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1 /*
2  * Transparent proxy support for Linux/iptables
3  *
4  * Copyright (c) 2006-2010 BalaBit IT Ltd.
5  * Author: Balazs Scheidler, Krisztian Kovacs
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  *
11  */
12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 #include <linux/module.h>
14 #include <linux/skbuff.h>
15 #include <linux/ip.h>
16 #include <net/checksum.h>
17 #include <net/udp.h>
18 #include <net/tcp.h>
19 #include <net/inet_sock.h>
20 #include <net/inet_hashtables.h>
21 #include <linux/inetdevice.h>
22 #include <linux/netfilter/x_tables.h>
23 #include <linux/netfilter_ipv4/ip_tables.h>
24
25 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
26
27 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
28 #define XT_TPROXY_HAVE_IPV6 1
29 #include <net/if_inet6.h>
30 #include <net/addrconf.h>
31 #include <net/inet6_hashtables.h>
32 #include <linux/netfilter_ipv6/ip6_tables.h>
33 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
34 #endif
35
36 #include <linux/netfilter/xt_TPROXY.h>
37
38 enum nf_tproxy_lookup_t {
39          NFT_LOOKUP_LISTENER,
40          NFT_LOOKUP_ESTABLISHED,
41 };
42
43 static bool tproxy_sk_is_transparent(struct sock *sk)
44 {
45         switch (sk->sk_state) {
46         case TCP_TIME_WAIT:
47                 if (inet_twsk(sk)->tw_transparent)
48                         return true;
49                 break;
50         case TCP_NEW_SYN_RECV:
51                 if (inet_rsk(inet_reqsk(sk))->no_srccheck)
52                         return true;
53                 break;
54         default:
55                 if (inet_sk(sk)->transparent)
56                         return true;
57         }
58
59         sock_gen_put(sk);
60         return false;
61 }
62
63 static inline __be32
64 tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr)
65 {
66         struct in_device *indev;
67         __be32 laddr;
68
69         if (user_laddr)
70                 return user_laddr;
71
72         laddr = 0;
73         rcu_read_lock();
74         indev = __in_dev_get_rcu(skb->dev);
75         for_primary_ifa(indev) {
76                 laddr = ifa->ifa_local;
77                 break;
78         } endfor_ifa(indev);
79         rcu_read_unlock();
80
81         return laddr ? laddr : daddr;
82 }
83
84 /*
85  * This is used when the user wants to intercept a connection matching
86  * an explicit iptables rule. In this case the sockets are assumed
87  * matching in preference order:
88  *
89  *   - match: if there's a fully established connection matching the
90  *     _packet_ tuple, it is returned, assuming the redirection
91  *     already took place and we process a packet belonging to an
92  *     established connection
93  *
94  *   - match: if there's a listening socket matching the redirection
95  *     (e.g. on-port & on-ip of the connection), it is returned,
96  *     regardless if it was bound to 0.0.0.0 or an explicit
97  *     address. The reasoning is that if there's an explicit rule, it
98  *     does not really matter if the listener is bound to an interface
99  *     or to 0. The user already stated that he wants redirection
100  *     (since he added the rule).
101  *
102  * Please note that there's an overlap between what a TPROXY target
103  * and a socket match will match. Normally if you have both rules the
104  * "socket" match will be the first one, effectively all packets
105  * belonging to established connections going through that one.
106  */
107 static inline struct sock *
108 nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb, void *hp,
109                       const u8 protocol,
110                       const __be32 saddr, const __be32 daddr,
111                       const __be16 sport, const __be16 dport,
112                       const struct net_device *in,
113                       const enum nf_tproxy_lookup_t lookup_type)
114 {
115         struct sock *sk;
116         struct tcphdr *tcph;
117
118         switch (protocol) {
119         case IPPROTO_TCP:
120                 switch (lookup_type) {
121                 case NFT_LOOKUP_LISTENER:
122                         tcph = hp;
123                         sk = inet_lookup_listener(net, &tcp_hashinfo, skb,
124                                                     ip_hdrlen(skb) +
125                                                       __tcp_hdrlen(tcph),
126                                                     saddr, sport,
127                                                     daddr, dport,
128                                                     in->ifindex);
129
130                         if (sk && !atomic_inc_not_zero(&sk->sk_refcnt))
131                                 sk = NULL;
132                         /* NOTE: we return listeners even if bound to
133                          * 0.0.0.0, those are filtered out in
134                          * xt_socket, since xt_TPROXY needs 0 bound
135                          * listeners too
136                          */
137                         break;
138                 case NFT_LOOKUP_ESTABLISHED:
139                         sk = inet_lookup_established(net, &tcp_hashinfo,
140                                                     saddr, sport, daddr, dport,
141                                                     in->ifindex);
142                         break;
143                 default:
144                         BUG();
145                 }
146                 break;
147         case IPPROTO_UDP:
148                 sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
149                                      in->ifindex);
150                 if (sk) {
151                         int connected = (sk->sk_state == TCP_ESTABLISHED);
152                         int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
153
154                         /* NOTE: we return listeners even if bound to
155                          * 0.0.0.0, those are filtered out in
156                          * xt_socket, since xt_TPROXY needs 0 bound
157                          * listeners too
158                          */
159                         if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
160                             (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
161                                 sock_put(sk);
162                                 sk = NULL;
163                         }
164                 }
165                 break;
166         default:
167                 WARN_ON(1);
168                 sk = NULL;
169         }
170
171         pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
172                  protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
173
174         return sk;
175 }
176
177 #ifdef XT_TPROXY_HAVE_IPV6
178 static inline struct sock *
179 nf_tproxy_get_sock_v6(struct net *net, struct sk_buff *skb, int thoff, void *hp,
180                       const u8 protocol,
181                       const struct in6_addr *saddr, const struct in6_addr *daddr,
182                       const __be16 sport, const __be16 dport,
183                       const struct net_device *in,
184                       const enum nf_tproxy_lookup_t lookup_type)
185 {
186         struct sock *sk;
187         struct tcphdr *tcph;
188
189         switch (protocol) {
190         case IPPROTO_TCP:
191                 switch (lookup_type) {
192                 case NFT_LOOKUP_LISTENER:
193                         tcph = hp;
194                         sk = inet6_lookup_listener(net, &tcp_hashinfo, skb,
195                                                    thoff + __tcp_hdrlen(tcph),
196                                                    saddr, sport,
197                                                    daddr, ntohs(dport),
198                                                    in->ifindex);
199
200                         if (sk && !atomic_inc_not_zero(&sk->sk_refcnt))
201                                 sk = NULL;
202                         /* NOTE: we return listeners even if bound to
203                          * 0.0.0.0, those are filtered out in
204                          * xt_socket, since xt_TPROXY needs 0 bound
205                          * listeners too
206                          */
207                         break;
208                 case NFT_LOOKUP_ESTABLISHED:
209                         sk = __inet6_lookup_established(net, &tcp_hashinfo,
210                                                         saddr, sport, daddr, ntohs(dport),
211                                                         in->ifindex);
212                         break;
213                 default:
214                         BUG();
215                 }
216                 break;
217         case IPPROTO_UDP:
218                 sk = udp6_lib_lookup(net, saddr, sport, daddr, dport,
219                                      in->ifindex);
220                 if (sk) {
221                         int connected = (sk->sk_state == TCP_ESTABLISHED);
222                         int wildcard = ipv6_addr_any(&sk->sk_v6_rcv_saddr);
223
224                         /* NOTE: we return listeners even if bound to
225                          * 0.0.0.0, those are filtered out in
226                          * xt_socket, since xt_TPROXY needs 0 bound
227                          * listeners too
228                          */
229                         if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
230                             (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
231                                 sock_put(sk);
232                                 sk = NULL;
233                         }
234                 }
235                 break;
236         default:
237                 WARN_ON(1);
238                 sk = NULL;
239         }
240
241         pr_debug("tproxy socket lookup: proto %u %pI6:%u -> %pI6:%u, lookup type: %d, sock %p\n",
242                  protocol, saddr, ntohs(sport), daddr, ntohs(dport), lookup_type, sk);
243
244         return sk;
245 }
246 #endif
247
248 /**
249  * tproxy_handle_time_wait4 - handle IPv4 TCP TIME_WAIT reopen redirections
250  * @skb:        The skb being processed.
251  * @laddr:      IPv4 address to redirect to or zero.
252  * @lport:      TCP port to redirect to or zero.
253  * @sk:         The TIME_WAIT TCP socket found by the lookup.
254  *
255  * We have to handle SYN packets arriving to TIME_WAIT sockets
256  * differently: instead of reopening the connection we should rather
257  * redirect the new connection to the proxy if there's a listener
258  * socket present.
259  *
260  * tproxy_handle_time_wait4() consumes the socket reference passed in.
261  *
262  * Returns the listener socket if there's one, the TIME_WAIT socket if
263  * no such listener is found, or NULL if the TCP header is incomplete.
264  */
265 static struct sock *
266 tproxy_handle_time_wait4(struct net *net, struct sk_buff *skb,
267                          __be32 laddr, __be16 lport, struct sock *sk)
268 {
269         const struct iphdr *iph = ip_hdr(skb);
270         struct tcphdr _hdr, *hp;
271
272         hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
273         if (hp == NULL) {
274                 inet_twsk_put(inet_twsk(sk));
275                 return NULL;
276         }
277
278         if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
279                 /* SYN to a TIME_WAIT socket, we'd rather redirect it
280                  * to a listener socket if there's one */
281                 struct sock *sk2;
282
283                 sk2 = nf_tproxy_get_sock_v4(net, skb, hp, iph->protocol,
284                                             iph->saddr, laddr ? laddr : iph->daddr,
285                                             hp->source, lport ? lport : hp->dest,
286                                             skb->dev, NFT_LOOKUP_LISTENER);
287                 if (sk2) {
288                         inet_twsk_deschedule_put(inet_twsk(sk));
289                         sk = sk2;
290                 }
291         }
292
293         return sk;
294 }
295
296 /* assign a socket to the skb -- consumes sk */
297 static void
298 nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk)
299 {
300         skb_orphan(skb);
301         skb->sk = sk;
302         skb->destructor = sock_edemux;
303 }
304
305 static unsigned int
306 tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport,
307            u_int32_t mark_mask, u_int32_t mark_value)
308 {
309         const struct iphdr *iph = ip_hdr(skb);
310         struct udphdr _hdr, *hp;
311         struct sock *sk;
312
313         hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
314         if (hp == NULL)
315                 return NF_DROP;
316
317         /* check if there's an ongoing connection on the packet
318          * addresses, this happens if the redirect already happened
319          * and the current packet belongs to an already established
320          * connection */
321         sk = nf_tproxy_get_sock_v4(net, skb, hp, iph->protocol,
322                                    iph->saddr, iph->daddr,
323                                    hp->source, hp->dest,
324                                    skb->dev, NFT_LOOKUP_ESTABLISHED);
325
326         laddr = tproxy_laddr4(skb, laddr, iph->daddr);
327         if (!lport)
328                 lport = hp->dest;
329
330         /* UDP has no TCP_TIME_WAIT state, so we never enter here */
331         if (sk && sk->sk_state == TCP_TIME_WAIT)
332                 /* reopening a TIME_WAIT connection needs special handling */
333                 sk = tproxy_handle_time_wait4(net, skb, laddr, lport, sk);
334         else if (!sk)
335                 /* no, there's no established connection, check if
336                  * there's a listener on the redirected addr/port */
337                 sk = nf_tproxy_get_sock_v4(net, skb, hp, iph->protocol,
338                                            iph->saddr, laddr,
339                                            hp->source, lport,
340                                            skb->dev, NFT_LOOKUP_LISTENER);
341
342         /* NOTE: assign_sock consumes our sk reference */
343         if (sk && tproxy_sk_is_transparent(sk)) {
344                 /* This should be in a separate target, but we don't do multiple
345                    targets on the same rule yet */
346                 skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
347
348                 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
349                          iph->protocol, &iph->daddr, ntohs(hp->dest),
350                          &laddr, ntohs(lport), skb->mark);
351
352                 nf_tproxy_assign_sock(skb, sk);
353                 return NF_ACCEPT;
354         }
355
356         pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
357                  iph->protocol, &iph->saddr, ntohs(hp->source),
358                  &iph->daddr, ntohs(hp->dest), skb->mark);
359         return NF_DROP;
360 }
361
362 static unsigned int
363 tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
364 {
365         const struct xt_tproxy_target_info *tgi = par->targinfo;
366
367         return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport,
368                           tgi->mark_mask, tgi->mark_value);
369 }
370
371 static unsigned int
372 tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
373 {
374         const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
375
376         return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport,
377                           tgi->mark_mask, tgi->mark_value);
378 }
379
380 #ifdef XT_TPROXY_HAVE_IPV6
381
382 static inline const struct in6_addr *
383 tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr,
384               const struct in6_addr *daddr)
385 {
386         struct inet6_dev *indev;
387         struct inet6_ifaddr *ifa;
388         struct in6_addr *laddr;
389
390         if (!ipv6_addr_any(user_laddr))
391                 return user_laddr;
392         laddr = NULL;
393
394         rcu_read_lock();
395         indev = __in6_dev_get(skb->dev);
396         if (indev) {
397                 read_lock_bh(&indev->lock);
398                 list_for_each_entry(ifa, &indev->addr_list, if_list) {
399                         if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED))
400                                 continue;
401
402                         laddr = &ifa->addr;
403                         break;
404                 }
405                 read_unlock_bh(&indev->lock);
406         }
407         rcu_read_unlock();
408
409         return laddr ? laddr : daddr;
410 }
411
412 /**
413  * tproxy_handle_time_wait6 - handle IPv6 TCP TIME_WAIT reopen redirections
414  * @skb:        The skb being processed.
415  * @tproto:     Transport protocol.
416  * @thoff:      Transport protocol header offset.
417  * @par:        Iptables target parameters.
418  * @sk:         The TIME_WAIT TCP socket found by the lookup.
419  *
420  * We have to handle SYN packets arriving to TIME_WAIT sockets
421  * differently: instead of reopening the connection we should rather
422  * redirect the new connection to the proxy if there's a listener
423  * socket present.
424  *
425  * tproxy_handle_time_wait6() consumes the socket reference passed in.
426  *
427  * Returns the listener socket if there's one, the TIME_WAIT socket if
428  * no such listener is found, or NULL if the TCP header is incomplete.
429  */
430 static struct sock *
431 tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff,
432                          const struct xt_action_param *par,
433                          struct sock *sk)
434 {
435         const struct ipv6hdr *iph = ipv6_hdr(skb);
436         struct tcphdr _hdr, *hp;
437         const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
438
439         hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
440         if (hp == NULL) {
441                 inet_twsk_put(inet_twsk(sk));
442                 return NULL;
443         }
444
445         if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
446                 /* SYN to a TIME_WAIT socket, we'd rather redirect it
447                  * to a listener socket if there's one */
448                 struct sock *sk2;
449
450                 sk2 = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, hp, tproto,
451                                             &iph->saddr,
452                                             tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr),
453                                             hp->source,
454                                             tgi->lport ? tgi->lport : hp->dest,
455                                             skb->dev, NFT_LOOKUP_LISTENER);
456                 if (sk2) {
457                         inet_twsk_deschedule_put(inet_twsk(sk));
458                         sk = sk2;
459                 }
460         }
461
462         return sk;
463 }
464
465 static unsigned int
466 tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
467 {
468         const struct ipv6hdr *iph = ipv6_hdr(skb);
469         const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
470         struct udphdr _hdr, *hp;
471         struct sock *sk;
472         const struct in6_addr *laddr;
473         __be16 lport;
474         int thoff = 0;
475         int tproto;
476
477         tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
478         if (tproto < 0) {
479                 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
480                 return NF_DROP;
481         }
482
483         hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
484         if (hp == NULL) {
485                 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
486                 return NF_DROP;
487         }
488
489         /* check if there's an ongoing connection on the packet
490          * addresses, this happens if the redirect already happened
491          * and the current packet belongs to an already established
492          * connection */
493         sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, hp, tproto,
494                                    &iph->saddr, &iph->daddr,
495                                    hp->source, hp->dest,
496                                    xt_in(par), NFT_LOOKUP_ESTABLISHED);
497
498         laddr = tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
499         lport = tgi->lport ? tgi->lport : hp->dest;
500
501         /* UDP has no TCP_TIME_WAIT state, so we never enter here */
502         if (sk && sk->sk_state == TCP_TIME_WAIT)
503                 /* reopening a TIME_WAIT connection needs special handling */
504                 sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, sk);
505         else if (!sk)
506                 /* no there's no established connection, check if
507                  * there's a listener on the redirected addr/port */
508                 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, hp,
509                                            tproto, &iph->saddr, laddr,
510                                            hp->source, lport,
511                                            xt_in(par), NFT_LOOKUP_LISTENER);
512
513         /* NOTE: assign_sock consumes our sk reference */
514         if (sk && tproxy_sk_is_transparent(sk)) {
515                 /* This should be in a separate target, but we don't do multiple
516                    targets on the same rule yet */
517                 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
518
519                 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
520                          tproto, &iph->saddr, ntohs(hp->source),
521                          laddr, ntohs(lport), skb->mark);
522
523                 nf_tproxy_assign_sock(skb, sk);
524                 return NF_ACCEPT;
525         }
526
527         pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
528                  tproto, &iph->saddr, ntohs(hp->source),
529                  &iph->daddr, ntohs(hp->dest), skb->mark);
530
531         return NF_DROP;
532 }
533
534 static int tproxy_tg6_check(const struct xt_tgchk_param *par)
535 {
536         const struct ip6t_ip6 *i = par->entryinfo;
537         int err;
538
539         err = nf_defrag_ipv6_enable(par->net);
540         if (err)
541                 return err;
542
543         if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
544             !(i->invflags & IP6T_INV_PROTO))
545                 return 0;
546
547         pr_info("Can be used only in combination with "
548                 "either -p tcp or -p udp\n");
549         return -EINVAL;
550 }
551 #endif
552
553 static int tproxy_tg4_check(const struct xt_tgchk_param *par)
554 {
555         const struct ipt_ip *i = par->entryinfo;
556         int err;
557
558         err = nf_defrag_ipv4_enable(par->net);
559         if (err)
560                 return err;
561
562         if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
563             && !(i->invflags & IPT_INV_PROTO))
564                 return 0;
565
566         pr_info("Can be used only in combination with "
567                 "either -p tcp or -p udp\n");
568         return -EINVAL;
569 }
570
571 static struct xt_target tproxy_tg_reg[] __read_mostly = {
572         {
573                 .name           = "TPROXY",
574                 .family         = NFPROTO_IPV4,
575                 .table          = "mangle",
576                 .target         = tproxy_tg4_v0,
577                 .revision       = 0,
578                 .targetsize     = sizeof(struct xt_tproxy_target_info),
579                 .checkentry     = tproxy_tg4_check,
580                 .hooks          = 1 << NF_INET_PRE_ROUTING,
581                 .me             = THIS_MODULE,
582         },
583         {
584                 .name           = "TPROXY",
585                 .family         = NFPROTO_IPV4,
586                 .table          = "mangle",
587                 .target         = tproxy_tg4_v1,
588                 .revision       = 1,
589                 .targetsize     = sizeof(struct xt_tproxy_target_info_v1),
590                 .checkentry     = tproxy_tg4_check,
591                 .hooks          = 1 << NF_INET_PRE_ROUTING,
592                 .me             = THIS_MODULE,
593         },
594 #ifdef XT_TPROXY_HAVE_IPV6
595         {
596                 .name           = "TPROXY",
597                 .family         = NFPROTO_IPV6,
598                 .table          = "mangle",
599                 .target         = tproxy_tg6_v1,
600                 .revision       = 1,
601                 .targetsize     = sizeof(struct xt_tproxy_target_info_v1),
602                 .checkentry     = tproxy_tg6_check,
603                 .hooks          = 1 << NF_INET_PRE_ROUTING,
604                 .me             = THIS_MODULE,
605         },
606 #endif
607
608 };
609
610 static int __init tproxy_tg_init(void)
611 {
612         return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
613 }
614
615 static void __exit tproxy_tg_exit(void)
616 {
617         xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
618 }
619
620 module_init(tproxy_tg_init);
621 module_exit(tproxy_tg_exit);
622 MODULE_LICENSE("GPL");
623 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
624 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
625 MODULE_ALIAS("ipt_TPROXY");
626 MODULE_ALIAS("ip6t_TPROXY");