2 * Copyright (c) 2008, 2009, 2010, 2011, 2012 Nicira Networks.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
18 #include "socket-util.h"
19 #include <arpa/inet.h>
29 #include <sys/resource.h>
30 #include <sys/socket.h>
34 #include "dynamic-string.h"
35 #include "fatal-signal.h"
39 #if AF_PACKET && __linux__
40 #include <linux/if_packet.h>
43 #include "netlink-protocol.h"
44 #include "netlink-socket.h"
47 VLOG_DEFINE_THIS_MODULE(socket_util);
49 /* #ifdefs make it a pain to maintain code: you have to try to build both ways.
50 * Thus, this file compiles all of the code regardless of the target, by
51 * writing "if (LINUX)" instead of "#ifdef __linux__". */
62 static int getsockopt_int(int fd, int level, int option, const char *optname,
65 /* Sets 'fd' to non-blocking mode. Returns 0 if successful, otherwise a
66 * positive errno value. */
68 set_nonblocking(int fd)
70 int flags = fcntl(fd, F_GETFL, 0);
72 if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) != -1) {
75 VLOG_ERR("fcntl(F_SETFL) failed: %s", strerror(errno));
79 VLOG_ERR("fcntl(F_GETFL) failed: %s", strerror(errno));
85 rlim_is_finite(rlim_t limit)
87 if (limit == RLIM_INFINITY) {
91 #ifdef RLIM_SAVED_CUR /* FreeBSD 8.0 lacks RLIM_SAVED_CUR. */
92 if (limit == RLIM_SAVED_CUR) {
97 #ifdef RLIM_SAVED_MAX /* FreeBSD 8.0 lacks RLIM_SAVED_MAX. */
98 if (limit == RLIM_SAVED_MAX) {
106 /* Returns the maximum valid FD value, plus 1. */
110 static int max_fds = -1;
113 if (!getrlimit(RLIMIT_NOFILE, &r) && rlim_is_finite(r.rlim_cur)) {
114 max_fds = r.rlim_cur;
116 VLOG_WARN("failed to obtain fd limit, defaulting to 1024");
123 /* Translates 'host_name', which must be a string representation of an IP
124 * address, into a numeric IP address in '*addr'. Returns 0 if successful,
125 * otherwise a positive errno value. */
127 lookup_ip(const char *host_name, struct in_addr *addr)
129 if (!inet_aton(host_name, addr)) {
130 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
131 VLOG_ERR_RL(&rl, "\"%s\" is not a valid IP address", host_name);
137 /* Translates 'host_name', which must be a string representation of an IPv6
138 * address, into a numeric IPv6 address in '*addr'. Returns 0 if successful,
139 * otherwise a positive errno value. */
141 lookup_ipv6(const char *host_name, struct in6_addr *addr)
143 if (inet_pton(AF_INET6, host_name, addr) != 1) {
144 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
145 VLOG_ERR_RL(&rl, "\"%s\" is not a valid IPv6 address", host_name);
151 /* Translates 'host_name', which must be a host name or a string representation
152 * of an IP address, into a numeric IP address in '*addr'. Returns 0 if
153 * successful, otherwise a positive errno value.
155 * Most Open vSwitch code should not use this because it causes deadlocks:
156 * gethostbyname() sends out a DNS request but that starts a new flow for which
157 * OVS must set up a flow, but it can't because it's waiting for a DNS reply.
158 * The synchronous lookup also delays other activty. (Of course we can solve
159 * this but it doesn't seem worthwhile quite yet.) */
161 lookup_hostname(const char *host_name, struct in_addr *addr)
165 if (inet_aton(host_name, addr)) {
169 h = gethostbyname(host_name);
171 *addr = *(struct in_addr *) h->h_addr;
175 return (h_errno == HOST_NOT_FOUND ? ENOENT
176 : h_errno == TRY_AGAIN ? EAGAIN
177 : h_errno == NO_RECOVERY ? EIO
178 : h_errno == NO_ADDRESS ? ENXIO
182 /* Returns the error condition associated with socket 'fd' and resets the
183 * socket's error status. */
185 get_socket_error(int fd)
189 if (getsockopt_int(fd, SOL_SOCKET, SO_ERROR, "SO_ERROR", &error)) {
196 check_connection_completion(int fd)
202 pfd.events = POLLOUT;
204 retval = poll(&pfd, 1, 0);
205 } while (retval < 0 && errno == EINTR);
207 return get_socket_error(fd);
208 } else if (retval < 0) {
209 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 10);
210 VLOG_ERR_RL(&rl, "poll: %s", strerror(errno));
217 /* Drain all the data currently in the receive queue of a datagram socket (and
218 * possibly additional data). There is no way to know how many packets are in
219 * the receive queue, but we do know that the total number of bytes queued does
220 * not exceed the receive buffer size, so we pull packets until none are left
221 * or we've read that many bytes. */
227 rcvbuf = get_socket_rcvbuf(fd);
233 /* In Linux, specifying MSG_TRUNC in the flags argument causes the
234 * datagram length to be returned, even if that is longer than the
235 * buffer provided. Thus, we can use a 1-byte buffer to discard the
236 * incoming datagram and still be able to account how many bytes were
237 * removed from the receive buffer.
239 * On other Unix-like OSes, MSG_TRUNC has no effect in the flags
241 char buffer[LINUX ? 1 : 2048];
242 ssize_t n_bytes = recv(fd, buffer, sizeof buffer,
243 MSG_TRUNC | MSG_DONTWAIT);
244 if (n_bytes <= 0 || n_bytes >= rcvbuf) {
252 /* Returns the size of socket 'sock''s receive buffer (SO_RCVBUF), or a
253 * negative errno value if an error occurs. */
255 get_socket_rcvbuf(int sock)
260 error = getsockopt_int(sock, SOL_SOCKET, SO_RCVBUF, "SO_RCVBUF", &rcvbuf);
261 return error ? -error : rcvbuf;
264 /* Reads and discards up to 'n' datagrams from 'fd', stopping as soon as no
265 * more data can be immediately read. ('fd' should therefore be in
266 * non-blocking mode.)*/
268 drain_fd(int fd, size_t n_packets)
270 for (; n_packets > 0; n_packets--) {
271 /* 'buffer' only needs to be 1 byte long in most circumstances. This
272 * size is defensive against the possibility that we someday want to
273 * use a Linux tap device without TUN_NO_PI, in which case a buffer
274 * smaller than sizeof(struct tun_pi) will give EINVAL on read. */
276 if (read(fd, buffer, sizeof buffer) <= 0) {
282 /* Stores in '*un' a sockaddr_un that refers to file 'name'. Stores in
283 * '*un_len' the size of the sockaddr_un. */
285 make_sockaddr_un__(const char *name, struct sockaddr_un *un, socklen_t *un_len)
287 un->sun_family = AF_UNIX;
288 ovs_strzcpy(un->sun_path, name, sizeof un->sun_path);
289 *un_len = (offsetof(struct sockaddr_un, sun_path)
290 + strlen (un->sun_path) + 1);
293 /* Stores in '*un' a sockaddr_un that refers to file 'name'. Stores in
294 * '*un_len' the size of the sockaddr_un.
296 * Returns 0 on success, otherwise a positive errno value. On success,
297 * '*dirfdp' is either -1 or a nonnegative file descriptor that the caller
298 * should close after using '*un' to bind or connect. On failure, '*dirfdp' is
301 make_sockaddr_un(const char *name, struct sockaddr_un *un, socklen_t *un_len,
304 enum { MAX_UN_LEN = sizeof un->sun_path - 1 };
307 if (strlen(name) > MAX_UN_LEN) {
308 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 1);
311 /* 'name' is too long to fit in a sockaddr_un, but we have a
312 * workaround for that on Linux: shorten it by opening a file
313 * descriptor for the directory part of the name and indirecting
314 * through /proc/self/fd/<dirfd>/<basename>. */
319 dir = dir_name(name);
320 base = base_name(name);
322 dirfd = open(dir, O_DIRECTORY | O_RDONLY);
329 short_name = xasprintf("/proc/self/fd/%d/%s", dirfd, base);
333 if (strlen(short_name) <= MAX_UN_LEN) {
334 make_sockaddr_un__(short_name, un, un_len);
342 VLOG_WARN_RL(&rl, "Unix socket name %s is longer than maximum "
343 "%d bytes (even shortened)", name, MAX_UN_LEN);
345 /* 'name' is too long and we have no workaround. */
346 VLOG_WARN_RL(&rl, "Unix socket name %s is longer than maximum "
347 "%d bytes", name, MAX_UN_LEN);
352 make_sockaddr_un__(name, un, un_len);
357 /* Binds Unix domain socket 'fd' to a file with permissions 0700. */
359 bind_unix_socket(int fd, struct sockaddr *sun, socklen_t sun_len)
361 /* According to _Unix Network Programming_, umask should affect bind(). */
362 mode_t old_umask = umask(0077);
363 int error = bind(fd, sun, sun_len) ? errno : 0;
368 /* Creates a Unix domain socket in the given 'style' (either SOCK_DGRAM or
369 * SOCK_STREAM) that is bound to '*bind_path' (if 'bind_path' is non-null) and
370 * connected to '*connect_path' (if 'connect_path' is non-null). If 'nonblock'
371 * is true, the socket is made non-blocking. If 'passcred' is true, the socket
372 * is configured to receive SCM_CREDENTIALS control messages.
374 * Returns the socket's fd if successful, otherwise a negative errno value. */
376 make_unix_socket(int style, bool nonblock, bool passcred OVS_UNUSED,
377 const char *bind_path, const char *connect_path)
382 fd = socket(PF_UNIX, style, 0);
387 /* Set nonblocking mode right away, if we want it. This prevents blocking
388 * in connect(), if connect_path != NULL. (In turn, that's a corner case:
389 * it will only happen if style is SOCK_STREAM or SOCK_SEQPACKET, and only
390 * if a backlog of un-accepted connections has built up in the kernel.) */
392 int flags = fcntl(fd, F_GETFL, 0);
397 if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
404 struct sockaddr_un un;
408 if (unlink(bind_path) && errno != ENOENT) {
409 VLOG_WARN("unlinking \"%s\": %s\n", bind_path, strerror(errno));
411 fatal_signal_add_file_to_unlink(bind_path);
413 error = make_sockaddr_un(bind_path, &un, &un_len, &dirfd);
415 error = bind_unix_socket(fd, (struct sockaddr *) &un, un_len);
426 struct sockaddr_un un;
430 error = make_sockaddr_un(connect_path, &un, &un_len, &dirfd);
432 && connect(fd, (struct sockaddr*) &un, un_len)
433 && errno != EINPROGRESS) {
444 #ifdef SCM_CREDENTIALS
447 if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &enable, sizeof(enable))) {
457 if (error == EAGAIN) {
461 fatal_signal_unlink_file_now(bind_path);
468 get_unix_name_len(socklen_t sun_len)
470 return (sun_len >= offsetof(struct sockaddr_un, sun_path)
471 ? sun_len - offsetof(struct sockaddr_un, sun_path)
476 guess_netmask(ovs_be32 ip_)
478 uint32_t ip = ntohl(ip_);
479 return ((ip >> 31) == 0 ? htonl(0xff000000) /* Class A */
480 : (ip >> 30) == 2 ? htonl(0xffff0000) /* Class B */
481 : (ip >> 29) == 6 ? htonl(0xffffff00) /* Class C */
482 : htonl(0)); /* ??? */
485 /* Parses 'target', which should be a string in the format "<host>[:<port>]".
486 * <host> is required. If 'default_port' is nonzero then <port> is optional
487 * and defaults to 'default_port'.
489 * On success, returns true and stores the parsed remote address into '*sinp'.
490 * On failure, logs an error, stores zeros into '*sinp', and returns false. */
492 inet_parse_active(const char *target_, uint16_t default_port,
493 struct sockaddr_in *sinp)
495 char *target = xstrdup(target_);
496 char *save_ptr = NULL;
497 const char *host_name;
498 const char *port_string;
502 sinp->sin_family = AF_INET;
503 sinp->sin_port = htons(default_port);
506 host_name = strtok_r(target, ":", &save_ptr);
507 port_string = strtok_r(NULL, ":", &save_ptr);
509 VLOG_ERR("%s: bad peer name format", target_);
513 /* Look up IP, port. */
514 if (lookup_ip(host_name, &sinp->sin_addr)) {
517 if (port_string && atoi(port_string)) {
518 sinp->sin_port = htons(atoi(port_string));
519 } else if (!default_port) {
520 VLOG_ERR("%s: port number must be specified", target_);
528 memset(sinp, 0, sizeof *sinp);
534 /* Opens a non-blocking IPv4 socket of the specified 'style' and connects to
535 * 'target', which should be a string in the format "<host>[:<port>]". <host>
536 * is required. If 'default_port' is nonzero then <port> is optional and
537 * defaults to 'default_port'.
539 * 'style' should be SOCK_STREAM (for TCP) or SOCK_DGRAM (for UDP).
541 * On success, returns 0 (indicating connection complete) or EAGAIN (indicating
542 * connection in progress), in which case the new file descriptor is stored
543 * into '*fdp'. On failure, returns a positive errno value other than EAGAIN
544 * and stores -1 into '*fdp'.
546 * If 'sinp' is non-null, then on success the target address is stored into
549 * 'dscp' If not DSCP_INVALID, its value becomes the DSCP bits in the IP
550 * headers for the new connection. */
552 inet_open_active(int style, const char *target, uint16_t default_port,
553 struct sockaddr_in *sinp, int *fdp, uint8_t dscp)
555 struct sockaddr_in sin;
560 if (!inet_parse_active(target, default_port, &sin)) {
561 error = EAFNOSUPPORT;
565 /* Create non-blocking socket. */
566 fd = socket(AF_INET, style, 0);
568 VLOG_ERR("%s: socket: %s", target, strerror(errno));
572 error = set_nonblocking(fd);
577 /* The socket options set here ensure that the TOS bits are set during
578 * the connection establishment. If set after connect(), the handshake
579 * SYN frames will be sent with a TOS of 0. */
580 if (dscp != DSCP_INVALID) {
581 if (setsockopt(fd, IPPROTO_IP, IP_TOS, &dscp, sizeof dscp)) {
582 VLOG_ERR("%s: socket: %s", target, strerror(errno));
589 error = connect(fd, (struct sockaddr *) &sin, sizeof sin) == 0 ? 0 : errno;
590 if (error == EINPROGRESS) {
595 if (!error || error == EAGAIN) {
599 } else if (fd >= 0) {
606 /* Parses 'target', which should be a string in the format "[<port>][:<ip>]":
608 * - If 'default_port' is -1, then <port> is required. Otherwise, if
609 * <port> is omitted, then 'default_port' is used instead.
611 * - If <port> (or 'default_port', if used) is 0, then no port is bound
612 * and the TCP/IP stack will select a port.
614 * - If <ip> is omitted then the IP address is wildcarded.
616 * If successful, stores the address into '*sinp' and returns true; otherwise
617 * zeros '*sinp' and returns false. */
619 inet_parse_passive(const char *target_, int default_port,
620 struct sockaddr_in *sinp)
622 char *target = xstrdup(target_);
623 char *string_ptr = target;
624 const char *host_name;
625 const char *port_string;
629 /* Address defaults. */
630 memset(sinp, 0, sizeof *sinp);
631 sinp->sin_family = AF_INET;
632 sinp->sin_addr.s_addr = htonl(INADDR_ANY);
633 sinp->sin_port = htons(default_port);
635 /* Parse optional port number. */
636 port_string = strsep(&string_ptr, ":");
637 if (port_string && str_to_int(port_string, 10, &port)) {
638 sinp->sin_port = htons(port);
639 } else if (default_port < 0) {
640 VLOG_ERR("%s: port number must be specified", target_);
644 /* Parse optional bind IP. */
645 host_name = strsep(&string_ptr, ":");
646 if (host_name && host_name[0] && lookup_ip(host_name, &sinp->sin_addr)) {
654 memset(sinp, 0, sizeof *sinp);
661 /* Opens a non-blocking IPv4 socket of the specified 'style', binds to
662 * 'target', and listens for incoming connections. Parses 'target' in the same
663 * way was inet_parse_passive().
665 * 'style' should be SOCK_STREAM (for TCP) or SOCK_DGRAM (for UDP).
667 * For TCP, the socket will have SO_REUSEADDR turned on.
669 * On success, returns a non-negative file descriptor. On failure, returns a
670 * negative errno value.
672 * If 'sinp' is non-null, then on success the bound address is stored into
675 * 'dscp' If not DSCP_INVALID, its value becomes the DSCP bits in the IP
676 * headers for the new connection. */
678 inet_open_passive(int style, const char *target, int default_port,
679 struct sockaddr_in *sinp, uint8_t dscp)
681 struct sockaddr_in sin;
683 unsigned int yes = 1;
685 if (!inet_parse_passive(target, default_port, &sin)) {
686 return -EAFNOSUPPORT;
689 /* Create non-blocking socket, set SO_REUSEADDR. */
690 fd = socket(AF_INET, style, 0);
693 VLOG_ERR("%s: socket: %s", target, strerror(error));
696 error = set_nonblocking(fd);
700 if (style == SOCK_STREAM
701 && setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof yes) < 0) {
703 VLOG_ERR("%s: setsockopt(SO_REUSEADDR): %s", target, strerror(error));
708 if (bind(fd, (struct sockaddr *) &sin, sizeof sin) < 0) {
710 VLOG_ERR("%s: bind: %s", target, strerror(error));
714 /* The socket options set here ensure that the TOS bits are set during
715 * the connection establishment. If set after connect(), the handshake
716 * SYN frames will be sent with a TOS of 0. */
717 if (dscp != DSCP_INVALID) {
718 if (setsockopt(fd, IPPROTO_IP, IP_TOS, &dscp, sizeof dscp)) {
719 VLOG_ERR("%s: socket: %s", target, strerror(errno));
726 if (style == SOCK_STREAM && listen(fd, 10) < 0) {
728 VLOG_ERR("%s: listen: %s", target, strerror(error));
733 socklen_t sin_len = sizeof sin;
734 if (getsockname(fd, (struct sockaddr *) &sin, &sin_len) < 0){
736 VLOG_ERR("%s: getsockname: %s", target, strerror(error));
739 if (sin.sin_family != AF_INET || sin_len != sizeof sin) {
740 error = EAFNOSUPPORT;
741 VLOG_ERR("%s: getsockname: invalid socket name", target);
754 /* Returns a readable and writable fd for /dev/null, if successful, otherwise
755 * a negative errno value. The caller must not close the returned fd (because
756 * the same fd will be handed out to subsequent callers). */
760 static int null_fd = -1;
762 null_fd = open("/dev/null", O_RDWR);
765 VLOG_ERR("could not open /dev/null: %s", strerror(error));
773 read_fully(int fd, void *p_, size_t size, size_t *bytes_read)
779 ssize_t retval = read(fd, p, size);
781 *bytes_read += retval;
784 } else if (retval == 0) {
786 } else if (errno != EINTR) {
794 write_fully(int fd, const void *p_, size_t size, size_t *bytes_written)
796 const uint8_t *p = p_;
800 ssize_t retval = write(fd, p, size);
802 *bytes_written += retval;
805 } else if (retval == 0) {
806 VLOG_WARN("write returned 0");
808 } else if (errno != EINTR) {
815 /* Given file name 'file_name', fsyncs the directory in which it is contained.
816 * Returns 0 if successful, otherwise a positive errno value. */
818 fsync_parent_dir(const char *file_name)
824 dir = dir_name(file_name);
825 fd = open(dir, O_RDONLY);
828 if (errno == EINVAL || errno == EROFS) {
829 /* This directory does not support synchronization. Not
830 * really an error. */
833 VLOG_ERR("%s: fsync failed (%s)", dir, strerror(error));
839 VLOG_ERR("%s: open failed (%s)", dir, strerror(error));
846 /* Obtains the modification time of the file named 'file_name' to the greatest
847 * supported precision. If successful, stores the mtime in '*mtime' and
848 * returns 0. On error, returns a positive errno value and stores zeros in
851 get_mtime(const char *file_name, struct timespec *mtime)
855 if (!stat(file_name, &s)) {
856 mtime->tv_sec = s.st_mtime;
858 #if HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC
859 mtime->tv_nsec = s.st_mtim.tv_nsec;
860 #elif HAVE_STRUCT_STAT_ST_MTIMENSEC
861 mtime->tv_nsec = s.st_mtimensec;
868 mtime->tv_sec = mtime->tv_nsec = 0;
877 VLOG_FATAL("failed to create pipe (%s)", strerror(errno));
882 getsockopt_int(int fd, int level, int option, const char *optname, int *valuep)
884 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 10);
890 if (getsockopt(fd, level, option, &value, &len)) {
892 VLOG_ERR_RL(&rl, "getsockopt(%s): %s", optname, strerror(error));
893 } else if (len != sizeof value) {
895 VLOG_ERR_RL(&rl, "getsockopt(%s): value is %u bytes (expected %zu)",
896 optname, (unsigned int) len, sizeof value);
901 *valuep = error ? 0 : value;
906 describe_sockaddr(struct ds *string, int fd,
907 int (*getaddr)(int, struct sockaddr *, socklen_t *))
909 struct sockaddr_storage ss;
910 socklen_t len = sizeof ss;
912 if (!getaddr(fd, (struct sockaddr *) &ss, &len)) {
913 if (ss.ss_family == AF_INET) {
914 struct sockaddr_in sin;
916 memcpy(&sin, &ss, sizeof sin);
917 ds_put_format(string, IP_FMT":%"PRIu16,
918 IP_ARGS(&sin.sin_addr.s_addr), ntohs(sin.sin_port));
919 } else if (ss.ss_family == AF_UNIX) {
920 struct sockaddr_un sun;
924 memcpy(&sun, &ss, sizeof sun);
925 maxlen = len - offsetof(struct sockaddr_un, sun_path);
926 null = memchr(sun.sun_path, '\0', maxlen);
927 ds_put_buffer(string, sun.sun_path,
928 null ? null - sun.sun_path : maxlen);
931 else if (ss.ss_family == AF_NETLINK) {
934 /* SO_PROTOCOL was introduced in 2.6.32. Support it regardless of the version
935 * of the Linux kernel headers in use at build time. */
937 #define SO_PROTOCOL 38
940 if (!getsockopt_int(fd, SOL_SOCKET, SO_PROTOCOL, "SO_PROTOCOL",
944 ds_put_cstr(string, "NETLINK_ROUTE");
947 case NETLINK_GENERIC:
948 ds_put_cstr(string, "NETLINK_GENERIC");
952 ds_put_format(string, "AF_NETLINK family %d", protocol);
956 ds_put_cstr(string, "AF_NETLINK");
960 #if AF_PACKET && __linux__
961 else if (ss.ss_family == AF_PACKET) {
962 struct sockaddr_ll sll;
964 memcpy(&sll, &ss, sizeof sll);
965 ds_put_cstr(string, "AF_PACKET");
966 if (sll.sll_ifindex) {
969 if (if_indextoname(sll.sll_ifindex, name)) {
970 ds_put_format(string, "(%s)", name);
972 ds_put_format(string, "(ifindex=%d)", sll.sll_ifindex);
975 if (sll.sll_protocol) {
976 ds_put_format(string, "(protocol=0x%"PRIu16")",
977 ntohs(sll.sll_protocol));
981 else if (ss.ss_family == AF_UNSPEC) {
982 ds_put_cstr(string, "AF_UNSPEC");
984 ds_put_format(string, "AF_%d", (int) ss.ss_family);
992 put_fd_filename(struct ds *string, int fd)
998 linkname = xasprintf("/proc/self/fd/%d", fd);
999 n = readlink(linkname, buf, sizeof buf);
1001 ds_put_char(string, ' ');
1002 ds_put_buffer(string, buf, n);
1003 if (n > sizeof buf) {
1004 ds_put_cstr(string, "...");
1011 /* Returns a malloc()'d string describing 'fd', for use in logging. */
1019 if (fstat(fd, &s)) {
1020 ds_put_format(&string, "fstat failed (%s)", strerror(errno));
1021 } else if (S_ISSOCK(s.st_mode)) {
1022 describe_sockaddr(&string, fd, getsockname);
1023 ds_put_cstr(&string, "<->");
1024 describe_sockaddr(&string, fd, getpeername);
1026 ds_put_cstr(&string, (isatty(fd) ? "tty"
1027 : S_ISDIR(s.st_mode) ? "directory"
1028 : S_ISCHR(s.st_mode) ? "character device"
1029 : S_ISBLK(s.st_mode) ? "block device"
1030 : S_ISREG(s.st_mode) ? "file"
1031 : S_ISFIFO(s.st_mode) ? "FIFO"
1032 : S_ISLNK(s.st_mode) ? "symbolic link"
1035 put_fd_filename(&string, fd);
1038 return ds_steal_cstr(&string);