7 #include <sys/socket.h>
9 #include <netinet/in.h>
15 #include "stdio_impl.h"
19 #define PACKET_MAX 512
20 #define PTR_MAX (64 + sizeof ".in-addr.arpa")
22 static void cleanup(void *p)
27 int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt)
32 unsigned char _buf[64];
33 char line[64], *s, *z;
35 struct sockaddr_in sin;
36 struct sockaddr_in6 sin6;
37 } sa = {0}, ns[3] = {{0}};
40 int family = AF_UNSPEC;
41 unsigned char q[280] = "", *r = dest;
44 int got = 0, failed = 0;
45 int errcode = EAI_AGAIN;
52 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
54 /* Construct query template - RR and ID will be filled later */
55 if (strlen(name)-1 >= 254U) return EAI_NONAME;
57 strcpy((char *)q+13, name);
58 for (i=13; q[i]; i=j+1) {
59 for (j=i; q[j] && q[j] != '.'; j++);
60 if (j-i-1u > 62u) return EAI_NONAME;
66 /* Make a reasonably unpredictable id */
67 clock_gettime(CLOCK_REALTIME, &ts);
68 id = ts.tv_nsec + ts.tv_nsec/65536UL & 0xffff;
70 /* Get nameservers from resolv.conf, fallback to localhost */
71 f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf);
72 if (f) for (nns=0; nns<3 && fgets(line, sizeof line, f); ) {
73 if (strncmp(line, "nameserver", 10) || !isspace(line[10]))
75 for (s=line+11; isspace(*s); s++);
76 for (z=s; *z && !isspace(*z); z++);
78 if (__ipparse(ns+nns, family, s) < 0) continue;
79 ns[nns].sin.sin_port = htons(53);
80 family = ns[nns++].sin.sin_family;
81 sl = family==AF_INET6 ? sizeof sa.sin6 : sizeof sa.sin;
83 if (f) __fclose_ca(f);
85 ns[0].sin.sin_family = family = AF_INET;
86 ns[0].sin.sin_port = htons(53);
87 ns[0].sin.sin_addr.s_addr = htonl(0x7f000001);
92 pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
93 pthread_setcancelstate(cs, 0);
95 /* Get local address and open/bind a socket */
96 sa.sin.sin_family = family;
97 fd = socket(family, SOCK_DGRAM, 0);
98 if (bind(fd, (void *)&sa, sl) < 0) {
102 /* Nonblocking to work around Linux UDP select bug */
103 fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);
108 /* Loop until we timeout; break early on success */
109 for (; time(0)-t0 < TIMEOUT; ) {
111 /* Query all configured namservers in parallel */
112 for (i=0; i<rrcnt; i++) if (rr[i]) for (j=0; j<nns; j++) {
116 sendto(fd, q, ql, MSG_NOSIGNAL, (void *)&ns[j], sl);
119 /* Wait for a response, or until time to retry */
120 if (poll(&pfd, 1, RETRY) <= 0) continue;
122 /* Process any and all replies */
123 while (got+failed < rrcnt && (rlen = recvfrom(fd, r, 512, 0,
124 (void *)&sa, (socklen_t[1]){sl})) >= 2)
126 /* Ignore replies from addresses we didn't send to */
127 for (i=0; i<nns; i++) if (!memcmp(ns+i, &sa, sl)) break;
128 if (i==nns) continue;
130 /* Compute index of the query from id */
131 i = r[0]*256+r[1] - id & 0xffff;
132 if ((unsigned)i >= rrcnt || !rr[i]) continue;
134 /* Interpret the result code */
140 if (1) errcode = EAI_NONAME; else
146 /* Mark this record as answered */
151 /* Check to see if we have answers to all queries */
152 if (got+failed == rrcnt) break;
155 pthread_cleanup_pop(1);
157 /* Return the number of results, or an error code if none */
162 static void mkptr4(char *s, const unsigned char *ip)
164 sprintf(s, "%d.%d.%d.%d.in-addr.arpa",
165 ip[3], ip[2], ip[1], ip[0]);
168 static void mkptr6(char *s, const unsigned char *ip)
170 static const char xdigits[] = "0123456789abcdef";
172 for (i=15; i>=0; i--) {
173 *s++ = xdigits[ip[i]&15]; *s++ = '.';
174 *s++ = xdigits[ip[i]>>4]; *s++ = '.';
176 strcpy(s, "ip6.arpa");
179 int __dns_query(unsigned char *r, const void *a, int family, int ptr)
182 int rr[2], rrcnt = 1;
185 if (family == AF_INET6) mkptr6(buf, a);
189 } else if (family == AF_INET6) {
193 if (family != AF_INET) rr[rrcnt++] = RR_AAAA;
196 return __dns_doqueries(r, a, rr, rrcnt);
200 #define BITOP(a,b,op) \
201 ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
203 static int decname(char *s, const unsigned char *b, const unsigned char *p)
205 /* Remember jump destinations to detect loops and abort */
206 size_t seen[PACKET_MAX/8/sizeof(size_t)] = { 0 };
207 char *sz = s + HOST_NAME_MAX;
208 const unsigned char *pz = b+512;
210 if (p>=pz) return -1;
212 int j = (p[0]&1) | p[1];
213 if (BITOP(seen, j, &)) return -1;
217 if (p+*p+1>=pz || s+*p>=sz) return -1;
221 s[-1] = *p ? '.' : 0;
226 int __dns_get_rr(void *dest, size_t stride, size_t maxlen, size_t limit, const unsigned char *r, int rr, int dec)
228 int qdcount, ancount;
229 const unsigned char *p;
234 if ((r[3]&15)) return 0;
236 qdcount = r[4]*256 + r[5];
237 ancount = r[6]*256 + r[7];
238 if (qdcount+ancount > 64) return -1;
240 while (p-r < 512 && *p-1U < 127) p++;
241 if (*p>193 || (*p==193 && p[1]>254) || p>r+506)
246 while (p-r < 512 && *p-1U < 127) p++;
247 if (*p>193 || (*p==193 && p[1]>254) || p>r+506)
250 len = p[8]*256 + p[9];
251 if (p+len > r+512) return -1;
252 if (p[1]==rr && len <= maxlen) {
253 if (dec && decname(tmp, r, p+10)<0) return -1;
255 if (dec) strcpy(dest, tmp);
256 else memcpy(dest, p+10, len);
257 dest = (char *)dest + stride;
267 int __dns_count_addrs(const unsigned char *r, int cnt)
270 static const int p[2][2] = { { 4, RR_A }, { 16, RR_AAAA } };
273 for (i=0; i<2; i++) {
274 res = __dns_get_rr(0, 0, p[i][0], -1, r, p[i][1], 0);
275 if (res < 0) return res;