mirror of
git://git.code.sf.net/p/xtables-addons/xtables-addons
synced 2025-09-07 21:25:12 +02:00
Initial commit.
Populate the iptables-addons repository with two modules, xt_TARPIT and xt_TEE, as a starting point. Signed-off-by: Jan Engelhardt <jengelh@computergmbh.de>
This commit is contained in:
Jan Engelhardt
248
extensions/xt_TEE.c
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248
extensions/xt_TEE.c
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/*
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* This implements the TEE target.
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*
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* Copyright (C) 2007 Sebastian Claßen <sebastian.classen@freenet.de> and
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* CC Computer Consultants GmbH, 2007
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*
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* based on ipt_ROUTE.c from Cédric de Launois <delaunois@info.ucl.ac.be>
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*
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* This software is distributed under GNU GPL v2, 1991
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*/
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#include <linux/ip.h>
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#include <linux/module.h>
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#include <linux/route.h>
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#include <linux/skbuff.h>
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#include <net/checksum.h>
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#include <net/icmp.h>
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#include <net/ip.h>
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#include <net/route.h>
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#include <linux/netfilter/x_tables.h>
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#ifdef CONFIG_NETFILTER_XT_TARGET_TEE
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# include <linux/netfilter/xt_TEE.h>
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#else
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# include "xt_TEE.h"
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#endif
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#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
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# define WITH_CONNTRACK 1
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# include <net/netfilter/nf_conntrack.h>
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static struct nf_conn tee_track;
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#endif
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static const union nf_inet_addr zero_address;
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/*
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* Try to route the packet according to the routing keys specified in
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* route_info. Keys are :
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* - ifindex :
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* 0 if no oif preferred,
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* otherwise set to the index of the desired oif
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* - route_info->gateway :
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* 0 if no gateway specified,
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* otherwise set to the next host to which the pkt must be routed
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* If success, skb->dev is the output device to which the packet must
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* be sent and skb->dst is not NULL
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*
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* RETURN: false - if an error occured
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* true - if the packet was succesfully routed to the
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* destination desired
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*/
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static bool tee_routing(struct sk_buff *skb,
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const struct xt_tee_tginfo *info)
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{
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int err;
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struct rtable *rt;
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struct iphdr *iph = ip_hdr(skb);
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struct flowi fl = {
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.nl_u = {
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.ip4_u = {
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.daddr = info->gw.ip,
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.tos = RT_TOS(iph->tos),
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.scope = RT_SCOPE_UNIVERSE,
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}
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}
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};
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/* Trying to route the packet using the standard routing table. */
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err = ip_route_output_key(&rt, &fl);
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if (err != 0) {
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if (net_ratelimit())
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pr_debug(KBUILD_MODNAME
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": could not route packet (%d)", err);
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return false;
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}
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/* Drop old route. */
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dst_release(skb->dst);
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skb->dst = NULL;
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/*
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* Success if no oif specified or if the oif correspond to the
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* one desired.
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* [SC]: always the case, because we have no oif.
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*/
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skb->dst = &rt->u.dst;
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skb->dev = skb->dst->dev;
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skb->protocol = htons(ETH_P_IP);
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return true;
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}
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/*
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* Stolen from ip_finish_output2
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* PRE : skb->dev is set to the device we are leaving by
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* skb->dst is not NULL
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* POST: the packet is sent with the link layer header pushed
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* the packet is destroyed
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*/
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static void tee_ip_direct_send(struct sk_buff *skb)
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{
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const struct dst_entry *dst = skb->dst;
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const struct net_device *dev = dst->dev;
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unsigned int hh_len = LL_RESERVED_SPACE(dev);
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/* Be paranoid, rather than too clever. */
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if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops != NULL)) {
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struct sk_buff *skb2;
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skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
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if (skb2 == NULL) {
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kfree_skb(skb);
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return;
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}
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if (skb->sk != NULL)
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skb_set_owner_w(skb2, skb->sk);
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kfree_skb(skb);
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skb = skb2;
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}
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if (dst->hh != NULL) {
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neigh_hh_output(dst->hh, skb);
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} else if (dst->neighbour != NULL) {
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dst->neighbour->output(skb);
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} else {
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if (net_ratelimit())
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pr_debug(KBUILD_MODNAME "no hdr & no neighbour cache!\n");
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kfree_skb(skb);
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}
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}
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/*
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* To detect and deter routed packet loopback when using the --tee option, we
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* take a page out of the raw.patch book: on the copied skb, we set up a fake
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* ->nfct entry, pointing to the local &route_tee_track. We skip routing
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* packets when we see they already have that ->nfct.
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*/
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static unsigned int
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tee_tg(struct sk_buff *skb, const struct net_device *in,
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const struct net_device *out, unsigned int hooknum,
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const struct xt_target *target, const void *targinfo)
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{
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const struct xt_tee_tginfo *info = targinfo;
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#ifdef WITH_CONNTRACK
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if (skb->nfct == &tee_track.ct_general) {
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/*
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* Loopback - a packet we already routed, is to be
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* routed another time. Avoid that, now.
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*/
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if (net_ratelimit())
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pr_debug(KBUILD_MODNAME "loopback - DROP!\n");
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return NF_DROP;
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}
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#endif
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/*
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* If we are in INPUT, the checksum must be recalculated since
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* the length could have changed as a result of defragmentation.
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*/
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if (hooknum == NF_INET_LOCAL_IN) {
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struct iphdr *iph = ip_hdr(skb);
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iph->check = 0;
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iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
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}
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/*
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* Copy the skb, and route the copy. Will later return %XT_CONTINUE for
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* the original skb, which should continue on its way as if nothing has
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* happened. The copy should be independantly delivered to the TEE --gw.
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*/
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skb = skb_copy(skb, GFP_ATOMIC);
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if (skb == NULL) {
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if (net_ratelimit())
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pr_debug(KBUILD_MODNAME "copy failed!\n");
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return XT_CONTINUE;
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}
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#ifdef WITH_CONNTRACK
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/*
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* Tell conntrack to forget this packet since it may get confused
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* when a packet is leaving with dst address == our address.
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* Good idea? Dunno. Need advice.
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*
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* NEW: mark the skb with our &tee_track, so we avoid looping
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* on any already routed packet.
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*/
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nf_conntrack_put(skb->nfct);
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skb->nfct = &tee_track.ct_general;
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skb->nfctinfo = IP_CT_NEW;
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nf_conntrack_get(skb->nfct);
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#endif
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if (tee_routing(skb, info))
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tee_ip_direct_send(skb);
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return XT_CONTINUE;
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}
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static bool tee_tg_check(const char *tablename, const void *entry,
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const struct xt_target *target, void *targinfo,
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unsigned int hook_mask)
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{
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const struct xt_tee_tginfo *info = targinfo;
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/* 0.0.0.0 and :: not allowed */
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return memcmp(&info->gw, &zero_address, sizeof(zero_address)) != 0;
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}
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static struct xt_target tee_tg_reg __read_mostly = {
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.name = "TEE",
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.family = AF_INET,
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.table = "mangle",
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.target = tee_tg,
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.targetsize = sizeof(struct xt_tee_tginfo),
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.checkentry = tee_tg_check,
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.me = THIS_MODULE,
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};
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static int __init tee_tg_init(void)
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{
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#ifdef WITH_CONNTRACK
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/*
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* Set up fake conntrack (stolen from raw.patch):
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* - to never be deleted, not in any hashes
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*/
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atomic_set(&tee_track.ct_general.use, 1);
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/* - and look it like as a confirmed connection */
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set_bit(IPS_CONFIRMED_BIT, &tee_track.status);
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/* Initialize fake conntrack so that NAT will skip it */
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tee_track.status |= IPS_NAT_DONE_MASK;
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#endif
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return xt_register_target(&tee_tg_reg);
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}
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static void __exit tee_tg_exit(void)
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{
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xt_unregister_target(&tee_tg_reg);
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/* [SC]: shoud not we cleanup tee_track here? */
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}
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module_init(tee_tg_init);
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module_exit(tee_tg_exit);
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MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
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MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>");
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MODULE_DESCRIPTION("Xtables: Reroute packet copy");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("ipt_TEE");
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