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_in6 v6name;
100 struct sockaddr_in v4name;
101 struct sockaddr_in v4name_xlate;
103 struct in6_addr v6listen;
104 struct in6_addr v6listen_complete;
105 struct in_addr v4listen;
112 struct ip6_hdr v6hdr;
113 uint8_t data [MTU - sizeof (struct ip6_hdr)];
116 struct ip6_hdr v6hdr;
118 struct icmp6_hdr v6icmphdr;
119 struct my_sctphdr v6sctphdr;
120 struct tcphdr v6tcphdr ;
121 struct udphdr v6udphdr ;
123 struct udphdr v6udphdr;
124 struct my_sctphdr v6sctphdr;
131 #define v4tunpi6 ( v4data6.tun)
132 #define v4data ((uint8_t *) &v4data6.udata)
133 #define v4hdr6 (&v4data6.udata.idata.v6hdr)
134 #define v4src6 (&v4data6.udata.idata.v6hdr.ip6_src)
135 #define v4dst6 (&v4data6.udata.idata.v6hdr.ip6_dst)
137 #define v4v6payload ((uint16_t *) &v4data6.udata.ndata.adata)
138 #define v4v6plen ( v4data6.udata.ndata.v6hdr.ip6_plen)
139 #define v4v6nexthdr ( v4data6.udata.ndata.v6hdr.ip6_nxt)
140 #define v4v6hoplimit ( v4data6.udata.ndata.v6hdr.ip6_hops)
142 #define v4v6icmpdata ( v4data6.udata.ndata.adata.v6icmphdr.icmp6_data8)
143 #define v4v6icmptype ( v4data6.udata.ndata.adata.v6icmphdr.icmp6_type)
144 #define v4v6icmpcode ( v4data6.udata.ndata.adata.v6icmphdr.icmp6_code)
145 #define v4v6icmpcksum ( v4data6.udata.ndata.adata.v6icmphdr.icmp6_cksum)
147 #define v4v6sctpofs (offsetof (struct v4frame,adata.v6sctphdr))
148 #define v4v6sctpsrcport ( v4data6.udata.ndata.adata.v6sctphdr.source)
149 #define v4v6sctpdstport ( v4data6.udata.ndata.adata.v6sctphdr.dest)
150 #define v4v6sctpcksum ( v4data6.udata.ndata.adata.v6sctphdr.cksum)
152 #define v4v6tunsctpofs (offsetof (struct v4frame,adata.tdata.v6sctphdr))
153 #define v4v6tunsctpsrcport ( v4data6.udata.ndata.adata.tdata.v6sctphdr.source)
154 #define v4v6tunsctpdstport ( v4data6.udata.ndata.adata.tdata.v6sctphdr.dest)
155 #define v4v6tunsctpcksum ( v4data6.udata.ndata.adata.tdata.v6sctphdr.cksum)
157 #define v4v6tcpsrcport ( v4data6.udata.ndata.adata.v6tcphdr.source)
158 #define v4v6tcpdstport ( v4data6.udata.ndata.adata.v6tcphdr.dest)
159 #define v4v6tcpcksum ( v4data6.udata.ndata.adata.v6tcphdr.check)
161 #define v4v6udpsrcport ( v4data6.udata.ndata.adata.v6udphdr.source)
162 #define v4v6udpdstport ( v4data6.udata.ndata.adata.v6udphdr.dest)
163 #define v4v6udpcksum ( v4data6.udata.ndata.adata.v6udphdr.check)
165 #define v4ngbsoltarget (&v4data6.udata.ndata.adata.v6icmphdr.icmp6_data8 [4])
173 struct ip6_hdr v6hdr;
175 struct icmp6_hdr v6icmphdr;
176 struct my_sctphdr v6sctphdr;
177 struct tcphdr v6tcphdr ;
178 struct udphdr v6udphdr ;
180 struct udphdr v6udphdr;
181 struct my_sctphdr v6sctphdr;
189 #define v6tuncmd ( v6data6.tun)
190 #define v6data ( v6data6.udata.data)
191 #define v6hdr6 (&v6data6.udata.ndata.v6hdr)
192 #define v6src6 (&v6data6.udata.ndata.v6hdr.ip6_src)
193 #define v6dst6 (&v6data6.udata.ndata.v6hdr.ip6_dst)
194 #define v6hoplimit ( v6data6.udata.ndata.v6hdr.ip6_hops)
195 #define v6nexthdr ( v6data6.udata.ndata.v6hdr.ip6_nxt)
197 #define v6icmptype ( v6data6.udata.ndata.adata.v6icmphdr.icmp6_type)
198 #define v6icmpcksum ( v6data6.udata.ndata.adata.v6icmphdr.icmp6_cksum)
200 #define v6sctpcksum ( v6data6.udata.ndata.adata.v6sctphdr.cksum)
201 #define v6tunsctpcksum ( v6data6.udata.ndata.adata.tdata.v6sctphdr.cksum)
203 #define v6sctpofs (offsetof(struct v6frame,adata.v6sctphdr))
204 #define v6tunsctpofs (offsetof(struct v6frame,adata.tdata.v6sctphdr))
206 #define v6tcpcksum ( v6data6.udata.ndata.adata.v6tcphdr.check)
208 #define v6udpcksum ( v6data6.udata.ndata.adata.v6udphdr.check)
209 #define v6udpdstport ( v6data6.udata.ndata.adata.v6udphdr.dest)
210 #define v6udpsrcport ( v6data6.udata.ndata.adata.v6udphdr.source)
213 uint8_t router_linklocal_address [] = {
214 0xfe, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x00, 0x00,
217 uint8_t democlient_linklocal_address [] = {
218 0xfe, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x00, 0x01,
221 uint8_t allnodes_linklocal_address [] = {
222 0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x00, 0x01,
225 uint8_t allrouters_linklocal_address [] = {
226 0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x00, 0x02,
231 #ifndef MAXNUM_MASQHOST
232 #define MAXNUM_MASQHOST 4
235 uint16_t num_masqhost = 0;
236 uint8_t masqhost [MAXNUM_MASQHOST][16];
238 // ports for 's', 't', 'u' -- SCTP, TCP, UDP have increasing numbers
240 #ifndef MAXNUM_PORTPAIRS
241 #define MAXNUM_PORTPAIRS 10
244 // masqportpairs holds triples <lowport,highport,masqhostnr>
245 uint16_t num_masqportpairs [3] = { 0, 0, 0 };
246 uint16_t masqportpairs [3][3*MAXNUM_PORTPAIRS];
249 uint16_t icmp_num_portpairs = 0;
250 uint16_t icmp_portpairs [3] = { 1, 1, 0 };
260 #ifndef INTERFACE_NAME_6BED4
261 #define INTERFACE_NAME_6BED4 "6bed4"
265 #define HAVE_SETUP_TUNNEL
266 /* Implement the setup_tunnel() command for Linux.
267 * Return 1 on success, 0 on failure.
269 int setup_tunnel (void) {
270 v6sox = open ("/dev/net/tun", O_RDWR);
272 fprintf (stderr, "%s: Failed to access tunnel driver on /dev/net/tun: %s\n", program, strerror (errno));
277 memset (&ifreq, 0, sizeof (ifreq));
278 strncpy (ifreq.ifr_name, INTERFACE_NAME_6BED4, IFNAMSIZ);
279 ifreq.ifr_flags = IFF_TUN;
280 if (ok && (ioctl (v6sox, TUNSETIFF, (void *) &ifreq) == -1)) {
283 ifreq.ifr_name [IFNAMSIZ] = 0;
285 snprintf (cmd, 512, "/sbin/ip -6 addr flush dev %s", ifreq.ifr_name);
286 if (ok && system (cmd) != 0) {
289 snprintf (cmd, 512, "/sbin/ip addr add fe80::0 dev %s scope link", ifreq.ifr_name);
290 if (ok && system (cmd) != 0) {
293 snprintf (cmd, 512, "/sbin/ip -6 addr add %s dev %s", v6prefix, ifreq.ifr_name);
294 if (ok && system (cmd) != 0) {
297 snprintf (cmd, 512, "/sbin/ip link set %s up mtu 1280", ifreq.ifr_name);
298 if (ok && system (cmd) != 0) {
302 close (v6sox); /* This removes the tunnel interface */
303 fprintf (stderr, "Failed to setup tunnel \"%s\"\n", INTERFACE_NAME_6BED4);
317 /* Produce an IPv6 address following the 6bed4 structures.
318 * - The top half is taken from v6listen
319 * - The bottom contains IPv4 address and port from v4name
320 * - The last 14 bits are filled with the lanip parameter
322 void addr_6bed4 (struct in6_addr *dst_ip6, uint16_t lanip) {
323 memcpy (&dst_ip6->s6_addr [0], &v6listen, 8);
324 dst_ip6->s6_addr32 [2] = v4name.sin_addr.s_addr;
325 dst_ip6->s6_addr16 [6] = v4name.sin_port;
326 dst_ip6->s6_addr [14] = ((dst_ip6->s6_addr [8] & 0x03) << 6)
327 | ((lanip >> 8) & 0x3f);
328 dst_ip6->s6_addr [15] = (lanip & 0xff);
329 dst_ip6->s6_addr [8] &= 0xfc;
332 /* Calculate the ICMPv6 checksum field
334 uint16_t icmp6_checksum (struct in6_addr *src6, struct in6_addr *dst6,
335 uint16_t *payload, size_t payloadlen) {
336 uint16_t plenword = htons (payloadlen); // our ICMPv6 is small
337 uint16_t nxthword = htons (IPPROTO_ICMPV6);
338 uint16_t *area [] = { src6->s6_addr16, dst6->s6_addr16,
339 &plenword, &nxthword,
340 payload, &payload [2] };
341 uint8_t areawords [] = { 8, 8, 1, 1, 1, (payloadlen >> 1) - 2 };
344 for (i=0; i < 6; i++) {
345 for (j=0; j<areawords [i]; j++) {
346 csum += ntohs (area [i] [j]);
349 csum = (csum & 0xffff) + (csum >> 16);
350 csum = (csum & 0xffff) + (csum >> 16);
351 csum = htons (~csum);
356 /* Mangle a packet by replacing an IPv6 address, correcting the checksum.
357 * In all of ICMPv6, UDPv6, TCPv6, SCTPv6, the checksumming is a 1's cpl
358 * of a sum of 16-bit words; the position of the words don't matter and
359 * we can subtract the old address' words and add the new address' words.
360 * Or, as a result of the one's complement, the opposite. There is some
361 * inclusion of the top half of a 32-bit sum, but that is also neutral.
363 void masquerade_address (struct in6_addr *var,
364 const struct in6_addr *new,
365 uint16_t *csum_field) {
366 int32_t csum = ntohs (~*csum_field);
368 for (i=0; i<8; i++) {
369 csum -= ntohs (var->s6_addr16 [i]);
370 var->s6_addr16 [i] = new->s6_addr16 [i];
371 csum += ntohs (var->s6_addr16 [i]);
373 csum = (csum & 0xffff) + (csum >> 16);
374 csum = (csum & 0xffff) + (csum >> 16);
375 *csum_field = htons (~csum);
379 /* Send an ICMPv6 reply. This is constructed at the tunnel end, from
380 * the incoming message. The parameter indicates how many bytes the
381 * ICMPv6 package counts after the ICMPv6 header. It must be 4 (mod 8).
383 * Actions: v4/udp src becomes dest, set v4/udp/v6 src, len, cksum, send.
384 * reply is always to v4src6, except that if it starts with
385 * 0x00,0x00 it will be replaced with allnodes_linklocal_address.
387 void icmp6_reply (size_t icmp6bodylen) {
389 if ((icmp6bodylen & 0x07) != 4) {
390 return; /* illegal length, drop */
392 v4v6plen = htons (icmp6bodylen + 4);
394 (v4src6->s6_addr16 [0])
396 : allnodes_linklocal_address,
398 memcpy (v4src6, router_linklocal_address, 16);
399 v4v6icmpcksum = icmp6_checksum (v4src6, v4dst6,
400 v4v6payload, ntohs (v4v6plen));
402 // Send the message to the IPv4 originator port
403 printf ("Sending ICMPv6-IPv6-UDP-IPv4 to %d.%d.%d.%d:%d, result = %zd\n",
404 ((uint8_t *) &v4name.sin_addr.s_addr) [0],
405 ((uint8_t *) &v4name.sin_addr.s_addr) [1],
406 ((uint8_t *) &v4name.sin_addr.s_addr) [2],
407 ((uint8_t *) &v4name.sin_addr.s_addr) [3],
408 ntohs (v4name.sin_port),
411 sizeof (struct ip6_hdr) + 4 + icmp6bodylen,
413 (struct sockaddr *) &v4name, sizeof (v4name)));
417 /* Append the current prefix to an ICMPv6 message. Incoming optidx
418 * and return values signify original and new offset for ICMPv6 options.
419 * The endlife parameter must be set to obtain zero lifetimes, thus
420 * instructing the tunnel client to stop using an invalid prefix.
422 size_t icmp6_prefix (size_t optidx, uint8_t endlife) {
423 v4v6icmpdata [optidx++] = 3; // Type
424 v4v6icmpdata [optidx++] = 4; // Length
425 v4v6icmpdata [optidx++] = 114; // This is a /114 prefix
426 v4v6icmpdata [optidx++] = 0xc0; // L=1, A=1, Reserved1=0
427 memset (v4v6icmpdata + optidx, endlife? 0x00: 0xff, 8);
429 // Valid Lifetime: Zero / Infinite
430 // Preferred Lifetime: Zero / Infinite
431 memset (v4v6icmpdata + optidx, 0, 4);
434 addr_6bed4 ((struct in6_addr *) (v4v6icmpdata + optidx), 0);
444 * Append a Destination Link-Layer Address Option to an ICMPv6
445 * message. The address is comprised from the remote's UDP port
446 * and IPv4 address, as seen by the router. They are supplied
447 * in that order, in network byte order. The resulting address
448 * is 6 bytes, but even though that makes it look like a MAC
449 * address, it really is another beast.
450 * Note that no effort is made in the router to recognise the
451 * "illegal port number" 0x3333 -- the client needs a message
452 * and will recognise it and act on it.
454 size_t icmp6_dest_linkaddr (size_t optidx) {
455 uint8_t typelen [2] = { ND_OPT_DESTINATION_LINKADDR, 1 };
456 memcpy (v4v6icmpdata + optidx + 0, &typelen, 2);
457 v4v6icmpdata [optidx + 2] = ntohs (v4name.sin_port) & 0xff;
458 v4v6icmpdata [optidx + 3] = ntohs (v4name.sin_port) >> 8;
459 memcpy (v4v6icmpdata + optidx + 4, &v4name.sin_addr, 4);
466 * Test if an address is a local override. This function is compiled-in
467 * to support hosts with a /64 from their own ISP and nothing more; they
468 * need to access local IPv6 addresses. We rely on the 6bed4 port being
469 * 0 to decide that an address cannot be anything but a local override.
470 * Define LOCAL_OVERRIDES_PORT0 to enable this feature.
472 #ifdef LOCAL_OVERRIDES_PORT0
473 static inline bool is_local_override (struct in6_addr *ip6) {
474 return (ip6->s6_addr16 [6] == 0) && (memcmp (ip6->s6_addr, &v6listen, 8) == 0);
477 #define is_local_override(_) false
482 * Test if the provided IPv6 address matches the prefix used for 6bed4.
483 *TODO: This is oversimplistic, it only cares for the Hetzner /64
485 static inline bool is_6bed4 (struct in6_addr *ip6) {
486 return memcmp (&v6listen, ip6->s6_addr, 8) == 0;
489 /* Test if the provided IPv6 address matches the fc64::/16 prefix.
490 * If so, the traffic may be bounced using 6bed4 traffic, but it
491 * must not be relayed to the native IPv6 side.
492 * TODO: Perhaps allow only configured <netid>, so fc64:<netid>::/32
494 static inline bool is_fc64 (struct in6_addr *ip6) {
495 return ip6->s6_addr16 [0] == htons (0xfc64);
498 /* Test if the src and destination share the same /114 and the destination
499 * fills up the rest with zero bits; in other words, test that this is a
500 * package targeted from a 6bed4peer node to its 6bed4router. This is used
501 * to distinguish special ICMPv6 messages, as well as masquerading targets.
503 static inline bool is_mine (struct in6_addr *src6, struct in6_addr *dst6) {
504 return ((dst6->s6_addr [15] == 0x00)
505 && ((dst6->s6_addr [14] & 0x3f) == 0x00)
506 && (memcmp (dst6->s6_addr, src6->s6_addr, 14) == 0));
511 * Validate the originator's IPv6 address. It should match the
512 * UDP/IPv4 coordinates of the receiving 6bed4 socket. Also,
513 * the /64 prefix (but not the /114 prefix!) must match v6listen.
515 bool validate_originator (struct in6_addr *ip6) {
518 // Require non-local top halves to match our v6listen_linklocal address
519 // We will enforce our own fallback address (and fc64:<netid>::/32)
520 if (memcmp (ip6, v6listen_linklocal, 8) != 0) {
521 if (memcmp (&v6listen, ip6->s6_addr, 8) != 0) {
526 // Require the sender port to appear in its IPv6 address
527 if (v4name.sin_port != ip6->s6_addr16 [6]) {
531 // Require the sender address to appear in its IPv6 address
532 addr = ntohl (ip6->s6_addr32 [2]) & 0xfcffffff;
533 addr |= ((uint32_t) (ip6->s6_addr [14] & 0xc0)) << (24-6);
534 if (addr != ntohl (v4name.sin_addr.s_addr)) {
538 // We passed with flying colours
545 * Major packet processing functions
550 * Respond to a Router Solicitation received over the 6bed4 Network.
552 void handle_6bed4_router_solicit (void) {
553 struct in6_addr observed;
554 v4v6icmptype = ND_ROUTER_ADVERT;
555 v4v6icmpdata [0] = 0; // Cur Hop Limit: unspec
556 v4v6icmpdata [1] = 0x18; // M=0, O=0
559 // TODO: wire says 0x44 for router_adv.flags
561 memset (v4v6icmpdata+writepos, 0xff, 2+4+4);
562 // Router Lifetime: max, 18.2h
563 // Reachable Time: max
564 // Retrans Timer: max
566 writepos = icmp6_prefix (writepos, 0);
567 icmp6_reply (writepos);
571 /* Handle the IPv4 message pointed at by msg as a neighbouring command.
573 * Type Code ICMPv6 meaning Handling
574 * ---- ---- ----------------------------- ----------------------------
575 * 133 0 Router Solicitation Send Router Advertisement
576 * 134 0 Router Advertisement Ignore
577 * 135 0 Neighbour Solicitation Send Neighbour Advertisement
578 * 136 0 Neighbour Advertisement Ignore
579 * 137 0 Redirect Ignore
581 void handle_4to6_nd (ssize_t v4ngbcmdlen) {
582 uint16_t srclinklayer;
583 if (v4ngbcmdlen < sizeof (struct ip6_hdr) + sizeof (struct icmp6_hdr)) {
586 if (v4v6icmpcode != 0) {
589 if (icmp6_checksum (v4src6, v4dst6,
590 v4v6payload, v4ngbcmdlen-sizeof (struct ip6_hdr)
591 ) != v4v6icmpcksum) {
595 // Approved. Perform neighbourly courtesy.
596 switch (v4v6icmptype) {
597 case ND_ROUTER_SOLICIT:
599 // Validate Router Solicitation
601 if (v4ngbcmdlen == sizeof (struct ip6_hdr) + 8 + 8) {
602 // One option is possible, the source link-layer address
603 if (v4v6icmpdata [4] != 1 || v4v6icmpdata [5] != 1) {
604 break; /* bad opton, ignore */
606 // The source link-layer address is end-aligned
607 srclinklayer = (v4v6icmpdata [10] << 8) | v4v6icmpdata [11];
608 if (srclinklayer == 0) {
609 break; /* illegal, ignore */
611 } else if (v4ngbcmdlen == sizeof (struct ip6_hdr) + 8) {
612 srclinklayer = 0; /* set for latter filling */
614 break; /* illegal length, drop */
617 // Having accepted the Router Advertisement, respond
618 handle_6bed4_router_solicit ();
620 case ND_NEIGHBOR_SOLICIT:
622 // Validate Neigbour Solicitation
623 if (!validate_originator (v4src6)) {
624 break; /* bad source address, drop */
626 if ((v4ngbcmdlen != sizeof (struct ip6_hdr) + 24) &&
627 (v4ngbcmdlen != sizeof (struct ip6_hdr) + 24 + 8)) {
628 break; /* funny length, drop */
630 if ((memcmp (v4ngbsoltarget, v6listen_linklocal, 16) != 0) &&
631 (memcmp (v4ngbsoltarget, v6listen_linklocal_complete, 16) != 0) &&
632 (memcmp (v4ngbsoltarget, &v6listen_complete, 16) != 0)) {
633 break; /* target not known here, drop */
636 // Construct Neigbour Advertisement
637 v4v6icmptype = ND_NEIGHBOR_ADVERT;
638 v4v6icmpdata [0] = 0xc0;
641 v4v6icmpdata [3] = 0x00; // R=1, S=1, O=1, Reserved=0
642 memcpy (v4v6icmpdata + 4, &v6listen_complete, 16);
643 // Append option: the target link-layer address
644 // Note: wire does not include target link-layer address
645 v4v6icmpdata [20] = 2; // Type: Target Link-Layer Addr
646 v4v6icmpdata [21] = 1; // Length: 1x 8 bytes
647 memcpy (v4v6icmpdata + 22, lladdr_6bed4, 6);
648 icmp6_reply (28); // 28 is the ICMPv6 response length
650 case ND_ROUTER_ADVERT:
651 case ND_NEIGHBOR_ADVERT:
659 * Forward a message to the masquerading target, or drop it. This is done
660 * with non-6bed4 packets that are sent from a 6bed4peer node to its
661 * 6bed4router address; see is_mine() for the definition. The general idea
662 * is that the address that is to be masqueraded can later be reconstructed
663 * from the 6bed4peer's address.
665 void handle_4to6_masquerading (ssize_t v4datalen) {
666 fprintf (stderr, "Traffic to 6bed4router may be fit for masquerading\n");
667 uint16_t *portpairs = NULL;
668 uint16_t numpairs = 0;
670 uint16_t *csum_field = NULL;
671 uint16_t sctp_offset = 0;
673 switch (v4v6nexthdr) {
675 portpairs = masqportpairs [0]; // 's'
676 numpairs = num_masqportpairs [0];
677 port = ntohs (v4v6sctpdstport);
678 csum_field = &skip_csum;
679 sctp_offset = v4v6sctpofs;
682 portpairs = masqportpairs [1]; // 't'
683 numpairs = num_masqportpairs [1];
684 port = ntohs (v4v6tcpdstport);
685 csum_field = &v4v6tcpcksum;
688 portpairs = masqportpairs [2]; // 'u'
689 numpairs = num_masqportpairs [2];
690 port = ntohs (v4v6udpdstport);
691 csum_field = &v4v6udpcksum;
692 if ((port == 9899) && (v4v6udpsrcport == v4v6udpdstport)) {
693 // SCTP tunneled over UDP (keep csum_field)
694 portpairs = masqportpairs [0];
695 numpairs = num_masqportpairs [0];
696 port = ntohs (v4v6tunsctpdstport);
697 sctp_offset = v4v6tunsctpofs;
701 portpairs = icmp_portpairs;
702 numpairs = icmp_num_portpairs;
703 port = icmp_portpairs [0];
704 csum_field = &v4v6icmpcksum;
709 fprintf (stderr, "DEBUG: Looking for masquerading of port %d in %d entries\n", port, numpairs);
710 while (numpairs-- > 0) {
711 if ((port >= portpairs [0]) && (port <= portpairs [1])) {
713 // Replace masqueraded address by 6bed4router's
714 fprintf (stderr, "DEBUG: Passing traffic to masquerading address number %d\n", portpairs [2]);
715 masquerade_address (v4dst6,
716 (struct in6_addr *) masqhost [portpairs [2]],
718 if (sctp_offset > 0) {
719 //TODO// Recompute SCTP's CRC-32 checksum
720 // recompute_sctp_checksum (ip6hdr, sctp_offset, framelen);
721 //BUT: SCTP checksum does not use pseudo IPhdr
722 //SO: Address masquerading goes undetected :-D
725 // Forward immediately, and return from this function
726 printf ("Writing Masqueraded IPv6, result = %zd\n",
727 write (v6sox, &v4data6, sizeof (struct tun_pi) + v4datalen));
733 // Silently skip the offered packet
738 * Forward a message received over the 6bed4 Network over IPv6.
739 * Note that existing checksums will work well, as only the
740 * Hop Limit has been altered, and this is not part of the
741 * checksum calculations.
743 void handle_4to6_plain_unicast (ssize_t v4datalen) {
744 printf ("Writing IPv6, result = %zd\n",
745 write (v6sox, &v4data6, sizeof (struct tun_pi) + v4datalen));
750 * Forward a 6bed4 message to another 6bed4 destination address.
751 * Local address prefixes fc64:<netid>:<ipv4>::/64 are also relayed.
752 * Note that existing checksums will work well, as only the
753 * Hop Limit has been altered, and this is not part of the
754 * checksum calculations.
756 void relay_4to4_plain_unicast (uint8_t* data, ssize_t v4datalen, struct in6_addr *ip6) {
757 v4name.sin_port = htons (ip6->s6_addr [12] << 8 | ip6->s6_addr [13]);
758 uint8_t *addr = (uint8_t *) &v4name.sin_addr.s_addr;
759 addr [0] = (ip6->s6_addr [8] & 0xfc) | ip6->s6_addr [14] >> 6;
760 memcpy (addr + 1, ip6->s6_addr + 9, 3);
761 printf ("Relaying over 6bed4 Network to %d.%d.%d.%d:%d, result = %zd\n",
762 ((uint8_t *) &v4name.sin_addr.s_addr) [0],
763 ((uint8_t *) &v4name.sin_addr.s_addr) [1],
764 ((uint8_t *) &v4name.sin_addr.s_addr) [2],
765 ((uint8_t *) &v4name.sin_addr.s_addr) [3],
766 ntohs (v4name.sin_port),
770 (struct sockaddr *) &v4name, sizeof (v4name)));
774 /* Receive a tunnel package, and route it to either the handler for the
775 * tunnel protocol, or to the handler that checks and then unpacks the
778 void handle_4to6 (void) {
781 socklen_t adrlen = sizeof (v4name);
783 // Receive IPv4 package, which may be tunneled or a tunnel request
784 buflen = recvfrom (v4sox,
787 (struct sockaddr *) &v4name, &adrlen
790 printf ("%s: Error receiving IPv4-side package: %s",
791 program, strerror (errno));
794 if (buflen < sizeof (struct ip6_hdr)) {
797 if ((v4data [0] & 0xf0) != 0x60) {
798 // Not an IPv6 packet
802 // Handle the tunneled IPv6 package (dependent on its class)
803 if ((v4v6nexthdr == IPPROTO_ICMPV6) &&
804 (v4v6icmptype >= 133) && (v4v6icmptype <= 137)) {
806 // Not Plain: Router Adv/Sol, Neighbor Adv/Sol, Redirect
807 if (v4v6hoplimit != 255) {
810 handle_4to6_nd (buflen);
811 } else if (is_mine (v4src6, v4dst6)) {
812 handle_4to6_masquerading (buflen);
813 } else if ((v4dst6->s6_addr [0] != 0xff) && !(v4dst6->s6_addr [8] & 0x01)) {
816 if (is_local_override (v4dst6)) {
817 // Accept 6bed4 clients, but not forged IPv6 senders
818 if (!validate_originator (v4src6)) {
821 handle_4to6_plain_unicast (buflen);
822 } else if (validate_originator (v4src6)) {
823 if (v4v6hoplimit-- <= 1) {
826 if (is_6bed4 (v4dst6) || is_fc64 (v4dst6)) {
827 relay_4to4_plain_unicast (v4data, buflen, v4dst6);
829 handle_4to6_plain_unicast (buflen);
831 } else if (is_6bed4 (v4src6)) {
832 // The sender must not have kept NAT/firewall holes
833 // open and should be instructed about a change in
834 // its 6bed4 Link-Local Address.
835 handle_6bed4_router_solicit ();
840 //OPTIONAL// validate_originator, hoplimit, relay_mcast.
846 /* Receive an IPv6 package, check its address and pickup IPv4 address and
847 * port, then package it as a tunnel message and forward it to IPv4:port.
849 void handle_6to4 (void) {
852 // Receive the IPv6 package and ensure a consistent size
853 size_t rawlen = read (v6sox, &v6data6, sizeof (v6data6));
855 return; /* error reading, drop */
857 if (rawlen < sizeof (struct tun_pi) + sizeof (struct ip6_hdr) + 1) {
858 return; /* too small, drop */
860 if (v6tuncmd.proto != htons (ETH_P_IPV6)) {
861 return; /* no IPv6, drop */
863 if ((v6nexthdr == IPPROTO_ICMPV6) &&
864 (v6icmptype >= 133) && (v6icmptype <= 137)) {
865 return; /* not plain IPv6, drop */
867 if (v6hoplimit-- <= 1) {
868 // TODO: Send back an ICMPv6 error message
869 return; /* hop limit exceeded, drop */
871 if ((v6dst6->s6_addr [0] == 0xff) /* TODO:UDP_PORT_NOT_YET_FORCED_TO_EVEN || (v6dst6->s6_addr [8] & 0x01) */ ) {
872 printf ("Received multicast IPv6 data, flags=0x%04x, proto=0x%04x\n", v6tuncmd.flags, v6tuncmd.proto);
873 //OPTIONAL// handle_6to4_plain_multicast ()
874 return; /* multicast, drop */
876 printf ("Received plain unicast IPv6 data, flags=0x%04x, proto=0x%04x\n", v6tuncmd.flags, v6tuncmd.proto);
878 // Replace masqueraded addresses configured with -m and its default ::1
879 //TODO// Better use the port number to find the find the masqhost
880 for (mqh=0; mqh<num_masqhost; mqh++) {
881 if (memcmp (v6src6, masqhost [mqh], 16) == 0) {
882 printf ("Masqueraded sender address in 6to4 set to the client's 6bed4router address\n");
883 uint16_t *csum_field = NULL;
885 struct in6_addr masq_src;
886 uint16_t sctp_offset = 0;
889 csum_field = &fake_csum;
890 sctp_offset = v6sctpofs;
893 csum_field = &v6tcpcksum;
896 csum_field = &v6udpcksum;
897 if ((v6udpsrcport == v6udpdstport) &&
898 (v6udpsrcport == htons (9899))) {
899 // SCTP tunneled over UDP
900 sctp_offset = v6tunsctpofs;
904 csum_field = &v6icmpcksum;
910 // Construct v6src6 from v6dst6, ending in 14 zero bits
911 memcpy (&masq_src, v6dst6, 16);
912 masq_src.s6_addr16 [7] &= htons (0xc000);
913 fprintf (stderr, "Masquerading cksum.old = 0x%04x, ", ntohs (*csum_field));
914 masquerade_address (v6src6, &masq_src, csum_field);
915 if (sctp_offset > 0) {
916 //TODO// Recompute SCTP's CRC-32 checksum
917 // recompute_sctp_checksum (ip6hdr, sctp_offset, framelen);
918 //BUT: SCTP checksum does not use pseudo IPhdr
919 //SO: Address masquerading goes undetected :-D
921 fprintf (stderr, "cksum.new = 0x%04x\n", ntohs (*csum_field));
926 // Ensure that the incoming IPv6 address is properly formatted
927 // Note that this avoids access to ::1/128, fe80::/10, fec0::/10
928 #ifndef TODO_PERMIT_BOUNCE_FOR_32BIT_PREFIX
929 if (memcmp (v6dst6, &v6listen, 8) != 0) {
933 if (v6dst6->s6_addr32 [0] != v6listen.s6_addr32 [0]) {
934 // Mismatch /32 so this is not going to fly (anywhere)
936 } else if (v6dst6->s6_addr32 [1] != v6listen.s6_addr32 [1]) {
937 // Match /32 but mismatch /64 -- relay to proper fallback
938 // that fc64::/16 is not welcome in 6to4 processing
939 //TODO//OVER_6bed4// relay_6to6_plain_unicast (v6data, rawlen - sizeof (struct tun_pi), v6dst6);
943 // Harvest socket address data from destination IPv6, then send
944 relay_4to4_plain_unicast (v6data, rawlen - sizeof (struct tun_pi), v6dst6);
948 /* Run the daemon core code, passing information between IPv4 and IPv6 and
949 * responding to tunnel requests if so requested.
951 void run_daemon (void) {
956 int nfds = (v4sox < v6sox)? (v6sox + 1): (v4sox + 1);
958 select (nfds, &io, NULL, NULL, NULL);
959 if (FD_ISSET (v4sox, &io)) {
964 if (FD_ISSET (v6sox, &io)) {
974 /* Option descriptive data structures */
976 char *short_opt = "l:L:d:hit:u:s:m:x:";
978 struct option long_opt [] = {
979 { "v4listen", 1, NULL, 'l' },
980 { "v6prefix", 1, NULL, 'L' },
981 { "tundev", 1, NULL, 'd' },
982 { "help", 0, NULL, 'h' },
983 { "icmp", 0, NULL, 'i' },
984 { "tcp", 1, NULL, 't' },
985 { "udp", 1, NULL, 'u' },
986 { "sctp", 1, NULL, 's' },
987 { "masqhost", 1, NULL, 'm' },
988 { "xlate", 1, NULL, 'x' },
989 // { "fallback4", 1 NULL, 'f' },
990 // { "fallback6", 1, NULL, 'F' },
991 { NULL, 0, NULL, 0 } /* Array termination */
994 /* Parse commandline arguments (and start to process them).
995 * Return 1 on success, 0 on failure.
997 int process_args (int argc, char *argv []) {
999 int help = (argc == 1);
1003 switch (opt = getopt_long (argc, argv, short_opt, long_opt, NULL)) {
1006 if (optind != argc) {
1007 fprintf (stderr, "%s: Extra arguments not permitted: %s...\n", program, argv [optind]);
1012 if (v4name.sin_family != 0) {
1014 fprintf (stderr, "%s: Only one -l argument is permitted\n", program);
1017 v4name.sin_family = AF_INET;
1019 if (inet_pton (AF_INET, optarg, &v4name.sin_addr) <= 0) {
1021 fprintf (stderr, "%s: Failed to parse IPv4 address %s\n", program, optarg);
1024 memcpy (&v4listen, &v4name.sin_addr, 4);
1027 if (v4name_xlate.sin_family != 0) {
1029 fprintf (stderr, "%s: At most one -x argument is permitted\n", program);
1032 v4name_xlate.sin_family = AF_INET;
1033 ((uint8_t *) &v4name_xlate.sin_addr.s_addr) [0] = 127;
1034 ((uint8_t *) &v4name_xlate.sin_addr.s_addr) [1] = 0;
1035 ((uint8_t *) &v4name_xlate.sin_addr.s_addr) [2] = 0;
1036 ((uint8_t *) &v4name_xlate.sin_addr.s_addr) [3] = 1;
1037 int port = atoi (optarg);
1038 if ((port <= 0) || (port > 65535)) {
1040 fprintf (stderr, "%s: Port number for -x out of range\n", program);
1043 v4name_xlate.sin_port = htons (port);
1048 fprintf (stderr, "%s: Only one -L argument is permitted\n", program);
1051 char *slash64 = strchr (optarg, '/');
1052 if (!slash64 || strcmp (slash64, "/64") != 0) {
1054 fprintf (stderr, "%s: The -L argument must be an explicit /64 prefix and not %s\n", program, slash64? slash64: "implied");
1058 v6server = strdup (optarg);
1061 if (!v6server || (inet_pton (AF_INET6, v6server, &v6listen) <= 0)) {
1063 fprintf (stderr, "%s: Failed to parse IPv6 prefix %s\n", program, optarg);
1066 if (v6listen.s6_addr32 [2] || v6listen.s6_addr32 [3]) {
1068 fprintf (stderr, "%s: IPv6 prefix contains bits beyond its /64 prefix: %s\n", program, optarg);
1075 fprintf (stderr, "%s: Multiple -d arguments are not permitted\n", program);
1078 v6sox = open (optarg, O_RDWR);
1081 fprintf (stderr, "%s: Failed to open tunnel device %s: %s\n", program, optarg, strerror (errno));
1089 // Masqueraded port (range) for SCTP, TCP, UDP
1090 //TODO// Should we support ICMPv6 as well? [honeypots]
1091 if (num_masqhost == 0) {
1092 //TODO// Reference v6listen instead of ::1
1093 inet_pton (AF_INET6, "::1", masqhost [0]);
1096 // Temporary variables in local scope
1098 if (icmp_num_portpairs > 0) {
1099 fprintf (stderr, "%s: Only one ICMP masquerading setting is possible\n", program);
1103 icmp_portpairs [2] = num_masqhost - 1;
1104 icmp_num_portpairs++;
1106 unsigned long fromport, toport;
1107 uint16_t *portpairs;
1109 if (*optarg != ':') {
1110 fromport = strtoul (optarg, &optarg, 10);
1114 if (*optarg != ':') {
1116 } else if (*++optarg) {
1117 toport = strtoul (optarg, &optarg, 10);
1121 if (errno || *optarg) {
1122 fprintf (stderr, "%s: Failed to parse port or port:port\n", program);
1126 if ((fromport < 1) || (fromport > toport) || (toport > 65535)) {
1127 fprintf (stderr, "%s: Invalid port or port range\n", program);
1131 if (++num_masqportpairs [opt-'s'] >= MAXNUM_PORTPAIRS) {
1132 fprintf (stderr, "%s: You cannot define so many ports / port pairs\n", program);
1136 portpairs = &masqportpairs [opt-'s'][3*(num_masqportpairs [opt-'s']-1)];
1137 portpairs [0] = fromport;
1138 portpairs [1] = toport;
1139 portpairs [2] = num_masqhost-1;
1143 // Masqueraded host for TCP, UDP, SCTP (default is ::1)
1144 if (++num_masqhost >= MAXNUM_MASQHOST) {
1145 fprintf (stderr, "%s: No more than %d masquering hosts can be specified\n", program, MAXNUM_MASQHOST);
1149 if (inet_pton (AF_INET6, optarg, masqhost [num_masqhost]) != 1) {
1150 fprintf (stderr, "%s: Unsupported masquerading host \"%s\"\n", program, optarg);
1158 // // Fallback addresses for IPv4, IPv6
1159 // ok = 0; //TODO:IMPLEMENT//
1164 /* continue into 'h' to produce usage information */
1174 #ifdef HAVE_SETUP_TUNNEL
1175 fprintf (stderr, "Usage: %s [-d /dev/tunX] -l <v4server> -L <v6prefix>/64 [-x <port>]\n %s -h\n", program, program);
1176 fprintf (stderr, "\tUse -s|-t|-u to masquerade a port (range) to last -m host or ::1\n");
1178 fprintf (stderr, "Usage: %s -d /dev/tunX -l <v4server> -L <v6prefix>/64\n %s -h\n", program, program);
1179 fprintf (stderr, "\tUse -s|-t|-u to masquerade a port (range) to last -m host of ::1\n");
1183 if (v4name.sin_family == 0) {
1184 fprintf (stderr, "%s: Use -l to specify an IPv4 address for the tunnel interface\n", program);
1187 if (v4name_xlate.sin_family == 0) {
1188 memcpy (&v4name_xlate, &v4name, sizeof (v4name_xlate));
1190 v4server = "127.0.0.1";
1192 v4sox = socket (AF_INET, SOCK_DGRAM, 0);
1194 fprintf (stderr, "%s: Failed to allocate UDPv4 socket: %s\n", program, strerror (errno));
1197 if (bind (v4sox, (struct sockaddr *) &v4name_xlate, sizeof (v4name_xlate)) != 0) {
1198 fprintf (stderr, "%s: Failed to bind to UDPv4 %s:%d: %s\n", program, v4server, ntohs (v4name_xlate.sin_port), strerror (errno));
1204 #ifdef HAVE_SETUP_TUNNEL
1206 if (geteuid () != 0) {
1207 fprintf (stderr, "%s: You should be root, or use -d to specify an accessible tunnel device\n", program);
1210 ok = setup_tunnel ();
1213 fprintf (stderr, "%s: Use -L to specify a /64 prefix on the IPv6 side\n", program);
1216 #else /* ! HAVE_SETUP_TUNNEL */
1218 fprintf (stderr, "%s: You must specify a tunnel device with -d that is accessible to you\n", program);
1221 #endif /* HAVE_SETUP_TUNNEL */
1226 /* The main program parses commandline arguments and forks off the daemon
1228 int main (int argc, char *argv []) {
1232 memset (&v6name , 0, sizeof (v6name ));
1233 memset (&v4name , 0, sizeof (v4name ));
1234 memset (&v4name_xlate, 0, sizeof (v4name_xlate));
1235 v6name.sin6_family = AF_INET6;
1236 v4name.sin_port = htons (UDP_PORT_6BED4); /* 6BED4 standard port */
1238 v4tunpi6.proto = htons (ETH_P_IPV6);
1240 // Parse commandline arguments
1241 if (!process_args (argc, argv)) {
1245 // Setup a few addresses for later comparison/reproduction
1246 // * lladdr_6bed4 is the 6bed4 Link-Local Address
1247 // * v6listen_complete is the router's full IPv6 address (with if-id)
1248 // * v6listen_linklocal_complete is fe80::/64 plus the router's if-id
1249 // A few others have already been setup at this time
1250 // * v6listen is the router's 6bed4 prefix ending in 64 zero bits
1251 // * v6listen_linklocal is the address fe80::/128
1253 lladdr_6bed4 [0] = UDP_PORT_6BED4 & 0xff;
1254 lladdr_6bed4 [1] = UDP_PORT_6BED4 >> 8;
1255 memcpy (lladdr_6bed4 + 2, (uint8_t *) &v4name.sin_addr, 4);
1256 addr_6bed4 (&v6listen_complete, 0);
1258 memcpy (v6listen_linklocal_complete, v6listen_linklocal, 8);
1259 memcpy (v6listen_linklocal_complete + 8, &v6listen_complete.s6_addr [8], 8);
1260 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]);
1261 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]));
1262 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]));
1263 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]));
1264 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]));
1266 // Start the main daemon process
1267 #ifdef SKIP_TESTING_KLUDGE_IN_FOREGROUND
1269 case -1: /* Error forking */
1270 fprintf (stderr, "%s: Failed to fork: %s\n", program, strerror (errno));
1272 case 0: /* Child process */
1274 //TODO: tmp.support for ^printf// close (1);
1279 default: /* Parent process */
1288 // Report successful creation of the daemon