions(+)
Index: linux-2.6/include/linux/netfilter/xt_TEE.h
===================================================================
--- /dev/null
+++ linux-2.6/include/linux/netfilter/xt_TEE.h
@@ -0,0 +1,12 @@
+#ifndef _XT_TEE_TARGET_H
+#define _XT_TEE_TARGET_H
+
+struct xt_tee_target_info {
+ union {
+ /* Address of gateway */
+ u_int32_t gateway_v4;
+ u_int32_t gateway_v6[4];
+ };
+};
+
+#endif /* _XT_TEE_TARGET_H */
Index: linux-2.6/net/netfilter/Kconfig
===================================================================
--- linux-2.6.orig/net/netfilter/Kconfig
+++ linux-2.6/net/netfilter/Kconfig
@@ -411,6 +411,19 @@ config NETFILTER_XT_TARGET_TCPMSS
To compile it as a module, choose M here. If unsure, say N.
+config NETFILTER_XT_TARGET_TEE
+ tristate '"TEE" target support'
+ depends on NETFILTER_XTABLES && IP_NF_MANGLE
+ ---help---
+ This option adds a "TEE" target, which enables you to duplicate
+ packets and route those duplicates to a different gateway.
+
+ The target has to be used inside the mangle table.
+
+ If you want to compile it as a module, say M here and read
+ Documentation/modules.txt. The module will be called xt_TEE.ko.
+ If unsure, say N.
+
config NETFILTER_XT_MATCH_COMMENT
tristate '"comment" match support'
depends on NETFILTER_XTABLES
Index: linux-2.6/net/netfilter/Makefile
===================================================================
--- linux-2.6.orig/net/netfilter/Makefile
+++ linux-2.6/net/netfilter/Makefile
@@ -48,6 +48,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE
obj-$(CONFIG_NETFILTER_XT_TARGET_NOTRACK) += xt_NOTRACK.o
obj-$(CONFIG_NETFILTER_XT_TARGET_SECMARK) += xt_SECMARK.o
obj-$(CONFIG_NETFILTER_XT_TARGET_TCPMSS) += xt_TCPMSS.o
+obj-$(CONFIG_NETFILTER_XT_TARGET_TEE) += xt_TEE.o
obj-$(CONFIG_NETFILTER_XT_TARGET_TRACE) += xt_TRACE.o
# matches
Index: linux-2.6/net/netfilter/xt_TEE.c
===================================================================
--- /dev/null
+++ linux-2.6/net/netfilter/xt_TEE.c
@@ -0,0 +1,240 @@
+/*
+ * This implements the TEE target.
+ *
+ * Copyright (C) 2007 Sebastian Classen <sebastian.classen@xxxxxxxxxx> and
+ * CC Computer Consultants GmbH, 2007
+ * (Contact: Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx>)
+ *
+ * based on ipt_ROUTE.c from Cédric de Launois <delaunois@xxxxxxxxxxxxxx>
+ *
+ * This software is distributed under GNU GPL v2, 1991
+ */
+#include <linux/ip.h>
+#include <linux/module.h>
+#include <linux/route.h>
+#include <linux/skbuff.h>
+#include <net/checksum.h>
+#include <net/icmp.h>
+#include <net/ip.h>
+#include <net/route.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_TEE.h>
+
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+# define WITH_CONNTRACK 1
+# include <net/netfilter/nf_conntrack.h>
+static struct nf_conn tee_track;
+#endif
+
+/*
+ * Try to route the packet according to the routing keys specified in
+ * route_info. Keys are :
+ * - ifindex :
+ * 0 if no oif preferred,
+ * otherwise set to the index of the desired oif
+ * - route_info->gateway :
+ * 0 if no gateway specified,
+ * otherwise set to the next host to which the pkt must be routed
+ * If success, skb->dev is the output device to which the packet must
+ * be sent and skb->dst is not NULL
+ *
+ * RETURN: false - if an error occured
+ * true - if the packet was succesfully routed to the
+ * destination desired
+ */
+static bool tee_routing(struct sk_buff *skb,
+ const struct xt_tee_target_info *info)
+{
+ int err;
+ struct rtable *rt;
+ struct iphdr *iph = ip_hdr(skb);
+ struct flowi fl = {
+ .nl_u = {
+ .ip4_u = {
+ .daddr = iph->daddr,
+ .tos = RT_TOS(iph->tos),
+ .scope = RT_SCOPE_UNIVERSE,
+ }
+ }
+ };
+
+ /* The destination address may be overloaded by the target */
+ if (info->gateway_v4 != 0)
+ fl.fl4_dst = info->gateway_v4;
+
+ /* Trying to route the packet using the standard routing table. */
+ err = ip_route_output_key(&rt, &fl);
+ if (err != 0) {
+ if (net_ratelimit())
+ pr_debug(KBUILD_MODNAME
+ ": could not route packet (%d)", err);
+ return false;
+ }
+
+ /* Drop old route. */
+ dst_release(skb->dst);
+ skb->dst = NULL;
+
+ /*
+ * Success if no oif specified or if the oif correspond to the
+ * one desired.
+ * [SC]: always the case, because we have no oif.
+ */
+ skb->dst = &rt->u.dst;
+ skb->dev = skb->dst->dev;
+ skb->protocol = htons(ETH_P_IP);
+ return true;
+}
+
+/*
+ * Stolen from ip_finish_output2
+ * PRE : skb->dev is set to the device we are leaving by
+ * skb->dst is not NULL
+ * POST: the packet is sent with the link layer header pushed
+ * the packet is destroyed
+ */
+static void tee_ip_direct_send(struct sk_buff *skb)
+{
+ const struct dst_entry *dst = skb->dst;
+ const struct net_device *dev = dst->dev;
+ unsigned int hh_len = LL_RESERVED_SPACE(dev);
+
+ /* Be paranoid, rather than too clever. */
+ if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops != NULL)) {
+ struct sk_buff *skb2;
+
+ skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
+ if (skb2 == NULL) {
+ kfree_skb(skb);
+ return;
+ }
+ if (skb->sk != NULL)
+ skb_set_owner_w(skb2, skb->sk);
+ kfree_skb(skb);
+ skb = skb2;
+ }
+
+ if (dst->hh != NULL) {
+ neigh_hh_output(dst->hh, skb);
+ } else if (dst->neighbour != NULL) {
+ dst->neighbour->output(skb);
+ } else {
+ if (net_ratelimit())
+ pr_debug(KBUILD_MODNAME "no hdr & no neighbour cache!\n");
+ kfree_skb(skb);
+ }
+}
+
+/*
+ * To detect and deter routed packet loopback when using the --tee option, we
+ * take a page out of the raw.patch book: on the copied skb, we set up a fake
+ * ->nfct entry, pointing to the local &route_tee_track. We skip routing
+ * packets when we see they already have that ->nfct.
+ */
+static unsigned int
+tee_tg(struct sk_buff *skb, const struct net_device *in,
+ const struct net_device *out, unsigned int hooknum,
+ const struct xt_target *target, const void *targinfo)
+{
+ const struct xt_tee_target_info *info = targinfo;
+
+#ifdef WITH_CONNTRACK
+ if (skb->nfct == &tee_track.ct_general) {
+ /*
+ * Loopback - a packet we already routed, is to be
+ * routed another time. Avoid that, now.
+ */
+ if (net_ratelimit())
+ pr_debug(KBUILD_MODNAME "loopback - DROP!\n");
+ return NF_DROP;
+ }
+#endif
+
+ /*
+ * If we are in INPUT, the checksum must be recalculated since
+ * the length could have changed as a result of defragmentation.
+ */
+ if (hooknum == NF_INET_LOCAL_IN) {
+ struct iphdr *iph = ip_hdr(skb);
+ iph->check = 0;
+ iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
+ }
+
+ /*
+ * Copy the skb, and route the copy. Will later return %XT_CONTINUE for
+ * the original skb, which should continue on its way as if nothing has
+ * happened. The copy should be independantly delivered to the TEE --gw.
+ */
+ skb = skb_copy(skb, GFP_ATOMIC);
+ if (skb == NULL) {
+ if (net_ratelimit())
+ pr_debug(KBUILD_MODNAME "copy failed!\n");
+ return XT_CONTINUE;
+ }
+
+#ifdef WITH_CONNTRACK
+ /*
+ * Tell conntrack to forget this packet since it may get confused
+ * when a packet is leaving with dst address == our address.
+ * Good idea? Dunno. Need advice.
+ *
+ * NEW: mark the skb with our &tee_track, so we avoid looping
+ * on any already routed packet.
+ */
+ nf_conntrack_put(skb->nfct);
+ skb->nfct = &tee_track.ct_general;
+ skb->nfctinfo = IP_CT_NEW;
+ nf_conntrack_get(skb->nfct);
+#endif
+
+ if (info->gateway_v4 != 0) {
+ if (tee_routing(skb, info))
+ tee_ip_direct_send(skb);
+ } else {
+ if (net_ratelimit())
+ pr_debug(KBUILD_MODNAME ": no parameter!\n");
+ }
+
+ return XT_CONTINUE;
+}
+
+static struct xt_target tee_tg_reg __read_mostly = {
+ .name = "TEE",
+ .family = AF_INET,
+ .table = "mangle",
+ .target = tee_tg,
+ .targetsize = sizeof(struct xt_tee_target_info),
+ .me = THIS_MODULE,
+};
+
+static int __init tee_tg_init(void)
+{
+#ifdef WITH_CONNTRACK
+ /*
+ * Set up fake conntrack (stolen from raw.patch):
+ * - to never be deleted, not in any hashes
+ */
+ atomic_set(&tee_track.ct_general.use, 1);
+
+ /* - and look it like as a confirmed connection */
+ set_bit(IPS_CONFIRMED_BIT, &tee_track.status);
+
+ /* Initialize fake conntrack so that NAT will skip it */
+ tee_track.status |= IPS_NAT_DONE_MASK;
+#endif
+
+ return xt_register_target(&tee_tg_reg);
+}
+
+static void __exit tee_tg_exit(void)
+{
+ xt_unregister_target(&tee_tg_reg);
+ /* [SC]: shoud not we cleanup tee_track here? */
+}
+
+module_init(tee_tg_init);
+module_exit(tee_tg_exit);
+MODULE_AUTHOR("Sebastian Classen <sebastian.classen@xxxxxxxxxx>, Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("netfilter \"TEE\" target module");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_TEE");
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