1 /* 6bed4/router.c -- traffic forwarding daemon for public TSP service
3 * This is an implementation of the profile that makes TSP service publicly
4 * usable, that is without authentication. However to avoid abuse of such
5 * a service, it is not anonymous -- IPv6 addresses contain the IPv4 address
8 * This is an implementation of neighbour and router discovery over a
9 * tunnel that packs IPv6 inside UDP/IPv4. This tunnel mechanism is
10 * targeted specifically at embedded devices that are to function on
11 * any network, including IPv4-only, while being designed as IPv6-only
12 * devices with a fallback to this tunnel.
14 * Interestingly, as a side-effect of this design the router daemon can be
15 * stateless. Any further requirements that are stateful are most likely
16 * filtering, and that can be solved in stateful firewall configuration.
18 * The intention of TSP is to enable IPv4-only hosts to connecto to
19 * IPv6 services; the public TSP profile adds to that the ability to
20 * do it in a temporary manner.
22 * TODO: Should we translate ICMPv4 --> ICMPv6?
24 * From: Rick van Rein <rick@openfortress.nl>
40 #include <sys/types.h>
41 #include <sys/socket.h>
43 #include <sys/select.h>
44 #include <sys/ioctl.h>
46 #include <netinet/in.h>
47 #include <netinet/ip.h>
48 #include <netinet/ip6.h>
49 #include <netinet/tcp.h>
50 #include <netinet/udp.h>
51 #include <netinet/icmp6.h>
52 #include <arpa/inet.h>
55 #include <linux/if_tun.h>
56 #include <linux/if_ether.h>
59 /* The following will initially fail, due to an IANA obligation to avoid
60 * default builds with non-standard options.
68 * The HAVE_SETUP_TUNNEL variable is used to determine whether absense of
69 * the -d option leads to an error, or to an attempt to setup the tunnel.
70 * The setup_tunnel() function used for that is defined per platform, such
71 * as for LINUX. Remember to maintain the manpage's optionality for -d.
73 #undef HAVE_SETUP_TUNNEL
76 /* Global variables */
78 /* SCTP structures are far from standardised, so we define our own header */
80 uint16_t source, dest;
90 char *v4server = NULL;
91 char *v6server = NULL;
92 char *v6prefix = NULL;
94 const uint8_t v6listen_linklocal [16] = { 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
95 uint8_t v6listen_linklocal_complete [16] = { 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
97 uint8_t lladdr_6bed4 [6];
99 struct sockaddr_in v4name;
100 struct sockaddr_in6 v6name;
102 struct in6_addr v6listen;
103 struct in6_addr v6listen_complete;
104 struct in_addr v4listen;
111 struct ip6_hdr v6hdr;
112 uint8_t data [MTU - sizeof (struct ip6_hdr)];
115 struct ip6_hdr v6hdr;
117 struct icmp6_hdr v6icmphdr;
118 struct my_sctphdr v6sctphdr;
119 struct tcphdr v6tcphdr ;
120 struct udphdr v6udphdr ;
122 struct udphdr v6udphdr;
123 struct my_sctphdr v6sctphdr;
130 #define v4tunpi6 ( v4data6.tun)
131 #define v4data ((uint8_t *) &v4data6.udata)
132 #define v4hdr6 (&v4data6.udata.idata.v6hdr)
133 #define v4src6 (&v4data6.udata.idata.v6hdr.ip6_src)
134 #define v4dst6 (&v4data6.udata.idata.v6hdr.ip6_dst)
136 #define v4v6payload ((uint16_t *) &v4data6.udata.ndata.adata)
137 #define v4v6plen ( v4data6.udata.ndata.v6hdr.ip6_plen)
138 #define v4v6nexthdr ( v4data6.udata.ndata.v6hdr.ip6_nxt)
139 #define v4v6hoplimit ( v4data6.udata.ndata.v6hdr.ip6_hops)
141 #define v4v6icmpdata ( v4data6.udata.ndata.adata.v6icmphdr.icmp6_data8)
142 #define v4v6icmptype ( v4data6.udata.ndata.adata.v6icmphdr.icmp6_type)
143 #define v4v6icmpcode ( v4data6.udata.ndata.adata.v6icmphdr.icmp6_code)
144 #define v4v6icmpcksum ( v4data6.udata.ndata.adata.v6icmphdr.icmp6_cksum)
146 #define v4v6sctpofs (offsetof (struct v4frame,adata.v6sctphdr))
147 #define v4v6sctpsrcport ( v4data6.udata.ndata.adata.v6sctphdr.source)
148 #define v4v6sctpdstport ( v4data6.udata.ndata.adata.v6sctphdr.dest)
149 #define v4v6sctpcksum ( v4data6.udata.ndata.adata.v6sctphdr.cksum)
151 #define v4v6tunsctpofs (offsetof (struct v4frame,adata.tdata.v6sctphdr))
152 #define v4v6tunsctpsrcport ( v4data6.udata.ndata.adata.tdata.v6sctphdr.source)
153 #define v4v6tunsctpdstport ( v4data6.udata.ndata.adata.tdata.v6sctphdr.dest)
154 #define v4v6tunsctpcksum ( v4data6.udata.ndata.adata.tdata.v6sctphdr.cksum)
156 #define v4v6tcpsrcport ( v4data6.udata.ndata.adata.v6tcphdr.source)
157 #define v4v6tcpdstport ( v4data6.udata.ndata.adata.v6tcphdr.dest)
158 #define v4v6tcpcksum ( v4data6.udata.ndata.adata.v6tcphdr.check)
160 #define v4v6udpsrcport ( v4data6.udata.ndata.adata.v6udphdr.source)
161 #define v4v6udpdstport ( v4data6.udata.ndata.adata.v6udphdr.dest)
162 #define v4v6udpcksum ( v4data6.udata.ndata.adata.v6udphdr.check)
164 #define v4ngbsoltarget (&v4data6.udata.ndata.adata.v6icmphdr.icmp6_data8 [4])
172 struct ip6_hdr v6hdr;
174 struct icmp6_hdr v6icmphdr;
175 struct my_sctphdr v6sctphdr;
176 struct tcphdr v6tcphdr ;
177 struct udphdr v6udphdr ;
179 struct udphdr v6udphdr;
180 struct my_sctphdr v6sctphdr;
188 #define v6tuncmd ( v6data6.tun)
189 #define v6data ( v6data6.udata.data)
190 #define v6hdr6 (&v6data6.udata.ndata.v6hdr)
191 #define v6src6 (&v6data6.udata.ndata.v6hdr.ip6_src)
192 #define v6dst6 (&v6data6.udata.ndata.v6hdr.ip6_dst)
193 #define v6hoplimit ( v6data6.udata.ndata.v6hdr.ip6_hops)
194 #define v6nexthdr ( v6data6.udata.ndata.v6hdr.ip6_nxt)
196 #define v6icmptype ( v6data6.udata.ndata.adata.v6icmphdr.icmp6_type)
197 #define v6icmpcksum ( v6data6.udata.ndata.adata.v6icmphdr.icmp6_cksum)
199 #define v6sctpcksum ( v6data6.udata.ndata.adata.v6sctphdr.cksum)
200 #define v6tunsctpcksum ( v6data6.udata.ndata.adata.tdata.v6sctphdr.cksum)
202 #define v6sctpofs (offsetof(struct v6frame,adata.v6sctphdr))
203 #define v6tunsctpofs (offsetof(struct v6frame,adata.tdata.v6sctphdr))
205 #define v6tcpcksum ( v6data6.udata.ndata.adata.v6tcphdr.check)
207 #define v6udpcksum ( v6data6.udata.ndata.adata.v6udphdr.check)
208 #define v6udpdstport ( v6data6.udata.ndata.adata.v6udphdr.dest)
209 #define v6udpsrcport ( v6data6.udata.ndata.adata.v6udphdr.source)
212 uint8_t router_linklocal_address [] = {
213 0xfe, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x00, 0x00,
216 uint8_t democlient_linklocal_address [] = {
217 0xfe, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x00, 0x01,
220 uint8_t allnodes_linklocal_address [] = {
221 0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x00, 0x01,
224 uint8_t allrouters_linklocal_address [] = {
225 0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x00, 0x02,
230 #ifndef MAXNUM_MASQHOST
231 #define MAXNUM_MASQHOST 4
234 uint16_t num_masqhost = 0;
235 uint8_t masqhost [MAXNUM_MASQHOST][16];
237 // ports for 's', 't', 'u' -- SCTP, TCP, UDP have increasing numbers
239 #ifndef MAXNUM_PORTPAIRS
240 #define MAXNUM_PORTPAIRS 10
243 // masqportpairs holds triples <lowport,highport,masqhostnr>
244 uint16_t num_masqportpairs [3] = { 0, 0, 0 };
245 uint16_t masqportpairs [3][3*MAXNUM_PORTPAIRS];
248 uint16_t icmp_num_portpairs = 0;
249 uint16_t icmp_portpairs [3] = { 1, 1, 0 };
259 #ifndef INTERFACE_NAME_6BED4
260 #define INTERFACE_NAME_6BED4 "6bed4"
264 #define HAVE_SETUP_TUNNEL
265 /* Implement the setup_tunnel() command for Linux.
266 * Return 1 on success, 0 on failure.
268 int setup_tunnel (void) {
269 v6sox = open ("/dev/net/tun", O_RDWR);
271 fprintf (stderr, "%s: Failed to access tunnel driver on /dev/net/tun: %s\n", program, strerror (errno));
276 memset (&ifreq, 0, sizeof (ifreq));
277 strncpy (ifreq.ifr_name, INTERFACE_NAME_6BED4, IFNAMSIZ);
278 ifreq.ifr_flags = IFF_TUN;
279 if (ok && (ioctl (v6sox, TUNSETIFF, (void *) &ifreq) == -1)) {
282 ifreq.ifr_name [IFNAMSIZ] = 0;
284 snprintf (cmd, 512, "/sbin/ip -6 addr flush dev %s", ifreq.ifr_name);
285 if (ok && system (cmd) != 0) {
288 snprintf (cmd, 512, "/sbin/ip addr add fe80::0 dev %s scope link", ifreq.ifr_name);
289 if (ok && system (cmd) != 0) {
292 snprintf (cmd, 512, "/sbin/ip -6 addr add %s dev %s", v6prefix, ifreq.ifr_name);
293 if (ok && system (cmd) != 0) {
296 snprintf (cmd, 512, "/sbin/ip link set %s up mtu 1280", ifreq.ifr_name);
297 if (ok && system (cmd) != 0) {
301 close (v6sox); /* This removes the tunnel interface */
302 fprintf (stderr, "Failed to setup tunnel \"%s\"\n", INTERFACE_NAME_6BED4);
316 /* Produce an IPv6 address following the 6bed4 structures.
317 * - The top half is taken from v6listen
318 * - The bottom contains IPv4 address and port from v4name
319 * - The last 14 bits are filled with the lanip parameter
321 void addr_6bed4 (struct in6_addr *dst_ip6, uint16_t lanip) {
322 memcpy (&dst_ip6->s6_addr [0], &v6listen, 8);
323 dst_ip6->s6_addr32 [2] = v4name.sin_addr.s_addr;
324 dst_ip6->s6_addr16 [6] = v4name.sin_port;
325 dst_ip6->s6_addr [14] = ((dst_ip6->s6_addr [8] & 0x03) << 6)
326 | ((lanip >> 8) & 0x3f);
327 dst_ip6->s6_addr [15] = (lanip & 0xff);
328 dst_ip6->s6_addr [8] &= 0xfc;
331 /* Calculate the ICMPv6 checksum field
333 uint16_t icmp6_checksum (struct in6_addr *src6, struct in6_addr *dst6,
334 uint16_t *payload, size_t payloadlen) {
335 uint16_t plenword = htons (payloadlen); // our ICMPv6 is small
336 uint16_t nxthword = htons (IPPROTO_ICMPV6);
337 uint16_t *area [] = { src6->s6_addr16, dst6->s6_addr16,
338 &plenword, &nxthword,
339 payload, &payload [2] };
340 uint8_t areawords [] = { 8, 8, 1, 1, 1, (payloadlen >> 1) - 2 };
343 for (i=0; i < 6; i++) {
344 for (j=0; j<areawords [i]; j++) {
345 csum += ntohs (area [i] [j]);
348 csum = (csum & 0xffff) + (csum >> 16);
349 csum = (csum & 0xffff) + (csum >> 16);
350 csum = htons (~csum);
355 /* Mangle a packet by replacing an IPv6 address, correcting the checksum.
356 * In all of ICMPv6, UDPv6, TCPv6, SCTPv6, the checksumming is a 1's cpl
357 * of a sum of 16-bit words; the position of the words don't matter and
358 * we can subtract the old address' words and add the new address' words.
359 * Or, as a result of the one's complement, the opposite. There is some
360 * inclusion of the top half of a 32-bit sum, but that is also neutral.
362 void masquerade_address (struct in6_addr *var,
363 const struct in6_addr *new,
364 uint16_t *csum_field) {
365 int32_t csum = ntohs (~*csum_field);
367 for (i=0; i<8; i++) {
368 csum -= ntohs (var->s6_addr16 [i]);
369 var->s6_addr16 [i] = new->s6_addr16 [i];
370 csum += ntohs (var->s6_addr16 [i]);
372 csum = (csum & 0xffff) + (csum >> 16);
373 csum = (csum & 0xffff) + (csum >> 16);
374 *csum_field = htons (~csum);
378 /* Send an ICMPv6 reply. This is constructed at the tunnel end, from
379 * the incoming message. The parameter indicates how many bytes the
380 * ICMPv6 package counts after the ICMPv6 header. It must be 4 (mod 8).
382 * Actions: v4/udp src becomes dest, set v4/udp/v6 src, len, cksum, send.
383 * reply is always to v4src6, except that if it starts with
384 * 0x00,0x00 it will be replaced with allnodes_linklocal_address.
386 void icmp6_reply (size_t icmp6bodylen) {
388 if ((icmp6bodylen & 0x07) != 4) {
389 return; /* illegal length, drop */
391 v4v6plen = htons (icmp6bodylen + 4);
393 (v4src6->s6_addr16 [0])
395 : allnodes_linklocal_address,
397 memcpy (v4src6, router_linklocal_address, 16);
398 v4v6icmpcksum = icmp6_checksum (v4src6, v4dst6,
399 v4v6payload, ntohs (v4v6plen));
401 // Send the message to the IPv4 originator port
402 printf ("Sending ICMPv6-IPv6-UDP-IPv4 to %d.%d.%d.%d:%d, result = %zd\n",
403 ((uint8_t *) &v4name.sin_addr.s_addr) [0],
404 ((uint8_t *) &v4name.sin_addr.s_addr) [1],
405 ((uint8_t *) &v4name.sin_addr.s_addr) [2],
406 ((uint8_t *) &v4name.sin_addr.s_addr) [3],
407 ntohs (v4name.sin_port),
410 sizeof (struct ip6_hdr) + 4 + icmp6bodylen,
412 (struct sockaddr *) &v4name, sizeof (v4name)));
416 /* Append the current prefix to an ICMPv6 message. Incoming optidx
417 * and return values signify original and new offset for ICMPv6 options.
418 * The endlife parameter must be set to obtain zero lifetimes, thus
419 * instructing the tunnel client to stop using an invalid prefix.
421 size_t icmp6_prefix (size_t optidx, uint8_t endlife) {
422 v4v6icmpdata [optidx++] = 3; // Type
423 v4v6icmpdata [optidx++] = 4; // Length
424 v4v6icmpdata [optidx++] = 114; // This is a /114 prefix
425 v4v6icmpdata [optidx++] = 0xc0; // L=1, A=1, Reserved1=0
426 memset (v4v6icmpdata + optidx, endlife? 0x00: 0xff, 8);
428 // Valid Lifetime: Zero / Infinite
429 // Preferred Lifetime: Zero / Infinite
430 memset (v4v6icmpdata + optidx, 0, 4);
433 addr_6bed4 ((struct in6_addr *) (v4v6icmpdata + optidx), 0);
443 * Append a Destination Link-Layer Address Option to an ICMPv6
444 * message. The address is comprised from the remote's UDP port
445 * and IPv4 address, as seen by the router. They are supplied
446 * in that order, in network byte order. The resulting address
447 * is 6 bytes, but even though that makes it look like a MAC
448 * address, it really is another beast.
449 * Note that no effort is made in the router to recognise the
450 * "illegal port number" 0x3333 -- the client needs a message
451 * and will recognise it and act on it.
453 size_t icmp6_dest_linkaddr (size_t optidx) {
454 uint8_t typelen [2] = { ND_OPT_DESTINATION_LINKADDR, 1 };
455 memcpy (v4v6icmpdata + optidx + 0, &typelen, 2);
456 v4v6icmpdata [optidx + 2] = ntohs (v4name.sin_port) & 0xff;
457 v4v6icmpdata [optidx + 3] = ntohs (v4name.sin_port) >> 8;
458 memcpy (v4v6icmpdata + optidx + 4, &v4name.sin_addr, 4);
465 * Test if an address is a local override. This function is compiled-in
466 * to support hosts with a /64 from their own ISP and nothing more; they
467 * need to access local IPv6 addresses. We rely on the 6bed4 port being
468 * 0 to decide that an address cannot be anything but a local override.
469 * Define LOCAL_OVERRIDES_PORT0 to enable this feature.
471 #ifdef LOCAL_OVERRIDES_PORT0
472 static inline bool is_local_override (struct in6_addr *ip6) {
473 return (ip6->s6_addr16 [6] == 0) && (memcmp (ip6->s6_addr, &v6listen, 8) == 0);
476 #define is_local_override(_) false
481 * Test if the provided IPv6 address matches the prefix used for 6bed4.
482 *TODO: This is oversimplistic, it only cares for the Hetzner /64
484 static inline bool is_6bed4 (struct in6_addr *ip6) {
485 return memcmp (&v6listen, ip6->s6_addr, 8) == 0;
488 /* Test if the provided IPv6 address matches the fc64::/16 prefix.
489 * If so, the traffic may be bounced using 6bed4 traffic, but it
490 * must not be relayed to the native IPv6 side.
491 * TODO: Perhaps allow only configured <netid>, so fc64:<netid>::/32
493 static inline bool is_fc64 (struct in6_addr *ip6) {
494 return ip6->s6_addr16 [0] == htons (0xfc64);
497 /* Test if the src and destination share the same /114 and the destination
498 * fills up the rest with zero bits; in other words, test that this is a
499 * package targeted from a 6bed4peer node to its 6bed4router. This is used
500 * to distinguish special ICMPv6 messages, as well as masquerading targets.
502 static inline bool is_mine (struct in6_addr *src6, struct in6_addr *dst6) {
503 return ((dst6->s6_addr [15] == 0x00)
504 && ((dst6->s6_addr [14] & 0x3f) == 0x00)
505 && (memcmp (dst6->s6_addr, src6->s6_addr, 14) == 0));
510 * Validate the originator's IPv6 address. It should match the
511 * UDP/IPv4 coordinates of the receiving 6bed4 socket. Also,
512 * the /64 prefix (but not the /114 prefix!) must match v6listen.
514 bool validate_originator (struct in6_addr *ip6) {
517 // Require non-local top halves to match our v6listen_linklocal address
518 // We will enforce our own fallback address (and fc64:<netid>::/32)
519 if (memcmp (ip6, v6listen_linklocal, 8) != 0) {
520 if (memcmp (&v6listen, ip6->s6_addr, 8) != 0) {
525 // Require the sender port to appear in its IPv6 address
526 if (v4name.sin_port != ip6->s6_addr16 [6]) {
530 // Require the sender address to appear in its IPv6 address
531 addr = ntohl (ip6->s6_addr32 [2]) & 0xfcffffff;
532 addr |= ((uint32_t) (ip6->s6_addr [14] & 0xc0)) << (24-6);
533 if (addr != ntohl (v4name.sin_addr.s_addr)) {
537 // We passed with flying colours
544 * Major packet processing functions
549 * Respond to a Router Solicitation received over the 6bed4 Network.
551 void handle_6bed4_router_solicit (void) {
552 struct in6_addr observed;
553 v4v6icmptype = ND_ROUTER_ADVERT;
554 v4v6icmpdata [0] = 0; // Cur Hop Limit: unspec
555 v4v6icmpdata [1] = 0x18; // M=0, O=0
558 // TODO: wire says 0x44 for router_adv.flags
560 memset (v4v6icmpdata+writepos, 0xff, 2+4+4);
561 // Router Lifetime: max, 18.2h
562 // Reachable Time: max
563 // Retrans Timer: max
565 writepos = icmp6_prefix (writepos, 0);
566 icmp6_reply (writepos);
570 /* Handle the IPv4 message pointed at by msg as a neighbouring command.
572 * Type Code ICMPv6 meaning Handling
573 * ---- ---- ----------------------------- ----------------------------
574 * 133 0 Router Solicitation Send Router Advertisement
575 * 134 0 Router Advertisement Ignore
576 * 135 0 Neighbour Solicitation Send Neighbour Advertisement
577 * 136 0 Neighbour Advertisement Ignore
578 * 137 0 Redirect Ignore
580 void handle_4to6_nd (ssize_t v4ngbcmdlen) {
581 uint16_t srclinklayer;
582 if (v4ngbcmdlen < sizeof (struct ip6_hdr) + sizeof (struct icmp6_hdr)) {
585 if (v4v6icmpcode != 0) {
588 if (icmp6_checksum (v4src6, v4dst6,
589 v4v6payload, v4ngbcmdlen-sizeof (struct ip6_hdr)
590 ) != v4v6icmpcksum) {
594 // Approved. Perform neighbourly courtesy.
595 switch (v4v6icmptype) {
596 case ND_ROUTER_SOLICIT:
598 // Validate Router Solicitation
600 if (v4ngbcmdlen == sizeof (struct ip6_hdr) + 8 + 8) {
601 // One option is possible, the source link-layer address
602 if (v4v6icmpdata [4] != 1 || v4v6icmpdata [5] != 1) {
603 break; /* bad opton, ignore */
605 // The source link-layer address is end-aligned
606 srclinklayer = (v4v6icmpdata [10] << 8) | v4v6icmpdata [11];
607 if (srclinklayer == 0) {
608 break; /* illegal, ignore */
610 } else if (v4ngbcmdlen == sizeof (struct ip6_hdr) + 8) {
611 srclinklayer = 0; /* set for latter filling */
613 break; /* illegal length, drop */
616 // Having accepted the Router Advertisement, respond
617 handle_6bed4_router_solicit ();
619 case ND_NEIGHBOR_SOLICIT:
621 // Validate Neigbour Solicitation
622 if (!validate_originator (v4src6)) {
623 break; /* bad source address, drop */
625 if ((v4ngbcmdlen != sizeof (struct ip6_hdr) + 24) &&
626 (v4ngbcmdlen != sizeof (struct ip6_hdr) + 24 + 8)) {
627 break; /* funny length, drop */
629 if ((memcmp (v4ngbsoltarget, v6listen_linklocal, 16) != 0) &&
630 (memcmp (v4ngbsoltarget, v6listen_linklocal_complete, 16) != 0) &&
631 (memcmp (v4ngbsoltarget, &v6listen_complete, 16) != 0)) {
632 break; /* target not known here, drop */
635 // Construct Neigbour Advertisement
636 v4v6icmptype = ND_NEIGHBOR_ADVERT;
637 v4v6icmpdata [0] = 0xc0;
640 v4v6icmpdata [3] = 0x00; // R=1, S=1, O=1, Reserved=0
641 memcpy (v4v6icmpdata + 4, &v6listen_complete, 16);
642 // Append option: the target link-layer address
643 // Note: wire does not include target link-layer address
644 v4v6icmpdata [20] = 2; // Type: Target Link-Layer Addr
645 v4v6icmpdata [21] = 1; // Length: 1x 8 bytes
646 memcpy (v4v6icmpdata + 22, lladdr_6bed4, 6);
647 icmp6_reply (28); // 28 is the ICMPv6 response length
649 case ND_ROUTER_ADVERT:
650 case ND_NEIGHBOR_ADVERT:
658 * Forward a message to the masquerading target, or drop it. This is done
659 * with non-6bed4 packets that are sent from a 6bed4peer node to its
660 * 6bed4router address; see is_mine() for the definition. The general idea
661 * is that the address that is to be masqueraded can later be reconstructed
662 * from the 6bed4peer's address.
664 void handle_4to6_masquerading (ssize_t v4datalen) {
665 fprintf (stderr, "Traffic to 6bed4router may be fit for masquerading\n");
666 uint16_t *portpairs = NULL;
667 uint16_t numpairs = 0;
669 uint16_t *csum_field = NULL;
670 uint16_t sctp_offset = 0;
672 switch (v4v6nexthdr) {
674 portpairs = masqportpairs [0]; // 's'
675 numpairs = num_masqportpairs [0];
676 port = ntohs (v4v6sctpdstport);
677 csum_field = &skip_csum;
678 sctp_offset = v4v6sctpofs;
681 portpairs = masqportpairs [1]; // 't'
682 numpairs = num_masqportpairs [1];
683 port = ntohs (v4v6tcpdstport);
684 csum_field = &v4v6tcpcksum;
687 portpairs = masqportpairs [2]; // 'u'
688 numpairs = num_masqportpairs [2];
689 port = ntohs (v4v6udpdstport);
690 csum_field = &v4v6udpcksum;
691 if ((port == 9899) && (v4v6udpsrcport == v4v6udpdstport)) {
692 // SCTP tunneled over UDP (keep csum_field)
693 portpairs = masqportpairs [0];
694 numpairs = num_masqportpairs [0];
695 port = ntohs (v4v6tunsctpdstport);
696 sctp_offset = v4v6tunsctpofs;
700 portpairs = icmp_portpairs;
701 numpairs = icmp_num_portpairs;
702 port = icmp_portpairs [0];
703 csum_field = &v4v6icmpcksum;
708 fprintf (stderr, "DEBUG: Looking for masquerading of port %d in %d entries\n", port, numpairs);
709 while (numpairs-- > 0) {
710 if ((port >= portpairs [0]) && (port <= portpairs [1])) {
712 // Replace masqueraded address by 6bed4router's
713 fprintf (stderr, "DEBUG: Passing traffic to masquerading address number %d\n", portpairs [2]);
714 masquerade_address (v4dst6,
715 (struct in6_addr *) masqhost [portpairs [2]],
717 if (sctp_offset > 0) {
718 //TODO// Recompute SCTP's CRC-32 checksum
719 // recompute_sctp_checksum (ip6hdr, sctp_offset, framelen);
720 //BUT: SCTP checksum does not use pseudo IPhdr
721 //SO: Address masquerading goes undetected :-D
724 // Forward immediately, and return from this function
725 printf ("Writing Masqueraded IPv6, result = %zd\n",
726 write (v6sox, &v4data6, sizeof (struct tun_pi) + v4datalen));
732 // Silently skip the offered packet
737 * Forward a message received over the 6bed4 Network over IPv6.
738 * Note that existing checksums will work well, as only the
739 * Hop Limit has been altered, and this is not part of the
740 * checksum calculations.
742 void handle_4to6_plain_unicast (ssize_t v4datalen) {
743 printf ("Writing IPv6, result = %zd\n",
744 write (v6sox, &v4data6, sizeof (struct tun_pi) + v4datalen));
749 * Forward a 6bed4 message to another 6bed4 destination address.
750 * Local address prefixes fc64:<netid>:<ipv4>::/64 are also relayed.
751 * Note that existing checksums will work well, as only the
752 * Hop Limit has been altered, and this is not part of the
753 * checksum calculations.
755 void relay_4to4_plain_unicast (uint8_t* data, ssize_t v4datalen, struct in6_addr *ip6) {
756 v4name.sin_port = htons (ip6->s6_addr [12] << 8 | ip6->s6_addr [13]);
757 uint8_t *addr = (uint8_t *) &v4name.sin_addr.s_addr;
758 addr [0] = (ip6->s6_addr [8] & 0xfc) | ip6->s6_addr [14] >> 6;
759 memcpy (addr + 1, ip6->s6_addr + 9, 3);
760 printf ("Relaying over 6bed4 Network to %d.%d.%d.%d:%d, result = %zd\n",
761 ((uint8_t *) &v4name.sin_addr.s_addr) [0],
762 ((uint8_t *) &v4name.sin_addr.s_addr) [1],
763 ((uint8_t *) &v4name.sin_addr.s_addr) [2],
764 ((uint8_t *) &v4name.sin_addr.s_addr) [3],
765 ntohs (v4name.sin_port),
769 (struct sockaddr *) &v4name, sizeof (v4name)));
773 /* Receive a tunnel package, and route it to either the handler for the
774 * tunnel protocol, or to the handler that checks and then unpacks the
777 void handle_4to6 (void) {
780 socklen_t adrlen = sizeof (v4name);
782 // Receive IPv4 package, which may be tunneled or a tunnel request
783 buflen = recvfrom (v4sox,
786 (struct sockaddr *) &v4name, &adrlen
789 printf ("%s: Error receiving IPv4-side package: %s",
790 program, strerror (errno));
793 if (buflen < sizeof (struct ip6_hdr)) {
796 if ((v4data [0] & 0xf0) != 0x60) {
797 // Not an IPv6 packet
801 // Handle the tunneled IPv6 package (dependent on its class)
802 if ((v4v6nexthdr == IPPROTO_ICMPV6) &&
803 (v4v6icmptype >= 133) && (v4v6icmptype <= 137)) {
805 // Not Plain: Router Adv/Sol, Neighbor Adv/Sol, Redirect
806 if (v4v6hoplimit != 255) {
809 handle_4to6_nd (buflen);
810 } else if (is_mine (v4src6, v4dst6)) {
811 handle_4to6_masquerading (buflen);
812 } else if ((v4dst6->s6_addr [0] != 0xff) && !(v4dst6->s6_addr [8] & 0x01)) {
815 if (is_local_override (v4dst6)) {
816 handle_4to6_plain_unicast (buflen);
817 } else if (validate_originator (v4src6)) {
818 if (v4v6hoplimit-- <= 1) {
821 if (is_6bed4 (v4dst6) || is_fc64 (v4dst6)) {
822 relay_4to4_plain_unicast (v4data, buflen, v4dst6);
824 handle_4to6_plain_unicast (buflen);
826 } else if (is_6bed4 (v4src6)) {
827 // The sender must not have kept NAT/firewall holes
828 // open and should be instructed about a change in
829 // its 6bed4 Link-Local Address.
830 handle_6bed4_router_solicit ();
835 //OPTIONAL// validate_originator, hoplimit, relay_mcast.
841 /* Receive an IPv6 package, check its address and pickup IPv4 address and
842 * port, then package it as a tunnel message and forward it to IPv4:port.
844 void handle_6to4 (void) {
847 // Receive the IPv6 package and ensure a consistent size
848 size_t rawlen = read (v6sox, &v6data6, sizeof (v6data6));
850 return; /* error reading, drop */
852 if (rawlen < sizeof (struct tun_pi) + sizeof (struct ip6_hdr) + 1) {
853 return; /* too small, drop */
855 if (v6tuncmd.proto != htons (ETH_P_IPV6)) {
856 return; /* no IPv6, drop */
858 if ((v6nexthdr == IPPROTO_ICMPV6) &&
859 (v6icmptype >= 133) && (v6icmptype <= 137)) {
860 return; /* not plain IPv6, drop */
862 if (v6hoplimit-- <= 1) {
863 // TODO: Send back an ICMPv6 error message
864 return; /* hop limit exceeded, drop */
866 if ((v6dst6->s6_addr [0] == 0xff) /* TODO:UDP_PORT_NOT_YET_FORCED_TO_EVEN || (v6dst6->s6_addr [8] & 0x01) */ ) {
867 printf ("Received multicast IPv6 data, flags=0x%04x, proto=0x%04x\n", v6tuncmd.flags, v6tuncmd.proto);
868 //OPTIONAL// handle_6to4_plain_multicast ()
869 return; /* multicast, drop */
871 printf ("Received plain unicast IPv6 data, flags=0x%04x, proto=0x%04x\n", v6tuncmd.flags, v6tuncmd.proto);
873 // Replace masqueraded addresses configured with -m and its default ::1
874 //TODO// Better use the port number to find the find the masqhost
875 for (mqh=0; mqh<num_masqhost; mqh++) {
876 if (memcmp (v6src6, masqhost [mqh], 16) == 0) {
877 printf ("Masqueraded sender address in 6to4 set to the client's 6bed4router address\n");
878 uint16_t *csum_field = NULL;
880 struct in6_addr masq_src;
881 uint16_t sctp_offset = 0;
884 csum_field = &fake_csum;
885 sctp_offset = v6sctpofs;
888 csum_field = &v6tcpcksum;
891 csum_field = &v6udpcksum;
892 if ((v6udpsrcport == v6udpdstport) &&
893 (v6udpsrcport == htons (9899))) {
894 // SCTP tunneled over UDP
895 sctp_offset = v6tunsctpofs;
899 csum_field = &v6icmpcksum;
905 // Construct v6src6 from v6dst6, ending in 14 zero bits
906 memcpy (&masq_src, v6dst6, 16);
907 masq_src.s6_addr16 [7] &= htons (0xc000);
908 fprintf (stderr, "Masquerading cksum.old = 0x%04x, ", ntohs (*csum_field));
909 masquerade_address (v6src6, &masq_src, csum_field);
910 if (sctp_offset > 0) {
911 //TODO// Recompute SCTP's CRC-32 checksum
912 // recompute_sctp_checksum (ip6hdr, sctp_offset, framelen);
913 //BUT: SCTP checksum does not use pseudo IPhdr
914 //SO: Address masquerading goes undetected :-D
916 fprintf (stderr, "cksum.new = 0x%04x\n", ntohs (*csum_field));
921 // Ensure that the incoming IPv6 address is properly formatted
922 // Note that this avoids access to ::1/128, fe80::/10, fec0::/10
923 #ifndef TODO_PERMIT_BOUNCE_FOR_32BIT_PREFIX
924 if (memcmp (v6dst6, &v6listen, 8) != 0) {
928 if (v6dst6->s6_addr32 [0] != v6listen.s6_addr32 [0]) {
929 // Mismatch /32 so this is not going to fly (anywhere)
931 } else if (v6dst6->s6_addr32 [1] != v6listen.s6_addr32 [1]) {
932 // Match /32 but mismatch /64 -- relay to proper fallback
933 // that fc64::/16 is not welcome in 6to4 processing
934 //TODO//OVER_6bed4// relay_6to6_plain_unicast (v6data, rawlen - sizeof (struct tun_pi), v6dst6);
938 // Harvest socket address data from destination IPv6, then send
939 relay_4to4_plain_unicast (v6data, rawlen - sizeof (struct tun_pi), v6dst6);
943 /* Run the daemon core code, passing information between IPv4 and IPv6 and
944 * responding to tunnel requests if so requested.
946 void run_daemon (void) {
951 int nfds = (v4sox < v6sox)? (v6sox + 1): (v4sox + 1);
953 select (nfds, &io, NULL, NULL, NULL);
954 if (FD_ISSET (v4sox, &io)) {
959 if (FD_ISSET (v6sox, &io)) {
969 /* Option descriptive data structures */
971 char *short_opt = "l:L:d:hit:u:s:m:";
973 struct option long_opt [] = {
974 { "v4listen", 1, NULL, 'l' },
975 { "v6prefix", 1, NULL, 'L' },
976 { "tundev", 1, NULL, 'd' },
977 { "help", 0, NULL, 'h' },
978 { "icmp", 0, NULL, 'i' },
979 { "tcp", 1, NULL, 't' },
980 { "udp", 1, NULL, 'u' },
981 { "sctp", 1, NULL, 's' },
982 { "masqhost", 1, NULL, 'm' },
983 // { "fallback4", 1 NULL, 'f' },
984 // { "fallback6", 1, NULL, 'F' },
985 { NULL, 0, NULL, 0 } /* Array termination */
988 /* Parse commandline arguments (and start to process them).
989 * Return 1 on success, 0 on failure.
991 int process_args (int argc, char *argv []) {
993 int help = (argc == 1);
997 switch (opt = getopt_long (argc, argv, short_opt, long_opt, NULL)) {
1000 if (optind != argc) {
1001 fprintf (stderr, "%s: Extra arguments not permitted: %s...\n", program, argv [optind]);
1008 fprintf (stderr, "%s: Only one -l argument is permitted\n", program);
1012 if (inet_pton (AF_INET, optarg, &v4name.sin_addr) <= 0) {
1014 fprintf (stderr, "%s: Failed to parse IPv4 address %s\n", program, optarg);
1017 memcpy (&v4listen, &v4name.sin_addr, 4);
1018 v4sox = socket (AF_INET, SOCK_DGRAM, 0);
1021 fprintf (stderr, "%s: Failed to allocate UDPv4 socket: %s\n", program, strerror (errno));
1024 if (bind (v4sox, (struct sockaddr *) &v4name, sizeof (v4name)) != 0) {
1026 fprintf (stderr, "%s: Failed to bind to UDPv4 %s:%d: %s\n", program, optarg, ntohs (v4name.sin_port), strerror (errno));
1033 fprintf (stderr, "%s: Only one -L argument is permitted\n", program);
1036 char *slash64 = strchr (optarg, '/');
1037 if (!slash64 || strcmp (slash64, "/64") != 0) {
1039 fprintf (stderr, "%s: The -L argument must be an explicit /64 prefix and not %s\n", program, slash64? slash64: "implied");
1043 v6server = strdup (optarg);
1046 if (!v6server || (inet_pton (AF_INET6, v6server, &v6listen) <= 0)) {
1048 fprintf (stderr, "%s: Failed to parse IPv6 prefix %s\n", program, optarg);
1051 if (v6listen.s6_addr32 [2] || v6listen.s6_addr32 [3]) {
1053 fprintf (stderr, "%s: IPv6 prefix contains bits beyond its /64 prefix: %s\n", program, optarg);
1060 fprintf (stderr, "%s: Multiple -d arguments are not permitted\n", program);
1063 v6sox = open (optarg, O_RDWR);
1066 fprintf (stderr, "%s: Failed to open tunnel device %s: %s\n", program, optarg, strerror (errno));
1074 // Masqueraded port (range) for SCTP, TCP, UDP
1075 //TODO// Should we support ICMPv6 as well? [honeypots]
1076 if (num_masqhost == 0) {
1077 //TODO// Reference v6listen instead of ::1
1078 inet_pton (AF_INET6, "::1", masqhost [0]);
1081 // Temporary variables in local scope
1083 if (icmp_num_portpairs > 0) {
1084 fprintf (stderr, "%s: Only one ICMP masquerading setting is possible\n", program);
1088 icmp_portpairs [2] = num_masqhost - 1;
1089 icmp_num_portpairs++;
1091 unsigned long fromport, toport;
1092 uint16_t *portpairs;
1094 if (*optarg != ':') {
1095 fromport = strtoul (optarg, &optarg, 10);
1099 if (*optarg != ':') {
1101 } else if (*++optarg) {
1102 toport = strtoul (optarg, &optarg, 10);
1106 if (errno || *optarg) {
1107 fprintf (stderr, "%s: Failed to parse port or port:port\n", program);
1111 if ((fromport < 1) || (fromport > toport) || (toport > 65535)) {
1112 fprintf (stderr, "%s: Invalid port or port range\n", program);
1116 if (++num_masqportpairs [opt-'s'] >= MAXNUM_PORTPAIRS) {
1117 fprintf (stderr, "%s: You cannot define so many ports / port pairs\n", program);
1121 portpairs = &masqportpairs [opt-'s'][3*(num_masqportpairs [opt-'s']-1)];
1122 portpairs [0] = fromport;
1123 portpairs [1] = toport;
1124 portpairs [2] = num_masqhost-1;
1128 // Masqueraded host for TCP, UDP, SCTP (default is ::1)
1129 if (++num_masqhost >= MAXNUM_MASQHOST) {
1130 fprintf (stderr, "%s: No more than %d masquering hosts can be specified\n", program, MAXNUM_MASQHOST);
1134 if (inet_pton (AF_INET6, optarg, masqhost [num_masqhost]) != 1) {
1135 fprintf (stderr, "%s: Unsupported masquerading host \"%s\"\n", program, optarg);
1143 // // Fallback addresses for IPv4, IPv6
1144 // ok = 0; //TODO:IMPLEMENT//
1149 /* continue into 'h' to produce usage information */
1159 #ifdef HAVE_SETUP_TUNNEL
1160 fprintf (stderr, "Usage: %s [-d /dev/tunX] -l <v4server> -L <v6prefix>/64\n %s -h\n", program, program);
1161 fprintf (stderr, "\tUse -s|-t|-u to masquerade a port (range) to last -m host or ::1\n");
1163 fprintf (stderr, "Usage: %s -d /dev/tunX -l <v4server> -L <v6prefix>/64\n %s -h\n", program, program);
1164 fprintf (stderr, "\tUse -s|-t|-u to masquerade a port (range) to last -m host of ::1\n");
1172 fprintf (stderr, "%s: Use -l to specify an IPv4 address for the tunnel interface\n", program);
1176 fprintf (stderr, "%s: Use -L to specify a /64 prefix on the IPv6 side\n", program);
1179 #ifdef HAVE_SETUP_TUNNEL
1181 if (geteuid () != 0) {
1182 fprintf (stderr, "%s: You should be root, or use -d to specify an accessible tunnel device\n", program);
1185 ok = setup_tunnel ();
1187 #else /* ! HAVE_SETUP_TUNNEL */
1189 fprintf (stderr, "%s: You must specify a tunnel device with -d that is accessible to you\n", program);
1192 #endif /* HAVE_SETUP_TUNNEL */
1197 /* The main program parses commandline arguments and forks off the daemon
1199 int main (int argc, char *argv []) {
1203 memset (&v4name, 0, sizeof (v4name));
1204 memset (&v6name, 0, sizeof (v6name));
1205 v4name.sin_family = AF_INET ;
1206 v6name.sin6_family = AF_INET6;
1207 v4name.sin_port = htons (UDP_PORT_6BED4); /* 6BED4 standard port */
1209 v4tunpi6.proto = htons (ETH_P_IPV6);
1211 // Parse commandline arguments
1212 if (!process_args (argc, argv)) {
1216 // Setup a few addresses for later comparison/reproduction
1217 // * lladdr_6bed4 is the 6bed4 Link-Local Address
1218 // * v6listen_complete is the router's full IPv6 address (with if-id)
1219 // * v6listen_linklocal_complete is fe80::/64 plus the router's if-id
1220 // A few others have already been setup at this time
1221 // * v6listen is the router's 6bed4 prefix ending in 64 zero bits
1222 // * v6listen_linklocal is the address fe80::/128
1224 lladdr_6bed4 [0] = UDP_PORT_6BED4 & 0xff;
1225 lladdr_6bed4 [1] = UDP_PORT_6BED4 >> 8;
1226 memcpy (lladdr_6bed4 + 2, (uint8_t *) &v4name.sin_addr, 4);
1227 addr_6bed4 (&v6listen_complete, 0);
1229 memcpy (v6listen_linklocal_complete, v6listen_linklocal, 8);
1230 memcpy (v6listen_linklocal_complete + 8, &v6listen_complete.s6_addr [8], 8);
1231 printf ("LISTEN lladdr_6bed4 = %02x:%02x:%02x:%02x:%02x:%02x\n", lladdr_6bed4 [0], lladdr_6bed4 [1], lladdr_6bed4 [2], lladdr_6bed4 [3], lladdr_6bed4 [4], lladdr_6bed4 [5]);
1232 printf ("LISTEN v6listen = %x:%x:%x:%x:%x:%x:%x:%x\n", htons (v6listen.s6_addr16 [0]), htons (v6listen.s6_addr16 [1]), htons (v6listen.s6_addr16 [2]), htons (v6listen.s6_addr16 [3]), htons (v6listen.s6_addr16 [4]), htons (v6listen.s6_addr16 [5]), htons (v6listen.s6_addr16 [6]), htons (v6listen.s6_addr16 [7]));
1233 printf ("LISTEN v6listen_complete = %x:%x:%x:%x:%x:%x:%x:%x\n", htons (v6listen_complete.s6_addr16 [0]), htons (v6listen_complete.s6_addr16 [1]), htons (v6listen_complete.s6_addr16 [2]), htons (v6listen_complete.s6_addr16 [3]), htons (v6listen_complete.s6_addr16 [4]), htons (v6listen_complete.s6_addr16 [5]), htons (v6listen_complete.s6_addr16 [6]), htons (v6listen_complete.s6_addr16 [7]));
1234 printf ("LISTEN v6listen_linklocal = %x:%x:%x:%x:%x:%x:%x:%x\n", htons (((uint16_t *) v6listen_linklocal) [0]), htons (((uint16_t *) v6listen_linklocal) [1]), htons (((uint16_t *) v6listen_linklocal) [2]), htons (((uint16_t *) v6listen_linklocal) [3]), htons (((uint16_t *) v6listen_linklocal) [4]), htons (((uint16_t *) v6listen_linklocal) [5]), htons (((uint16_t *) v6listen_linklocal) [6]), htons (((uint16_t *) v6listen_linklocal) [7]));
1235 printf ("LISTEN v6listen_linklocal_complete = %x:%x:%x:%x:%x:%x:%x:%x\n", htons (((uint16_t *) v6listen_linklocal_complete) [0]), htons (((uint16_t *) v6listen_linklocal_complete) [1]), htons (((uint16_t *) v6listen_linklocal_complete) [2]), htons (((uint16_t *) v6listen_linklocal_complete) [3]), htons (((uint16_t *) v6listen_linklocal_complete) [4]), htons (((uint16_t *) v6listen_linklocal_complete) [5]), htons (((uint16_t *) v6listen_linklocal_complete) [6]), htons (((uint16_t *) v6listen_linklocal_complete) [7]));
1237 // Start the main daemon process
1238 #ifdef SKIP_TESTING_KLUDGE_IN_FOREGROUND
1240 case -1: /* Error forking */
1241 fprintf (stderr, "%s: Failed to fork: %s\n", program, strerror (errno));
1243 case 0: /* Child process */
1245 //TODO: tmp.support for ^printf// close (1);
1250 default: /* Parent process */
1259 // Report successful creation of the daemon