1 #include <sys/socket.h>
2 #include <netinet/in.h>
14 #include "stdio_impl.h"
17 static int is_valid_hostname(const char *host)
19 const unsigned char *s;
20 if (strnlen(host, 255)-1 >= 254 || mbstowcs(0, host, 0) == -1) return 0;
21 for (s=(void *)host; *s>=0x80 || *s=='.' || *s=='-' || isalnum(*s); s++);
25 static int name_from_null(struct address buf[static 2], const char *name, int family, int flags)
29 if (flags & AI_PASSIVE) {
30 if (family != AF_INET6)
31 buf[cnt++] = (struct address){ .family = AF_INET };
32 if (family != AF_INET)
33 buf[cnt++] = (struct address){ .family = AF_INET6 };
35 if (family != AF_INET6)
36 buf[cnt++] = (struct address){ .family = AF_INET, .addr = { 127,0,0,1 } };
37 if (family != AF_INET)
38 buf[cnt++] = (struct address){ .family = AF_INET6, .addr = { [15] = 1 } };
43 static int name_from_numeric(struct address buf[static 1], const char *name, int family)
45 return __lookup_ipliteral(buf, name, family);
48 static int name_from_hosts(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
51 size_t l = strlen(name);
52 int cnt = 0, badfam = 0;
53 unsigned char _buf[1032];
54 FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf);
55 if (!f) switch (errno) {
63 while (fgets(line, sizeof line, f) && cnt < MAXADDRS) {
66 if ((p=strchr(line, '#'))) *p++='\n', *p=0;
67 for(p=line+1; (p=strstr(p, name)) &&
68 (!isspace(p[-1]) || !isspace(p[l])); p++);
71 /* Isolate IP address to parse */
72 for (p=line; *p && !isspace(*p); p++);
74 switch (name_from_numeric(buf+cnt, line, family)) {
85 /* Extract first name as canonical name */
86 for (; *p && isspace(*p); p++);
87 for (z=p; *z && !isspace(*z); z++);
89 if (is_valid_hostname(p)) memcpy(canon, p, z-p+1);
92 return cnt ? cnt : badfam;
96 struct address *addrs;
101 int __dns_parse(const unsigned char *, int, int (*)(void *, int, const void *, int, const void *), void *);
102 int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
103 int __res_mkquery(int, const char *, int, int, const unsigned char *, int, const unsigned char*, unsigned char *, int);
104 int __res_msend_rc(int, const unsigned char *const *, const int *, unsigned char *const *, int *, int, const struct resolvconf *);
110 static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
113 struct dpc_ctx *ctx = c;
116 if (len != 4) return -1;
117 ctx->addrs[ctx->cnt].family = AF_INET;
118 ctx->addrs[ctx->cnt].scopeid = 0;
119 memcpy(ctx->addrs[ctx->cnt++].addr, data, 4);
122 if (len != 16) return -1;
123 ctx->addrs[ctx->cnt].family = AF_INET6;
124 ctx->addrs[ctx->cnt].scopeid = 0;
125 memcpy(ctx->addrs[ctx->cnt++].addr, data, 16);
128 if (__dn_expand(packet, (const unsigned char *)packet + 512,
129 data, tmp, sizeof tmp) > 0 && is_valid_hostname(tmp))
130 strcpy(ctx->canon, tmp);
136 static int name_from_dns(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, const struct resolvconf *conf)
138 unsigned char qbuf[2][280], abuf[2][512];
139 const unsigned char *qp[2] = { qbuf[0], qbuf[1] };
140 unsigned char *ap[2] = { abuf[0], abuf[1] };
141 int qlens[2], alens[2];
143 struct dpc_ctx ctx = { .addrs = buf, .canon = canon };
144 static const struct { int af; int rr; } afrr[2] = {
145 { .af = AF_INET6, .rr = RR_A },
146 { .af = AF_INET, .rr = RR_AAAA },
149 for (i=0; i<2; i++) {
150 if (family != afrr[i].af) {
151 qlens[nq] = __res_mkquery(0, name, 1, afrr[i].rr,
152 0, 0, 0, qbuf[nq], sizeof *qbuf);
159 if (__res_msend_rc(nq, qp, qlens, ap, alens, sizeof *abuf, conf) < 0)
163 __dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
165 if (ctx.cnt) return ctx.cnt;
166 if (alens[0] < 4 || (abuf[0][3] & 15) == 2) return EAI_AGAIN;
167 if ((abuf[0][3] & 15) == 0) return EAI_NONAME;
168 if ((abuf[0][3] & 15) == 3) return 0;
172 static int name_from_dns_search(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
175 struct resolvconf conf;
179 if (__get_resolv_conf(&conf, search, sizeof search) < 0) return -1;
181 /* Count dots, suppress search when >=ndots or name ends in
182 * a dot, which is an explicit request for global scope. */
183 for (dots=l=0; name[l]; l++) if (name[l]=='.') dots++;
184 if (dots >= conf.ndots || name[l-1]=='.') *search = 0;
186 /* This can never happen; the caller already checked length. */
187 if (l >= 256) return EAI_NONAME;
189 /* Name with search domain appended is setup in canon[]. This both
190 * provides the desired default canonical name (if the requested
191 * name is not a CNAME record) and serves as a buffer for passing
192 * the full requested name to name_from_dns. */
193 memcpy(canon, name, l);
196 for (p=search; *p; p=z) {
197 for (; isspace(*p); p++);
198 for (z=p; *z && !isspace(*z); z++);
200 if (z-p < 256 - l - 1) {
201 memcpy(canon+l+1, p, z-p);
203 int cnt = name_from_dns(buf, canon, canon, family, &conf);
209 return name_from_dns(buf, canon, name, family, &conf);
212 static const struct policy {
213 unsigned char addr[16];
214 unsigned char len, mask;
215 unsigned char prec, label;
217 { "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1", 15, 0xff, 50, 0 },
218 { "\0\0\0\0\0\0\0\0\0\0\xff\xff", 11, 0xff, 35, 4 },
219 { "\x20\2", 1, 0xff, 30, 2 },
220 { "\x20\1", 3, 0xff, 5, 5 },
221 { "\xfc", 0, 0xfe, 3, 13 },
223 /* These are deprecated and/or returned to the address
224 * pool, so despite the RFC, treating them as special
225 * is probably wrong. */
226 { "", 11, 0xff, 1, 3 },
227 { "\xfe\xc0", 1, 0xc0, 1, 11 },
228 { "\x3f\xfe", 1, 0xff, 1, 12 },
230 /* Last rule must match all addresses to stop loop. */
234 static const struct policy *policyof(const struct in6_addr *a)
238 if (memcmp(a->s6_addr, defpolicy[i].addr, defpolicy[i].len))
240 if ((a->s6_addr[defpolicy[i].len] & defpolicy[i].mask)
241 != defpolicy[i].addr[defpolicy[i].len])
247 static int labelof(const struct in6_addr *a)
249 return policyof(a)->label;
252 static int scopeof(const struct in6_addr *a)
254 if (IN6_IS_ADDR_MULTICAST(a)) return a->s6_addr[1] & 15;
255 if (IN6_IS_ADDR_LINKLOCAL(a)) return 2;
256 if (IN6_IS_ADDR_LOOPBACK(a)) return 2;
257 if (IN6_IS_ADDR_SITELOCAL(a)) return 5;
261 static int prefixmatch(const struct in6_addr *s, const struct in6_addr *d)
263 /* FIXME: The common prefix length should be limited to no greater
264 * than the nominal length of the prefix portion of the source
265 * address. However the definition of the source prefix length is
266 * not clear and thus this limiting is not yet implemented. */
268 for (i=0; i<128 && !((s->s6_addr[i/8]^d->s6_addr[i/8])&(128>>(i%8))); i++);
272 #define DAS_USABLE 0x40000000
273 #define DAS_MATCHINGSCOPE 0x20000000
274 #define DAS_MATCHINGLABEL 0x10000000
275 #define DAS_PREC_SHIFT 20
276 #define DAS_SCOPE_SHIFT 16
277 #define DAS_PREFIX_SHIFT 8
278 #define DAS_ORDER_SHIFT 0
280 static int addrcmp(const void *_a, const void *_b)
282 const struct address *a = _a, *b = _b;
283 return b->sortkey - a->sortkey;
286 int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, int flags)
292 /* reject empty name and check len so it fits into temp bufs */
293 size_t l = strnlen(name, 255);
296 memcpy(canon, name, l+1);
299 /* Procedurally, a request for v6 addresses with the v4-mapped
300 * flag set is like a request for unspecified family, followed
301 * by filtering of the results. */
302 if (flags & AI_V4MAPPED) {
303 if (family == AF_INET6) family = AF_UNSPEC;
304 else flags -= AI_V4MAPPED;
307 /* Try each backend until there's at least one result. */
308 cnt = name_from_null(buf, name, family, flags);
309 if (!cnt) cnt = name_from_numeric(buf, name, family);
310 if (!cnt && !(flags & AI_NUMERICHOST)) {
311 cnt = name_from_hosts(buf, canon, name, family);
312 if (!cnt) cnt = name_from_dns_search(buf, canon, name, family);
314 if (cnt<=0) return cnt ? cnt : EAI_NONAME;
316 /* Filter/transform results for v4-mapped lookup, if requested. */
317 if (flags & AI_V4MAPPED) {
318 if (!(flags & AI_ALL)) {
319 /* If any v6 results exist, remove v4 results. */
320 for (i=0; i<cnt && buf[i].family != AF_INET6; i++);
322 for (j=0; i<cnt; i++) {
323 if (buf[i].family == AF_INET6)
329 /* Translate any remaining v4 results to v6 */
330 for (i=0; i<cnt; i++) {
331 if (buf[i].family != AF_INET) continue;
332 memcpy(buf[i].addr+12, buf[i].addr, 4);
333 memcpy(buf[i].addr, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
334 buf[i].family = AF_INET6;
338 /* No further processing is needed if there are fewer than 2
339 * results or if there are only IPv4 results. */
340 if (cnt<2 || family==AF_INET) return cnt;
341 for (i=0; i<cnt; i++) if (buf[i].family != AF_INET) break;
342 if (i==cnt) return cnt;
345 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
347 /* The following implements a subset of RFC 3484/6724 destination
348 * address selection by generating a single 31-bit sort key for
349 * each address. Rules 3, 4, and 7 are omitted for having
350 * excessive runtime and code size cost and dubious benefit.
351 * So far the label/precedence table cannot be customized. */
352 for (i=0; i<cnt; i++) {
354 struct sockaddr_in6 sa, da = {
355 .sin6_family = AF_INET6,
356 .sin6_scope_id = buf[i].scopeid,
359 if (buf[i].family == AF_INET6) {
360 memcpy(da.sin6_addr.s6_addr, buf[i].addr, 16);
362 memcpy(da.sin6_addr.s6_addr,
363 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
364 memcpy(da.sin6_addr.s6_addr+12, buf[i].addr, 4);
366 const struct policy *dpolicy = policyof(&da.sin6_addr);
367 int dscope = scopeof(&da.sin6_addr);
368 int dlabel = dpolicy->label;
369 int dprec = dpolicy->prec;
371 int fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP);
373 if (!connect(fd, (void *)&da, sizeof da)) {
375 if (!getsockname(fd, (void *)&sa,
376 &(socklen_t){sizeof sa})) {
377 if (dscope == scopeof(&sa.sin6_addr))
378 key |= DAS_MATCHINGSCOPE;
379 if (dlabel == labelof(&sa.sin6_addr))
380 key |= DAS_MATCHINGLABEL;
381 prefixlen = prefixmatch(&sa.sin6_addr,
387 key |= dprec << DAS_PREC_SHIFT;
388 key |= (15-dscope) << DAS_SCOPE_SHIFT;
389 key |= prefixlen << DAS_PREFIX_SHIFT;
390 key |= (MAXADDRS-i) << DAS_ORDER_SHIFT;
391 buf[i].sortkey = key;
393 qsort(buf, cnt, sizeof *buf, addrcmp);
395 pthread_setcancelstate(cs, 0);