2 This file is part of systemd.
4 Copyright 2010 Lennart Poettering
6 systemd is free software; you can redistribute it and/or modify it
7 under the terms of the GNU Lesser General Public License as published by
8 the Free Software Foundation; either version 2.1 of the License, or
9 (at your option) any later version.
11 systemd is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public License
17 along with systemd; If not, see <http://www.gnu.org/licenses/>.
20 #include <arpa/inet.h>
25 #include <netinet/ip.h>
33 #include "alloc-util.h"
36 #include "format-util.h"
40 #include "parse-util.h"
41 #include "path-util.h"
42 #include "socket-util.h"
43 #include "string-table.h"
44 #include "string-util.h"
46 #include "user-util.h"
50 #if 0 /// UNNEEDED by elogind
52 # define IDN_FLAGS (NI_IDN|NI_IDN_USE_STD3_ASCII_RULES)
57 int socket_address_parse(SocketAddress *a, const char *s) {
66 a->type = SOCK_STREAM;
69 /* IPv6 in [x:.....:z]:p notation */
75 n = strndupa(s+1, e-s-1);
78 if (inet_pton(AF_INET6, n, &a->sockaddr.in6.sin6_addr) <= 0)
79 return errno > 0 ? -errno : -EINVAL;
90 if (u <= 0 || u > 0xFFFF)
93 a->sockaddr.in6.sin6_family = AF_INET6;
94 a->sockaddr.in6.sin6_port = htobe16((uint16_t)u);
95 a->size = sizeof(struct sockaddr_in6);
97 } else if (*s == '/') {
103 if (l >= sizeof(a->sockaddr.un.sun_path))
106 a->sockaddr.un.sun_family = AF_UNIX;
107 memcpy(a->sockaddr.un.sun_path, s, l);
108 a->size = offsetof(struct sockaddr_un, sun_path) + l + 1;
110 } else if (*s == '@') {
111 /* Abstract AF_UNIX socket */
115 if (l >= sizeof(a->sockaddr.un.sun_path) - 1)
118 a->sockaddr.un.sun_family = AF_UNIX;
119 memcpy(a->sockaddr.un.sun_path+1, s+1, l);
120 a->size = offsetof(struct sockaddr_un, sun_path) + 1 + l;
122 } else if (startswith(s, "vsock:")) {
123 /* AF_VSOCK socket in vsock:cid:port notation */
124 const char *cid_start = s + strlen("vsock:");
126 e = strchr(cid_start, ':');
130 r = safe_atou(e+1, &u);
134 n = strndupa(cid_start, e - cid_start);
136 r = safe_atou(n, &a->sockaddr.vm.svm_cid);
140 a->sockaddr.vm.svm_cid = VMADDR_CID_ANY;
142 a->sockaddr.vm.svm_family = AF_VSOCK;
143 a->sockaddr.vm.svm_port = u;
144 a->size = sizeof(struct sockaddr_vm);
149 r = safe_atou(e+1, &u);
153 if (u <= 0 || u > 0xFFFF)
156 n = strndupa(s, e-s);
158 /* IPv4 in w.x.y.z:p notation? */
159 r = inet_pton(AF_INET, n, &a->sockaddr.in.sin_addr);
164 /* Gotcha, it's a traditional IPv4 address */
165 a->sockaddr.in.sin_family = AF_INET;
166 a->sockaddr.in.sin_port = htobe16((uint16_t)u);
167 a->size = sizeof(struct sockaddr_in);
171 if (strlen(n) > IF_NAMESIZE-1)
174 /* Uh, our last resort, an interface name */
175 idx = if_nametoindex(n);
179 a->sockaddr.in6.sin6_family = AF_INET6;
180 a->sockaddr.in6.sin6_port = htobe16((uint16_t)u);
181 a->sockaddr.in6.sin6_scope_id = idx;
182 a->sockaddr.in6.sin6_addr = in6addr_any;
183 a->size = sizeof(struct sockaddr_in6);
188 r = safe_atou(s, &u);
192 if (u <= 0 || u > 0xFFFF)
195 if (socket_ipv6_is_supported()) {
196 a->sockaddr.in6.sin6_family = AF_INET6;
197 a->sockaddr.in6.sin6_port = htobe16((uint16_t)u);
198 a->sockaddr.in6.sin6_addr = in6addr_any;
199 a->size = sizeof(struct sockaddr_in6);
201 a->sockaddr.in.sin_family = AF_INET;
202 a->sockaddr.in.sin_port = htobe16((uint16_t)u);
203 a->sockaddr.in.sin_addr.s_addr = INADDR_ANY;
204 a->size = sizeof(struct sockaddr_in);
212 int socket_address_parse_and_warn(SocketAddress *a, const char *s) {
216 /* Similar to socket_address_parse() but warns for IPv6 sockets when we don't support them. */
218 r = socket_address_parse(&b, s);
222 if (!socket_ipv6_is_supported() && b.sockaddr.sa.sa_family == AF_INET6) {
223 log_warning("Binding to IPv6 address not available since kernel does not support IPv6.");
224 return -EAFNOSUPPORT;
231 int socket_address_parse_netlink(SocketAddress *a, const char *s) {
234 _cleanup_free_ char *sfamily = NULL;
242 if (sscanf(s, "%ms %u", &sfamily, &group) < 1)
243 return errno > 0 ? -errno : -EINVAL;
245 family = netlink_family_from_string(sfamily);
249 a->sockaddr.nl.nl_family = AF_NETLINK;
250 a->sockaddr.nl.nl_groups = group;
253 a->size = sizeof(struct sockaddr_nl);
254 a->protocol = family;
259 int socket_address_verify(const SocketAddress *a) {
262 switch (socket_address_family(a)) {
265 if (a->size != sizeof(struct sockaddr_in))
268 if (a->sockaddr.in.sin_port == 0)
271 if (a->type != SOCK_STREAM && a->type != SOCK_DGRAM)
277 if (a->size != sizeof(struct sockaddr_in6))
280 if (a->sockaddr.in6.sin6_port == 0)
283 if (a->type != SOCK_STREAM && a->type != SOCK_DGRAM)
289 if (a->size < offsetof(struct sockaddr_un, sun_path))
292 if (a->size > offsetof(struct sockaddr_un, sun_path)) {
294 if (a->sockaddr.un.sun_path[0] != 0) {
298 e = memchr(a->sockaddr.un.sun_path, 0, sizeof(a->sockaddr.un.sun_path));
302 if (a->size != offsetof(struct sockaddr_un, sun_path) + (e - a->sockaddr.un.sun_path) + 1)
307 if (a->type != SOCK_STREAM && a->type != SOCK_DGRAM && a->type != SOCK_SEQPACKET)
314 if (a->size != sizeof(struct sockaddr_nl))
317 if (a->type != SOCK_RAW && a->type != SOCK_DGRAM)
323 if (a->size != sizeof(struct sockaddr_vm))
326 if (a->type != SOCK_STREAM && a->type != SOCK_DGRAM)
332 return -EAFNOSUPPORT;
336 int socket_address_print(const SocketAddress *a, char **ret) {
342 r = socket_address_verify(a);
346 if (socket_address_family(a) == AF_NETLINK) {
347 _cleanup_free_ char *sfamily = NULL;
349 r = netlink_family_to_string_alloc(a->protocol, &sfamily);
353 r = asprintf(ret, "%s %u", sfamily, a->sockaddr.nl.nl_groups);
360 return sockaddr_pretty(&a->sockaddr.sa, a->size, false, true, ret);
363 bool socket_address_can_accept(const SocketAddress *a) {
367 a->type == SOCK_STREAM ||
368 a->type == SOCK_SEQPACKET;
371 bool socket_address_equal(const SocketAddress *a, const SocketAddress *b) {
375 /* Invalid addresses are unequal to all */
376 if (socket_address_verify(a) < 0 ||
377 socket_address_verify(b) < 0)
380 if (a->type != b->type)
383 if (socket_address_family(a) != socket_address_family(b))
386 switch (socket_address_family(a)) {
389 if (a->sockaddr.in.sin_addr.s_addr != b->sockaddr.in.sin_addr.s_addr)
392 if (a->sockaddr.in.sin_port != b->sockaddr.in.sin_port)
398 if (memcmp(&a->sockaddr.in6.sin6_addr, &b->sockaddr.in6.sin6_addr, sizeof(a->sockaddr.in6.sin6_addr)) != 0)
401 if (a->sockaddr.in6.sin6_port != b->sockaddr.in6.sin6_port)
407 if (a->size <= offsetof(struct sockaddr_un, sun_path) ||
408 b->size <= offsetof(struct sockaddr_un, sun_path))
411 if ((a->sockaddr.un.sun_path[0] == 0) != (b->sockaddr.un.sun_path[0] == 0))
414 if (a->sockaddr.un.sun_path[0]) {
415 if (!path_equal_or_files_same(a->sockaddr.un.sun_path, b->sockaddr.un.sun_path, 0))
418 if (a->size != b->size)
421 if (memcmp(a->sockaddr.un.sun_path, b->sockaddr.un.sun_path, a->size) != 0)
428 if (a->protocol != b->protocol)
431 if (a->sockaddr.nl.nl_groups != b->sockaddr.nl.nl_groups)
437 if (a->sockaddr.vm.svm_cid != b->sockaddr.vm.svm_cid)
440 if (a->sockaddr.vm.svm_port != b->sockaddr.vm.svm_port)
446 /* Cannot compare, so we assume the addresses are different */
453 bool socket_address_is(const SocketAddress *a, const char *s, int type) {
454 struct SocketAddress b;
459 if (socket_address_parse(&b, s) < 0)
464 return socket_address_equal(a, &b);
467 bool socket_address_is_netlink(const SocketAddress *a, const char *s) {
468 struct SocketAddress b;
473 if (socket_address_parse_netlink(&b, s) < 0)
476 return socket_address_equal(a, &b);
479 const char* socket_address_get_path(const SocketAddress *a) {
482 if (socket_address_family(a) != AF_UNIX)
485 if (a->sockaddr.un.sun_path[0] == 0)
488 return a->sockaddr.un.sun_path;
491 bool socket_ipv6_is_supported(void) {
492 if (access("/proc/net/if_inet6", F_OK) != 0)
498 bool socket_address_matches_fd(const SocketAddress *a, int fd) {
505 b.size = sizeof(b.sockaddr);
506 if (getsockname(fd, &b.sockaddr.sa, &b.size) < 0)
509 if (b.sockaddr.sa.sa_family != a->sockaddr.sa.sa_family)
512 solen = sizeof(b.type);
513 if (getsockopt(fd, SOL_SOCKET, SO_TYPE, &b.type, &solen) < 0)
516 if (b.type != a->type)
519 if (a->protocol != 0) {
520 solen = sizeof(b.protocol);
521 if (getsockopt(fd, SOL_SOCKET, SO_PROTOCOL, &b.protocol, &solen) < 0)
524 if (b.protocol != a->protocol)
528 return socket_address_equal(a, &b);
531 int sockaddr_port(const struct sockaddr *_sa, unsigned *port) {
532 union sockaddr_union *sa = (union sockaddr_union*) _sa;
536 switch (sa->sa.sa_family) {
538 *port = be16toh(sa->in.sin_port);
542 *port = be16toh(sa->in6.sin6_port);
546 *port = sa->vm.svm_port;
550 return -EAFNOSUPPORT;
554 int sockaddr_pretty(const struct sockaddr *_sa, socklen_t salen, bool translate_ipv6, bool include_port, char **ret) {
555 union sockaddr_union *sa = (union sockaddr_union*) _sa;
560 assert(salen >= sizeof(sa->sa.sa_family));
562 switch (sa->sa.sa_family) {
567 a = be32toh(sa->in.sin_addr.s_addr);
572 a >> 24, (a >> 16) & 0xFF, (a >> 8) & 0xFF, a & 0xFF,
573 be16toh(sa->in.sin_port));
577 a >> 24, (a >> 16) & 0xFF, (a >> 8) & 0xFF, a & 0xFF);
584 static const unsigned char ipv4_prefix[] = {
585 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF
588 if (translate_ipv6 &&
589 memcmp(&sa->in6.sin6_addr, ipv4_prefix, sizeof(ipv4_prefix)) == 0) {
590 const uint8_t *a = sa->in6.sin6_addr.s6_addr+12;
594 a[0], a[1], a[2], a[3],
595 be16toh(sa->in6.sin6_port));
599 a[0], a[1], a[2], a[3]);
603 char a[INET6_ADDRSTRLEN];
605 inet_ntop(AF_INET6, &sa->in6.sin6_addr, a, sizeof(a));
611 be16toh(sa->in6.sin6_port));
625 if (salen <= offsetof(struct sockaddr_un, sun_path)) {
626 p = strdup("<unnamed>");
630 } else if (sa->un.sun_path[0] == 0) {
633 /* FIXME: We assume we can print the
634 * socket path here and that it hasn't
635 * more than one NUL byte. That is
636 * actually an invalid assumption */
638 p = new(char, sizeof(sa->un.sun_path)+1);
643 memcpy(p+1, sa->un.sun_path+1, sizeof(sa->un.sun_path)-1);
644 p[sizeof(sa->un.sun_path)] = 0;
647 p = strndup(sa->un.sun_path, sizeof(sa->un.sun_path));
661 r = asprintf(&p, "vsock:%u", sa->vm.svm_cid);
675 int getpeername_pretty(int fd, bool include_port, char **ret) {
676 union sockaddr_union sa;
677 socklen_t salen = sizeof(sa);
683 if (getpeername(fd, &sa.sa, &salen) < 0)
686 if (sa.sa.sa_family == AF_UNIX) {
687 struct ucred ucred = {};
689 /* UNIX connection sockets are anonymous, so let's use
690 * PID/UID as pretty credentials instead */
692 r = getpeercred(fd, &ucred);
696 if (asprintf(ret, "PID "PID_FMT"/UID "UID_FMT, ucred.pid, ucred.uid) < 0)
702 /* For remote sockets we translate IPv6 addresses back to IPv4
703 * if applicable, since that's nicer. */
705 return sockaddr_pretty(&sa.sa, salen, true, include_port, ret);
708 int getsockname_pretty(int fd, char **ret) {
709 union sockaddr_union sa;
710 socklen_t salen = sizeof(sa);
715 if (getsockname(fd, &sa.sa, &salen) < 0)
718 /* For local sockets we do not translate IPv6 addresses back
719 * to IPv6 if applicable, since this is usually used for
720 * listening sockets where the difference between IPv4 and
723 return sockaddr_pretty(&sa.sa, salen, false, true, ret);
726 int socknameinfo_pretty(union sockaddr_union *sa, socklen_t salen, char **_ret) {
728 char host[NI_MAXHOST], *ret;
732 r = getnameinfo(&sa->sa, salen, host, sizeof(host), NULL, 0, IDN_FLAGS);
734 int saved_errno = errno;
736 r = sockaddr_pretty(&sa->sa, salen, true, true, &ret);
740 log_debug_errno(saved_errno, "getnameinfo(%s) failed: %m", ret);
751 int getnameinfo_pretty(int fd, char **ret) {
752 union sockaddr_union sa;
753 socklen_t salen = sizeof(sa);
758 if (getsockname(fd, &sa.sa, &salen) < 0)
761 return socknameinfo_pretty(&sa, salen, ret);
764 int socket_address_unlink(SocketAddress *a) {
767 if (socket_address_family(a) != AF_UNIX)
770 if (a->sockaddr.un.sun_path[0] == 0)
773 if (unlink(a->sockaddr.un.sun_path) < 0)
779 static const char* const netlink_family_table[] = {
780 [NETLINK_ROUTE] = "route",
781 [NETLINK_FIREWALL] = "firewall",
782 [NETLINK_INET_DIAG] = "inet-diag",
783 [NETLINK_NFLOG] = "nflog",
784 [NETLINK_XFRM] = "xfrm",
785 [NETLINK_SELINUX] = "selinux",
786 [NETLINK_ISCSI] = "iscsi",
787 [NETLINK_AUDIT] = "audit",
788 [NETLINK_FIB_LOOKUP] = "fib-lookup",
789 [NETLINK_CONNECTOR] = "connector",
790 [NETLINK_NETFILTER] = "netfilter",
791 [NETLINK_IP6_FW] = "ip6-fw",
792 [NETLINK_DNRTMSG] = "dnrtmsg",
793 [NETLINK_KOBJECT_UEVENT] = "kobject-uevent",
794 [NETLINK_GENERIC] = "generic",
795 [NETLINK_SCSITRANSPORT] = "scsitransport",
796 [NETLINK_ECRYPTFS] = "ecryptfs"
799 DEFINE_STRING_TABLE_LOOKUP_WITH_FALLBACK(netlink_family, int, INT_MAX);
801 static const char* const socket_address_bind_ipv6_only_table[_SOCKET_ADDRESS_BIND_IPV6_ONLY_MAX] = {
802 [SOCKET_ADDRESS_DEFAULT] = "default",
803 [SOCKET_ADDRESS_BOTH] = "both",
804 [SOCKET_ADDRESS_IPV6_ONLY] = "ipv6-only"
807 DEFINE_STRING_TABLE_LOOKUP(socket_address_bind_ipv6_only, SocketAddressBindIPv6Only);
809 bool sockaddr_equal(const union sockaddr_union *a, const union sockaddr_union *b) {
813 if (a->sa.sa_family != b->sa.sa_family)
816 if (a->sa.sa_family == AF_INET)
817 return a->in.sin_addr.s_addr == b->in.sin_addr.s_addr;
819 if (a->sa.sa_family == AF_INET6)
820 return memcmp(&a->in6.sin6_addr, &b->in6.sin6_addr, sizeof(a->in6.sin6_addr)) == 0;
822 if (a->sa.sa_family == AF_VSOCK)
823 return a->vm.svm_cid == b->vm.svm_cid;
829 int fd_inc_sndbuf(int fd, size_t n) {
831 socklen_t l = sizeof(value);
833 r = getsockopt(fd, SOL_SOCKET, SO_SNDBUF, &value, &l);
834 if (r >= 0 && l == sizeof(value) && (size_t) value >= n*2)
837 /* If we have the privileges we will ignore the kernel limit. */
840 if (setsockopt(fd, SOL_SOCKET, SO_SNDBUFFORCE, &value, sizeof(value)) < 0)
841 if (setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &value, sizeof(value)) < 0)
847 int fd_inc_rcvbuf(int fd, size_t n) {
849 socklen_t l = sizeof(value);
851 r = getsockopt(fd, SOL_SOCKET, SO_RCVBUF, &value, &l);
852 if (r >= 0 && l == sizeof(value) && (size_t) value >= n*2)
855 /* If we have the privileges we will ignore the kernel limit. */
858 if (setsockopt(fd, SOL_SOCKET, SO_RCVBUFFORCE, &value, sizeof(value)) < 0)
859 if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &value, sizeof(value)) < 0)
864 #if 0 /// UNNEEDED by elogind
865 static const char* const ip_tos_table[] = {
866 [IPTOS_LOWDELAY] = "low-delay",
867 [IPTOS_THROUGHPUT] = "throughput",
868 [IPTOS_RELIABILITY] = "reliability",
869 [IPTOS_LOWCOST] = "low-cost",
872 DEFINE_STRING_TABLE_LOOKUP_WITH_FALLBACK(ip_tos, int, 0xff);
874 bool ifname_valid(const char *p) {
877 /* Checks whether a network interface name is valid. This is inspired by dev_valid_name() in the kernel sources
878 * but slightly stricter, as we only allow non-control, non-space ASCII characters in the interface name. We
879 * also don't permit names that only container numbers, to avoid confusion with numeric interface indexes. */
884 if (strlen(p) >= IFNAMSIZ)
887 if (dot_or_dot_dot(p))
891 if ((unsigned char) *p >= 127U)
894 if ((unsigned char) *p <= 32U)
897 if (*p == ':' || *p == '/')
900 numeric = numeric && (*p >= '0' && *p <= '9');
910 bool address_label_valid(const char *p) {
915 if (strlen(p) >= IFNAMSIZ)
919 if ((uint8_t) *p >= 127U)
922 if ((uint8_t) *p <= 31U)
931 int getpeercred(int fd, struct ucred *ucred) {
932 socklen_t n = sizeof(struct ucred);
939 r = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &u, &n);
943 if (n != sizeof(struct ucred))
946 /* Check if the data is actually useful and not suppressed due
947 * to namespacing issues */
950 if (u.uid == UID_INVALID)
952 if (u.gid == GID_INVALID)
959 int getpeersec(int fd, char **ret) {
971 r = getsockopt(fd, SOL_SOCKET, SO_PEERSEC, s, &n);
982 r = getsockopt(fd, SOL_SOCKET, SO_PEERSEC, s, &n);
1001 const struct sockaddr *sa, socklen_t len,
1005 struct cmsghdr cmsghdr;
1006 uint8_t buf[CMSG_SPACE(sizeof(int))];
1008 struct msghdr mh = {
1009 .msg_name = (struct sockaddr*) sa,
1011 .msg_control = &control,
1012 .msg_controllen = sizeof(control),
1014 struct cmsghdr *cmsg;
1016 assert(transport_fd >= 0);
1019 cmsg = CMSG_FIRSTHDR(&mh);
1020 cmsg->cmsg_level = SOL_SOCKET;
1021 cmsg->cmsg_type = SCM_RIGHTS;
1022 cmsg->cmsg_len = CMSG_LEN(sizeof(int));
1023 memcpy(CMSG_DATA(cmsg), &fd, sizeof(int));
1025 mh.msg_controllen = CMSG_SPACE(sizeof(int));
1026 if (sendmsg(transport_fd, &mh, MSG_NOSIGNAL | flags) < 0)
1032 #if 0 /// UNNEEDED by elogind
1033 int receive_one_fd(int transport_fd, int flags) {
1035 struct cmsghdr cmsghdr;
1036 uint8_t buf[CMSG_SPACE(sizeof(int))];
1038 struct msghdr mh = {
1039 .msg_control = &control,
1040 .msg_controllen = sizeof(control),
1042 struct cmsghdr *cmsg, *found = NULL;
1044 assert(transport_fd >= 0);
1047 * Receive a single FD via @transport_fd. We don't care for
1048 * the transport-type. We retrieve a single FD at most, so for
1049 * packet-based transports, the caller must ensure to send
1050 * only a single FD per packet. This is best used in
1051 * combination with send_one_fd().
1054 if (recvmsg(transport_fd, &mh, MSG_NOSIGNAL | MSG_CMSG_CLOEXEC | flags) < 0)
1057 CMSG_FOREACH(cmsg, &mh) {
1058 if (cmsg->cmsg_level == SOL_SOCKET &&
1059 cmsg->cmsg_type == SCM_RIGHTS &&
1060 cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
1068 cmsg_close_all(&mh);
1072 return *(int*) CMSG_DATA(found);
1075 ssize_t next_datagram_size_fd(int fd) {
1079 /* This is a bit like FIONREAD/SIOCINQ, however a bit more powerful. The difference being: recv(MSG_PEEK) will
1080 * actually cause the next datagram in the queue to be validated regarding checksums, which FIONREAD doesn't
1081 * do. This difference is actually of major importance as we need to be sure that the size returned here
1082 * actually matches what we will read with recvmsg() next, as otherwise we might end up allocating a buffer of
1083 * the wrong size. */
1085 l = recv(fd, NULL, 0, MSG_PEEK|MSG_TRUNC);
1087 if (errno == EOPNOTSUPP || errno == EFAULT)
1100 /* Some sockets (AF_PACKET) do not support null-sized recv() with MSG_TRUNC set, let's fall back to FIONREAD
1101 * for them. Checksums don't matter for raw sockets anyway, hence this should be fine. */
1103 if (ioctl(fd, FIONREAD, &k) < 0)
1109 int flush_accept(int fd) {
1111 struct pollfd pollfd = {
1118 /* Similar to flush_fd() but flushes all incoming connection by accepting them and immediately closing them. */
1123 r = poll(&pollfd, 1, 0);
1133 cfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);
1138 if (errno == EAGAIN)
1148 struct cmsghdr* cmsg_find(struct msghdr *mh, int level, int type, socklen_t length) {
1149 struct cmsghdr *cmsg;
1153 CMSG_FOREACH(cmsg, mh)
1154 if (cmsg->cmsg_level == level &&
1155 cmsg->cmsg_type == type &&
1156 (length == (socklen_t) -1 || length == cmsg->cmsg_len))
1162 int socket_ioctl_fd(void) {
1165 /* Create a socket to invoke the various network interface ioctl()s on. Traditionally only AF_INET was good for
1166 * that. Since kernel 4.6 AF_NETLINK works for this too. We first try to use AF_INET hence, but if that's not
1167 * available (for example, because it is made unavailable via SECCOMP or such), we'll fall back to the more
1168 * generic AF_NETLINK. */
1170 fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC, 0);
1172 fd = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_GENERIC);