2 * 6in4 - tunnel client for automatic 6to4 or configured v6-in-v4 tunnels.
11 * IPv6 and related IP protocols & their numbers:
13 * ipv6 41 IPv6 # Internet Protocol, version 6
14 * ipv6-route 43 IPv6-Route # Routing Header for IPv6
15 * ipv6-frag 44 IPv6-Frag # Fragment Header for IPv6
16 * esp 50 ESP # Encapsulating Security Payload
17 * ah 51 AH # Authentication Header
18 * ipv6-icmp 58 IPv6-ICMP icmp6 # ICMP version 6
19 * ipv6-nonxt 59 IPv6-NoNxt # No Next Header for IPv6
20 * ipv6-opts 60 IPv6-Opts # Destination Options for IPv6
24 IP_IPV6PROTO = 41, /* IPv4 protocol number for IPv6 */
25 IP_ESPPROTO = 50, /* IP v4 and v6 protocol number */
26 IP_AHPROTO = 51, /* IP v4 and v6 protocol number */
31 typedef struct Iphdr Iphdr;
34 uchar vihl; /* Version and header length */
35 uchar tos; /* Type of service */
36 uchar length[2]; /* packet length */
37 uchar id[2]; /* Identification */
38 uchar frag[2]; /* Fragment information */
39 uchar ttl; /* Time to live */
40 uchar proto; /* Protocol */
41 uchar cksum[2]; /* Header checksum */
42 uchar src[4]; /* Ip source (uchar ordering unimportant) */
43 uchar dst[4]; /* Ip destination (uchar ordering unimportant) */
47 #define STFHDR offsetof(Iphdr, payload[0])
53 uchar local6[IPaddrlen];
54 uchar remote6[IPaddrlen];
55 uchar remote4[IPaddrlen];
56 uchar localmask[IPaddrlen];
57 uchar localnet[IPaddrlen];
58 uchar myip[IPaddrlen];
60 /* magic anycast address from rfc3068 */
61 uchar anycast6to4[IPv4addrlen] = { 192, 88, 99, 1 };
63 static char *net = "/net";
65 static int badipv4(uchar*);
66 static int badipv6(uchar*);
67 static void ip2tunnel(int, int);
68 static void tunnel2ip(int, int);
73 fprint(2, "usage: %s [-ag] [-x mtpt] [local6[/mask]] [remote4 [remote6]]\n",
81 uchar *ipv4 = &myip[IPaddrlen - IPv4addrlen];
83 return smprint("%ux:%2.2x%2.2x:%2.2x%2.2x::1/48", V6to4pfx,
84 ipv4[0], ipv4[1], ipv4[2], ipv4[3]);
87 /* process non-option arguments */
89 procargs(int argc, char **argv)
95 else if (strcmp(argv[0], "-") == 0) {
104 /* local v6 address (mask defaults to /128) */
105 memcpy(localmask, IPallbits, sizeof localmask);
106 p = strchr(loc6, '/');
108 parseipmask(localmask, p);
111 if (parseip(local6, loc6) == -1)
112 sysfatal("bad local v6 address %s", loc6);
115 if (argc >= 1 && argv[0][0] == '/') {
116 parseipmask(localmask, *argv++);
120 fprint(2, "local6 %I %M\n", local6, localmask);
122 /* remote v4 address (defaults to anycast 6to4) */
124 if (parseip(remote4, *argv++) == -1)
125 sysfatal("bad remote v4 address %s", argv[-1]);
130 v4tov6(remote4, anycast6to4);
134 fprint(2, "remote4 %I\n", remote4);
136 /* remote v6 address (defaults to link-local w/ v4 as interface part) */
138 if (parseip(remote6, *argv++) == -1)
139 sysfatal("bad remote v6 address %s", argv[-1]);
142 remote6[0] = 0xFE; /* link local */
144 memcpy(remote6 + IPv4off, remote4 + IPv4off, IPv4addrlen);
150 maskip(local6, localmask, localnet);
152 fprint(2, "localnet %I remote6 %I\n", localnet, remote6);
156 setup(int *v6net, int *tunp)
160 char buf[128], path[64];
163 * gain access to IPv6-in-IPv4 packets
165 p = seprint(buf, buf + sizeof buf, "%s/ipmux!proto=%2.2x|%2.2x;dst=%V",
166 net, IP_IPV6PROTO, IP_ICMPV6PROTO, myip + IPv4off);
168 seprint(p, buf + sizeof buf, ";src=%V", remote4 + IPv4off);
169 *tunp = dial(buf, 0, 0, 0);
171 sysfatal("can't access ipv6-in-ipv4 with dial str %s: %r", buf);
173 fprint(2, "dialed %s for v6-in-v4 access\n", buf);
176 * open local IPv6 interface (as a packet interface)
179 cl = smprint("%s/ipifc/clone", net);
180 cfd = open(cl, ORDWR); /* allocate a conversation */
182 if (cfd < 0 || (n = read(cfd, buf, sizeof buf - 1)) <= 0)
183 sysfatal("can't make packet interface %s: %r", cl);
185 fprint(2, "cloned %s as local v6 interface\n", cl);
189 snprint(path, sizeof path, "%s/ipifc/%s/data", net, buf);
190 *v6net = open(path, ORDWR);
191 if (*v6net < 0 || fprint(cfd, "bind pkt") < 0)
192 sysfatal("can't bind packet interface: %r");
193 /* 1280 is MTU, apparently from rfc2460 */
194 if (fprint(cfd, "add %I /128 %I 1280", local6, remote6) <= 0)
195 sysfatal("can't set local ipv6 address: %r");
198 fprint(2, "opened & bound %s as local v6 interface\n", path);
201 /* route global addresses through the tunnel to remote6 */
202 ir = smprint("%s/iproute", net);
203 cfd = open(ir, OWRITE);
204 if (cfd >= 0 && debug)
205 fprint(2, "injected 2000::/3 %I into %s\n", remote6, ir);
207 if (cfd < 0 || fprint(cfd, "add 2000:: /3 %I", remote6) <= 0)
208 sysfatal("can't set default global route: %r");
213 runtunnel(int v6net, int tunnel)
215 /* run the tunnel copying in the background */
216 switch (rfork(RFPROC|RFNOWAIT|RFMEM|RFNOTEG)) {
225 switch (rfork(RFPROC|RFNOWAIT|RFMEM)) {
229 tunnel2ip(tunnel, v6net);
232 ip2tunnel(v6net, tunnel);
235 exits("tunnel gone");
239 main(int argc, char **argv)
243 fmtinstall('I', eipfmt);
244 fmtinstall('V', eipfmt);
245 fmtinstall('M', eipfmt);
258 net = EARGF(usage());
264 if (myipaddr(myip, net) < 0)
265 sysfatal("can't find my ipv4 address on %s", net);
267 sysfatal("my ip, %I, is not a v4 address", myip);
269 procargs(argc, argv);
270 setup(&v6net, &tunnel);
271 runtunnel(v6net, tunnel);
275 * based on libthread's threadsetname, but drags in less library code.
276 * actually just sets the arguments displayed.
279 procsetname(char *fmt, ...)
287 cmdname = vsmprint(fmt, arg);
291 snprint(buf, sizeof buf, "#p/%d/args", getpid());
292 if((fd = open(buf, OWRITE)) >= 0){
293 write(fd, cmdname, strlen(cmdname)+1);
300 * encapsulate v6 packets from the packet interface in v4 ones
301 * and send them into the tunnel.
304 ip2tunnel(int in, int out)
312 procsetname("v6 %I -> tunnel", local6);
314 procsetname("v6 %I -> tunnel %I %I", local6, remote4, remote6);
316 /* populate v4 header */
318 op->vihl = IP_VER4 | 5; /* hdr is 5 longs? */
319 memcpy(op->src, myip + IPv4off, sizeof op->src);
322 /* get a V6 packet destined for the tunnel */
323 ip = (Ip6hdr*)(buf + STFHDR);
324 while ((n = read(in, ip, sizeof buf - STFHDR)) > 0) {
325 /* if not IPV6, drop it */
326 if ((ip->vcf[0] & 0xF0) != IP_VER6)
329 /* check length: drop if too short, trim if too long */
330 m = nhgets(ip->ploadlen) + IPV6HDR_LEN;
336 /* drop if v6 source or destination address is naughty */
337 if (badipv6(ip->src) ||
338 (!equivip6(ip->dst, remote6) && badipv6(ip->dst))) {
339 syslog(0, "6in4", "egress filtered %I -> %I",
344 op->proto = ip->proto;
346 fprint(2, "v6 to tunnel %I -> %I\n", ip->src, ip->dst);
347 /* send 6to4 packets directly to ipv4 target */
348 if ((ip->dst[0]<<8 | ip->dst[1]) == V6to4pfx)
349 memcpy(op->dst, ip->dst+2, sizeof op->dst);
351 memcpy(op->dst, remote4+IPv4off, sizeof op->dst);
354 /* pass packet to the other end of the tunnel */
355 if (write(out, op, n) != n) {
356 syslog(0, "6in4", "error writing to tunnel (%r), giving up");
363 * decapsulate v6 packets from v4 ones from the tunnel
364 * and forward them to the packet interface
367 tunnel2ip(int in, int out)
376 procsetname("tunnel -> v6 %I", local6);
378 procsetname("tunnel %I %I -> v6 %I", remote4, remote6, local6);
381 /* get a packet from the tunnel */
382 n = read(in, buf, sizeof buf);
383 ip = (Iphdr*)(buf + IPaddrlen);
386 syslog(0, "6in4", "error reading from tunnel (%r), giving up");
390 /* if not IPv4 nor IPv4 protocol IPv6 nor ICMPv6, drop it */
391 if ((ip->vihl & 0xF0) != IP_VER4 ||
392 ip->proto != IP_IPV6PROTO && ip->proto != IP_ICMPV6PROTO)
395 /* check length: drop if too short, trim if too long */
396 m = nhgets(ip->length);
402 op = (Ip6hdr*)(buf + IPaddrlen + STFHDR);
406 * don't relay: just accept packets for local host/subnet
407 * (this blocks link-local and multicast addresses as well)
409 maskip(op->dst, localmask, a);
410 if (!equivip6(a, localnet)) {
411 syslog(0, "6in4", "ingress filtered %I -> %I",
416 fprint(2, "tunnel to v6 %I -> %I\n", op->src, op->dst);
418 /* pass V6 packet to the interface */
419 if (write(out, op, n) != n) {
420 syslog(0, "6in4", "error writing to packet interface (%r), giving up");
430 case 0: /* unassigned */
431 case 10: /* private */
432 case 127: /* loopback */
435 return a[1] >= 16; /* 172.16.0.0/12 private */
437 return a[1] == 168; /* 192.168.0.0/16 private */
439 return a[1] == 254; /* 169.254.0.0/16 DHCP link-local */
441 /* 224.0.0.0/4 multicast, 240.0.0.0/4 reserved, broadcast */
446 * 0x0000/16 prefix = v4 compatible, v4 mapped, loopback, unspecified...
447 * site-local is now deprecated, rfc3879
452 int h = a[0]<<8 | a[1];
454 return h == 0 || ISIPV6MCAST(a) || ISIPV6LINKLOCAL(a) ||
455 h == V6to4pfx && badipv4(a+2);