1#include <sys/socket.h>
2#include <netinet/in.h>
3#include <netdb.h>
4#include <arpa/inet.h>
5#include <stdint.h>
6#include <string.h>
7#include <poll.h>
8#include <time.h>
9#include <ctype.h>
10#include <unistd.h>
11#include <errno.h>
12#include <pthread.h>
13#include "stdio_impl.h"
14#include "syscall.h"
15#include "lookup.h"
16
17static void cleanup(void *p)
18{
19	__syscall(SYS_close, (intptr_t)p);
20}
21
22static unsigned long mtime()
23{
24	struct timespec ts;
25	clock_gettime(CLOCK_REALTIME, &ts);
26	return (unsigned long)ts.tv_sec * 1000
27		+ ts.tv_nsec / 1000000;
28}
29
30int __res_msend_rc(int nqueries, const unsigned char *const *queries,
31	const int *qlens, unsigned char *const *answers, int *alens, int asize,
32	const struct resolvconf *conf)
33{
34	int fd;
35	int timeout, attempts, retry_interval, servfail_retry;
36	union {
37		struct sockaddr_in sin;
38		struct sockaddr_in6 sin6;
39	} sa = {0}, ns[MAXNS] = {{0}};
40	socklen_t sl = sizeof sa.sin;
41	int nns = 0;
42	int family = AF_INET;
43	int rlen;
44	int next;
45	int i, j;
46	int cs;
47	struct pollfd pfd;
48	unsigned long t0, t1, t2;
49
50	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
51
52	timeout = 1000*conf->timeout;
53	attempts = conf->attempts;
54
55	for (nns=0; nns<conf->nns; nns++) {
56		const struct address *iplit = &conf->ns[nns];
57		if (iplit->family == AF_INET) {
58			memcpy(&ns[nns].sin.sin_addr, iplit->addr, 4);
59			ns[nns].sin.sin_port = htons(53);
60			ns[nns].sin.sin_family = AF_INET;
61		} else {
62			sl = sizeof sa.sin6;
63			memcpy(&ns[nns].sin6.sin6_addr, iplit->addr, 16);
64			ns[nns].sin6.sin6_port = htons(53);
65			ns[nns].sin6.sin6_scope_id = iplit->scopeid;
66			ns[nns].sin6.sin6_family = family = AF_INET6;
67		}
68	}
69
70	/* Get local address and open/bind a socket */
71	sa.sin.sin_family = family;
72	fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
73
74	/* Handle case where system lacks IPv6 support */
75	if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
76		fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
77		family = AF_INET;
78	}
79	if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) return -1;
80
81	/* Past this point, there are no errors. Each individual query will
82	 * yield either no reply (indicated by zero length) or an answer
83	 * packet which is up to the caller to interpret. */
84
85	pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
86	pthread_setcancelstate(cs, 0);
87
88	/* Convert any IPv4 addresses in a mixed environment to v4-mapped */
89	if (family == AF_INET6) {
90		setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
91		for (i=0; i<nns; i++) {
92			if (ns[i].sin.sin_family != AF_INET) continue;
93			memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
94				&ns[i].sin.sin_addr, 4);
95			memcpy(ns[i].sin6.sin6_addr.s6_addr,
96				"\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
97			ns[i].sin6.sin6_family = AF_INET6;
98			ns[i].sin6.sin6_flowinfo = 0;
99			ns[i].sin6.sin6_scope_id = 0;
100		}
101	}
102
103	memset(alens, 0, sizeof *alens * nqueries);
104
105	pfd.fd = fd;
106	pfd.events = POLLIN;
107	retry_interval = timeout / attempts;
108	next = 0;
109	t0 = t2 = mtime();
110	t1 = t2 - retry_interval;
111
112	for (; t2-t0 < timeout; t2=mtime()) {
113		if (t2-t1 >= retry_interval) {
114			/* Query all configured namservers in parallel */
115			for (i=0; i<nqueries; i++)
116				if (!alens[i])
117					for (j=0; j<nns; j++)
118						sendto(fd, queries[i],
119							qlens[i], MSG_NOSIGNAL,
120							(void *)&ns[j], sl);
121			t1 = t2;
122			servfail_retry = 2 * nqueries;
123		}
124
125		/* Wait for a response, or until time to retry */
126		if (poll(&pfd, 1, t1+retry_interval-t2) <= 0) continue;
127
128		while ((rlen = recvfrom(fd, answers[next], asize, 0,
129		  (void *)&sa, (socklen_t[1]){sl})) >= 0) {
130
131			/* Ignore non-identifiable packets */
132			if (rlen < 4) continue;
133
134			/* Ignore replies from addresses we didn't send to */
135			for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
136			if (j==nns) continue;
137
138			/* Find which query this answer goes with, if any */
139			for (i=next; i<nqueries && (
140				answers[next][0] != queries[i][0] ||
141				answers[next][1] != queries[i][1] ); i++);
142			if (i==nqueries) continue;
143			if (alens[i]) continue;
144
145			/* Only accept positive or negative responses;
146			 * retry immediately on server failure, and ignore
147			 * all other codes such as refusal. */
148			switch (answers[next][3] & 15) {
149			case 0:
150			case 3:
151				break;
152			case 2:
153				if (servfail_retry && servfail_retry--)
154					sendto(fd, queries[i],
155						qlens[i], MSG_NOSIGNAL,
156						(void *)&ns[j], sl);
157			default:
158				continue;
159			}
160
161			/* Store answer in the right slot, or update next
162			 * available temp slot if it's already in place. */
163			alens[i] = rlen;
164			if (i == next)
165				for (; next<nqueries && alens[next]; next++);
166			else
167				memcpy(answers[i], answers[next], rlen);
168
169			if (next == nqueries) goto out;
170		}
171	}
172out:
173	pthread_cleanup_pop(1);
174
175	return 0;
176}
177
178int __res_msend(int nqueries, const unsigned char *const *queries,
179	const int *qlens, unsigned char *const *answers, int *alens, int asize)
180{
181	struct resolvconf conf;
182	if (__get_resolv_conf(&conf, 0, 0) < 0) return -1;
183	return __res_msend_rc(nqueries, queries, qlens, answers, alens, asize, &conf);
184}
185