#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <stdint.h>
#include <string.h>
#include <poll.h>
#include <time.h>
#include <ctype.h>
#include <unistd.h>
#include <errno.h>
#include <pthread.h>
#include "stdio_impl.h"
#include "syscall.h"
#include "lookup.h"
static void cleanup(void *p)
{
__syscall(SYS_close, (intptr_t)p);
}
static unsigned long mtime()
{
struct timespec ts;
clock_gettime(CLOCK_REALTIME, &ts);
return (unsigned long)ts.tv_sec * 1000
+ ts.tv_nsec / 1000000;
}
int __res_msend(int nqueries, const unsigned char *const *queries,
const int *qlens, unsigned char *const *answers, int *alens, int asize)
{
int fd;
FILE *f, _f;
unsigned char _buf[256];
char line[64], *s, *z;
int timeout = 5000, attempts = 2, retry_interval, servfail_retry;
union {
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
} sa = {0}, ns[3] = {{0}};
socklen_t sl = sizeof sa.sin;
int nns = 0;
int family = AF_INET;
int rlen;
int next;
int i, j;
int cs;
struct pollfd pfd;
unsigned long t0, t1, t2;
struct address iplit;
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
/* 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, "options", 7) && isspace(line[7])) {
unsigned long x;
char *p, *z;
p = strstr(line, "timeout:");
if (p && isdigit(p[8])) {
p += 8;
x = strtoul(p, &z, 10);
if (z != p) timeout = x < 30 ? x*1000 : 30000;
}
p = strstr(line, "attempts:");
if (p && isdigit(p[9])) {
p += 9;
x = strtoul(p, &z, 10);
if (z != p) attempts = x < 10 ? x : 10;
if (!attempts) attempts = 1;
}
}
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 (__lookup_ipliteral(&iplit, s, AF_UNSPEC)>0) {
if (iplit.family == AF_INET) {
memcpy(&ns[nns].sin.sin_addr, iplit.addr, 4);
ns[nns].sin.sin_port = htons(53);
ns[nns++].sin.sin_family = AF_INET;
} else {
sl = sizeof sa.sin6;
memcpy(&ns[nns].sin6.sin6_addr, iplit.addr, 16);
ns[nns].sin6.sin6_port = htons(53);
ns[nns].sin6.sin6_scope_id = iplit.scopeid;
ns[nns++].sin6.sin6_family = family = AF_INET6;
}
}
}
if (f) __fclose_ca(f);
if (!nns) {
ns[0].sin.sin_family = AF_INET;
ns[0].sin.sin_port = htons(53);
ns[0].sin.sin_addr.s_addr = htonl(0x7f000001);
nns=1;
}
/* Get local address and open/bind a socket */
sa.sin.sin_family = family;
fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
/* Handle case where system lacks IPv6 support */
if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
family = AF_INET;
}
if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) return -1;
/* Past this point, there are no errors. Each individual query will
* yield either no reply (indicated by zero length) or an answer
* packet which is up to the caller to interpret. */
pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
pthread_setcancelstate(cs, 0);
/* Convert any IPv4 addresses in a mixed environment to v4-mapped */
if (family == AF_INET6) {
setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
for (i=0; i<nns; i++) {
if (ns[i].sin.sin_family != AF_INET) continue;
memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
&ns[i].sin.sin_addr, 4);
memcpy(ns[i].sin6.sin6_addr.s6_addr,
"\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
ns[i].sin6.sin6_family = AF_INET6;
ns[i].sin6.sin6_flowinfo = 0;
ns[i].sin6.sin6_scope_id = 0;
}
}
memset(alens, 0, sizeof *alens * nqueries);
pfd.fd = fd;
pfd.events = POLLIN;
retry_interval = timeout / attempts;
next = 0;
t0 = t2 = mtime();
t1 = t2 - retry_interval;
for (; t2-t0 < timeout; t2=mtime()) {
if (t2-t1 >= retry_interval) {
/* Query all configured namservers in parallel */
for (i=0; i<nqueries; i++)
if (!alens[i])
for (j=0; j<nns; j++)
sendto(fd, queries[i],
qlens[i], MSG_NOSIGNAL,
(void *)&ns[j], sl);
t1 = t2;
servfail_retry = 2 * nqueries;
}
/* Wait for a response, or until time to retry */
if (poll(&pfd, 1, t1+retry_interval-t2) <= 0) continue;
while ((rlen = recvfrom(fd, answers[next], asize, 0,
(void *)&sa, (socklen_t[1]){sl})) >= 0) {
/* Ignore non-identifiable packets */
if (rlen < 4) continue;
/* Ignore replies from addresses we didn't send to */
for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
if (j==nns) continue;
/* Find which query this answer goes with, if any */
for (i=next; i<nqueries && (
answers[next][0] != queries[i][0] ||
answers[next][1] != queries[i][1] ); i++);
if (i==nqueries) continue;
if (alens[i]) continue;
/* Only accept positive or negative responses;
* retry immediately on server failure, and ignore
* all other codes such as refusal. */
switch (answers[next][3] & 15) {
case 0:
case 3:
break;
case 2:
if (servfail_retry && servfail_retry--)
sendto(fd, queries[i],
qlens[i], MSG_NOSIGNAL,
(void *)&ns[j], sl);
default:
continue;
}
/* Store answer in the right slot, or update next
* available temp slot if it's already in place. */
alens[i] = rlen;
if (i == next)
for (; next<nqueries && alens[next]; next++);
else
memcpy(answers[i], answers[next], rlen);
if (next == nqueries) goto out;
}
}
out:
pthread_cleanup_pop(1);
return 0;
}
