/*** This file is part of systemd. Copyright 2010 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. ***/ #include <arpa/inet.h> #include <errno.h> #include <limits.h> #include <net/if.h> #include <netdb.h> #include <netinet/ip.h> #include <poll.h> #include <stddef.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include "alloc-util.h" #include "fd-util.h" #include "fileio.h" #include "formats-util.h" #include "log.h" #include "macro.h" #include "missing.h" #include "parse-util.h" #include "path-util.h" #include "socket-util.h" #include "string-table.h" #include "string-util.h" #include "strv.h" #include "user-util.h" #include "utf8.h" #include "util.h" int socket_address_parse(SocketAddress *a, const char *s) { char *e, *n; unsigned u; int r; assert(a); assert(s); zero(*a); a->type = SOCK_STREAM; if (*s == '[') { /* IPv6 in [x:.....:z]:p notation */ e = strchr(s+1, ']'); if (!e) return -EINVAL; n = strndupa(s+1, e-s-1); errno = 0; if (inet_pton(AF_INET6, n, &a->sockaddr.in6.sin6_addr) <= 0) return errno > 0 ? -errno : -EINVAL; e++; if (*e != ':') return -EINVAL; e++; r = safe_atou(e, &u); if (r < 0) return r; if (u <= 0 || u > 0xFFFF) return -EINVAL; a->sockaddr.in6.sin6_family = AF_INET6; a->sockaddr.in6.sin6_port = htobe16((uint16_t)u); a->size = sizeof(struct sockaddr_in6); } else if (*s == '/') { /* AF_UNIX socket */ size_t l; l = strlen(s); if (l >= sizeof(a->sockaddr.un.sun_path)) return -EINVAL; a->sockaddr.un.sun_family = AF_UNIX; memcpy(a->sockaddr.un.sun_path, s, l); a->size = offsetof(struct sockaddr_un, sun_path) + l + 1; } else if (*s == '@') { /* Abstract AF_UNIX socket */ size_t l; l = strlen(s+1); if (l >= sizeof(a->sockaddr.un.sun_path) - 1) return -EINVAL; a->sockaddr.un.sun_family = AF_UNIX; memcpy(a->sockaddr.un.sun_path+1, s+1, l); a->size = offsetof(struct sockaddr_un, sun_path) + 1 + l; } else { e = strchr(s, ':'); if (e) { r = safe_atou(e+1, &u); if (r < 0) return r; if (u <= 0 || u > 0xFFFF) return -EINVAL; n = strndupa(s, e-s); /* IPv4 in w.x.y.z:p notation? */ r = inet_pton(AF_INET, n, &a->sockaddr.in.sin_addr); if (r < 0) return -errno; if (r > 0) { /* Gotcha, it's a traditional IPv4 address */ a->sockaddr.in.sin_family = AF_INET; a->sockaddr.in.sin_port = htobe16((uint16_t)u); a->size = sizeof(struct sockaddr_in); } else { unsigned idx; if (strlen(n) > IF_NAMESIZE-1) return -EINVAL; /* Uh, our last resort, an interface name */ idx = if_nametoindex(n); if (idx == 0) return -EINVAL; a->sockaddr.in6.sin6_family = AF_INET6; a->sockaddr.in6.sin6_port = htobe16((uint16_t)u); a->sockaddr.in6.sin6_scope_id = idx; a->sockaddr.in6.sin6_addr = in6addr_any; a->size = sizeof(struct sockaddr_in6); } } else { /* Just a port */ r = safe_atou(s, &u); if (r < 0) return r; if (u <= 0 || u > 0xFFFF) return -EINVAL; if (socket_ipv6_is_supported()) { a->sockaddr.in6.sin6_family = AF_INET6; a->sockaddr.in6.sin6_port = htobe16((uint16_t)u); a->sockaddr.in6.sin6_addr = in6addr_any; a->size = sizeof(struct sockaddr_in6); } else { a->sockaddr.in.sin_family = AF_INET; a->sockaddr.in.sin_port = htobe16((uint16_t)u); a->sockaddr.in.sin_addr.s_addr = INADDR_ANY; a->size = sizeof(struct sockaddr_in); } } } return 0; } int socket_address_parse_and_warn(SocketAddress *a, const char *s) { SocketAddress b; int r; /* Similar to socket_address_parse() but warns for IPv6 sockets when we don't support them. */ r = socket_address_parse(&b, s); if (r < 0) return r; if (!socket_ipv6_is_supported() && b.sockaddr.sa.sa_family == AF_INET6) { log_warning("Binding to IPv6 address not available since kernel does not support IPv6."); return -EAFNOSUPPORT; } *a = b; return 0; } int socket_address_parse_netlink(SocketAddress *a, const char *s) { int family; unsigned group = 0; _cleanup_free_ char *sfamily = NULL; assert(a); assert(s); zero(*a); a->type = SOCK_RAW; errno = 0; if (sscanf(s, "%ms %u", &sfamily, &group) < 1) return errno > 0 ? -errno : -EINVAL; family = netlink_family_from_string(sfamily); if (family < 0) return -EINVAL; a->sockaddr.nl.nl_family = AF_NETLINK; a->sockaddr.nl.nl_groups = group; a->type = SOCK_RAW; a->size = sizeof(struct sockaddr_nl); a->protocol = family; return 0; } int socket_address_verify(const SocketAddress *a) { assert(a); switch (socket_address_family(a)) { case AF_INET: if (a->size != sizeof(struct sockaddr_in)) return -EINVAL; if (a->sockaddr.in.sin_port == 0) return -EINVAL; if (a->type != SOCK_STREAM && a->type != SOCK_DGRAM) return -EINVAL; return 0; case AF_INET6: if (a->size != sizeof(struct sockaddr_in6)) return -EINVAL; if (a->sockaddr.in6.sin6_port == 0) return -EINVAL; if (a->type != SOCK_STREAM && a->type != SOCK_DGRAM) return -EINVAL; return 0; case AF_UNIX: if (a->size < offsetof(struct sockaddr_un, sun_path)) return -EINVAL; if (a->size > offsetof(struct sockaddr_un, sun_path)) { if (a->sockaddr.un.sun_path[0] != 0) { char *e; /* path */ e = memchr(a->sockaddr.un.sun_path, 0, sizeof(a->sockaddr.un.sun_path)); if (!e) return -EINVAL; if (a->size != offsetof(struct sockaddr_un, sun_path) + (e - a->sockaddr.un.sun_path) + 1) return -EINVAL; } } if (a->type != SOCK_STREAM && a->type != SOCK_DGRAM && a->type != SOCK_SEQPACKET) return -EINVAL; return 0; case AF_NETLINK: if (a->size != sizeof(struct sockaddr_nl)) return -EINVAL; if (a->type != SOCK_RAW && a->type != SOCK_DGRAM) return -EINVAL; return 0; default: return -EAFNOSUPPORT; } } int socket_address_print(const SocketAddress *a, char **ret) { int r; assert(a); assert(ret); r = socket_address_verify(a); if (r < 0) return r; if (socket_address_family(a) == AF_NETLINK) { _cleanup_free_ char *sfamily = NULL; r = netlink_family_to_string_alloc(a->protocol, &sfamily); if (r < 0) return r; r = asprintf(ret, "%s %u", sfamily, a->sockaddr.nl.nl_groups); if (r < 0) return -ENOMEM; return 0; } return sockaddr_pretty(&a->sockaddr.sa, a->size, false, true, ret); } bool socket_address_can_accept(const SocketAddress *a) { assert(a); return a->type == SOCK_STREAM || a->type == SOCK_SEQPACKET; } bool socket_address_equal(const SocketAddress *a, const SocketAddress *b) { assert(a); assert(b); /* Invalid addresses are unequal to all */ if (socket_address_verify(a) < 0 || socket_address_verify(b) < 0) return false; if (a->type != b->type) return false; if (socket_address_family(a) != socket_address_family(b)) return false; switch (socket_address_family(a)) { case AF_INET: if (a->sockaddr.in.sin_addr.s_addr != b->sockaddr.in.sin_addr.s_addr) return false; if (a->sockaddr.in.sin_port != b->sockaddr.in.sin_port) return false; break; case AF_INET6: if (memcmp(&a->sockaddr.in6.sin6_addr, &b->sockaddr.in6.sin6_addr, sizeof(a->sockaddr.in6.sin6_addr)) != 0) return false; if (a->sockaddr.in6.sin6_port != b->sockaddr.in6.sin6_port) return false; break; case AF_UNIX: if (a->size <= offsetof(struct sockaddr_un, sun_path) || b->size <= offsetof(struct sockaddr_un, sun_path)) return false; if ((a->sockaddr.un.sun_path[0] == 0) != (b->sockaddr.un.sun_path[0] == 0)) return false; if (a->sockaddr.un.sun_path[0]) { if (!path_equal_or_files_same(a->sockaddr.un.sun_path, b->sockaddr.un.sun_path)) return false; } else { if (a->size != b->size) return false; if (memcmp(a->sockaddr.un.sun_path, b->sockaddr.un.sun_path, a->size) != 0) return false; } break; case AF_NETLINK: if (a->protocol != b->protocol) return false; if (a->sockaddr.nl.nl_groups != b->sockaddr.nl.nl_groups) return false; break; default: /* Cannot compare, so we assume the addresses are different */ return false; } return true; } bool socket_address_is(const SocketAddress *a, const char *s, int type) { struct SocketAddress b; assert(a); assert(s); if (socket_address_parse(&b, s) < 0) return false; b.type = type; return socket_address_equal(a, &b); } bool socket_address_is_netlink(const SocketAddress *a, const char *s) { struct SocketAddress b; assert(a); assert(s); if (socket_address_parse_netlink(&b, s) < 0) return false; return socket_address_equal(a, &b); } const char* socket_address_get_path(const SocketAddress *a) { assert(a); if (socket_address_family(a) != AF_UNIX) return NULL; if (a->sockaddr.un.sun_path[0] == 0) return NULL; return a->sockaddr.un.sun_path; } bool socket_ipv6_is_supported(void) { if (access("/proc/net/sockstat6", F_OK) != 0) return false; return true; } bool socket_address_matches_fd(const SocketAddress *a, int fd) { SocketAddress b; socklen_t solen; assert(a); assert(fd >= 0); b.size = sizeof(b.sockaddr); if (getsockname(fd, &b.sockaddr.sa, &b.size) < 0) return false; if (b.sockaddr.sa.sa_family != a->sockaddr.sa.sa_family) return false; solen = sizeof(b.type); if (getsockopt(fd, SOL_SOCKET, SO_TYPE, &b.type, &solen) < 0) return false; if (b.type != a->type) return false; if (a->protocol != 0) { solen = sizeof(b.protocol); if (getsockopt(fd, SOL_SOCKET, SO_PROTOCOL, &b.protocol, &solen) < 0) return false; if (b.protocol != a->protocol) return false; } return socket_address_equal(a, &b); } int sockaddr_port(const struct sockaddr *_sa) { union sockaddr_union *sa = (union sockaddr_union*) _sa; assert(sa); if (!IN_SET(sa->sa.sa_family, AF_INET, AF_INET6)) return -EAFNOSUPPORT; return be16toh(sa->sa.sa_family == AF_INET6 ? sa->in6.sin6_port : sa->in.sin_port); } int sockaddr_pretty(const struct sockaddr *_sa, socklen_t salen, bool translate_ipv6, bool include_port, char **ret) { union sockaddr_union *sa = (union sockaddr_union*) _sa; char *p; int r; assert(sa); assert(salen >= sizeof(sa->sa.sa_family)); switch (sa->sa.sa_family) { case AF_INET: { uint32_t a; a = be32toh(sa->in.sin_addr.s_addr); if (include_port) r = asprintf(&p, "%u.%u.%u.%u:%u", a >> 24, (a >> 16) & 0xFF, (a >> 8) & 0xFF, a & 0xFF, be16toh(sa->in.sin_port)); else r = asprintf(&p, "%u.%u.%u.%u", a >> 24, (a >> 16) & 0xFF, (a >> 8) & 0xFF, a & 0xFF); if (r < 0) return -ENOMEM; break; } case AF_INET6: { static const unsigned char ipv4_prefix[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF }; if (translate_ipv6 && memcmp(&sa->in6.sin6_addr, ipv4_prefix, sizeof(ipv4_prefix)) == 0) { const uint8_t *a = sa->in6.sin6_addr.s6_addr+12; if (include_port) r = asprintf(&p, "%u.%u.%u.%u:%u", a[0], a[1], a[2], a[3], be16toh(sa->in6.sin6_port)); else r = asprintf(&p, "%u.%u.%u.%u", a[0], a[1], a[2], a[3]); if (r < 0) return -ENOMEM; } else { char a[INET6_ADDRSTRLEN]; inet_ntop(AF_INET6, &sa->in6.sin6_addr, a, sizeof(a)); if (include_port) { r = asprintf(&p, "[%s]:%u", a, be16toh(sa->in6.sin6_port)); if (r < 0) return -ENOMEM; } else { p = strdup(a); if (!p) return -ENOMEM; } } break; } case AF_UNIX: if (salen <= offsetof(struct sockaddr_un, sun_path)) { p = strdup("<unnamed>"); if (!p) return -ENOMEM; } else if (sa->un.sun_path[0] == 0) { /* abstract */ /* FIXME: We assume we can print the * socket path here and that it hasn't * more than one NUL byte. That is * actually an invalid assumption */ p = new(char, sizeof(sa->un.sun_path)+1); if (!p) return -ENOMEM; p[0] = '@'; memcpy(p+1, sa->un.sun_path+1, sizeof(sa->un.sun_path)-1); p[sizeof(sa->un.sun_path)] = 0; } else { p = strndup(sa->un.sun_path, sizeof(sa->un.sun_path)); if (!p) return -ENOMEM; } break; default: return -EOPNOTSUPP; } *ret = p; return 0; } int getpeername_pretty(int fd, bool include_port, char **ret) { union sockaddr_union sa; socklen_t salen = sizeof(sa); int r; assert(fd >= 0); assert(ret); if (getpeername(fd, &sa.sa, &salen) < 0) return -errno; if (sa.sa.sa_family == AF_UNIX) { struct ucred ucred = {}; /* UNIX connection sockets are anonymous, so let's use * PID/UID as pretty credentials instead */ r = getpeercred(fd, &ucred); if (r < 0) return r; if (asprintf(ret, "PID "PID_FMT"/UID "UID_FMT, ucred.pid, ucred.uid) < 0) return -ENOMEM; return 0; } /* For remote sockets we translate IPv6 addresses back to IPv4 * if applicable, since that's nicer. */ return sockaddr_pretty(&sa.sa, salen, true, include_port, ret); } int getsockname_pretty(int fd, char **ret) { union sockaddr_union sa; socklen_t salen = sizeof(sa); assert(fd >= 0); assert(ret); if (getsockname(fd, &sa.sa, &salen) < 0) return -errno; /* For local sockets we do not translate IPv6 addresses back * to IPv6 if applicable, since this is usually used for * listening sockets where the difference between IPv4 and * IPv6 matters. */ return sockaddr_pretty(&sa.sa, salen, false, true, ret); } int socknameinfo_pretty(union sockaddr_union *sa, socklen_t salen, char **_ret) { int r; char host[NI_MAXHOST], *ret; assert(_ret); r = getnameinfo(&sa->sa, salen, host, sizeof(host), NULL, 0, NI_IDN|NI_IDN_USE_STD3_ASCII_RULES); if (r != 0) { int saved_errno = errno; r = sockaddr_pretty(&sa->sa, salen, true, true, &ret); if (r < 0) return r; log_debug_errno(saved_errno, "getnameinfo(%s) failed: %m", ret); } else { ret = strdup(host); if (!ret) return -ENOMEM; } *_ret = ret; return 0; } int getnameinfo_pretty(int fd, char **ret) { union sockaddr_union sa; socklen_t salen = sizeof(sa); assert(fd >= 0); assert(ret); if (getsockname(fd, &sa.sa, &salen) < 0) return -errno; return socknameinfo_pretty(&sa, salen, ret); } int socket_address_unlink(SocketAddress *a) { assert(a); if (socket_address_family(a) != AF_UNIX) return 0; if (a->sockaddr.un.sun_path[0] == 0) return 0; if (unlink(a->sockaddr.un.sun_path) < 0) return -errno; return 1; } static const char* const netlink_family_table[] = { [NETLINK_ROUTE] = "route", [NETLINK_FIREWALL] = "firewall", [NETLINK_INET_DIAG] = "inet-diag", [NETLINK_NFLOG] = "nflog", [NETLINK_XFRM] = "xfrm", [NETLINK_SELINUX] = "selinux", [NETLINK_ISCSI] = "iscsi", [NETLINK_AUDIT] = "audit", [NETLINK_FIB_LOOKUP] = "fib-lookup", [NETLINK_CONNECTOR] = "connector", [NETLINK_NETFILTER] = "netfilter", [NETLINK_IP6_FW] = "ip6-fw", [NETLINK_DNRTMSG] = "dnrtmsg", [NETLINK_KOBJECT_UEVENT] = "kobject-uevent", [NETLINK_GENERIC] = "generic", [NETLINK_SCSITRANSPORT] = "scsitransport", [NETLINK_ECRYPTFS] = "ecryptfs" }; DEFINE_STRING_TABLE_LOOKUP_WITH_FALLBACK(netlink_family, int, INT_MAX); static const char* const socket_address_bind_ipv6_only_table[_SOCKET_ADDRESS_BIND_IPV6_ONLY_MAX] = { [SOCKET_ADDRESS_DEFAULT] = "default", [SOCKET_ADDRESS_BOTH] = "both", [SOCKET_ADDRESS_IPV6_ONLY] = "ipv6-only" }; DEFINE_STRING_TABLE_LOOKUP(socket_address_bind_ipv6_only, SocketAddressBindIPv6Only); bool sockaddr_equal(const union sockaddr_union *a, const union sockaddr_union *b) { assert(a); assert(b); if (a->sa.sa_family != b->sa.sa_family) return false; if (a->sa.sa_family == AF_INET) return a->in.sin_addr.s_addr == b->in.sin_addr.s_addr; if (a->sa.sa_family == AF_INET6) return memcmp(&a->in6.sin6_addr, &b->in6.sin6_addr, sizeof(a->in6.sin6_addr)) == 0; return false; } int fd_inc_sndbuf(int fd, size_t n) { int r, value; socklen_t l = sizeof(value); r = getsockopt(fd, SOL_SOCKET, SO_SNDBUF, &value, &l); if (r >= 0 && l == sizeof(value) && (size_t) value >= n*2) return 0; /* If we have the privileges we will ignore the kernel limit. */ value = (int) n; if (setsockopt(fd, SOL_SOCKET, SO_SNDBUFFORCE, &value, sizeof(value)) < 0) if (setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &value, sizeof(value)) < 0) return -errno; return 1; } int fd_inc_rcvbuf(int fd, size_t n) { int r, value; socklen_t l = sizeof(value); r = getsockopt(fd, SOL_SOCKET, SO_RCVBUF, &value, &l); if (r >= 0 && l == sizeof(value) && (size_t) value >= n*2) return 0; /* If we have the privileges we will ignore the kernel limit. */ value = (int) n; if (setsockopt(fd, SOL_SOCKET, SO_RCVBUFFORCE, &value, sizeof(value)) < 0) if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &value, sizeof(value)) < 0) return -errno; return 1; } static const char* const ip_tos_table[] = { [IPTOS_LOWDELAY] = "low-delay", [IPTOS_THROUGHPUT] = "throughput", [IPTOS_RELIABILITY] = "reliability", [IPTOS_LOWCOST] = "low-cost", }; DEFINE_STRING_TABLE_LOOKUP_WITH_FALLBACK(ip_tos, int, 0xff); bool ifname_valid(const char *p) { bool numeric = true; /* Checks whether a network interface name is valid. This is inspired by dev_valid_name() in the kernel sources * but slightly stricter, as we only allow non-control, non-space ASCII characters in the interface name. We * also don't permit names that only container numbers, to avoid confusion with numeric interface indexes. */ if (isempty(p)) return false; if (strlen(p) >= IFNAMSIZ) return false; if (STR_IN_SET(p, ".", "..")) return false; while (*p) { if ((unsigned char) *p >= 127U) return false; if ((unsigned char) *p <= 32U) return false; if (*p == ':' || *p == '/') return false; numeric = numeric && (*p >= '0' && *p <= '9'); p++; } if (numeric) return false; return true; } int getpeercred(int fd, struct ucred *ucred) { socklen_t n = sizeof(struct ucred); struct ucred u; int r; assert(fd >= 0); assert(ucred); r = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &u, &n); if (r < 0) return -errno; if (n != sizeof(struct ucred)) return -EIO; /* Check if the data is actually useful and not suppressed due * to namespacing issues */ if (u.pid <= 0) return -ENODATA; if (u.uid == UID_INVALID) return -ENODATA; if (u.gid == GID_INVALID) return -ENODATA; *ucred = u; return 0; } int getpeersec(int fd, char **ret) { socklen_t n = 64; char *s; int r; assert(fd >= 0); assert(ret); s = new0(char, n); if (!s) return -ENOMEM; r = getsockopt(fd, SOL_SOCKET, SO_PEERSEC, s, &n); if (r < 0) { free(s); if (errno != ERANGE) return -errno; s = new0(char, n); if (!s) return -ENOMEM; r = getsockopt(fd, SOL_SOCKET, SO_PEERSEC, s, &n); if (r < 0) { free(s); return -errno; } } if (isempty(s)) { free(s); return -EOPNOTSUPP; } *ret = s; return 0; } int send_one_fd_sa( int transport_fd, int fd, const struct sockaddr *sa, socklen_t len, int flags) { union { struct cmsghdr cmsghdr; uint8_t buf[CMSG_SPACE(sizeof(int))]; } control = {}; struct msghdr mh = { .msg_name = (struct sockaddr*) sa, .msg_namelen = len, .msg_control = &control, .msg_controllen = sizeof(control), }; struct cmsghdr *cmsg; assert(transport_fd >= 0); assert(fd >= 0); cmsg = CMSG_FIRSTHDR(&mh); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_RIGHTS; cmsg->cmsg_len = CMSG_LEN(sizeof(int)); memcpy(CMSG_DATA(cmsg), &fd, sizeof(int)); mh.msg_controllen = CMSG_SPACE(sizeof(int)); if (sendmsg(transport_fd, &mh, MSG_NOSIGNAL | flags) < 0) return -errno; return 0; } int receive_one_fd(int transport_fd, int flags) { union { struct cmsghdr cmsghdr; uint8_t buf[CMSG_SPACE(sizeof(int))]; } control = {}; struct msghdr mh = { .msg_control = &control, .msg_controllen = sizeof(control), }; struct cmsghdr *cmsg, *found = NULL; assert(transport_fd >= 0); /* * Receive a single FD via @transport_fd. We don't care for * the transport-type. We retrieve a single FD at most, so for * packet-based transports, the caller must ensure to send * only a single FD per packet. This is best used in * combination with send_one_fd(). */ if (recvmsg(transport_fd, &mh, MSG_NOSIGNAL | MSG_CMSG_CLOEXEC | flags) < 0) return -errno; CMSG_FOREACH(cmsg, &mh) { if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS && cmsg->cmsg_len == CMSG_LEN(sizeof(int))) { assert(!found); found = cmsg; break; } } if (!found) { cmsg_close_all(&mh); return -EIO; } return *(int*) CMSG_DATA(found); } ssize_t next_datagram_size_fd(int fd) { ssize_t l; int k; /* This is a bit like FIONREAD/SIOCINQ, however a bit more powerful. The difference being: recv(MSG_PEEK) will * actually cause the next datagram in the queue to be validated regarding checksums, which FIONREAD doesn't * do. This difference is actually of major importance as we need to be sure that the size returned here * actually matches what we will read with recvmsg() next, as otherwise we might end up allocating a buffer of * the wrong size. */ l = recv(fd, NULL, 0, MSG_PEEK|MSG_TRUNC); if (l < 0) { if (errno == EOPNOTSUPP || errno == EFAULT) goto fallback; return -errno; } if (l == 0) goto fallback; return l; fallback: k = 0; /* Some sockets (AF_PACKET) do not support null-sized recv() with MSG_TRUNC set, let's fall back to FIONREAD * for them. Checksums don't matter for raw sockets anyway, hence this should be fine. */ if (ioctl(fd, FIONREAD, &k) < 0) return -errno; return (ssize_t) k; } int flush_accept(int fd) { struct pollfd pollfd = { .fd = fd, .events = POLLIN, }; int r; /* Similar to flush_fd() but flushes all incoming connection by accepting them and immediately closing them. */ for (;;) { int cfd; r = poll(&pollfd, 1, 0); if (r < 0) { if (errno == EINTR) continue; return -errno; } else if (r == 0) return 0; cfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC); if (cfd < 0) { if (errno == EINTR) continue; if (errno == EAGAIN) return 0; return -errno; } close(cfd); } }