common/socket.c - third_party/libusbmuxd - Git at Google

 /*
  * socket.c
  *
  * Copyright (C) 2012-2020 Nikias Bassen <nikias@gmx.li>
  * Copyright (C) 2012 Martin Szulecki <m.szulecki@libimobiledevice.org>
  *
  * This library 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.
  *
  * This library 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 this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */

 #ifdef HAVE_CONFIG_H
 #include <config.h>
 #endif
 #include <stdio.h>
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <errno.h>
 #include <sys/time.h>
 #include <sys/stat.h>
 #ifdef WIN32
 #include <winsock2.h>
 #include <ws2tcpip.h>
 #include <windows.h>
 static int wsa_init = 0;
 #else
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <netinet/in.h>
 #include <netinet/tcp.h>
 #include <netdb.h>
 #include <arpa/inet.h>
 #include <fcntl.h>
 #ifdef AF_INET6
 #include <net/if.h>
 #include <ifaddrs.h>
 #endif
 #endif
 #include "socket.h"

 #define RECV_TIMEOUT 20000
 #define CONNECT_TIMEOUT 5000

 #ifndef EAFNOSUPPORT
 #define EAFNOSUPPORT 102
 #endif
 #ifndef ECONNRESET
 #define ECONNRESET 108
 #endif
 #ifndef ETIMEDOUT
 #define ETIMEDOUT 138
 #endif

 static int verbose = 0;

 void socket_set_verbose(int level)
 {
 	verbose = level;
 }

 const char *socket_addr_to_string(struct sockaddr *addr, char *addr_out, size_t addr_out_size)
 {
 #ifdef WIN32
 	WSADATA wsa_data;
 	if (!wsa_init) {
 		if (WSAStartup(MAKEWORD(2,2), &wsa_data) != ERROR_SUCCESS) {
 			fprintf(stderr, "WSAStartup failed!\n");
 			ExitProcess(-1);
 		}
 		wsa_init = 1;
 	}
 	DWORD addr_out_len = addr_out_size;
 	DWORD addrlen = 0;

 	if (addr->sa_family == AF_INET) {
 		addrlen = sizeof(struct sockaddr_in);
 	}
 #ifdef AF_INET6
 	else if (addr->sa_family == AF_INET6) {
 		addrlen = sizeof(struct sockaddr_in6);
 	}
 #endif
 	else {
 		errno = EAFNOSUPPORT;
 		return NULL;
 	}

 	if (WSAAddressToString(addr, addrlen, NULL, addr_out, &addr_out_len) == 0) {
 		return addr_out;
 	}
 #else
 	const void *addrdata = NULL;

 	if (addr->sa_family == AF_INET) {
 		addrdata = &((struct sockaddr_in*)addr)->sin_addr;
 	}
 #ifdef AF_INET6
 	else if (addr->sa_family == AF_INET6) {
 		addrdata = &((struct sockaddr_in6*)addr)->sin6_addr;
 	}
 #endif
 	else {
 		errno = EAFNOSUPPORT;
 		return NULL;
 	}

 	if (inet_ntop(addr->sa_family, addrdata, addr_out, addr_out_size)) {
 		return addr_out;
 	}
 #endif
 	return NULL;
 }

 #ifndef WIN32
 int socket_create_unix(const char *filename)
 {
 	struct sockaddr_un name;
 	int sock;
 #ifdef SO_NOSIGPIPE
 	int yes = 1;
 #endif

 	// remove if still present
 	unlink(filename);

 	/* Create the socket. */
 	sock = socket(PF_UNIX, SOCK_STREAM, 0);
 	if (sock < 0) {
 		perror("socket");
 		return -1;
 	}

 #ifdef SO_NOSIGPIPE
 	if (setsockopt(sock, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
 		perror("setsockopt()");
 		socket_close(sock);
 		return -1;
 	}
 #endif

 	/* Bind a name to the socket. */
 	name.sun_family = AF_UNIX;
 	strncpy(name.sun_path, filename, sizeof(name.sun_path));
 	name.sun_path[sizeof(name.sun_path) - 1] = '\0';

 	if (bind(sock, (struct sockaddr*)&name, sizeof(name)) < 0) {
 		perror("bind");
 		socket_close(sock);
 		return -1;
 	}

 	if (listen(sock, 100) < 0) {
 		perror("listen");
 		socket_close(sock);
 		return -1;
 	}

 	return sock;
 }

 int socket_connect_unix(const char *filename)
 {
 	struct sockaddr_un name;
 	int sfd = -1;
 	struct stat fst;
 #ifdef SO_NOSIGPIPE
 	int yes = 1;
 #endif
 	int bufsize = 0x20000;

 	// check if socket file exists...
 	if (stat(filename, &fst) != 0) {
 		if (verbose >= 2)
 			fprintf(stderr, "%s: stat '%s': %s\n", __func__, filename,
 					strerror(errno));
 		return -1;
 	}
 	// ... and if it is a unix domain socket
 	if (!S_ISSOCK(fst.st_mode)) {
 		if (verbose >= 2)
 			fprintf(stderr, "%s: File '%s' is not a socket!\n", __func__,
 					filename);
 		return -1;
 	}
 	// make a new socket
 	if ((sfd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) {
 		if (verbose >= 2)
 			fprintf(stderr, "%s: socket: %s\n", __func__, strerror(errno));
 		return -1;
 	}

 	if (setsockopt(sfd, SOL_SOCKET, SO_SNDBUF, (void*)&bufsize, sizeof(int)) == -1) {
 		perror("Could not set send buffer for socket");
 	}

 	if (setsockopt(sfd, SOL_SOCKET, SO_RCVBUF, (void*)&bufsize, sizeof(int)) == -1) {
 		perror("Could not set receive buffer for socket");
 	}

 #ifdef SO_NOSIGPIPE
 	if (setsockopt(sfd, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
 		perror("setsockopt()");
 		socket_close(sfd);
 		return -1;
 	}
 #endif
 	// and connect to 'filename'
 	name.sun_family = AF_UNIX;
 	strncpy(name.sun_path, filename, sizeof(name.sun_path));
 	name.sun_path[sizeof(name.sun_path) - 1] = 0;

 	int flags = fcntl(sfd, F_GETFL, 0);
 	fcntl(sfd, F_SETFL, flags | O_NONBLOCK);

 	do {
 		if (connect(sfd, (struct sockaddr*)&name, sizeof(name)) != -1) {
 			break;
 		}
 		if (errno == EINPROGRESS) {
 			fd_set fds;
 			FD_ZERO(&fds);
 			FD_SET(sfd, &fds);

 			struct timeval timeout;
 			timeout.tv_sec = CONNECT_TIMEOUT / 1000;
 			timeout.tv_usec = (CONNECT_TIMEOUT - (timeout.tv_sec * 1000)) * 1000;
 			if (select(sfd + 1, NULL, &fds, NULL, &timeout) == 1) {
 				int so_error;
 				socklen_t len = sizeof(so_error);
 				getsockopt(sfd, SOL_SOCKET, SO_ERROR, (void*)&so_error, &len);
 				if (so_error == 0) {
 					break;
 				}
 			}
 		}
 		socket_close(sfd);
 		sfd = -1;
 	} while (0);

 	if (sfd < 0) {
 		if (verbose >= 2)
 			fprintf(stderr, "%s: connect: %s\n", __func__, strerror(errno));
 		return -1;
 	}

 	return sfd;
 }
 #endif

 int socket_create(const char* addr, uint16_t port)
 {
 	int sfd = -1;
 	int yes = 1;
 	struct addrinfo hints;
 	struct addrinfo *result, *rp;
 	char portstr[8];
 	int res;
 #ifdef WIN32
 	WSADATA wsa_data;
 	if (!wsa_init) {
 		if (WSAStartup(MAKEWORD(2,2), &wsa_data) != ERROR_SUCCESS) {
 			fprintf(stderr, "WSAStartup failed!\n");
 			ExitProcess(-1);
 		}
 		wsa_init = 1;
 	}
 #endif

 	memset(&hints, '\0', sizeof(struct addrinfo));
 	hints.ai_family = AF_UNSPEC;
 	hints.ai_socktype = SOCK_STREAM;
 	hints.ai_flags = AI_PASSIVE | AI_NUMERICSERV;
 	hints.ai_protocol = IPPROTO_TCP;

 	sprintf(portstr, "%d", port);

 	if (!addr) {
 		addr = "localhost";
 	}
 	res = getaddrinfo(addr, portstr, &hints, &result);
 	if (res != 0) {
 		fprintf(stderr, "%s: getaddrinfo: %s\n", __func__, gai_strerror(res));
 		return -1;
 	}

 	for (rp = result; rp != NULL; rp = rp->ai_next) {
 		sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
 		if (sfd == -1) {
 			continue;
 		}

 		if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (void*)&yes, sizeof(int)) == -1) {
 			perror("setsockopt()");
 			socket_close(sfd);
 			continue;
 		}

 #ifdef SO_NOSIGPIPE
 		if (setsockopt(sfd, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
 			perror("setsockopt()");
 			socket_close(sfd);
 			continue;
 		}
 #endif

 #if defined(AF_INET6) && defined(IPV6_V6ONLY)
 		if (rp->ai_family == AF_INET6) {
 			if (setsockopt(sfd, IPPROTO_IPV6, IPV6_V6ONLY, (void*)&yes, sizeof(int)) == -1) {
 				perror("setsockopt() IPV6_V6ONLY");
 			}
 		}
 #endif

 		if (bind(sfd, rp->ai_addr, rp->ai_addrlen) < 0) {
 			perror("bind()");
 			socket_close(sfd);
 			continue;
 		}

 		if (listen(sfd, 100) < 0) {
 			perror("listen()");
 			socket_close(sfd);
 			continue;
 		}
 		break;
 	}

 	freeaddrinfo(result);

 	if (rp == NULL) {
 		return -1;
 	}

 	return sfd;
 }

 #ifdef AF_INET6
 static uint32_t _in6_addr_scope(struct in6_addr* addr)
 {
 	uint32_t scope = 0;

 	if (IN6_IS_ADDR_MULTICAST(addr)) {
 		if (IN6_IS_ADDR_MC_NODELOCAL(addr)) {
 			scope = 1;
 		} else if (IN6_IS_ADDR_MC_LINKLOCAL(addr)) {
 			scope = 2;
 		} else if (IN6_IS_ADDR_MC_SITELOCAL(addr)) {
 			scope = 5;
 		}

 		return scope;
 	}

 	if (IN6_IS_ADDR_LINKLOCAL(addr)) {
 		scope = 2;
 	} else if (IN6_IS_ADDR_LOOPBACK(addr)) {
 		scope = 2;
 	} else if (IN6_IS_ADDR_SITELOCAL(addr)) {
 		scope = 5;
 	} else if (IN6_IS_ADDR_UNSPECIFIED(addr)) {
 		scope = 0;
 	}

 	return scope;
 }

 static int32_t _sockaddr_in6_scope_id(struct sockaddr_in6* addr)
 {
 	int32_t res = -1;
 	struct ifaddrs *ifaddr, *ifa;
 	uint32_t addr_scope;

 	/* get scope for requested address */
 	addr_scope = _in6_addr_scope(&addr->sin6_addr);
 	if (addr_scope == 0) {
 		/* global scope doesn't need a specific scope id */
 		return addr_scope;
 	}

 	/* get interfaces */
 	if (getifaddrs(&ifaddr) == -1) {
 		perror("getifaddrs");
 		return res;
 	}

 	/* loop over interfaces */
 	for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
 		/* skip if no address is available */
 		if (ifa->ifa_addr == NULL) {
 			continue;
 		}

 		/* skip if wrong family */
 		if (ifa->ifa_addr->sa_family != AF_INET6) {
 			continue;
 		}

 		/* skip if not up */
 		if ((ifa->ifa_flags & IFF_UP) == 0) {
 			continue;
 		}

 		/* skip if not running */
 		if ((ifa->ifa_flags & IFF_RUNNING) == 0) {
 			continue;
 		}

 		struct sockaddr_in6* addr_in = (struct sockaddr_in6*)ifa->ifa_addr;

 		/* skip if scopes do not match */
 		if (_in6_addr_scope(&addr_in->sin6_addr) != addr_scope) {
 			continue;
 		}

 		/* use if address is equal */
 		if (memcmp(&addr->sin6_addr.s6_addr, &addr_in->sin6_addr.s6_addr, sizeof(addr_in->sin6_addr.s6_addr)) == 0) {
 			/* if scope id equals the requested one then assume it was valid */
 			if (addr->sin6_scope_id == addr_in->sin6_scope_id) {
 				res = addr_in->sin6_scope_id;
 				break;
 			} else {
 				if ((addr_in->sin6_scope_id > addr->sin6_scope_id) && (res >= 0)) {
 					// use last valid scope id as we're past the requested scope id
 					break;
 				}
 				res = addr_in->sin6_scope_id;
 				continue;
 			}
 		}

 		/* skip loopback interface if not already matched exactly above */
 		if ((ifa->ifa_flags & IFF_LOOPBACK) != 0) {
 			continue;
 		}

 		if ((addr_in->sin6_scope_id > addr->sin6_scope_id) && (res >= 0)) {
 			// use last valid scope id as we're past the requested scope id
 			break;
 		}

 		res = addr_in->sin6_scope_id;

 		/* if scope id equals the requested one then assume it was valid */
 		if (addr->sin6_scope_id == addr_in->sin6_scope_id) {
 			/* set the scope id of this interface as most likely candidate */
 			break;
 		}
 	}

 	freeifaddrs(ifaddr);

 	return res;
 }
 #endif

 int socket_connect_addr(struct sockaddr* addr, uint16_t port)
 {
 	int sfd = -1;
 	int yes = 1;
 	int bufsize = 0x20000;
 	int addrlen = 0;
 #ifdef WIN32
 	u_long l_yes = 1;
 	WSADATA wsa_data;
 	if (!wsa_init) {
 		if (WSAStartup(MAKEWORD(2,2), &wsa_data) != ERROR_SUCCESS) {
 			fprintf(stderr, "WSAStartup failed!\n");
 			ExitProcess(-1);
 		}
 		wsa_init = 1;
 	}
 #endif

 	if (addr->sa_family == AF_INET) {
 		struct sockaddr_in* addr_in = (struct sockaddr_in*)addr;
 		addr_in->sin_port = htons(port);
 		addrlen = sizeof(struct sockaddr_in);
 	}
 #ifdef AF_INET6
 	else if (addr->sa_family == AF_INET6) {
 		struct sockaddr_in6* addr_in = (struct sockaddr_in6*)addr;
 		addr_in->sin6_port = htons(port);

 		/*
 		 * IPv6 Routing Magic:
 		 *
 		 * If the scope of the address is a link-local one, IPv6 requires the
 		 * scope id set to an interface number to allow proper routing. However,
 		 * as the provided sockaddr might contain a wrong scope id, we must find
 		 * a scope id from a suitable interface on this system or routing might
 		 * fail. An IPv6 guru should have another look though...
 		 */
 		addr_in->sin6_scope_id = _sockaddr_in6_scope_id(addr_in);

 		addrlen = sizeof(struct sockaddr_in6);
 	}
 #endif
 	else {
 		fprintf(stderr, "ERROR: Unsupported address family");
 		return -1;
 	}

 	sfd = socket(addr->sa_family, SOCK_STREAM, IPPROTO_TCP);
 	if (sfd == -1) {
 		perror("socket()");
 		return -1;
 	}

 #ifdef SO_NOSIGPIPE
 	if (setsockopt(sfd, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
 		perror("setsockopt()");
 		socket_close(sfd);
 		return -1;
 	}
 #endif

 	if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (void*)&yes, sizeof(int)) == -1) {
 		perror("setsockopt()");
 		socket_close(sfd);
 		return -1;
 	}

 #ifdef WIN32
 	ioctlsocket(sfd, FIONBIO, &l_yes);
 #else
 	int flags = fcntl(sfd, F_GETFL, 0);
 	fcntl(sfd, F_SETFL, flags | O_NONBLOCK);
 #endif

 	do {
 		if (connect(sfd, addr, addrlen) != -1) {
 			break;
 		}
 #ifdef WIN32
 		if (WSAGetLastError() == WSAEWOULDBLOCK)
 #else
 		if (errno == EINPROGRESS)
 #endif
 		{
 			fd_set fds;
 			FD_ZERO(&fds);
 			FD_SET(sfd, &fds);

 			struct timeval timeout;
 			timeout.tv_sec = CONNECT_TIMEOUT / 1000;
 			timeout.tv_usec = (CONNECT_TIMEOUT - (timeout.tv_sec * 1000)) * 1000;
 			if (select(sfd + 1, NULL, &fds, NULL, &timeout) == 1) {
 				int so_error;
 				socklen_t len = sizeof(so_error);
 				getsockopt(sfd, SOL_SOCKET, SO_ERROR, (void*)&so_error, &len);
 				if (so_error == 0) {
 					errno = 0;
 					break;
 				}
 				errno = so_error;
 			}
 		}
 		socket_close(sfd);
 		sfd = -1;
 	} while (0);

 	if (sfd < 0) {
 		if (verbose >= 2) {
 			char addrtxt[48];
 			socket_addr_to_string(addr, addrtxt, sizeof(addrtxt));
 			fprintf(stderr, "%s: Could not connect to %s port %d\n", __func__, addrtxt, port);
 		}
 		return -1;
 	}

 	if (setsockopt(sfd, IPPROTO_TCP, TCP_NODELAY, (void*)&yes, sizeof(int)) == -1) {
 		perror("Could not set TCP_NODELAY on socket");
 	}

 	if (setsockopt(sfd, SOL_SOCKET, SO_SNDBUF, (void*)&bufsize, sizeof(int)) == -1) {
 		perror("Could not set send buffer for socket");
 	}

 	if (setsockopt(sfd, SOL_SOCKET, SO_RCVBUF, (void*)&bufsize, sizeof(int)) == -1) {
 		perror("Could not set receive buffer for socket");
 	}

 	return sfd;
 }

 int socket_connect(const char *addr, uint16_t port)
 {
 	int sfd = -1;
 	int yes = 1;
 	int bufsize = 0x20000;
 	struct addrinfo hints;
 	struct addrinfo *result, *rp;
 	char portstr[8];
 	int res;
 #ifdef WIN32
 	u_long l_yes = 1;
 	WSADATA wsa_data;
 	if (!wsa_init) {
 		if (WSAStartup(MAKEWORD(2,2), &wsa_data) != ERROR_SUCCESS) {
 			fprintf(stderr, "WSAStartup failed!\n");
 			ExitProcess(-1);
 		}
 		wsa_init = 1;
 	}
 #else
 	int flags = 0;
 #endif

 	if (!addr) {
 		errno = EINVAL;
 		return -1;
 	}

 	memset(&hints, '\0', sizeof(struct addrinfo));
 	hints.ai_family = AF_UNSPEC;
 	hints.ai_socktype = SOCK_STREAM;
 	hints.ai_flags = AI_NUMERICSERV;
 	hints.ai_protocol = IPPROTO_TCP;

 	sprintf(portstr, "%d", port);

 	res = getaddrinfo(addr, portstr, &hints, &result);
 	if (res != 0) {
 		fprintf(stderr, "%s: getaddrinfo: %s\n", __func__, gai_strerror(res));
 		return -1;
 	}

 	for (rp = result; rp != NULL; rp = rp->ai_next) {
 		sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
 		if (sfd == -1) {
 			continue;
 		}

 #ifdef SO_NOSIGPIPE
 		if (setsockopt(sfd, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
 			perror("setsockopt()");
 			socket_close(sfd);
 			return -1;
 		}
 #endif

 		if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (void*)&yes, sizeof(int)) == -1) {
 			perror("setsockopt()");
 			socket_close(sfd);
 			continue;
 		}

 #ifdef WIN32
 		ioctlsocket(sfd, FIONBIO, &l_yes);
 #else
 		flags = fcntl(sfd, F_GETFL, 0);
 		fcntl(sfd, F_SETFL, flags | O_NONBLOCK);
 #endif

 		if (connect(sfd, rp->ai_addr, rp->ai_addrlen) != -1) {
 			break;
 		}
 #ifdef WIN32
 		if (WSAGetLastError() == WSAEWOULDBLOCK)
 #else
 		if (errno == EINPROGRESS)
 #endif
 		{
 			fd_set fds;
 			FD_ZERO(&fds);
 			FD_SET(sfd, &fds);

 			struct timeval timeout;
 			timeout.tv_sec = CONNECT_TIMEOUT / 1000;
 			timeout.tv_usec = (CONNECT_TIMEOUT - (timeout.tv_sec * 1000)) * 1000;
 			if (select(sfd + 1, NULL, &fds, NULL, &timeout) == 1) {
 				int so_error;
 				socklen_t len = sizeof(so_error);
 				getsockopt(sfd, SOL_SOCKET, SO_ERROR, (void*)&so_error, &len);
 				if (so_error == 0) {
 					break;
 				}
 			}
 		}
 		socket_close(sfd);
 	}

 	freeaddrinfo(result);

 	if (rp == NULL) {
 		if (verbose >= 2)
 			fprintf(stderr, "%s: Could not connect to %s:%d\n", __func__, addr, port);
 		return -1;
 	}

 	if (setsockopt(sfd, IPPROTO_TCP, TCP_NODELAY, (void*)&yes, sizeof(int)) == -1) {
 		perror("Could not set TCP_NODELAY on socket");
 	}

 	if (setsockopt(sfd, SOL_SOCKET, SO_SNDBUF, (void*)&bufsize, sizeof(int)) == -1) {
 		perror("Could not set send buffer for socket");
 	}

 	if (setsockopt(sfd, SOL_SOCKET, SO_RCVBUF, (void*)&bufsize, sizeof(int)) == -1) {
 		perror("Could not set receive buffer for socket");
 	}

 	return sfd;
 }

 int socket_check_fd(int fd, fd_mode fdm, unsigned int timeout)
 {
 	fd_set fds;
 	int sret;
 	int eagain;
 	struct timeval to;
 	struct timeval *pto;

 	if (fd < 0) {
 		if (verbose >= 2)
 			fprintf(stderr, "ERROR: invalid fd in check_fd %d\n", fd);
 		return -1;
 	}

 	FD_ZERO(&fds);
 	FD_SET(fd, &fds);

 	sret = -1;

 	do {
 		if (timeout > 0) {
 			to.tv_sec = (time_t) (timeout / 1000);
 			to.tv_usec = (time_t) ((timeout - (to.tv_sec * 1000)) * 1000);
 			pto = &to;
 		} else {
 			pto = NULL;
 		}
 		eagain = 0;
 		switch (fdm) {
 		case FDM_READ:
 			sret = select(fd + 1, &fds, NULL, NULL, pto);
 			break;
 		case FDM_WRITE:
 			sret = select(fd + 1, NULL, &fds, NULL, pto);
 			break;
 		case FDM_EXCEPT:
 			sret = select(fd + 1, NULL, NULL, &fds, pto);
 			break;
 		default:
 			return -1;
 		}

 		if (sret < 0) {
 			switch (errno) {
 			case EINTR:
 				// interrupt signal in select
 				if (verbose >= 2)
 					fprintf(stderr, "%s: EINTR\n", __func__);
 				eagain = 1;
 				break;
 			case EAGAIN:
 				if (verbose >= 2)
 					fprintf(stderr, "%s: EAGAIN\n", __func__);
 				break;
 			default:
 				if (verbose >= 2)
 					fprintf(stderr, "%s: select failed: %s\n", __func__,
 							strerror(errno));
 				return -1;
 			}
 		} else if (sret == 0) {
 			if (verbose >= 2)
 				fprintf(stderr, "%s: timeout\n", __func__);
 			return -ETIMEDOUT;
 		}
 	} while (eagain);

 	return sret;
 }

 int socket_accept(int fd, uint16_t port)
 {
 #ifdef WIN32
 	int addr_len;
 #else
 	socklen_t addr_len;
 #endif
 	int result;
 	struct sockaddr_storage addr;
 	addr_len = sizeof(addr);

 	result = accept(fd, (struct sockaddr*)&addr, &addr_len);

 	return result;
 }

 int socket_shutdown(int fd, int how)
 {
 	return shutdown(fd, how);
 }

 int socket_close(int fd) {
 #ifdef WIN32
 	return closesocket(fd);
 #else
 	return close(fd);
 #endif
 }

 int socket_receive(int fd, void *data, size_t length)
 {
 	return socket_receive_timeout(fd, data, length, 0, RECV_TIMEOUT);
 }

 int socket_peek(int fd, void *data, size_t length)
 {
 	return socket_receive_timeout(fd, data, length, MSG_PEEK, RECV_TIMEOUT);
 }

 int socket_receive_timeout(int fd, void *data, size_t length, int flags,
 					 unsigned int timeout)
 {
 	int res;
 	int result;

 	// check if data is available
 	res = socket_check_fd(fd, FDM_READ, timeout);
 	if (res <= 0) {
 		return res;
 	}
 	// if we get here, there _is_ data available
 	result = recv(fd, data, length, flags);
 	if (res > 0 && result == 0) {
 		// but this is an error condition
 		if (verbose >= 3)
 			fprintf(stderr, "%s: fd=%d recv returned 0\n", __func__, fd);
 		return -ECONNRESET;
 	}
 	if (result < 0) {
 		return -errno;
 	}
 	return result;
 }

 int socket_send(int fd, void *data, size_t length)
 {
 	int flags = 0;
 	int res = socket_check_fd(fd, FDM_WRITE, 1000);
 	if (res <= 0) {
 		return res;
 	}
 #ifdef MSG_NOSIGNAL
 	flags |= MSG_NOSIGNAL;
 #endif
 	return send(fd, data, length, flags);
 }
	/*
	* socket.c
	*
	* Copyright (C) 2012-2020 Nikias Bassen <nikias@gmx.li>
	* Copyright (C) 2012 Martin Szulecki <m.szulecki@libimobiledevice.org>
	*
	* This library 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.
	*
	* This library 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 this library; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	#ifdef HAVE_CONFIG_H
	#include <config.h>
	#endif
	#include <stdio.h>
	#include <stddef.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>
	#include <errno.h>
	#include <sys/time.h>
	#include <sys/stat.h>
	#ifdef WIN32
	#include <winsock2.h>
	#include <ws2tcpip.h>
	#include <windows.h>
	static int wsa_init = 0;
	#else
	#include <sys/socket.h>
	#include <sys/un.h>
	#include <netinet/in.h>
	#include <netinet/tcp.h>
	#include <netdb.h>
	#include <arpa/inet.h>
	#include <fcntl.h>
	#ifdef AF_INET6
	#include <net/if.h>
	#include <ifaddrs.h>
	#endif
	#endif
	#include "socket.h"

	#define RECV_TIMEOUT 20000
	#define CONNECT_TIMEOUT 5000

	#ifndef EAFNOSUPPORT
	#define EAFNOSUPPORT 102
	#endif
	#ifndef ECONNRESET
	#define ECONNRESET 108
	#endif
	#ifndef ETIMEDOUT
	#define ETIMEDOUT 138
	#endif

	static int verbose = 0;

	void socket_set_verbose(int level)
	{
	verbose = level;
	}

	const char socket_addr_to_string(struct sockaddr addr, char *addr_out, size_t addr_out_size)
	{
	#ifdef WIN32
	WSADATA wsa_data;
	if (!wsa_init) {
	if (WSAStartup(MAKEWORD(2,2), &wsa_data) != ERROR_SUCCESS) {
	fprintf(stderr, "WSAStartup failed!\n");
	ExitProcess(-1);
	}
	wsa_init = 1;
	}
	DWORD addr_out_len = addr_out_size;
	DWORD addrlen = 0;

	if (addr->sa_family == AF_INET) {
	addrlen = sizeof(struct sockaddr_in);
	}
	#ifdef AF_INET6
	else if (addr->sa_family == AF_INET6) {
	addrlen = sizeof(struct sockaddr_in6);
	}
	#endif
	else {
	errno = EAFNOSUPPORT;
	return NULL;
	}

	if (WSAAddressToString(addr, addrlen, NULL, addr_out, &addr_out_len) == 0) {
	return addr_out;
	}
	#else
	const void *addrdata = NULL;

	if (addr->sa_family == AF_INET) {
	addrdata = &((struct sockaddr_in*)addr)->sin_addr;
	}
	#ifdef AF_INET6
	else if (addr->sa_family == AF_INET6) {
	addrdata = &((struct sockaddr_in6*)addr)->sin6_addr;
	}
	#endif
	else {
	errno = EAFNOSUPPORT;
	return NULL;
	}

	if (inet_ntop(addr->sa_family, addrdata, addr_out, addr_out_size)) {
	return addr_out;
	}
	#endif
	return NULL;
	}

	#ifndef WIN32
	int socket_create_unix(const char *filename)
	{
	struct sockaddr_un name;
	int sock;
	#ifdef SO_NOSIGPIPE
	int yes = 1;
	#endif

	// remove if still present
	unlink(filename);

	/* Create the socket. */
	sock = socket(PF_UNIX, SOCK_STREAM, 0);
	if (sock < 0) {
	perror("socket");
	return -1;
	}

	#ifdef SO_NOSIGPIPE
	if (setsockopt(sock, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
	perror("setsockopt()");
	socket_close(sock);
	return -1;
	}
	#endif

	/* Bind a name to the socket. */
	name.sun_family = AF_UNIX;
	strncpy(name.sun_path, filename, sizeof(name.sun_path));
	name.sun_path[sizeof(name.sun_path) - 1] = '\0';

	if (bind(sock, (struct sockaddr*)&name, sizeof(name)) < 0) {
	perror("bind");
	socket_close(sock);
	return -1;
	}

	if (listen(sock, 100) < 0) {
	perror("listen");
	socket_close(sock);
	return -1;
	}

	return sock;
	}

	int socket_connect_unix(const char *filename)
	{
	struct sockaddr_un name;
	int sfd = -1;
	struct stat fst;
	#ifdef SO_NOSIGPIPE
	int yes = 1;
	#endif
	int bufsize = 0x20000;

	// check if socket file exists...
	if (stat(filename, &fst) != 0) {
	if (verbose >= 2)
	fprintf(stderr, "%s: stat '%s': %s\n", __func__, filename,
	strerror(errno));
	return -1;
	}
	// ... and if it is a unix domain socket
	if (!S_ISSOCK(fst.st_mode)) {
	if (verbose >= 2)
	fprintf(stderr, "%s: File '%s' is not a socket!\n", __func__,
	filename);
	return -1;
	}
	// make a new socket
	if ((sfd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) {
	if (verbose >= 2)
	fprintf(stderr, "%s: socket: %s\n", __func__, strerror(errno));
	return -1;
	}

	if (setsockopt(sfd, SOL_SOCKET, SO_SNDBUF, (void*)&bufsize, sizeof(int)) == -1) {
	perror("Could not set send buffer for socket");
	}

	if (setsockopt(sfd, SOL_SOCKET, SO_RCVBUF, (void*)&bufsize, sizeof(int)) == -1) {
	perror("Could not set receive buffer for socket");
	}

	#ifdef SO_NOSIGPIPE
	if (setsockopt(sfd, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
	perror("setsockopt()");
	socket_close(sfd);
	return -1;
	}
	#endif
	// and connect to 'filename'
	name.sun_family = AF_UNIX;
	strncpy(name.sun_path, filename, sizeof(name.sun_path));
	name.sun_path[sizeof(name.sun_path) - 1] = 0;

	int flags = fcntl(sfd, F_GETFL, 0);
	fcntl(sfd, F_SETFL, flags \| O_NONBLOCK);

	do {
	if (connect(sfd, (struct sockaddr*)&name, sizeof(name)) != -1) {
	break;
	}
	if (errno == EINPROGRESS) {
	fd_set fds;
	FD_ZERO(&fds);
	FD_SET(sfd, &fds);

	struct timeval timeout;
	timeout.tv_sec = CONNECT_TIMEOUT / 1000;
	timeout.tv_usec = (CONNECT_TIMEOUT - (timeout.tv_sec * 1000)) * 1000;
	if (select(sfd + 1, NULL, &fds, NULL, &timeout) == 1) {
	int so_error;
	socklen_t len = sizeof(so_error);
	getsockopt(sfd, SOL_SOCKET, SO_ERROR, (void*)&so_error, &len);
	if (so_error == 0) {
	break;
	}
	}
	}
	socket_close(sfd);
	sfd = -1;
	} while (0);

	if (sfd < 0) {
	if (verbose >= 2)
	fprintf(stderr, "%s: connect: %s\n", __func__, strerror(errno));
	return -1;
	}

	return sfd;
	}
	#endif

	int socket_create(const char* addr, uint16_t port)
	{
	int sfd = -1;
	int yes = 1;
	struct addrinfo hints;
	struct addrinfo result, rp;
	char portstr[8];
	int res;
	#ifdef WIN32
	WSADATA wsa_data;
	if (!wsa_init) {
	if (WSAStartup(MAKEWORD(2,2), &wsa_data) != ERROR_SUCCESS) {
	fprintf(stderr, "WSAStartup failed!\n");
	ExitProcess(-1);
	}
	wsa_init = 1;
	}
	#endif

	memset(&hints, '\0', sizeof(struct addrinfo));
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_flags = AI_PASSIVE \| AI_NUMERICSERV;
	hints.ai_protocol = IPPROTO_TCP;

	sprintf(portstr, "%d", port);

	if (!addr) {
	addr = "localhost";
	}
	res = getaddrinfo(addr, portstr, &hints, &result);
	if (res != 0) {
	fprintf(stderr, "%s: getaddrinfo: %s\n", __func__, gai_strerror(res));
	return -1;
	}

	for (rp = result; rp != NULL; rp = rp->ai_next) {
	sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
	if (sfd == -1) {
	continue;
	}

	if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (void*)&yes, sizeof(int)) == -1) {
	perror("setsockopt()");
	socket_close(sfd);
	continue;
	}

	#ifdef SO_NOSIGPIPE
	if (setsockopt(sfd, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
	perror("setsockopt()");
	socket_close(sfd);
	continue;
	}
	#endif

	#if defined(AF_INET6) && defined(IPV6_V6ONLY)
	if (rp->ai_family == AF_INET6) {
	if (setsockopt(sfd, IPPROTO_IPV6, IPV6_V6ONLY, (void*)&yes, sizeof(int)) == -1) {
	perror("setsockopt() IPV6_V6ONLY");
	}
	}
	#endif

	if (bind(sfd, rp->ai_addr, rp->ai_addrlen) < 0) {
	perror("bind()");
	socket_close(sfd);
	continue;
	}

	if (listen(sfd, 100) < 0) {
	perror("listen()");
	socket_close(sfd);
	continue;
	}
	break;
	}

	freeaddrinfo(result);

	if (rp == NULL) {
	return -1;
	}

	return sfd;
	}

	#ifdef AF_INET6
	static uint32_t _in6_addr_scope(struct in6_addr* addr)
	{
	uint32_t scope = 0;

	if (IN6_IS_ADDR_MULTICAST(addr)) {
	if (IN6_IS_ADDR_MC_NODELOCAL(addr)) {
	scope = 1;
	} else if (IN6_IS_ADDR_MC_LINKLOCAL(addr)) {
	scope = 2;
	} else if (IN6_IS_ADDR_MC_SITELOCAL(addr)) {
	scope = 5;
	}

	return scope;
	}

	if (IN6_IS_ADDR_LINKLOCAL(addr)) {
	scope = 2;
	} else if (IN6_IS_ADDR_LOOPBACK(addr)) {
	scope = 2;
	} else if (IN6_IS_ADDR_SITELOCAL(addr)) {
	scope = 5;
	} else if (IN6_IS_ADDR_UNSPECIFIED(addr)) {
	scope = 0;
	}

	return scope;
	}

	static int32_t _sockaddr_in6_scope_id(struct sockaddr_in6* addr)
	{
	int32_t res = -1;
	struct ifaddrs ifaddr, ifa;
	uint32_t addr_scope;

	/* get scope for requested address */
	addr_scope = _in6_addr_scope(&addr->sin6_addr);
	if (addr_scope == 0) {
	/* global scope doesn't need a specific scope id */
	return addr_scope;
	}

	/* get interfaces */
	if (getifaddrs(&ifaddr) == -1) {
	perror("getifaddrs");
	return res;
	}

	/* loop over interfaces */
	for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
	/* skip if no address is available */
	if (ifa->ifa_addr == NULL) {
	continue;
	}

	/* skip if wrong family */
	if (ifa->ifa_addr->sa_family != AF_INET6) {
	continue;
	}

	/* skip if not up */
	if ((ifa->ifa_flags & IFF_UP) == 0) {
	continue;
	}

	/* skip if not running */
	if ((ifa->ifa_flags & IFF_RUNNING) == 0) {
	continue;
	}

	struct sockaddr_in6* addr_in = (struct sockaddr_in6*)ifa->ifa_addr;

	/* skip if scopes do not match */
	if (_in6_addr_scope(&addr_in->sin6_addr) != addr_scope) {
	continue;
	}

	/* use if address is equal */
	if (memcmp(&addr->sin6_addr.s6_addr, &addr_in->sin6_addr.s6_addr, sizeof(addr_in->sin6_addr.s6_addr)) == 0) {
	/* if scope id equals the requested one then assume it was valid */
	if (addr->sin6_scope_id == addr_in->sin6_scope_id) {
	res = addr_in->sin6_scope_id;
	break;
	} else {
	if ((addr_in->sin6_scope_id > addr->sin6_scope_id) && (res >= 0)) {
	// use last valid scope id as we're past the requested scope id
	break;
	}
	res = addr_in->sin6_scope_id;
	continue;
	}
	}

	/* skip loopback interface if not already matched exactly above */
	if ((ifa->ifa_flags & IFF_LOOPBACK) != 0) {
	continue;
	}

	if ((addr_in->sin6_scope_id > addr->sin6_scope_id) && (res >= 0)) {
	// use last valid scope id as we're past the requested scope id
	break;
	}

	res = addr_in->sin6_scope_id;

	/* if scope id equals the requested one then assume it was valid */
	if (addr->sin6_scope_id == addr_in->sin6_scope_id) {
	/* set the scope id of this interface as most likely candidate */
	break;
	}
	}

	freeifaddrs(ifaddr);

	return res;
	}
	#endif

	int socket_connect_addr(struct sockaddr* addr, uint16_t port)
	{
	int sfd = -1;
	int yes = 1;
	int bufsize = 0x20000;
	int addrlen = 0;
	#ifdef WIN32
	u_long l_yes = 1;
	WSADATA wsa_data;
	if (!wsa_init) {
	if (WSAStartup(MAKEWORD(2,2), &wsa_data) != ERROR_SUCCESS) {
	fprintf(stderr, "WSAStartup failed!\n");
	ExitProcess(-1);
	}
	wsa_init = 1;
	}
	#endif

	if (addr->sa_family == AF_INET) {
	struct sockaddr_in* addr_in = (struct sockaddr_in*)addr;
	addr_in->sin_port = htons(port);
	addrlen = sizeof(struct sockaddr_in);
	}
	#ifdef AF_INET6
	else if (addr->sa_family == AF_INET6) {
	struct sockaddr_in6* addr_in = (struct sockaddr_in6*)addr;
	addr_in->sin6_port = htons(port);

	/*
	* IPv6 Routing Magic:
	*
	* If the scope of the address is a link-local one, IPv6 requires the
	* scope id set to an interface number to allow proper routing. However,
	* as the provided sockaddr might contain a wrong scope id, we must find
	* a scope id from a suitable interface on this system or routing might
	* fail. An IPv6 guru should have another look though...
	*/
	addr_in->sin6_scope_id = _sockaddr_in6_scope_id(addr_in);

	addrlen = sizeof(struct sockaddr_in6);
	}
	#endif
	else {
	fprintf(stderr, "ERROR: Unsupported address family");
	return -1;
	}

	sfd = socket(addr->sa_family, SOCK_STREAM, IPPROTO_TCP);
	if (sfd == -1) {
	perror("socket()");
	return -1;
	}

	#ifdef SO_NOSIGPIPE
	if (setsockopt(sfd, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
	perror("setsockopt()");
	socket_close(sfd);
	return -1;
	}
	#endif

	if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (void*)&yes, sizeof(int)) == -1) {
	perror("setsockopt()");
	socket_close(sfd);
	return -1;
	}

	#ifdef WIN32
	ioctlsocket(sfd, FIONBIO, &l_yes);
	#else
	int flags = fcntl(sfd, F_GETFL, 0);
	fcntl(sfd, F_SETFL, flags \| O_NONBLOCK);
	#endif

	do {
	if (connect(sfd, addr, addrlen) != -1) {
	break;
	}
	#ifdef WIN32
	if (WSAGetLastError() == WSAEWOULDBLOCK)
	#else
	if (errno == EINPROGRESS)
	#endif
	{
	fd_set fds;
	FD_ZERO(&fds);
	FD_SET(sfd, &fds);

	struct timeval timeout;
	timeout.tv_sec = CONNECT_TIMEOUT / 1000;
	timeout.tv_usec = (CONNECT_TIMEOUT - (timeout.tv_sec * 1000)) * 1000;
	if (select(sfd + 1, NULL, &fds, NULL, &timeout) == 1) {
	int so_error;
	socklen_t len = sizeof(so_error);
	getsockopt(sfd, SOL_SOCKET, SO_ERROR, (void*)&so_error, &len);
	if (so_error == 0) {
	errno = 0;
	break;
	}
	errno = so_error;
	}
	}
	socket_close(sfd);
	sfd = -1;
	} while (0);

	if (sfd < 0) {
	if (verbose >= 2) {
	char addrtxt[48];
	socket_addr_to_string(addr, addrtxt, sizeof(addrtxt));
	fprintf(stderr, "%s: Could not connect to %s port %d\n", __func__, addrtxt, port);
	}
	return -1;
	}

	if (setsockopt(sfd, IPPROTO_TCP, TCP_NODELAY, (void*)&yes, sizeof(int)) == -1) {
	perror("Could not set TCP_NODELAY on socket");
	}

	if (setsockopt(sfd, SOL_SOCKET, SO_SNDBUF, (void*)&bufsize, sizeof(int)) == -1) {
	perror("Could not set send buffer for socket");
	}

	if (setsockopt(sfd, SOL_SOCKET, SO_RCVBUF, (void*)&bufsize, sizeof(int)) == -1) {
	perror("Could not set receive buffer for socket");
	}

	return sfd;
	}

	int socket_connect(const char *addr, uint16_t port)
	{
	int sfd = -1;
	int yes = 1;
	int bufsize = 0x20000;
	struct addrinfo hints;
	struct addrinfo result, rp;
	char portstr[8];
	int res;
	#ifdef WIN32
	u_long l_yes = 1;
	WSADATA wsa_data;
	if (!wsa_init) {
	if (WSAStartup(MAKEWORD(2,2), &wsa_data) != ERROR_SUCCESS) {
	fprintf(stderr, "WSAStartup failed!\n");
	ExitProcess(-1);
	}
	wsa_init = 1;
	}
	#else
	int flags = 0;
	#endif

	if (!addr) {
	errno = EINVAL;
	return -1;
	}

	memset(&hints, '\0', sizeof(struct addrinfo));
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_flags = AI_NUMERICSERV;
	hints.ai_protocol = IPPROTO_TCP;

	sprintf(portstr, "%d", port);

	res = getaddrinfo(addr, portstr, &hints, &result);
	if (res != 0) {
	fprintf(stderr, "%s: getaddrinfo: %s\n", __func__, gai_strerror(res));
	return -1;
	}

	for (rp = result; rp != NULL; rp = rp->ai_next) {
	sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
	if (sfd == -1) {
	continue;
	}

	#ifdef SO_NOSIGPIPE
	if (setsockopt(sfd, SOL_SOCKET, SO_NOSIGPIPE, (void*)&yes, sizeof(int)) == -1) {
	perror("setsockopt()");
	socket_close(sfd);
	return -1;
	}
	#endif

	if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (void*)&yes, sizeof(int)) == -1) {
	perror("setsockopt()");
	socket_close(sfd);
	continue;
	}

	#ifdef WIN32
	ioctlsocket(sfd, FIONBIO, &l_yes);
	#else
	flags = fcntl(sfd, F_GETFL, 0);
	fcntl(sfd, F_SETFL, flags \| O_NONBLOCK);
	#endif

	if (connect(sfd, rp->ai_addr, rp->ai_addrlen) != -1) {
	break;
	}
	#ifdef WIN32
	if (WSAGetLastError() == WSAEWOULDBLOCK)
	#else
	if (errno == EINPROGRESS)
	#endif
	{
	fd_set fds;
	FD_ZERO(&fds);
	FD_SET(sfd, &fds);

	struct timeval timeout;
	timeout.tv_sec = CONNECT_TIMEOUT / 1000;
	timeout.tv_usec = (CONNECT_TIMEOUT - (timeout.tv_sec * 1000)) * 1000;
	if (select(sfd + 1, NULL, &fds, NULL, &timeout) == 1) {
	int so_error;
	socklen_t len = sizeof(so_error);
	getsockopt(sfd, SOL_SOCKET, SO_ERROR, (void*)&so_error, &len);
	if (so_error == 0) {
	break;
	}
	}
	}
	socket_close(sfd);
	}

	freeaddrinfo(result);

	if (rp == NULL) {
	if (verbose >= 2)
	fprintf(stderr, "%s: Could not connect to %s:%d\n", __func__, addr, port);
	return -1;
	}

	if (setsockopt(sfd, IPPROTO_TCP, TCP_NODELAY, (void*)&yes, sizeof(int)) == -1) {
	perror("Could not set TCP_NODELAY on socket");
	}

	if (setsockopt(sfd, SOL_SOCKET, SO_SNDBUF, (void*)&bufsize, sizeof(int)) == -1) {
	perror("Could not set send buffer for socket");
	}

	if (setsockopt(sfd, SOL_SOCKET, SO_RCVBUF, (void*)&bufsize, sizeof(int)) == -1) {
	perror("Could not set receive buffer for socket");
	}

	return sfd;
	}

	int socket_check_fd(int fd, fd_mode fdm, unsigned int timeout)
	{
	fd_set fds;
	int sret;
	int eagain;
	struct timeval to;
	struct timeval *pto;

	if (fd < 0) {
	if (verbose >= 2)
	fprintf(stderr, "ERROR: invalid fd in check_fd %d\n", fd);
	return -1;
	}

	FD_ZERO(&fds);
	FD_SET(fd, &fds);

	sret = -1;

	do {
	if (timeout > 0) {
	to.tv_sec = (time_t) (timeout / 1000);
	to.tv_usec = (time_t) ((timeout - (to.tv_sec * 1000)) * 1000);
	pto = &to;
	} else {
	pto = NULL;
	}
	eagain = 0;
	switch (fdm) {
	case FDM_READ:
	sret = select(fd + 1, &fds, NULL, NULL, pto);
	break;
	case FDM_WRITE:
	sret = select(fd + 1, NULL, &fds, NULL, pto);
	break;
	case FDM_EXCEPT:
	sret = select(fd + 1, NULL, NULL, &fds, pto);
	break;
	default:
	return -1;
	}

	if (sret < 0) {
	switch (errno) {
	case EINTR:
	// interrupt signal in select
	if (verbose >= 2)
	fprintf(stderr, "%s: EINTR\n", __func__);
	eagain = 1;
	break;
	case EAGAIN:
	if (verbose >= 2)
	fprintf(stderr, "%s: EAGAIN\n", __func__);
	break;
	default:
	if (verbose >= 2)
	fprintf(stderr, "%s: select failed: %s\n", __func__,
	strerror(errno));
	return -1;
	}
	} else if (sret == 0) {
	if (verbose >= 2)
	fprintf(stderr, "%s: timeout\n", __func__);
	return -ETIMEDOUT;
	}
	} while (eagain);

	return sret;
	}

	int socket_accept(int fd, uint16_t port)
	{
	#ifdef WIN32
	int addr_len;
	#else
	socklen_t addr_len;
	#endif
	int result;
	struct sockaddr_storage addr;
	addr_len = sizeof(addr);

	result = accept(fd, (struct sockaddr*)&addr, &addr_len);

	return result;
	}

	int socket_shutdown(int fd, int how)
	{
	return shutdown(fd, how);
	}

	int socket_close(int fd) {
	#ifdef WIN32
	return closesocket(fd);
	#else
	return close(fd);
	#endif
	}

	int socket_receive(int fd, void *data, size_t length)
	{
	return socket_receive_timeout(fd, data, length, 0, RECV_TIMEOUT);
	}

	int socket_peek(int fd, void *data, size_t length)
	{
	return socket_receive_timeout(fd, data, length, MSG_PEEK, RECV_TIMEOUT);
	}

	int socket_receive_timeout(int fd, void *data, size_t length, int flags,
	unsigned int timeout)
	{
	int res;
	int result;

	// check if data is available
	res = socket_check_fd(fd, FDM_READ, timeout);
	if (res <= 0) {
	return res;
	}
	// if we get here, there _is_ data available
	result = recv(fd, data, length, flags);
	if (res > 0 && result == 0) {
	// but this is an error condition
	if (verbose >= 3)
	fprintf(stderr, "%s: fd=%d recv returned 0\n", __func__, fd);
	return -ECONNRESET;
	}
	if (result < 0) {
	return -errno;
	}
	return result;
	}

	int socket_send(int fd, void *data, size_t length)
	{
	int flags = 0;
	int res = socket_check_fd(fd, FDM_WRITE, 1000);
	if (res <= 0) {
	return res;
	}
	#ifdef MSG_NOSIGNAL
	flags \|= MSG_NOSIGNAL;
	#endif
	return send(fd, data, length, flags);
	}