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#include <stdint.h>
#include <netdb.h>
#include <stdio.h>
#include <fcntl.h>
#include <limits.h>
#include <string.h>
#include <sys/socket.h>
#include <poll.h>
#include <netinet/in.h>
#include <time.h>
#include <ctype.h>
#include <unistd.h>
#include <pthread.h>
#include "__dns.h"
#include "stdio_impl.h"
#define TIMEOUT 5
#define RETRY 1000
#define PACKET_MAX 512
#define PTR_MAX (64 + sizeof ".in-addr.arpa")
int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt)
{
time_t t0 = time(0);
int fd;
FILE *f, _f;
unsigned char _buf[64];
char line[64], *s, *z;
union {
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
} sa = {0}, ns[3] = {{0}};
socklen_t sl;
int nns = 0;
int family = AF_UNSPEC;
unsigned char q[280] = "", *r = dest;
int ql;
int rlen;
int got = 0, failed = 0;
int errcode = EAI_AGAIN;
int i, j;
struct timespec ts;
struct pollfd pfd;
int id;
int cs;
/* Construct query template - RR and ID will be filled later */
if (strlen(name)-1 >= 254U) return EAI_NONAME;
q[2] = q[5] = 1;
strcpy((char *)q+13, name);
for (i=13; q[i]; i=j+1) {
for (j=i; q[j] && q[j] != '.'; j++);
if (j-i-1u > 62u) return EAI_NONAME;
q[i-1] = j-i;
}
q[i+3] = 1;
ql = i+4;
/* Make a reasonably unpredictable id */
clock_gettime(CLOCK_REALTIME, &ts);
id = ts.tv_nsec + ts.tv_nsec/65536UL & 0xffff;
/* Get nameservers from resolv.conf, fallback to localhost */
f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf);
if (f) for (nns=0; nns<3 && fgets(line, sizeof line, f); ) {
if (strncmp(line, "nameserver", 10) || !isspace(line[10]))
continue;
for (s=line+11; isspace(*s); s++);
for (z=s; *z && !isspace(*z); z++);
*z=0;
if (__ipparse(ns+nns, family, s) < 0) continue;
ns[nns].sin.sin_port = htons(53);
family = ns[nns++].sin.sin_family;
sl = family==AF_INET6 ? sizeof sa.sin6 : sizeof sa.sin;
}
if (f) __fclose_ca(f);
if (!nns) {
ns[0].sin.sin_family = AF_INET;
ns[0].sin.sin_port = htons(53);
nns=1;
sl = sizeof sa.sin;
}
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
/* Get local address and open/bind a socket */
sa.sin.sin_family = family;
fd = socket(family, SOCK_DGRAM, 0);
if (bind(fd, (void *)&sa, sl) < 0) {
errcode = EAI_SYSTEM;
goto out;
}
/* Nonblocking to work around Linux UDP select bug */
fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);
pfd.fd = fd;
pfd.events = POLLIN;
/* Loop until we timeout; break early on success */
for (; time(0)-t0 < TIMEOUT; ) {
/* Query all configured namservers in parallel */
for (i=0; i<rrcnt; i++) if (rr[i]) for (j=0; j<nns; j++) {
q[0] = id+i >> 8;
q[1] = id+i;
q[ql-3] = rr[i];
sendto(fd, q, ql, MSG_NOSIGNAL, (void *)&ns[j], sl);
}
/* Wait for a response, or until time to retry */
if (poll(&pfd, 1, RETRY) <= 0) continue;
/* Process any and all replies */
while (got+failed < rrcnt && (rlen = recvfrom(fd, r, 512, 0,
(void *)&sa, (socklen_t[1]){sl})) >= 2)
{
/* Ignore replies from addresses we didn't send to */
for (i=0; i<nns; i++) if (!memcmp(ns+i, &sa, sl)) break;
if (i==nns) continue;
/* Compute index of the query from id */
i = r[0]*256+r[1] - id & 0xffff;
if ((unsigned)i >= rrcnt || !rr[i]) continue;
/* Interpret the result code */
switch (r[3] & 15) {
case 0:
got++;
break;
case 3:
if (1) errcode = EAI_NONAME; else
default:
errcode = EAI_FAIL;
failed++;
}
/* Mark this record as answered */
rr[i] = 0;
r += 512;
}
/* Check to see if we have answers to all queries */
if (got+failed == rrcnt) break;
}
out:
close(fd);
pthread_setcancelstate(cs, 0);
/* Return the number of results, or an error code if none */
if (got) return got;
return errcode;
}
static void mkptr4(char *s, const unsigned char *ip)
{
sprintf(s, "%d.%d.%d.%d.in-addr.arpa",
ip[3], ip[2], ip[1], ip[0]);
}
static void mkptr6(char *s, const unsigned char *ip)
{
static const char xdigits[] = "0123456789abcdef";
int i;
for (i=15; i>=0; i--) {
*s++ = xdigits[ip[i]&15]; *s++ = '.';
*s++ = xdigits[ip[i]>>4]; *s++ = '.';
}
strcpy(s, "ip6.arpa");
}
int __dns_query(unsigned char *r, const void *a, int family, int ptr)
{
char buf[PTR_MAX];
int rr[2], rrcnt = 1;
if (ptr) {
if (family == AF_INET6) mkptr6(buf, a);
else mkptr4(buf, a);
rr[0] = RR_PTR;
a = buf;
} else if (family == AF_INET6) {
rr[0] = RR_AAAA;
} else {
rr[0] = RR_A;
if (family != AF_INET) rr[rrcnt++] = RR_AAAA;
}
return __dns_doqueries(r, a, rr, rrcnt);
}
#define BITOP(a,b,op) \
((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
static int decname(char *s, const unsigned char *b, const unsigned char *p)
{
/* Remember jump destinations to detect loops and abort */
size_t seen[PACKET_MAX/8/sizeof(size_t)] = { 0 };
char *sz = s + HOST_NAME_MAX;
const unsigned char *pz = b+512;
for (;;) {
if (p>=pz) return -1;
else if (*p&0xc0) {
int j = (p[0]&1) | p[1];
if (BITOP(seen, j, &)) return -1;
BITOP(seen, j, |=);
p = b + j;
} else if (*p) {
if (p+*p+1>=pz || s+*p>=sz) return -1;
memcpy(s, p+1, *p);
s += *p+1;
p += *p+1;
s[-1] = *p ? '.' : 0;
} else return 0;
}
}
int __dns_get_rr(void *dest, size_t stride, size_t maxlen, size_t limit, const unsigned char *r, int rr, int dec)
{
int qdcount, ancount;
const unsigned char *p;
char tmp[256];
int found = 0;
int len;
if ((r[3]&15)) return 0;
p = r+12;
qdcount = r[4]*256 + r[5];
ancount = r[6]*256 + r[7];
if (qdcount+ancount > 64) return -1;
while (qdcount--) {
while (p-r < 512 && *p-1U < 127) p++;
if (*p>193 || (*p==193 && p[1]>254) || p>r+506)
return -1;
p += 5 + !!*p;
}
while (ancount--) {
while (p-r < 512 && *p-1U < 127) p++;
if (*p>193 || (*p==193 && p[1]>254) || p>r+506)
return -1;
p += 1 + !!*p;
len = p[8]*256 + p[9];
if (p+len > r+512) return -1;
if (p[1]==rr && len <= maxlen) {
if (dec && decname(tmp, r, p+10)<0) return -1;
if (dest && limit) {
if (dec) strcpy(dest, tmp);
else memcpy(dest, p+10, len);
dest = (char *)dest + stride;
limit--;
}
found++;
}
p += 10 + len;
}
return found;
}
int __dns_count_addrs(const unsigned char *r, int cnt)
{
int found=0, res, i;
static const int p[2][2] = { { 4, RR_A }, { 16, RR_AAAA } };
while (cnt--) {
for (i=0; i<2; i++) {
res = __dns_get_rr(0, 0, p[i][0], -1, r, p[i][1], 0);
if (res < 0) return res;
found += res;
}
r += 512;
}
return found;
}
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