b7806a18e075f091c87611b0c64e43bdf711500b
[paraslash.git] / net.c
1 /*
2 * Copyright (C) 2005-2013 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file net.c Networking-related helper functions. */
8
9 /*
10 * Since glibc 2.8, the _GNU_SOURCE feature test macro must be defined in order
11 * to obtain the definition of the ucred structure.
12 */
13 #define _GNU_SOURCE
14
15 #include <netinet/in.h>
16 #include <arpa/inet.h>
17 #include <sys/un.h>
18 #include <sys/types.h>
19 #include <sys/socket.h>
20 #include <netdb.h>
21
22 /* At least NetBSD needs these. */
23 #ifndef AI_V4MAPPED
24 #define AI_V4MAPPED 0
25 #endif
26 #ifndef AI_ALL
27 #define AI_ALL 0
28 #endif
29 #ifndef AI_ADDRCONFIG
30 #define AI_ADDRCONFIG 0
31 #endif
32
33 #include <regex.h>
34
35 #include "para.h"
36 #include "error.h"
37 #include "net.h"
38 #include "string.h"
39 #include "list.h"
40 #include "fd.h"
41
42 /**
43 * Parse and validate IPv4 address/netmask string.
44 *
45 * \param cidr Address in CIDR notation
46 * \param addr Copy of the IPv4 address part of \a cidr
47 * \param addrlen Size of \a addr in bytes
48 * \param netmask Value of the netmask part in \a cidr or the
49 * default of 32 if not specified.
50 *
51 * \return Pointer to \a addr if succesful, NULL on error.
52 * \sa RFC 4632
53 */
54 char *parse_cidr(const char *cidr,
55 char *addr, ssize_t addrlen,
56 int32_t *netmask)
57 {
58 const char *o = cidr;
59 char *c = addr, *end = c + (addrlen - 1);
60
61 *netmask = 0x20;
62
63 if (cidr == NULL || addrlen < 1)
64 goto failed;
65
66 for (o = cidr; (*c = *o == '/'? '\0' : *o); c++, o++)
67 if (c == end)
68 goto failed;
69
70 if (*o == '/')
71 if (para_atoi32(++o, netmask) < 0 ||
72 *netmask < 0 || *netmask > 0x20)
73 goto failed;
74
75 if (is_valid_ipv4_address(addr))
76 return addr;
77 failed:
78 *addr = '\0';
79 return NULL;
80 }
81
82
83 /**
84 * Match string as a candidate IPv4 address.
85 *
86 * \param address The string to match.
87 * \return True if \a address has "dot-quad" format.
88 */
89 static bool is_v4_dot_quad(const char *address)
90 {
91 bool result;
92 regex_t r;
93
94 assert(para_regcomp(&r, "^([0-9]+\\.){3}[0-9]+$",
95 REG_EXTENDED | REG_NOSUB) >= 0);
96 result = regexec(&r, address, 0, NULL, 0) == 0;
97 regfree(&r);
98 return result;
99 }
100
101 /**
102 * Perform basic syntax checking on the host-part of an URL:
103 *
104 * - Since ':' is invalid in IPv4 addresses and DNS names, the
105 * presence of ':' causes interpretation as IPv6 address;
106 * - next the first-match-wins algorithm from RFC 3986 is applied;
107 * - else the string is considered as DNS name, to be resolved later.
108 *
109 * \param host The host string to check.
110 * \return True if \a host passes the syntax checks.
111 *
112 * \sa RFC 3986, 3.2.2; RFC 1123, 2.1; RFC 1034, 3.5
113 */
114 static bool host_string_ok(const char *host)
115 {
116 if (host == NULL || *host == '\0')
117 return false;
118 if (strchr(host, ':') != NULL)
119 return is_valid_ipv6_address(host);
120 if (is_v4_dot_quad(host))
121 return is_valid_ipv4_address(host);
122 return true;
123 }
124
125 /**
126 * Parse and validate URL string.
127 *
128 * The URL syntax is loosely based on RFC 3986, supporting one of
129 * - "["host"]"[:port] for native IPv6 addresses and
130 * - host[:port] for IPv4 hostnames and DNS names.
131 *
132 * Native IPv6 addresses must be enclosed in square brackets, since
133 * otherwise there is an ambiguity with the port separator `:'.
134 * The 'port' part is always considered to be a number; if absent,
135 * it is set to -1, to indicate that a default port is to be used.
136 *
137 * The following are valid examples:
138 * - 10.10.1.1
139 * - 10.10.1.2:8000
140 * - localhost
141 * - localhost:8001
142 * - [::1]:8000
143 * - [badc0de::1]
144 *
145 * \param url The URL string to take apart.
146 * \param host To return the copied host part of \a url.
147 * \param hostlen The maximum length of \a host.
148 * \param port To return the port number (if any) of \a url.
149 *
150 * \return Pointer to \a host, or \p NULL if failed. If \p NULL is returned,
151 * \a host and \a port are undefined. If no port number was present in \a url,
152 * \a port is set to -1.
153 *
154 * \sa RFC 3986, 3.2.2/3.2.3
155 */
156 char *parse_url(const char *url,
157 char *host, ssize_t hostlen,
158 int32_t *port)
159 {
160 const char *o = url;
161 char *c = host, *end = c + (hostlen - 1);
162
163 *port = -1;
164
165 if (o == NULL || hostlen < 1)
166 goto failed;
167
168 if (*o == '[') {
169 for (++o; (*c = *o == ']' ? '\0' : *o); c++, o++)
170 if (c == end)
171 goto failed;
172
173 if (*o++ != ']' || (*o != '\0' && *o != ':'))
174 goto failed;
175 } else {
176 for (; (*c = *o == ':'? '\0' : *o); c++, o++) {
177 if (c == end && o[1])
178 goto failed;
179 }
180 }
181
182 if (*o == ':')
183 if (para_atoi32(++o, port) < 0 ||
184 *port < 0 || *port > 0xffff)
185 goto failed;
186 if (host_string_ok(host))
187 return host;
188 failed:
189 *host = '\0';
190 return NULL;
191 }
192
193 /**
194 * Stringify port number, resolve into service name where defined.
195 * \param port 2-byte port number, in host-byte-order.
196 * \param transport Transport protocol name (e.g. "udp", "tcp"), or NULL.
197 * \return Pointer to static result buffer.
198 *
199 * \sa getservent(3), services(5), nsswitch.conf(5)
200 */
201 const char *stringify_port(int port, const char *transport)
202 {
203 static char service[NI_MAXSERV];
204
205 if (port < 0 || port > 0xFFFF) {
206 snprintf(service, sizeof(service), "undefined (%d)", port);
207 } else {
208 struct servent *se = getservbyport(htons(port), transport);
209
210 if (se == NULL)
211 snprintf(service, sizeof(service), "%u", port);
212 else
213 snprintf(service, sizeof(service), "%s", se->s_name);
214 }
215 return service;
216 }
217
218 /**
219 * Determine the socket type for a given layer-4 protocol.
220 *
221 * \param l4type The symbolic name of the transport-layer protocol.
222 *
223 * \sa ip(7), socket(2)
224 */
225 static inline int sock_type(const unsigned l4type)
226 {
227 switch (l4type) {
228 case IPPROTO_UDP: return SOCK_DGRAM;
229 case IPPROTO_TCP: return SOCK_STREAM;
230 case IPPROTO_DCCP: return SOCK_DCCP;
231 }
232 return -1; /* not supported here */
233 }
234
235 /**
236 * Pretty-print transport-layer name.
237 */
238 static const char *layer4_name(const unsigned l4type)
239 {
240 switch (l4type) {
241 case IPPROTO_UDP: return "UDP";
242 case IPPROTO_TCP: return "TCP";
243 case IPPROTO_DCCP: return "DCCP";
244 }
245 return "UNKNOWN PROTOCOL";
246 }
247
248 /**
249 * Flowopts: Transport-layer independent encapsulation of socket options.
250 *
251 * These collect individual socket options into a queue, which is disposed of
252 * directly after makesock(). The 'pre_conn_opt' structure is for internal use
253 * only and should not be visible elsewhere.
254 *
255 * \sa setsockopt(2), makesock()
256 */
257 struct pre_conn_opt {
258 int sock_level; /**< Second argument to setsockopt() */
259 int sock_option; /**< Third argument to setsockopt() */
260 char *opt_name; /**< Stringified \a sock_option */
261 void *opt_val; /**< Fourth argument to setsockopt() */
262 socklen_t opt_len; /**< Fifth argument to setsockopt() */
263
264 struct list_head node; /**< FIFO, as sockopt order matters. */
265 };
266
267 /** FIFO list of pre-connection socket options to be set */
268 struct flowopts {
269 struct list_head sockopts;
270 };
271
272 /**
273 * Allocate and initialize a flowopt queue.
274 *
275 * \return A new structure to be passed to \ref flowopt_add(). It is
276 * automatically deallocated in \ref makesock().
277 */
278 struct flowopts *flowopt_new(void)
279 {
280 struct flowopts *new = para_malloc(sizeof(*new));
281
282 INIT_LIST_HEAD(&new->sockopts);
283 return new;
284 }
285
286 /**
287 * Append new socket option to flowopt queue.
288 *
289 * \param fo The flowopt queue to append to.
290 * \param lev Level at which \a opt resides.
291 * \param opt New option to add.
292 * \param name Stringified name of \a opt.
293 * \param val The value to set \a opt to.
294 * \param len Length of \a val.
295 *
296 * \sa setsockopt(2)
297 */
298 void flowopt_add(struct flowopts *fo, int lev, int opt,
299 const char *name, const void *val, int len)
300 {
301 struct pre_conn_opt *new = para_malloc(sizeof(*new));
302
303 new->sock_option = opt;
304 new->sock_level = lev;
305 new->opt_name = para_strdup(name);
306
307 if (val == NULL) {
308 new->opt_val = NULL;
309 new->opt_len = 0;
310 } else {
311 new->opt_val = para_malloc(len);
312 new->opt_len = len;
313 memcpy(new->opt_val, val, len);
314 }
315
316 list_add_tail(&new->node, &fo->sockopts);
317 }
318
319 /** Set the entire bunch of pre-connection options at once. */
320 static void flowopt_setopts(int sockfd, struct flowopts *fo)
321 {
322 struct pre_conn_opt *pc;
323
324 if (fo == NULL)
325 return;
326
327 list_for_each_entry(pc, &fo->sockopts, node)
328 if (setsockopt(sockfd, pc->sock_level, pc->sock_option,
329 pc->opt_val, pc->opt_len) < 0) {
330 PARA_EMERG_LOG("Can not set %s socket option: %s",
331 pc->opt_name, strerror(errno));
332 exit(EXIT_FAILURE);
333 }
334 }
335
336 static void flowopt_cleanup(struct flowopts *fo)
337 {
338 struct pre_conn_opt *cur, *next;
339
340 if (fo == NULL)
341 return;
342
343 list_for_each_entry_safe(cur, next, &fo->sockopts, node) {
344 free(cur->opt_name);
345 free(cur->opt_val);
346 free(cur);
347 }
348 free(fo);
349 }
350
351 /*
352 * Resolve an IPv4/IPv6 address.
353 *
354 * \param l4type The layer-4 type (\p IPPROTO_xxx).
355 * \param passive Whether \p AI_PASSIVE should be included as hint.
356 * \param host Remote or local hostname or IPv/6 address string.
357 * \param port_number Used to set the port in each returned address structure.
358 * \param result addrinfo structures are returned here.
359 *
360 * The interpretation of \a host depends on the value of \a passive. On a
361 * passive socket host is interpreted as an interface IPv4/6 address (can be
362 * left NULL). On an active socket, \a host is the peer DNS name or IPv4/6
363 * address to connect to.
364 *
365 * \return Standard.
366 *
367 * \sa getaddrinfo(3).
368 */
369 static int lookup_address(unsigned l4type, bool passive, const char *host,
370 int port_number, struct addrinfo **result)
371 {
372 int ret;
373 char port[6]; /* port number has at most 5 digits */
374 struct addrinfo *addr = NULL, hints;
375
376 *result = NULL;
377 sprintf(port, "%u", port_number & 0xffff);
378 /* Set up address hint structure */
379 memset(&hints, 0, sizeof(hints));
380 hints.ai_family = AF_UNSPEC;
381 hints.ai_socktype = sock_type(l4type);
382 /*
383 * getaddrinfo does not support SOCK_DCCP, so for the sake of lookup
384 * (and only then) pretend to be UDP.
385 */
386 if (l4type == IPPROTO_DCCP)
387 hints.ai_socktype = SOCK_DGRAM;
388 /* only use addresses available on the host */
389 hints.ai_flags = AI_ADDRCONFIG;
390 if (passive && host == NULL)
391 hints.ai_flags |= AI_PASSIVE;
392 /* Obtain local/remote address information */
393 ret = getaddrinfo(host, port, &hints, &addr);
394 if (ret != 0) {
395 PARA_ERROR_LOG("can not resolve %s address %s#%s: %s\n",
396 layer4_name(l4type),
397 host? host : (passive? "[loopback]" : "[localhost]"),
398 port, gai_strerror(ret));
399 return -E_ADDRESS_LOOKUP;
400 }
401 *result = addr;
402 return 1;
403 }
404
405 /*
406 * Create an active or passive socket.
407 *
408 * \param l4type \p IPPROTO_TCP, \p IPPROTO_UDP, or \p IPPROTO_DCCP.
409 * \param passive Whether to call bind(2) or connect(2).
410 * \param ai Address information as obtained from \ref lookup_address().
411 * \param fo Socket options to be set before making the connection.
412 *
413 * bind(2) is called on passive sockets, and connect(2) on active sockets. The
414 * algorithm tries all possible address combinations until it succeeds. If \a
415 * fo is supplied, options are set and cleanup is performed.
416 *
417 * \return File descriptor on success, \p E_MAKESOCK on errors.
418 *
419 * \sa \ref lookup_address(), \ref makesock(), ip(7), ipv6(7), bind(2),
420 * connect(2).
421 */
422 static int makesock_addrinfo(unsigned l4type, bool passive, struct addrinfo *ai,
423 struct flowopts *fo)
424 {
425 int ret = -E_MAKESOCK, on = 1, sockfd = -1;
426
427 for (; ai; ai = ai->ai_next) {
428 ret = socket(ai->ai_family, sock_type(l4type), l4type);
429 if (ret < 0)
430 continue;
431 sockfd = ret;
432 flowopt_setopts(sockfd, fo);
433 if (!passive) {
434 if (connect(sockfd, ai->ai_addr, ai->ai_addrlen) == 0)
435 return sockfd;
436 close(sockfd);
437 continue;
438 }
439 /*
440 * Reuse the address on passive sockets to avoid failure on
441 * restart (protocols using listen()) and when creating
442 * multiple listener instances (UDP multicast).
443 */
444 if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on,
445 sizeof(on)) == -1) {
446 ret = -ERRNO_TO_PARA_ERROR(errno);
447 close(sockfd);
448 PARA_ERROR_LOG("can not set SO_REUSEADDR: %s\n",
449 para_strerror(-ret));
450 return ret;
451 }
452 if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
453 close(sockfd);
454 continue;
455 }
456 return sockfd;
457 }
458 return -E_MAKESOCK;
459 }
460
461 /**
462 * Resolve IPv4/IPv6 address and create a ready-to-use active or passive socket.
463 *
464 * \param l4type The layer-4 type (\p IPPROTO_xxx).
465 * \param passive Whether this is a passive or active socket.
466 * \param host Passed to \ref lookup_address().
467 * \param port_number Passed to \ref lookup_address().
468 * \param fo Passed to \ref makesock_addrinfo().
469 *
470 * This creates a ready-made IPv4/v6 socket structure after looking up the
471 * necessary parameters. The function first calls \ref lookup_address() and
472 * passes the address information to makesock_addrinfo() to create and
473 * initialize the socket.
474 *
475 * \return The newly created file descriptor on success, a negative error code
476 * on failure.
477 *
478 * \sa \ref lookup_address(), \ref makesock_addrinfo().
479 */
480 int makesock(unsigned l4type, bool passive, const char *host, uint16_t port_number,
481 struct flowopts *fo)
482 {
483 struct addrinfo *ai;
484 int ret = lookup_address(l4type, passive, host, port_number, &ai);
485
486 if (ret >= 0)
487 ret = makesock_addrinfo(l4type, passive, ai, fo);
488 if (ai)
489 freeaddrinfo(ai);
490 flowopt_cleanup(fo);
491 if (ret < 0) {
492 PARA_ERROR_LOG("can not create %s socket %s#%d.\n",
493 layer4_name(l4type), host? host : (passive?
494 "[loopback]" : "[localhost]"), port_number);
495 }
496 return ret;
497 }
498
499 /**
500 * Create a passive / listening socket.
501 *
502 * \param l4type The transport-layer type (\p IPPROTO_xxx).
503 * \param port The decimal port number to listen on.
504 * \param fo Flowopts (if any) to set before starting to listen.
505 *
506 * \return Positive integer (socket descriptor) on success, negative value
507 * otherwise.
508 *
509 * \sa makesock(), ip(7), ipv6(7), bind(2), listen(2).
510 */
511 int para_listen(unsigned l4type, uint16_t port, struct flowopts *fo)
512 {
513 int ret, fd = makesock(l4type, 1, NULL, port, fo);
514
515 if (fd > 0) {
516 ret = listen(fd, BACKLOG);
517 if (ret < 0) {
518 ret = errno;
519 close(fd);
520 return -ERRNO_TO_PARA_ERROR(ret);
521 }
522 PARA_INFO_LOG("listening on %s port %u, fd %d\n",
523 layer4_name(l4type), port, fd);
524 }
525 return fd;
526 }
527
528 /**
529 * Determine IPv4/v6 socket address length.
530 * \param sa Container of IPv4 or IPv6 address.
531 * \return Address-family dependent address length.
532 */
533 static socklen_t salen(const struct sockaddr *sa)
534 {
535 assert(sa->sa_family == AF_INET || sa->sa_family == AF_INET6);
536
537 return sa->sa_family == AF_INET6
538 ? sizeof(struct sockaddr_in6)
539 : sizeof(struct sockaddr_in);
540 }
541
542 /** True if @ss holds a v6-mapped-v4 address (RFC 4291, 2.5.5.2) */
543 static bool SS_IS_ADDR_V4MAPPED(const struct sockaddr_storage *ss)
544 {
545 const struct sockaddr_in6 *ia6 = (const struct sockaddr_in6 *)ss;
546
547 return ss->ss_family == AF_INET6 && IN6_IS_ADDR_V4MAPPED(&ia6->sin6_addr);
548 }
549
550 /**
551 * Process IPv4/v6 address, turn v6-mapped-v4 address into normal IPv4 address.
552 * \param ss Container of IPv4/6 address.
553 * \return Pointer to normalized address (may be static storage).
554 *
555 * \sa RFC 3493
556 */
557 static const struct sockaddr *
558 normalize_ip_address(const struct sockaddr_storage *ss)
559 {
560 assert(ss->ss_family == AF_INET || ss->ss_family == AF_INET6);
561
562 if (SS_IS_ADDR_V4MAPPED(ss)) {
563 const struct sockaddr_in6 *ia6 = (const struct sockaddr_in6 *)ss;
564 static struct sockaddr_in ia;
565
566 ia.sin_family = AF_INET;
567 ia.sin_port = ia6->sin6_port;
568 memcpy(&ia.sin_addr.s_addr, &(ia6->sin6_addr.s6_addr[12]), 4);
569 return (const struct sockaddr *)&ia;
570 }
571 return (const struct sockaddr *)ss;
572 }
573
574 /**
575 * Generic/fallback MTU values
576 *
577 * These are taken from RFC 1122, RFC 2460, and RFC 5405.
578 * - RFC 1122, 3.3.3 defines EMTU_S ("Effective MTU for sending") and recommends
579 * to use an EMTU_S size of of 576 bytes if the IPv4 path MTU is unknown;
580 * - RFC 2460, 5. requires a minimum IPv6 MTU of 1280 bytes;
581 * - RFC 5405, 3.2 recommends that if path MTU discovery is not done,
582 * UDP senders should use the respective minimum values of EMTU_S.
583 */
584 static inline int generic_mtu(const int af_type)
585 {
586 return af_type == AF_INET6 ? 1280 : 576;
587 }
588
589 /** Crude approximation of IP header overhead - neglecting options. */
590 static inline int estimated_header_overhead(const int af_type)
591 {
592 return af_type == AF_INET6 ? 40 : 20;
593 }
594
595 /**
596 * Get the maximum transport-layer message size (MMS_S).
597 *
598 * \param sockfd The socket file descriptor.
599 *
600 * The socket must be connected. See RFC 1122, 3.3.3. If the protocol familiy
601 * could not be determined, \p AF_INET is assumed.
602 *
603 * \return The maximum message size of the address family type.
604 */
605 int generic_max_transport_msg_size(int sockfd)
606 {
607 struct sockaddr_storage ss;
608 socklen_t sslen = sizeof(ss);
609 int af_type = AF_INET;
610
611 if (getpeername(sockfd, (struct sockaddr *)&ss, &sslen) < 0) {
612 PARA_ERROR_LOG("can not determine remote address type: %s\n",
613 strerror(errno));
614 } else if (!SS_IS_ADDR_V4MAPPED(&ss)) {
615 af_type = ss.ss_family;
616 }
617 return generic_mtu(af_type) - estimated_header_overhead(af_type);
618 }
619
620 /**
621 * Look up the local or remote side of a connected socket structure.
622 *
623 * \param fd The socket descriptor of the connected socket.
624 * \param getname Either \p getsockname() for local, or \p getpeername() for
625 * remote side.
626 *
627 * \return A static character string identifying hostname and port of the
628 * chosen side in numeric host:port format.
629 *
630 * \sa getsockname(2), getpeername(2), parse_url(), getnameinfo(3),
631 * services(5), nsswitch.conf(5).
632 */
633 static char *__get_sock_name(int fd, typeof(getsockname) getname)
634 {
635 struct sockaddr_storage ss;
636 const struct sockaddr *sa;
637 socklen_t sslen = sizeof(ss);
638 char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];
639 static char output[sizeof(hbuf) + sizeof(sbuf) + 4];
640 int ret;
641
642 if (getname(fd, (struct sockaddr *)&ss, &sslen) < 0) {
643 PARA_ERROR_LOG("can not determine address from fd %d: %s\n",
644 fd, strerror(errno));
645 snprintf(output, sizeof(output), "(unknown)");
646 return output;
647 }
648 sa = normalize_ip_address(&ss);
649 ret = getnameinfo(sa, salen(sa), hbuf, sizeof(hbuf), sbuf,
650 sizeof(sbuf), NI_NUMERICHOST | NI_NUMERICSERV);
651 if (ret) {
652 PARA_WARNING_LOG("hostname lookup error (%s).\n",
653 gai_strerror(ret));
654 snprintf(output, sizeof(output), "(lookup error)");
655 } else if (sa->sa_family == AF_INET6)
656 snprintf(output, sizeof(output), "[%s]:%s", hbuf, sbuf);
657 else
658 snprintf(output, sizeof(output), "%s:%s", hbuf, sbuf);
659 return output;
660 }
661
662 /**
663 * Look up the local side of a connected socket structure.
664 *
665 * \param sockfd The file descriptor of the socket.
666 *
667 * \return A pointer to a static buffer containing hostname an port. This
668 * buffer must not be freed by the caller.
669 *
670 * \sa remote_name().
671 */
672 char *local_name(int sockfd)
673 {
674 return __get_sock_name(sockfd, getsockname);
675 }
676
677 /**
678 * Look up the remote side of a connected socket structure.
679 *
680 * \param sockfd The file descriptor of the socket.
681 *
682 * \return Analogous to the return value of \ref local_name() but for the
683 * remote side.
684 *
685 * \sa local_name().
686 */
687 char *remote_name(int sockfd)
688 {
689 return __get_sock_name(sockfd, getpeername);
690 }
691
692 /**
693 * Extract IPv4 or IPv6-mapped-IPv4 address from sockaddr_storage.
694 *
695 * \param ss Container of IPv4/6 address.
696 * \param ia Extracted IPv4 address (different from 0) or 0 if unsuccessful.
697 *
698 * \sa RFC 3493.
699 */
700 void extract_v4_addr(const struct sockaddr_storage *ss, struct in_addr *ia)
701 {
702 const struct sockaddr *sa = normalize_ip_address(ss);
703
704 memset(ia, 0, sizeof(*ia));
705 if (sa->sa_family == AF_INET)
706 *ia = ((struct sockaddr_in *)sa)->sin_addr;
707 }
708
709 /**
710 * Receive data from a file descriptor.
711 *
712 * \param fd The file descriptor.
713 * \param buf The buffer to write the data to.
714 * \param size The size of \a buf.
715 *
716 * Receive at most \a size bytes from file descriptor \a fd.
717 *
718 * \return The number of bytes received on success, negative on errors, zero if
719 * the peer has performed an orderly shutdown.
720 *
721 * \sa recv(2).
722 */
723 __must_check int recv_bin_buffer(int fd, char *buf, size_t size)
724 {
725 ssize_t n;
726
727 n = recv(fd, buf, size, 0);
728 if (n == -1)
729 return -ERRNO_TO_PARA_ERROR(errno);
730 return n;
731 }
732
733 /**
734 * Receive and write terminating NULL byte.
735 *
736 * \param fd The file descriptor.
737 * \param buf The buffer to write the data to.
738 * \param size The size of \a buf.
739 *
740 * Read at most \a size - 1 bytes from file descriptor \a fd and
741 * write a NULL byte at the end of the received data.
742 *
743 * \return The return value of the underlying call to \a recv_bin_buffer().
744 *
745 * \sa recv_bin_buffer()
746 */
747 int recv_buffer(int fd, char *buf, size_t size)
748 {
749 int n;
750
751 assert(size);
752 n = recv_bin_buffer(fd, buf, size - 1);
753 if (n >= 0)
754 buf[n] = '\0';
755 else
756 *buf = '\0';
757 return n;
758 }
759
760 /**
761 * Wrapper around the accept system call.
762 *
763 * \param fd The listening socket.
764 * \param rfds An optional fd_set pointer.
765 * \param addr Structure which is filled in with the address of the peer socket.
766 * \param size Should contain the size of the structure pointed to by \a addr.
767 * \param new_fd Result pointer.
768 *
769 * Accept incoming connections on \a addr, retry if interrupted. If \a rfds is
770 * not \p NULL, return 0 if \a fd is not set in \a rfds without calling accept().
771 *
772 * \return Negative on errors, zero if no connections are present to be accepted,
773 * one otherwise.
774 *
775 * \sa accept(2).
776 */
777 int para_accept(int fd, fd_set *rfds, void *addr, socklen_t size, int *new_fd)
778 {
779 int ret;
780
781 if (rfds && !FD_ISSET(fd, rfds))
782 return 0;
783 do
784 ret = accept(fd, (struct sockaddr *) addr, &size);
785 while (ret < 0 && errno == EINTR);
786
787 if (ret >= 0) {
788 *new_fd = ret;
789 return 1;
790 }
791 if (errno == EAGAIN || errno == EWOULDBLOCK)
792 return 0;
793 return -ERRNO_TO_PARA_ERROR(errno);
794 }
795
796 /**
797 * Probe the list of DCCP CCIDs configured on this host.
798 * \param ccid_array Pointer to return statically allocated array in.
799 * \return Number of elements returned in \a ccid_array or error.
800 *
801 * NB: This feature is only available on Linux > 2.6.30; on older kernels
802 * ENOPROTOOPT ("Protocol not available") will be returned.
803 */
804 int dccp_available_ccids(uint8_t **ccid_array)
805 {
806 static uint8_t ccids[DCCP_MAX_HOST_CCIDS];
807 socklen_t nccids = sizeof(ccids);
808 int ret, fd;
809
810 ret = fd = makesock(IPPROTO_DCCP, 1, NULL, 0, NULL);
811 if (ret < 0)
812 return ret;
813
814 if (getsockopt(fd, SOL_DCCP, DCCP_SOCKOPT_AVAILABLE_CCIDS,
815 ccids, &nccids) < 0) {
816 ret = errno;
817 close(fd);
818 PARA_ERROR_LOG("No DCCP_SOCKOPT_AVAILABLE_CCIDS: %s\n",
819 strerror(ret));
820 return -ERRNO_TO_PARA_ERROR(ret);
821 }
822
823 close(fd);
824 *ccid_array = ccids;
825 return nccids;
826 }
827
828 /**
829 * Prepare a structure for \p AF_UNIX socket addresses.
830 *
831 * \param u Pointer to the struct to be prepared.
832 * \param name The socket pathname.
833 *
834 * This just copies \a name to the sun_path component of \a u.
835 *
836 * \return Positive on success, \p -E_NAME_TOO_LONG if \a name is longer
837 * than \p UNIX_PATH_MAX.
838 */
839 static int init_unix_addr(struct sockaddr_un *u, const char *name)
840 {
841 if (strlen(name) >= UNIX_PATH_MAX)
842 return -E_NAME_TOO_LONG;
843 memset(u->sun_path, 0, UNIX_PATH_MAX);
844 u->sun_family = PF_UNIX;
845 strcpy(u->sun_path, name);
846 return 1;
847 }
848
849 /**
850 * Prepare, create, and bind a socket for local communication.
851 *
852 * \param name The socket pathname.
853 * \param unix_addr Pointer to the \p AF_UNIX socket structure.
854 * \param mode The desired mode of the socket.
855 *
856 * This function creates a local socket for sequenced, reliable,
857 * two-way, connection-based byte streams.
858 *
859 * \return The file descriptor, on success, negative on errors.
860 *
861 * \sa socket(2)
862 * \sa bind(2)
863 * \sa chmod(2)
864 */
865 int create_local_socket(const char *name, struct sockaddr_un *unix_addr,
866 mode_t mode)
867 {
868 int fd, ret;
869
870 ret = init_unix_addr(unix_addr, name);
871 if (ret < 0)
872 return ret;
873 ret = socket(PF_UNIX, SOCK_STREAM, 0);
874 if (ret < 0)
875 return -ERRNO_TO_PARA_ERROR(errno);
876 fd = ret;
877 ret = bind(fd, (struct sockaddr *) unix_addr, UNIX_PATH_MAX);
878 if (ret < 0) {
879 ret = -ERRNO_TO_PARA_ERROR(errno);
880 goto err;
881 }
882 ret = -E_CHMOD;
883 if (chmod(name, mode) < 0)
884 goto err;
885 return fd;
886 err:
887 close(fd);
888 return ret;
889 }
890
891 /**
892 * Prepare, create, and connect to a Unix domain socket for local communication.
893 *
894 * \param name The socket pathname.
895 *
896 * This function creates a local socket for sequenced, reliable, two-way,
897 * connection-based byte streams.
898 *
899 * \return The file descriptor of the connected socket on success, negative on
900 * errors.
901 *
902 * \sa create_local_socket(), unix(7), connect(2).
903 */
904 int connect_local_socket(const char *name)
905 {
906 struct sockaddr_un unix_addr;
907 int fd, ret;
908
909 PARA_DEBUG_LOG("connecting to %s\n", name);
910 ret = init_unix_addr(&unix_addr, name);
911 if (ret < 0)
912 return ret;
913 fd = socket(PF_UNIX, SOCK_STREAM, 0);
914 if (fd < 0)
915 return -ERRNO_TO_PARA_ERROR(errno);
916 if (connect(fd, (struct sockaddr *)&unix_addr, sizeof(unix_addr)) == -1) {
917 ret = -ERRNO_TO_PARA_ERROR(errno);
918 goto err;
919 }
920 return fd;
921 err:
922 close(fd);
923 return ret;
924 }
925
926 #ifndef HAVE_UCRED
927 ssize_t send_cred_buffer(int sock, char *buf)
928 {
929 return write_buffer(sock, buf);
930 }
931 int recv_cred_buffer(int fd, char *buf, size_t size)
932 {
933 return recv_buffer(fd, buf, size) > 0? 1 : -E_RECVMSG;
934 }
935 #else /* HAVE_UCRED */
936 /**
937 * Send \p NULL-terminated buffer and Unix credentials of the current process.
938 *
939 * \param sock The socket file descriptor.
940 * \param buf The buffer to be sent.
941 *
942 * \return On success, this call returns the number of characters sent. On
943 * error, \p -E_SENDMSG is returned.
944 *
945 * \sa sendmsg(2), okir's Black Hats Manual.
946 */
947 ssize_t send_cred_buffer(int sock, char *buf)
948 {
949 char control[sizeof(struct cmsghdr) + sizeof(struct ucred)];
950 struct msghdr msg;
951 struct cmsghdr *cmsg;
952 static struct iovec iov;
953 struct ucred c;
954 int ret;
955
956 /* Response data */
957 iov.iov_base = buf;
958 iov.iov_len = strlen(buf);
959 c.pid = getpid();
960 c.uid = getuid();
961 c.gid = getgid();
962 /* compose the message */
963 memset(&msg, 0, sizeof(msg));
964 msg.msg_iov = &iov;
965 msg.msg_iovlen = 1;
966 msg.msg_control = control;
967 msg.msg_controllen = sizeof(control);
968 /* attach the ucred struct */
969 cmsg = CMSG_FIRSTHDR(&msg);
970 cmsg->cmsg_level = SOL_SOCKET;
971 cmsg->cmsg_type = SCM_CREDENTIALS;
972 cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
973 *(struct ucred *)CMSG_DATA(cmsg) = c;
974 msg.msg_controllen = cmsg->cmsg_len;
975 ret = sendmsg(sock, &msg, 0);
976 if (ret < 0)
977 ret = -E_SENDMSG;
978 return ret;
979 }
980
981 static void dispose_fds(int *fds, unsigned num)
982 {
983 int i;
984
985 for (i = 0; i < num; i++)
986 close(fds[i]);
987 }
988
989 /**
990 * Receive a buffer and the Unix credentials of the sending process.
991 *
992 * \param fd the socket file descriptor.
993 * \param buf the buffer to store the message.
994 * \param size the size of \a buffer.
995 *
996 * \return negative on errors, the user id on success.
997 *
998 * \sa recvmsg(2), okir's Black Hats Manual.
999 */
1000 int recv_cred_buffer(int fd, char *buf, size_t size)
1001 {
1002 char control[255];
1003 struct msghdr msg;
1004 struct cmsghdr *cmsg;
1005 struct iovec iov;
1006 int result = 0;
1007 int yes = 1;
1008 struct ucred cred;
1009
1010 setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &yes, sizeof(int));
1011 memset(&msg, 0, sizeof(msg));
1012 memset(buf, 0, size);
1013 iov.iov_base = buf;
1014 iov.iov_len = size;
1015 msg.msg_iov = &iov;
1016 msg.msg_iovlen = 1;
1017 msg.msg_control = control;
1018 msg.msg_controllen = sizeof(control);
1019 if (recvmsg(fd, &msg, 0) < 0)
1020 return -E_RECVMSG;
1021 result = -E_SCM_CREDENTIALS;
1022 cmsg = CMSG_FIRSTHDR(&msg);
1023 while (cmsg) {
1024 if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type
1025 == SCM_CREDENTIALS) {
1026 memcpy(&cred, CMSG_DATA(cmsg), sizeof(struct ucred));
1027 result = cred.uid;
1028 } else
1029 if (cmsg->cmsg_level == SOL_SOCKET
1030 && cmsg->cmsg_type == SCM_RIGHTS) {
1031 dispose_fds((int *) CMSG_DATA(cmsg),
1032 (cmsg->cmsg_len - CMSG_LEN(0))
1033 / sizeof(int));
1034 }
1035 cmsg = CMSG_NXTHDR(&msg, cmsg);
1036 }
1037 return result;
1038 }
1039 #endif /* HAVE_UCRED */