1 #include <sys/socket.h>
2 #include <netinet/in.h>
13 #include "stdio_impl.h"
16 static int is_valid_hostname(const char *host)
18 const unsigned char *s;
19 if (strnlen(host, 255)-1 >= 254 || mbstowcs(0, host, 0) == -1) return 0;
20 for (s=(void *)host; *s>=0x80 || *s=='.' || *s=='-' || isalnum(*s); s++);
24 static int name_from_null(struct address buf[static 2], const char *name, int family, int flags)
28 if (flags & AI_PASSIVE) {
29 if (family != AF_INET6)
30 buf[cnt++] = (struct address){ .family = AF_INET };
31 if (family != AF_INET)
32 buf[cnt++] = (struct address){ .family = AF_INET6 };
34 if (family != AF_INET6)
35 buf[cnt++] = (struct address){ .family = AF_INET, .addr = { 127,0,0,1 } };
36 if (family != AF_INET)
37 buf[cnt++] = (struct address){ .family = AF_INET6, .addr = { [15] = 1 } };
42 static int name_from_numeric(struct address buf[static 1], const char *name, int family)
44 return __lookup_ipliteral(buf, name, family);
47 static int name_from_hosts(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
50 size_t l = strlen(name);
52 unsigned char _buf[1032];
53 FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf);
55 while (fgets(line, sizeof line, f) && cnt < MAXADDRS) {
58 if ((p=strchr(line, '#'))) *p++='\n', *p=0;
59 for(p=line+1; (p=strstr(p, name)) &&
60 (!isspace(p[-1]) || !isspace(p[l])); p++);
63 /* Isolate IP address to parse */
64 for (p=line; *p && !isspace(*p); p++);
66 if (name_from_numeric(buf+cnt, line, family))
69 /* Extract first name as canonical name */
70 for (; *p && isspace(*p); p++);
71 for (z=p; *z && !isspace(*z); z++);
73 if (is_valid_hostname(p)) memcpy(canon, p, z-p+1);
80 struct address *addrs;
85 int __dns_parse(const unsigned char *, int, int (*)(void *, int, const void *, int, const void *), void *);
86 int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
87 int __res_mkquery(int, const char *, int, int, const unsigned char *, int, const unsigned char*, unsigned char *, int);
88 int __res_msend(int, const unsigned char *const *, const int *, unsigned char *const *, int *, int);
94 static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
97 struct dpc_ctx *ctx = c;
100 if (len != 4) return -1;
101 ctx->addrs[ctx->cnt].family = AF_INET;
102 ctx->addrs[ctx->cnt].scopeid = 0;
103 memcpy(ctx->addrs[ctx->cnt++].addr, data, 4);
106 if (len != 16) return -1;
107 ctx->addrs[ctx->cnt].family = AF_INET6;
108 ctx->addrs[ctx->cnt].scopeid = 0;
109 memcpy(ctx->addrs[ctx->cnt++].addr, data, 16);
112 if (__dn_expand(packet, (const unsigned char *)packet + 512,
113 data, tmp, sizeof tmp) > 0 && is_valid_hostname(tmp))
114 strcpy(ctx->canon, tmp);
120 static int name_from_dns(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
122 unsigned char qbuf[2][280], abuf[2][512];
123 const unsigned char *qp[2] = { qbuf[0], qbuf[1] };
124 unsigned char *ap[2] = { abuf[0], abuf[1] };
125 int qlens[2], alens[2];
127 struct dpc_ctx ctx = { .addrs = buf, .canon = canon };
129 if (family != AF_INET6) {
130 qlens[nq] = __res_mkquery(0, name, 1, RR_A, 0, 0, 0,
131 qbuf[nq], sizeof *qbuf);
134 if (family != AF_INET) {
135 qlens[nq] = __res_mkquery(0, name, 1, RR_AAAA, 0, 0, 0,
136 qbuf[nq], sizeof *qbuf);
140 if (__res_msend(nq, qp, qlens, ap, alens, sizeof *abuf) < 0) return EAI_SYSTEM;
143 __dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
145 if (ctx.cnt) return ctx.cnt;
146 if (alens[0] < 4 || (abuf[0][3] & 15) == 2) return EAI_AGAIN;
147 if ((abuf[0][3] & 15) == 3) return EAI_NONAME;
151 static const struct policy {
152 unsigned char addr[16];
153 unsigned char len, mask;
154 unsigned char prec, label;
156 { "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1", 15, 0xff, 50, 0 },
157 { "\0\0\0\0\0\0\0\0\0\0\xff\xff", 11, 0xff, 35, 4 },
158 { "\x20\2", 1, 0xff, 30, 2 },
159 { "\x20\1", 3, 0xff, 5, 5 },
160 { "\xfc", 0, 0xfe, 3, 13 },
162 /* These are deprecated and/or returned to the address
163 * pool, so despite the RFC, treating them as special
164 * is probably wrong. */
165 { "", 11, 0xff, 1, 3 },
166 { "\xfe\xc0", 1, 0xc0, 1, 11 },
167 { "\x3f\xfe", 1, 0xff, 1, 12 },
169 /* Last rule must match all addresses to stop loop. */
173 static const struct policy *policyof(const struct in6_addr *a)
177 if (memcmp(a->s6_addr, defpolicy[i].addr, defpolicy[i].len))
179 if ((a->s6_addr[defpolicy[i].len] & defpolicy[i].mask)
180 != defpolicy[i].addr[defpolicy[i].len])
186 static int labelof(const struct in6_addr *a)
188 return policyof(a)->label;
191 static int scopeof(const struct in6_addr *a)
193 if (IN6_IS_ADDR_MULTICAST(a)) return a->s6_addr[1] & 15;
194 if (IN6_IS_ADDR_LINKLOCAL(a)) return 2;
195 if (IN6_IS_ADDR_LOOPBACK(a)) return 2;
196 if (IN6_IS_ADDR_SITELOCAL(a)) return 5;
200 static int prefixmatch(const struct in6_addr *s, const struct in6_addr *d)
202 /* FIXME: The common prefix length should be limited to no greater
203 * than the nominal length of the prefix portion of the source
204 * address. However the definition of the source prefix length is
205 * not clear and thus this limiting is not yet implemented. */
207 for (i=0; i<128 && !((s->s6_addr[i/8]^d->s6_addr[i/8])&(128>>(i%8))); i++);
211 #define DAS_USABLE 0x40000000
212 #define DAS_MATCHINGSCOPE 0x20000000
213 #define DAS_MATCHINGLABEL 0x10000000
214 #define DAS_PREC_SHIFT 20
215 #define DAS_SCOPE_SHIFT 16
216 #define DAS_PREFIX_SHIFT 8
217 #define DAS_ORDER_SHIFT 0
219 static int addrcmp(const void *_a, const void *_b)
221 const struct address *a = _a, *b = _b;
222 return b->sortkey - a->sortkey;
225 int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, int flags)
231 /* reject empty name and check len so it fits into temp bufs */
232 size_t l = strnlen(name, 255);
235 memcpy(canon, name, l+1);
238 /* Procedurally, a request for v6 addresses with the v4-mapped
239 * flag set is like a request for unspecified family, followed
240 * by filtering of the results. */
241 if (flags & AI_V4MAPPED) {
242 if (family == AF_INET6) family = AF_UNSPEC;
243 else flags -= AI_V4MAPPED;
246 /* Try each backend until there's at least one result. */
247 cnt = name_from_null(buf, name, family, flags);
248 if (!cnt) cnt = name_from_numeric(buf, name, family);
249 if (!cnt && !(flags & AI_NUMERICHOST)) {
250 cnt = name_from_hosts(buf, canon, name, family);
251 if (!cnt) cnt = name_from_dns(buf, canon, name, family);
253 if (cnt<=0) return cnt ? cnt : EAI_NONAME;
255 /* Filter/transform results for v4-mapped lookup, if requested. */
256 if (flags & AI_V4MAPPED) {
257 if (!(flags & AI_ALL)) {
258 /* If any v6 results exist, remove v4 results. */
259 for (i=0; i<cnt && buf[i].family != AF_INET6; i++);
261 for (j=0; i<cnt; i++) {
262 if (buf[i].family == AF_INET6)
268 /* Translate any remaining v4 results to v6 */
269 for (i=0; i<cnt; i++) {
270 if (buf[i].family != AF_INET) continue;
271 memcpy(buf[i].addr+12, buf[i].addr, 4);
272 memcpy(buf[i].addr, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
273 buf[i].family = AF_INET6;
277 /* No further processing is needed if there are fewer than 2
278 * results or if there are only IPv4 results. */
279 if (cnt<2 || family==AF_INET) return cnt;
280 for (i=0; buf[i].family == AF_INET; i++)
281 if (i==cnt) return cnt;
284 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
286 /* The following implements a subset of RFC 3484/6724 destination
287 * address selection by generating a single 31-bit sort key for
288 * each address. Rules 3, 4, and 7 are omitted for having
289 * excessive runtime and code size cost and dubious benefit.
290 * So far the label/precedence table cannot be customized. */
291 for (i=0; i<cnt; i++) {
293 struct sockaddr_in6 sa, da = {
294 .sin6_family = AF_INET6,
295 .sin6_scope_id = buf[i].scopeid,
298 if (buf[i].family == AF_INET6) {
299 memcpy(da.sin6_addr.s6_addr, buf[i].addr, 16);
301 memcpy(da.sin6_addr.s6_addr,
302 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
303 memcpy(da.sin6_addr.s6_addr+12, buf[i].addr, 4);
305 const struct policy *dpolicy = policyof(&da.sin6_addr);
306 int dscope = scopeof(&da.sin6_addr);
307 int dlabel = dpolicy->label;
308 int dprec = dpolicy->prec;
310 int fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP);
312 if (!connect(fd, (void *)&da, sizeof da)) {
314 if (!getsockname(fd, (void *)&sa,
315 &(socklen_t){sizeof sa})) {
316 if (dscope == scopeof(&sa.sin6_addr))
317 key |= DAS_MATCHINGSCOPE;
318 if (dlabel == labelof(&sa.sin6_addr))
319 key |= DAS_MATCHINGLABEL;
320 prefixlen = prefixmatch(&sa.sin6_addr,
326 key |= dprec << DAS_PREC_SHIFT;
327 key |= (15-dscope) << DAS_SCOPE_SHIFT;
328 key |= prefixlen << DAS_PREFIX_SHIFT;
329 key |= (MAXADDRS-i) << DAS_ORDER_SHIFT;
330 buf[i].sortkey = key;
332 qsort(buf, cnt, sizeof *buf, addrcmp);
334 pthread_setcancelstate(cs, 0);