Rich Felker
4f346b08b3
the buffer in getaddrinfo really only matters when /etc/hosts is huge, but in that case, the huge number of syscalls resulting from a tiny buffer would seriously impact the performance of every name lookup. the buffer in __dns.c has also been enlarged a bit so that typical resolv.conf files will fit fully in the buffer. there's no need to make it so large as to dominate the syscall overhead for large files, because resolv.conf should never be large.
283 lines
6.5 KiB
C
283 lines
6.5 KiB
C
#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")
|
|
|
|
static void cleanup(void *p)
|
|
{
|
|
close((intptr_t)p);
|
|
}
|
|
|
|
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[256];
|
|
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;
|
|
|
|
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &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 = family = AF_INET;
|
|
ns[0].sin.sin_port = htons(53);
|
|
ns[0].sin.sin_addr.s_addr = htonl(0x7f000001);
|
|
nns=1;
|
|
sl = sizeof sa.sin;
|
|
}
|
|
|
|
/* Get local address and open/bind a socket */
|
|
sa.sin.sin_family = family;
|
|
fd = socket(family, SOCK_DGRAM, 0);
|
|
|
|
pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
|
|
pthread_setcancelstate(cs, 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:
|
|
pthread_cleanup_pop(1);
|
|
|
|
/* 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;
|
|
}
|