1/*
2 * Copyright (C) 2004, 2005, 2007-2009, 2012-2014  Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 2000, 2001, 2003  Internet Software Consortium.
4 *
5 * Permission to use, copy, modify, and/or distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
10 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
11 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
12 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
13 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
15 * PERFORMANCE OF THIS SOFTWARE.
16 */
17
18/* $Id: context.c,v 1.55 2009/09/02 23:48:03 tbox Exp $ */
19
20/*! \file context.c
21   lwres_context_create() creates a #lwres_context_t structure for use in
22   lightweight resolver operations. It holds a socket and other data
23   needed for communicating with a resolver daemon. The new
24   lwres_context_t is returned through contextp, a pointer to a
25   lwres_context_t pointer. This lwres_context_t pointer must initially
26   be NULL, and is modified to point to the newly created
27   lwres_context_t.
28
29   When the lightweight resolver needs to perform dynamic memory
30   allocation, it will call malloc_function to allocate memory and
31   free_function to free it. If malloc_function and free_function are
32   NULL, memory is allocated using malloc and free. It is not
33   permitted to have a NULL malloc_function and a non-NULL free_function
34   or vice versa. arg is passed as the first parameter to the memory
35   allocation functions. If malloc_function and free_function are NULL,
36   arg is unused and should be passed as NULL.
37
38   Once memory for the structure has been allocated, it is initialized
39   using lwres_conf_init() and returned via *contextp.
40
41   lwres_context_destroy() destroys a #lwres_context_t, closing its
42   socket. contextp is a pointer to a pointer to the context that is to
43   be destroyed. The pointer will be set to NULL when the context has
44   been destroyed.
45
46   The context holds a serial number that is used to identify resolver
47   request packets and associate responses with the corresponding
48   requests. This serial number is controlled using
49   lwres_context_initserial() and lwres_context_nextserial().
50   lwres_context_initserial() sets the serial number for context *ctx to
51   serial. lwres_context_nextserial() increments the serial number and
52   returns the previous value.
53
54   Memory for a lightweight resolver context is allocated and freed using
55   lwres_context_allocmem() and lwres_context_freemem(). These use
56   whatever allocations were defined when the context was created with
57   lwres_context_create(). lwres_context_allocmem() allocates len bytes
58   of memory and if successful returns a pointer to the allocated
59   storage. lwres_context_freemem() frees len bytes of space starting at
60   location mem.
61
62   lwres_context_sendrecv() performs I/O for the context ctx. Data are
63   read and written from the context's socket. It writes data from
64   sendbase -- typically a lightweight resolver query packet -- and waits
65   for a reply which is copied to the receive buffer at recvbase. The
66   number of bytes that were written to this receive buffer is returned
67   in *recvd_len.
68
69\section context_return Return Values
70
71   lwres_context_create() returns #LWRES_R_NOMEMORY if memory for the
72   struct lwres_context could not be allocated, #LWRES_R_SUCCESS
73   otherwise.
74
75   Successful calls to the memory allocator lwres_context_allocmem()
76   return a pointer to the start of the allocated space. It returns NULL
77   if memory could not be allocated.
78
79   #LWRES_R_SUCCESS is returned when lwres_context_sendrecv() completes
80   successfully. #LWRES_R_IOERROR is returned if an I/O error occurs and
81   #LWRES_R_TIMEOUT is returned if lwres_context_sendrecv() times out
82   waiting for a response.
83
84\section context_see See Also
85
86   lwres_conf_init(), malloc, free.
87 */
88#include <config.h>
89
90#include <fcntl.h>
91#include <limits.h>
92#include <stdlib.h>
93#include <string.h>
94#include <time.h>
95#include <unistd.h>
96
97#include <lwres/lwres.h>
98#include <lwres/net.h>
99#include <lwres/platform.h>
100
101#ifdef LWRES_PLATFORM_NEEDSYSSELECTH
102#include <sys/select.h>
103#endif
104
105#include "context_p.h"
106#include "assert_p.h"
107
108/*!
109 * Some systems define the socket length argument as an int, some as size_t,
110 * some as socklen_t.  The last is what the current POSIX standard mandates.
111 * This definition is here so it can be portable but easily changed if needed.
112 */
113#ifndef LWRES_SOCKADDR_LEN_T
114#define LWRES_SOCKADDR_LEN_T unsigned int
115#endif
116
117/*!
118 * Make a socket nonblocking.
119 */
120#ifndef MAKE_NONBLOCKING
121#define MAKE_NONBLOCKING(sd, retval) \
122do { \
123	retval = fcntl(sd, F_GETFL, 0); \
124	if (retval != -1) { \
125		retval |= O_NONBLOCK; \
126		retval = fcntl(sd, F_SETFL, retval); \
127	} \
128} while (0)
129#endif
130
131LIBLWRES_EXTERNAL_DATA lwres_uint16_t lwres_udp_port = LWRES_UDP_PORT;
132LIBLWRES_EXTERNAL_DATA const char *lwres_resolv_conf = LWRES_RESOLV_CONF;
133
134static void *
135lwres_malloc(void *, size_t);
136
137static void
138lwres_free(void *, void *, size_t);
139
140/*!
141 * lwres_result_t
142 */
143static lwres_result_t
144context_connect(lwres_context_t *);
145
146/*%
147 * Creates a #lwres_context_t structure for use in
148 *  lightweight resolver operations.
149 */
150lwres_result_t
151lwres_context_create(lwres_context_t **contextp, void *arg,
152		     lwres_malloc_t malloc_function,
153		     lwres_free_t free_function,
154		     unsigned int flags)
155{
156	lwres_context_t *ctx;
157
158	REQUIRE(contextp != NULL && *contextp == NULL);
159
160	/*
161	 * If we were not given anything special to use, use our own
162	 * functions.  These are just wrappers around malloc() and free().
163	 */
164	if (malloc_function == NULL || free_function == NULL) {
165		REQUIRE(malloc_function == NULL);
166		REQUIRE(free_function == NULL);
167		malloc_function = lwres_malloc;
168		free_function = lwres_free;
169	}
170
171	ctx = malloc_function(arg, sizeof(lwres_context_t));
172	if (ctx == NULL)
173		return (LWRES_R_NOMEMORY);
174
175	/*
176	 * Set up the context.
177	 */
178	ctx->malloc = malloc_function;
179	ctx->free = free_function;
180	ctx->arg = arg;
181	ctx->sock = -1;
182
183	ctx->timeout = LWRES_DEFAULT_TIMEOUT;
184#ifndef WIN32
185	ctx->serial = time(NULL); /* XXXMLG or BEW */
186#else
187	ctx->serial = _time32(NULL);
188#endif
189
190	ctx->use_ipv4 = 1;
191	ctx->use_ipv6 = 1;
192	if ((flags & (LWRES_CONTEXT_USEIPV4 | LWRES_CONTEXT_USEIPV6)) ==
193	    LWRES_CONTEXT_USEIPV6) {
194		ctx->use_ipv4 = 0;
195	}
196	if ((flags & (LWRES_CONTEXT_USEIPV4 | LWRES_CONTEXT_USEIPV6)) ==
197	    LWRES_CONTEXT_USEIPV4) {
198		ctx->use_ipv6 = 0;
199	}
200
201	/*
202	 * Init resolv.conf bits.
203	 */
204	lwres_conf_init(ctx);
205
206	*contextp = ctx;
207	return (LWRES_R_SUCCESS);
208}
209
210/*%
211Destroys a #lwres_context_t, closing its socket.
212contextp is a pointer to a pointer to the context that is
213to be destroyed. The pointer will be set to NULL
214when the context has been destroyed.
215 */
216void
217lwres_context_destroy(lwres_context_t **contextp) {
218	lwres_context_t *ctx;
219
220	REQUIRE(contextp != NULL && *contextp != NULL);
221
222	ctx = *contextp;
223	*contextp = NULL;
224
225	if (ctx->sock != -1) {
226#ifdef WIN32
227		DestroySockets();
228#endif
229		(void)close(ctx->sock);
230		ctx->sock = -1;
231	}
232
233	CTXFREE(ctx, sizeof(lwres_context_t));
234}
235/*% Increments the serial number and returns the previous value. */
236lwres_uint32_t
237lwres_context_nextserial(lwres_context_t *ctx) {
238	REQUIRE(ctx != NULL);
239
240	return (ctx->serial++);
241}
242
243/*% Sets the serial number for context *ctx to serial. */
244void
245lwres_context_initserial(lwres_context_t *ctx, lwres_uint32_t serial) {
246	REQUIRE(ctx != NULL);
247
248	ctx->serial = serial;
249}
250
251/*% Frees len bytes of space starting at location mem. */
252void
253lwres_context_freemem(lwres_context_t *ctx, void *mem, size_t len) {
254	REQUIRE(mem != NULL);
255	REQUIRE(len != 0U);
256
257	CTXFREE(mem, len);
258}
259
260/*% Allocates len bytes of memory and if successful returns a pointer to the allocated storage. */
261void *
262lwres_context_allocmem(lwres_context_t *ctx, size_t len) {
263	REQUIRE(len != 0U);
264
265	return (CTXMALLOC(len));
266}
267
268static void *
269lwres_malloc(void *arg, size_t len) {
270	void *mem;
271
272	UNUSED(arg);
273
274	mem = malloc(len);
275	if (mem == NULL)
276		return (NULL);
277
278	memset(mem, 0xe5, len);
279
280	return (mem);
281}
282
283static void
284lwres_free(void *arg, void *mem, size_t len) {
285	UNUSED(arg);
286
287	memset(mem, 0xa9, len);
288	free(mem);
289}
290
291static lwres_result_t
292context_connect(lwres_context_t *ctx) {
293#ifndef WIN32
294	int s;
295#else
296	SOCKET s;
297#endif
298	int ret;
299	struct sockaddr_in sin;
300	struct sockaddr_in6 sin6;
301	struct sockaddr *sa;
302	LWRES_SOCKADDR_LEN_T salen;
303	int domain;
304
305	if (ctx->confdata.lwnext != 0) {
306		memmove(&ctx->address, &ctx->confdata.lwservers[0],
307			sizeof(lwres_addr_t));
308		LWRES_LINK_INIT(&ctx->address, link);
309	} else {
310		/* The default is the IPv4 loopback address 127.0.0.1. */
311		memset(&ctx->address, 0, sizeof(ctx->address));
312		ctx->address.family = LWRES_ADDRTYPE_V4;
313		ctx->address.length = 4;
314		ctx->address.address[0] = 127;
315		ctx->address.address[1] = 0;
316		ctx->address.address[2] = 0;
317		ctx->address.address[3] = 1;
318	}
319
320	if (ctx->address.family == LWRES_ADDRTYPE_V4) {
321		memmove(&sin.sin_addr, ctx->address.address,
322			sizeof(sin.sin_addr));
323		sin.sin_port = htons(lwres_udp_port);
324		sin.sin_family = AF_INET;
325		sa = (struct sockaddr *)&sin;
326		salen = sizeof(sin);
327		domain = PF_INET;
328	} else if (ctx->address.family == LWRES_ADDRTYPE_V6) {
329		memmove(&sin6.sin6_addr, ctx->address.address,
330			sizeof(sin6.sin6_addr));
331		sin6.sin6_port = htons(lwres_udp_port);
332		sin6.sin6_family = AF_INET6;
333		sa = (struct sockaddr *)&sin6;
334		salen = sizeof(sin6);
335		domain = PF_INET6;
336	} else
337		return (LWRES_R_IOERROR);
338
339#ifdef WIN32
340	InitSockets();
341#endif
342	s = socket(domain, SOCK_DGRAM, IPPROTO_UDP);
343#ifndef WIN32
344	if (s < 0) {
345		return (LWRES_R_IOERROR);
346	}
347#else
348	if (s == INVALID_SOCKET) {
349		DestroySockets();
350		return (LWRES_R_IOERROR);
351	}
352#endif
353
354	ret = connect(s, sa, salen);
355	if (ret != 0) {
356#ifdef WIN32
357		DestroySockets();
358#endif
359		(void)close(s);
360		return (LWRES_R_IOERROR);
361	}
362
363	MAKE_NONBLOCKING(s, ret);
364	if (ret < 0) {
365#ifdef WIN32
366		DestroySockets();
367#endif
368		(void)close(s);
369		return (LWRES_R_IOERROR);
370	}
371
372	ctx->sock = (int)s;
373
374	return (LWRES_R_SUCCESS);
375}
376
377int
378lwres_context_getsocket(lwres_context_t *ctx) {
379	return (ctx->sock);
380}
381
382lwres_result_t
383lwres_context_send(lwres_context_t *ctx,
384		   void *sendbase, int sendlen) {
385	int ret;
386	lwres_result_t lwresult;
387
388	if (ctx->sock == -1) {
389		lwresult = context_connect(ctx);
390		if (lwresult != LWRES_R_SUCCESS)
391			return (lwresult);
392		INSIST(ctx->sock >= 0);
393	}
394
395	ret = sendto(ctx->sock, sendbase, sendlen, 0, NULL, 0);
396	if (ret < 0)
397		return (LWRES_R_IOERROR);
398	if (ret != sendlen)
399		return (LWRES_R_IOERROR);
400
401	return (LWRES_R_SUCCESS);
402}
403
404lwres_result_t
405lwres_context_recv(lwres_context_t *ctx,
406		   void *recvbase, int recvlen,
407		   int *recvd_len)
408{
409	LWRES_SOCKADDR_LEN_T fromlen;
410	struct sockaddr_in sin;
411	struct sockaddr_in6 sin6;
412	struct sockaddr *sa;
413	int ret;
414
415	if (ctx->address.family == LWRES_ADDRTYPE_V4) {
416		sa = (struct sockaddr *)&sin;
417		fromlen = sizeof(sin);
418	} else {
419		sa = (struct sockaddr *)&sin6;
420		fromlen = sizeof(sin6);
421	}
422
423	/*
424	 * The address of fromlen is cast to void * to shut up compiler
425	 * warnings, namely on systems that have the sixth parameter
426	 * prototyped as a signed int when LWRES_SOCKADDR_LEN_T is
427	 * defined as unsigned.
428	 */
429	ret = recvfrom(ctx->sock, recvbase, recvlen, 0, sa, (void *)&fromlen);
430
431	if (ret < 0)
432		return (LWRES_R_IOERROR);
433
434	if (ret == recvlen)
435		return (LWRES_R_TOOLARGE);
436
437	/*
438	 * If we got something other than what we expect, have the caller
439	 * wait for another packet.  This can happen if an old result
440	 * comes in, or if someone is sending us random stuff.
441	 */
442	if (ctx->address.family == LWRES_ADDRTYPE_V4) {
443		if (fromlen != sizeof(sin)
444		    || memcmp(&sin.sin_addr, ctx->address.address,
445			      sizeof(sin.sin_addr)) != 0
446		    || sin.sin_port != htons(lwres_udp_port))
447			return (LWRES_R_RETRY);
448	} else {
449		if (fromlen != sizeof(sin6)
450		    || memcmp(&sin6.sin6_addr, ctx->address.address,
451			      sizeof(sin6.sin6_addr)) != 0
452		    || sin6.sin6_port != htons(lwres_udp_port))
453			return (LWRES_R_RETRY);
454	}
455
456	if (recvd_len != NULL)
457		*recvd_len = ret;
458
459	return (LWRES_R_SUCCESS);
460}
461
462/*% performs I/O for the context ctx. */
463lwres_result_t
464lwres_context_sendrecv(lwres_context_t *ctx,
465		       void *sendbase, int sendlen,
466		       void *recvbase, int recvlen,
467		       int *recvd_len)
468{
469	lwres_result_t result;
470	int ret2;
471	fd_set readfds;
472	struct timeval timeout;
473
474	/*
475	 * Type of tv_sec is 32 bits long.
476	 */
477	if (ctx->timeout <= 0x7FFFFFFFU)
478		timeout.tv_sec = (int)ctx->timeout;
479	else
480		timeout.tv_sec = 0x7FFFFFFF;
481
482	timeout.tv_usec = 0;
483
484	result = lwres_context_send(ctx, sendbase, sendlen);
485	if (result != LWRES_R_SUCCESS)
486		return (result);
487
488	/*
489	 * If this is not checked, select() can overflow,
490	 * causing corruption elsewhere.
491	 */
492	if (ctx->sock >= (int)FD_SETSIZE) {
493		close(ctx->sock);
494		ctx->sock = -1;
495		return (LWRES_R_IOERROR);
496	}
497
498 again:
499	FD_ZERO(&readfds);
500	FD_SET(ctx->sock, &readfds);
501	ret2 = select(ctx->sock + 1, &readfds, NULL, NULL, &timeout);
502
503	/*
504	 * What happened with select?
505	 */
506	if (ret2 < 0)
507		return (LWRES_R_IOERROR);
508	if (ret2 == 0)
509		return (LWRES_R_TIMEOUT);
510
511	result = lwres_context_recv(ctx, recvbase, recvlen, recvd_len);
512	if (result == LWRES_R_RETRY)
513		goto again;
514
515	return (result);
516}
517