diff options
Diffstat (limited to 'src/libbasic/socket-util.c')
| -rw-r--r-- | src/libbasic/socket-util.c | 972 |
1 files changed, 972 insertions, 0 deletions
diff --git a/src/libbasic/socket-util.c b/src/libbasic/socket-util.c new file mode 100644 index 0000000000..58512686e3 --- /dev/null +++ b/src/libbasic/socket-util.c @@ -0,0 +1,972 @@ +/*** + 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 <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 "user-util.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 = htons((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 = htons((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 = htons((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 = htons((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 = htons((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 ntohs(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 = ntohl(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, + ntohs(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], + ntohs(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, + ntohs(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); + +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 dosn'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) + 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; +} |