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 };
145 if (family != AF_INET6) {
146 qlens[nq] = __res_mkquery(0, name, 1, RR_A, 0, 0, 0,
147 qbuf[nq], sizeof *qbuf);
150 if (family != AF_INET) {
151 qlens[nq] = __res_mkquery(0, name, 1, RR_AAAA, 0, 0, 0,
152 qbuf[nq], sizeof *qbuf);
156 if (__res_msend_rc(nq, qp, qlens, ap, alens, sizeof *abuf, conf) < 0)
160 __dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
162 if (ctx.cnt) return ctx.cnt;
163 if (alens[0] < 4 || (abuf[0][3] & 15) == 2) return EAI_AGAIN;
164 if ((abuf[0][3] & 15) == 0) return EAI_NONAME;
165 if ((abuf[0][3] & 15) == 3) return 0;
169 static int name_from_dns_search(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
172 struct resolvconf conf;
176 if (__get_resolv_conf(&conf, search, sizeof search) < 0) return -1;
178 /* Count dots, suppress search when >=ndots or name ends in
179 * a dot, which is an explicit request for global scope. */
180 for (dots=l=0; name[l]; l++) if (name[l]=='.') dots++;
181 if (dots >= conf.ndots || name[l-1]=='.') *search = 0;
183 /* This can never happen; the caller already checked length. */
184 if (l >= 256) return EAI_NONAME;
186 /* Name with search domain appended is setup in canon[]. This both
187 * provides the desired default canonical name (if the requested
188 * name is not a CNAME record) and serves as a buffer for passing
189 * the full requested name to name_from_dns. */
190 memcpy(canon, name, l);
193 for (p=search; *p; p=z) {
194 for (; isspace(*p); p++);
195 for (z=p; *z && !isspace(*z); z++);
197 if (z-p < 256 - l - 1) {
198 memcpy(canon+l+1, p, z-p);
200 int cnt = name_from_dns(buf, canon, canon, family, &conf);
206 return name_from_dns(buf, canon, name, family, &conf);
209 static const struct policy {
210 unsigned char addr[16];
211 unsigned char len, mask;
212 unsigned char prec, label;
214 { "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1", 15, 0xff, 50, 0 },
215 { "\0\0\0\0\0\0\0\0\0\0\xff\xff", 11, 0xff, 35, 4 },
216 { "\x20\2", 1, 0xff, 30, 2 },
217 { "\x20\1", 3, 0xff, 5, 5 },
218 { "\xfc", 0, 0xfe, 3, 13 },
220 /* These are deprecated and/or returned to the address
221 * pool, so despite the RFC, treating them as special
222 * is probably wrong. */
223 { "", 11, 0xff, 1, 3 },
224 { "\xfe\xc0", 1, 0xc0, 1, 11 },
225 { "\x3f\xfe", 1, 0xff, 1, 12 },
227 /* Last rule must match all addresses to stop loop. */
231 static const struct policy *policyof(const struct in6_addr *a)
235 if (memcmp(a->s6_addr, defpolicy[i].addr, defpolicy[i].len))
237 if ((a->s6_addr[defpolicy[i].len] & defpolicy[i].mask)
238 != defpolicy[i].addr[defpolicy[i].len])
244 static int labelof(const struct in6_addr *a)
246 return policyof(a)->label;
249 static int scopeof(const struct in6_addr *a)
251 if (IN6_IS_ADDR_MULTICAST(a)) return a->s6_addr[1] & 15;
252 if (IN6_IS_ADDR_LINKLOCAL(a)) return 2;
253 if (IN6_IS_ADDR_LOOPBACK(a)) return 2;
254 if (IN6_IS_ADDR_SITELOCAL(a)) return 5;
258 static int prefixmatch(const struct in6_addr *s, const struct in6_addr *d)
260 /* FIXME: The common prefix length should be limited to no greater
261 * than the nominal length of the prefix portion of the source
262 * address. However the definition of the source prefix length is
263 * not clear and thus this limiting is not yet implemented. */
265 for (i=0; i<128 && !((s->s6_addr[i/8]^d->s6_addr[i/8])&(128>>(i%8))); i++);
269 #define DAS_USABLE 0x40000000
270 #define DAS_MATCHINGSCOPE 0x20000000
271 #define DAS_MATCHINGLABEL 0x10000000
272 #define DAS_PREC_SHIFT 20
273 #define DAS_SCOPE_SHIFT 16
274 #define DAS_PREFIX_SHIFT 8
275 #define DAS_ORDER_SHIFT 0
277 static int addrcmp(const void *_a, const void *_b)
279 const struct address *a = _a, *b = _b;
280 return b->sortkey - a->sortkey;
283 int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, int flags)
289 /* reject empty name and check len so it fits into temp bufs */
290 size_t l = strnlen(name, 255);
293 memcpy(canon, name, l+1);
296 /* Procedurally, a request for v6 addresses with the v4-mapped
297 * flag set is like a request for unspecified family, followed
298 * by filtering of the results. */
299 if (flags & AI_V4MAPPED) {
300 if (family == AF_INET6) family = AF_UNSPEC;
301 else flags -= AI_V4MAPPED;
304 /* Try each backend until there's at least one result. */
305 cnt = name_from_null(buf, name, family, flags);
306 if (!cnt) cnt = name_from_numeric(buf, name, family);
307 if (!cnt && !(flags & AI_NUMERICHOST)) {
308 cnt = name_from_hosts(buf, canon, name, family);
309 if (!cnt) cnt = name_from_dns_search(buf, canon, name, family);
311 if (cnt<=0) return cnt ? cnt : EAI_NONAME;
313 /* Filter/transform results for v4-mapped lookup, if requested. */
314 if (flags & AI_V4MAPPED) {
315 if (!(flags & AI_ALL)) {
316 /* If any v6 results exist, remove v4 results. */
317 for (i=0; i<cnt && buf[i].family != AF_INET6; i++);
319 for (j=0; i<cnt; i++) {
320 if (buf[i].family == AF_INET6)
326 /* Translate any remaining v4 results to v6 */
327 for (i=0; i<cnt; i++) {
328 if (buf[i].family != AF_INET) continue;
329 memcpy(buf[i].addr+12, buf[i].addr, 4);
330 memcpy(buf[i].addr, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
331 buf[i].family = AF_INET6;
335 /* No further processing is needed if there are fewer than 2
336 * results or if there are only IPv4 results. */
337 if (cnt<2 || family==AF_INET) return cnt;
338 for (i=0; buf[i].family == AF_INET; i++)
339 if (i==cnt) return cnt;
342 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
344 /* The following implements a subset of RFC 3484/6724 destination
345 * address selection by generating a single 31-bit sort key for
346 * each address. Rules 3, 4, and 7 are omitted for having
347 * excessive runtime and code size cost and dubious benefit.
348 * So far the label/precedence table cannot be customized. */
349 for (i=0; i<cnt; i++) {
351 struct sockaddr_in6 sa, da = {
352 .sin6_family = AF_INET6,
353 .sin6_scope_id = buf[i].scopeid,
356 if (buf[i].family == AF_INET6) {
357 memcpy(da.sin6_addr.s6_addr, buf[i].addr, 16);
359 memcpy(da.sin6_addr.s6_addr,
360 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
361 memcpy(da.sin6_addr.s6_addr+12, buf[i].addr, 4);
363 const struct policy *dpolicy = policyof(&da.sin6_addr);
364 int dscope = scopeof(&da.sin6_addr);
365 int dlabel = dpolicy->label;
366 int dprec = dpolicy->prec;
368 int fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP);
370 if (!connect(fd, (void *)&da, sizeof da)) {
372 if (!getsockname(fd, (void *)&sa,
373 &(socklen_t){sizeof sa})) {
374 if (dscope == scopeof(&sa.sin6_addr))
375 key |= DAS_MATCHINGSCOPE;
376 if (dlabel == labelof(&sa.sin6_addr))
377 key |= DAS_MATCHINGLABEL;
378 prefixlen = prefixmatch(&sa.sin6_addr,
384 key |= dprec << DAS_PREC_SHIFT;
385 key |= (15-dscope) << DAS_SCOPE_SHIFT;
386 key |= prefixlen << DAS_PREFIX_SHIFT;
387 key |= (MAXADDRS-i) << DAS_ORDER_SHIFT;
388 buf[i].sortkey = key;
390 qsort(buf, cnt, sizeof *buf, addrcmp);
392 pthread_setcancelstate(cs, 0);