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);
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 if (name_from_numeric(buf+cnt, line, family))
77 /* Extract first name as canonical name */
78 for (; *p && isspace(*p); p++);
79 for (z=p; *z && !isspace(*z); z++);
81 if (is_valid_hostname(p)) memcpy(canon, p, z-p+1);
88 struct address *addrs;
93 int __dns_parse(const unsigned char *, int, int (*)(void *, int, const void *, int, const void *), void *);
94 int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
95 int __res_mkquery(int, const char *, int, int, const unsigned char *, int, const unsigned char*, unsigned char *, int);
96 int __res_msend(int, const unsigned char *const *, const int *, unsigned char *const *, int *, int);
102 static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
105 struct dpc_ctx *ctx = c;
108 if (len != 4) return -1;
109 ctx->addrs[ctx->cnt].family = AF_INET;
110 ctx->addrs[ctx->cnt].scopeid = 0;
111 memcpy(ctx->addrs[ctx->cnt++].addr, data, 4);
114 if (len != 16) return -1;
115 ctx->addrs[ctx->cnt].family = AF_INET6;
116 ctx->addrs[ctx->cnt].scopeid = 0;
117 memcpy(ctx->addrs[ctx->cnt++].addr, data, 16);
120 if (__dn_expand(packet, (const unsigned char *)packet + 512,
121 data, tmp, sizeof tmp) > 0 && is_valid_hostname(tmp))
122 strcpy(ctx->canon, tmp);
128 static int name_from_dns(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
130 unsigned char qbuf[2][280], abuf[2][512];
131 const unsigned char *qp[2] = { qbuf[0], qbuf[1] };
132 unsigned char *ap[2] = { abuf[0], abuf[1] };
133 int qlens[2], alens[2];
135 struct dpc_ctx ctx = { .addrs = buf, .canon = canon };
137 if (family != AF_INET6) {
138 qlens[nq] = __res_mkquery(0, name, 1, RR_A, 0, 0, 0,
139 qbuf[nq], sizeof *qbuf);
142 if (family != AF_INET) {
143 qlens[nq] = __res_mkquery(0, name, 1, RR_AAAA, 0, 0, 0,
144 qbuf[nq], sizeof *qbuf);
148 if (__res_msend(nq, qp, qlens, ap, alens, sizeof *abuf) < 0) return EAI_SYSTEM;
151 __dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
153 if (ctx.cnt) return ctx.cnt;
154 if (alens[0] < 4 || (abuf[0][3] & 15) == 2) return EAI_AGAIN;
155 if ((abuf[0][3] & 15) == 3) return EAI_NONAME;
159 static const struct policy {
160 unsigned char addr[16];
161 unsigned char len, mask;
162 unsigned char prec, label;
164 { "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1", 15, 0xff, 50, 0 },
165 { "\0\0\0\0\0\0\0\0\0\0\xff\xff", 11, 0xff, 35, 4 },
166 { "\x20\2", 1, 0xff, 30, 2 },
167 { "\x20\1", 3, 0xff, 5, 5 },
168 { "\xfc", 0, 0xfe, 3, 13 },
170 /* These are deprecated and/or returned to the address
171 * pool, so despite the RFC, treating them as special
172 * is probably wrong. */
173 { "", 11, 0xff, 1, 3 },
174 { "\xfe\xc0", 1, 0xc0, 1, 11 },
175 { "\x3f\xfe", 1, 0xff, 1, 12 },
177 /* Last rule must match all addresses to stop loop. */
181 static const struct policy *policyof(const struct in6_addr *a)
185 if (memcmp(a->s6_addr, defpolicy[i].addr, defpolicy[i].len))
187 if ((a->s6_addr[defpolicy[i].len] & defpolicy[i].mask)
188 != defpolicy[i].addr[defpolicy[i].len])
194 static int labelof(const struct in6_addr *a)
196 return policyof(a)->label;
199 static int scopeof(const struct in6_addr *a)
201 if (IN6_IS_ADDR_MULTICAST(a)) return a->s6_addr[1] & 15;
202 if (IN6_IS_ADDR_LINKLOCAL(a)) return 2;
203 if (IN6_IS_ADDR_LOOPBACK(a)) return 2;
204 if (IN6_IS_ADDR_SITELOCAL(a)) return 5;
208 static int prefixmatch(const struct in6_addr *s, const struct in6_addr *d)
210 /* FIXME: The common prefix length should be limited to no greater
211 * than the nominal length of the prefix portion of the source
212 * address. However the definition of the source prefix length is
213 * not clear and thus this limiting is not yet implemented. */
215 for (i=0; i<128 && !((s->s6_addr[i/8]^d->s6_addr[i/8])&(128>>(i%8))); i++);
219 #define DAS_USABLE 0x40000000
220 #define DAS_MATCHINGSCOPE 0x20000000
221 #define DAS_MATCHINGLABEL 0x10000000
222 #define DAS_PREC_SHIFT 20
223 #define DAS_SCOPE_SHIFT 16
224 #define DAS_PREFIX_SHIFT 8
225 #define DAS_ORDER_SHIFT 0
227 static int addrcmp(const void *_a, const void *_b)
229 const struct address *a = _a, *b = _b;
230 return b->sortkey - a->sortkey;
233 int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, int flags)
239 /* reject empty name and check len so it fits into temp bufs */
240 size_t l = strnlen(name, 255);
243 memcpy(canon, name, l+1);
246 /* Procedurally, a request for v6 addresses with the v4-mapped
247 * flag set is like a request for unspecified family, followed
248 * by filtering of the results. */
249 if (flags & AI_V4MAPPED) {
250 if (family == AF_INET6) family = AF_UNSPEC;
251 else flags -= AI_V4MAPPED;
254 /* Try each backend until there's at least one result. */
255 cnt = name_from_null(buf, name, family, flags);
256 if (!cnt) cnt = name_from_numeric(buf, name, family);
257 if (!cnt && !(flags & AI_NUMERICHOST)) {
258 cnt = name_from_hosts(buf, canon, name, family);
259 if (!cnt) cnt = name_from_dns(buf, canon, name, family);
261 if (cnt<=0) return cnt ? cnt : EAI_NONAME;
263 /* Filter/transform results for v4-mapped lookup, if requested. */
264 if (flags & AI_V4MAPPED) {
265 if (!(flags & AI_ALL)) {
266 /* If any v6 results exist, remove v4 results. */
267 for (i=0; i<cnt && buf[i].family != AF_INET6; i++);
269 for (j=0; i<cnt; i++) {
270 if (buf[i].family == AF_INET6)
276 /* Translate any remaining v4 results to v6 */
277 for (i=0; i<cnt; i++) {
278 if (buf[i].family != AF_INET) continue;
279 memcpy(buf[i].addr+12, buf[i].addr, 4);
280 memcpy(buf[i].addr, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
281 buf[i].family = AF_INET6;
285 /* No further processing is needed if there are fewer than 2
286 * results or if there are only IPv4 results. */
287 if (cnt<2 || family==AF_INET) return cnt;
288 for (i=0; buf[i].family == AF_INET; i++)
289 if (i==cnt) return cnt;
292 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
294 /* The following implements a subset of RFC 3484/6724 destination
295 * address selection by generating a single 31-bit sort key for
296 * each address. Rules 3, 4, and 7 are omitted for having
297 * excessive runtime and code size cost and dubious benefit.
298 * So far the label/precedence table cannot be customized. */
299 for (i=0; i<cnt; i++) {
301 struct sockaddr_in6 sa, da = {
302 .sin6_family = AF_INET6,
303 .sin6_scope_id = buf[i].scopeid,
306 if (buf[i].family == AF_INET6) {
307 memcpy(da.sin6_addr.s6_addr, buf[i].addr, 16);
309 memcpy(da.sin6_addr.s6_addr,
310 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
311 memcpy(da.sin6_addr.s6_addr+12, buf[i].addr, 4);
313 const struct policy *dpolicy = policyof(&da.sin6_addr);
314 int dscope = scopeof(&da.sin6_addr);
315 int dlabel = dpolicy->label;
316 int dprec = dpolicy->prec;
318 int fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP);
320 if (!connect(fd, (void *)&da, sizeof da)) {
322 if (!getsockname(fd, (void *)&sa,
323 &(socklen_t){sizeof sa})) {
324 if (dscope == scopeof(&sa.sin6_addr))
325 key |= DAS_MATCHINGSCOPE;
326 if (dlabel == labelof(&sa.sin6_addr))
327 key |= DAS_MATCHINGLABEL;
328 prefixlen = prefixmatch(&sa.sin6_addr,
334 key |= dprec << DAS_PREC_SHIFT;
335 key |= (15-dscope) << DAS_SCOPE_SHIFT;
336 key |= prefixlen << DAS_PREFIX_SHIFT;
337 key |= (MAXADDRS-i) << DAS_ORDER_SHIFT;
338 buf[i].sortkey = key;
340 qsort(buf, cnt, sizeof *buf, addrcmp);
342 pthread_setcancelstate(cs, 0);