server.c - net/sshout-daemon - Rivoreo Source Code Repositories

 /* Secure Shout Host Oriented Unified Talk
  * Copyright 2015-2018 Rivoreo
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
  * Free Software Foundation, either version 3 of the License, or (at your
  * option) any later version.
  *
  * This program 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 General Public License for
  * more details.
  */

 #if defined __sun && defined __SVR4
 #define HAVE_GETPEERUCRED
 #endif

 #define _GNU_SOURCE
 #include "common.h"
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include "syncrw.h"
 #include <syslog.h>
 #include <string.h>
 #include <stdlib.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <errno.h>
 #include "file-helpers.h"
 #include <signal.h>
 #ifdef HAVE_UPDWTMPX
 #include <utmpx.h>
 #ifdef HAVE_GETPEERUCRED
 #include <ucred.h>
 #endif
 #endif

 static struct local_online_user online_users[FD_SETSIZE];

 static void syslog_perror(const char *ident) {
 	int e = errno;
 	syslog(LOG_ERR, "%s: %s (%d)", ident, strerror(e), e);
 }

 static void broadcast_user_state(const char *user_name, int on, const int *client_fds) {
 	unsigned int i = 0;
 	size_t packet_len = sizeof(struct local_packet) + USER_NAME_MAX_LENGTH;
 	struct local_packet *packet = malloc(packet_len);
 	if(!packet) {
 		syslog(LOG_ERR, "broadcast_user_state: out of memory");
 		return;
 	}
 	packet->length = packet_len - sizeof packet->length;
 	packet->type = on ? SSHOUT_LOCAL_USER_ONLINE : SSHOUT_LOCAL_USER_OFFLINE;
 	strncpy(packet->data, user_name, USER_NAME_MAX_LENGTH);
 	do {
 		if(online_users[i].id == -1) continue;
 		while(write(client_fds[online_users[i].id], packet, packet_len) < 0) {
 			if(errno == EINTR) continue;
 			syslog_perror("broadcast_user_state: write");
 			break;
 		}
 	} while(++i < sizeof online_users / sizeof *online_users);
 	free(packet);
 }

 #ifdef HAVE_UPDWTMPX
 static pid_t get_pid_from_unix_socket(int fd) {
 #ifdef SO_PEERCRED
 	struct ucred ucred;
 	socklen_t len = sizeof ucred;
 	if(getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &len) < 0) return -1;
 	return ucred.pid;
 #elif defined HAVE_GETPEERUCRED
 	ucred_t *ucred = NULL;
 	if(getpeerucred(fd, &ucred) < 0) return -1;
 	pid_t r = ucred_getpid(ucred);
 	ucred_free(ucred);
 	return r;
 #else
 	return -1;
 #endif
 }
 #endif

 static int user_online(int id, const char *user_name, const char *host_name, int *index, const int *client_fds) {
 	int found_dup = 0;
 	unsigned int i = 0;
 	while(online_users[i].id != -1) {
 		if(!found_dup && strcmp(online_users[i].user_name, user_name) == 0) found_dup = 1;
 		if(++i >= sizeof online_users / sizeof *online_users) {
 			syslog(LOG_WARNING, "cannot let user '%s' from %s login: too many users\n", user_name, host_name);
 			return -1;
 		}
 	}
 	struct local_online_user *p = online_users + i;
 	p->id = id;
 	strncpy(p->user_name, user_name, sizeof p->user_name);
 	strncpy(p->host_name, host_name, sizeof p->host_name);
 	*index = i;
 	while(!found_dup && ++i < sizeof online_users / sizeof *online_users) {
 		if(online_users[i].id != -1 && strcmp(online_users[i].user_name, user_name) == 0) found_dup = 1;
 	}
 	syslog(LOG_INFO, "user %s login from %s id %d dup %d", user_name, host_name, id, found_dup);
 #ifdef HAVE_UPDWTMPX
 	if(access("wtmpx", W_OK) == 0) {
 		struct timeval tv;
 		if(gettimeofday(&tv, NULL) == 0) {
 			pid_t pid = get_pid_from_unix_socket(client_fds[id]);
 			struct utmpx utx = {
 				.ut_type = USER_PROCESS,
 				.ut_pid = pid == -1 ? id : pid,
 				.ut_tv.tv_sec = tv.tv_sec,
 				.ut_tv.tv_usec = tv.tv_usec
 			};
 			snprintf(utx.ut_line, sizeof utx.ut_line, "%d", id);
 			strncpy(utx.ut_user, user_name, sizeof utx.ut_user);
 			strncpy(utx.ut_host, host_name, sizeof utx.ut_host);
 			updwtmpx("wtmpx", &utx);
 		}
 	}
 #endif
 	if(!found_dup) broadcast_user_state(user_name, 1, client_fds);
 	return 0;
 }

 static void user_offline(int id, const int *client_fds) {
 	int found_dup = 0;
 	unsigned int i = 0;
 	while(online_users[i].id != id) {
 		if(++i >= sizeof online_users / sizeof *online_users) return;
 	}
 	const char *user_name = online_users[i].user_name;
 #ifdef HAVE_UPDWTMPX
 	const char *host_name = online_users[i].host_name;
 #endif
 	online_users[i].id = -1;
 	i = 0;
 	while(i < sizeof online_users / sizeof *online_users) {
 		if(online_users[i].id != -1 && strcmp(online_users[i].user_name, user_name) == 0) {
 			found_dup = 1;
 			break;
 		}
 		i++;
 	}
 	if(!found_dup) broadcast_user_state(user_name, 0, client_fds);
 	syslog(LOG_INFO, "user %s logout id %d dup %d", user_name, id, found_dup);
 #ifdef HAVE_UPDWTMPX
 	if(access("wtmpx", W_OK) == 0) {
 		struct timeval tv;
 		if(gettimeofday(&tv, NULL) == 0) {
 			pid_t pid = get_pid_from_unix_socket(client_fds[id]);
 			struct utmpx utx = {
 				.ut_type = DEAD_PROCESS,
 				.ut_pid = pid == -1 ? id : pid,
 				.ut_tv.tv_sec = tv.tv_sec,
 				.ut_tv.tv_usec = tv.tv_usec
 			};
 			snprintf(utx.ut_line, sizeof utx.ut_line, "%d", id);
 			strncpy(utx.ut_user, user_name, sizeof utx.ut_user);
 			strncpy(utx.ut_host, host_name, sizeof utx.ut_host);
 			updwtmpx("wtmpx", &utx);
 		}
 	}
 #endif
 }

 static int send_online_users(int receiver_id, int receiver_fd) {
 	int r = 0;
 	unsigned int i = 0, count = 0;
 	do {
 		if(online_users[i].id != -1) count++;
 	} while(++i < sizeof online_users / sizeof *online_users);
 	size_t packet_length = sizeof(struct local_packet) + sizeof(struct local_online_users_info) + sizeof(struct local_online_user) * count;
 	struct local_packet *packet = malloc(packet_length);
 	if(!packet) {
 		syslog(LOG_ERR, "send_online_users: out of memory");
 		return 0;	// XXX
 	}
 	packet->length = packet_length - sizeof packet->length;
 	packet->type = SSHOUT_LOCAL_ONLINE_USERS_INFO;
 	struct local_online_users_info *info = (struct local_online_users_info *)packet->data;
 	info->your_id = receiver_id;
 	info->count = count;
 	i = 0;
 	for(i = 0; i < sizeof online_users / sizeof *online_users && count > 0; i++) {
 		if(online_users[i].id == -1) continue;
 		count--;
 		memcpy(info->user + count, online_users + i, sizeof(struct local_online_user));
 	}
 	if(sync_write(receiver_fd, packet, packet_length) < 0) {
 		syslog_perror("send_online_users: write");
 		r = -1;
 	}
 	free(packet);
 	return r;
 }

 static int dispatch_message(const struct local_online_user *sender, const struct local_message *msg, const int *client_fds) {
 	int r = 0;
 	unsigned int i = 0;
 	int found = 0;
 	int is_broadcast = strcmp(msg->msg_to, GLOBAL_NAME) == 0 || strcmp(msg->msg_to, "*") == 0;
 	size_t packet_len = sizeof(struct local_packet) + sizeof(struct local_message) + msg->msg_length;
 	struct local_packet *packet = malloc(packet_len);
 	if(!packet) {
 		syslog(LOG_ERR, "dispatch_message: out of memory");
 		return -1;
 	}
 	packet->length = packet_len - sizeof packet->length;
 	packet->type = SSHOUT_LOCAL_DISPATCH_MESSAGE;
 	memcpy(packet->data, msg, sizeof(struct local_message) + msg->msg_length);
 	strncpy(((struct local_message *)packet->data)->msg_from, sender->user_name, USER_NAME_MAX_LENGTH);
 	do {
 		if(online_users[i].id == -1) continue;
 		if(!is_broadcast && strcmp(online_users[i].user_name, msg->msg_to)) {
 			// Not the target user, but we also need to send the message back to sender
 			if(strcmp(online_users[i].user_name, sender->user_name)) continue;
 		} else found = 1;
 		if(sync_write(client_fds[online_users[i].id], packet, packet_len) < 0) {
 			//syslog(LOG_WARNING, "i = %d, id = %d, fd = %d", i, online_users[i].id, client_fds[online_users[i].id]);
 			syslog_perror("dispatch_message: write");
 			r = -1;
 		}
 	} while(++i < sizeof online_users / sizeof *online_users);
 	free(packet);
 	if(!found) {
 		packet_len = sizeof(struct local_packet) + USER_NAME_MAX_LENGTH;
 		packet = malloc(packet_len);
 		if(!packet) {
 			syslog(LOG_ERR, "dispatch_message: out of memory");
 			return -1;
 		}
 		packet->length = packet_len - sizeof packet->length;
 		packet->type = SSHOUT_LOCAL_USER_NOT_FOUND;
 		strncpy(packet->data, msg->msg_to, USER_NAME_MAX_LENGTH);
 		while(write(client_fds[sender->id], packet, packet_len) < 0) {
 			if(errno == EINTR) continue;
 			syslog_perror("dispatch_message: write");
 			r = -1;
 			break;
 		}
 	}
 	return r;
 }

 int server_mode(const struct sockaddr_un *socket_addr) {
 	static const struct timeval timeout = { .tv_sec = 2 };

 	FILE *pid_file = fopen("sshoutd.pid", "r");
 	if(pid_file) {
 		char buffer[16];
 		if(fgetline(pid_file, buffer, sizeof buffer) > 0) {
 			int pid = atoi(buffer);
 			if(pid > 0 && kill(pid, 0) == 0) {
 				fprintf(stderr, "Another server process %d is running\n", pid);
 				return 1;
 			}
 		}
 		fclose(pid_file);
 	}
 	pid_file = fopen("sshoutd.pid", "w");
 	if(!pid_file) {
 		perror("sshoutd.pid");
 		return 1;
 	}
 	if(fprintf(pid_file, "%d\n", (int)getpid()) < 0) {
 		perror("fprintf");
 		return 1;
 	}
 	if(fclose(pid_file) == EOF) {
 		perror("fclose");
 		return 1;
 	}
 	signal(SIGPIPE, SIG_IGN);
 	int fd = socket(AF_UNIX, SOCK_STREAM, 0);
 	if(fd == -1) {
 		perror("socket");
 		return 1;
 	}
 	//if(fcntl(fd, F_SETFL, O_NONBLOCK) < 0) syslog_perror("fcntl");
 	unlink(socket_addr->sun_path);
 	if(bind(fd, (struct sockaddr *)socket_addr, sizeof(struct sockaddr_un)) < 0) {
 		perror(socket_addr->sun_path);
 		close(fd);
 		return 1;
 	}
 	if(chmod(socket_addr->sun_path, 0600) < 0) {
 		perror(socket_addr->sun_path);
 		close(fd);
 		unlink(socket_addr->sun_path);
 		return 1;
 	}
 	if(listen(fd, 64) < 0) {
 		perror("listen");
 		close(fd);
 		unlink(socket_addr->sun_path);
 		return 1;
 	}

 	openlog("sshoutd", LOG_PID, LOG_DAEMON);

 	fd_set fdset;
 	FD_ZERO(&fdset);
 	FD_SET(fd, &fdset);
 	int max_fd = fd;

 	int client_fds[FD_SETSIZE];
 	struct private_buffer buffers[FD_SETSIZE];
 	int online_users_indexes[FD_SETSIZE];
 	int i;
 	for(i=0; i<FD_SETSIZE; i++) {
 		client_fds[i] = -1;
 		buffers[i].buffer = NULL;
 		online_users[i].id = -1;
 		online_users_indexes[i] = -1;
 	}

 	while(1) {
 		int have_client_fd_closed = 0;
 		fd_set rfdset = fdset;
 		int n = select(max_fd + 1, &rfdset, NULL, NULL, NULL);
 		if(n < 0) {
 			if(errno == EINTR) continue;
 			syslog_perror("select");
 			sleep(2);
 			continue;
 		}
 		if(FD_ISSET(fd, &rfdset)) {
 			struct sockaddr_un client_addr;
 			socklen_t addr_len = sizeof client_addr;
 			int cfd;
 			do {
 				cfd = accept(fd, (struct sockaddr *)&client_addr, &addr_len);
 			} while(cfd == -1 && errno == EINTR);
 			if(cfd == -1) {
 				syslog_perror("accept");
 				if(errno == EMFILE && n < 2) sleep(1);
 			} else {
 				syslog(LOG_INFO, "client fd %d\n", cfd);
 			        if(setsockopt(cfd, SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof timeout) < 0) syslog_perror("setsockopt");
 			        if(setsockopt(cfd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof timeout) < 0) syslog_perror("setsockopt");
 				i = 0;
 				while(1) {
 					if(i >= FD_SETSIZE) {
 						syslog(LOG_WARNING, "cannot add fd %d to set, too many clients\n", cfd);
 						close(cfd);
 						break;
 					}
 					if(client_fds[i] == -1) {
 						client_fds[i] = cfd;
 						FD_SET(cfd, &fdset);
 						if(cfd > max_fd) max_fd = cfd;
 						syslog(LOG_INFO, "client %d fd %d\n", i, cfd);
 						break;
 					}
 					i++;
 				}
 			}
 			n--;
 		}
 		for(i=0; n && i<FD_SETSIZE; i++) {
 			int cfd = client_fds[i];
 			if(cfd == -1) continue;
 			if(FD_ISSET(cfd, &rfdset)) {
 				n--;
 				struct local_packet *packet;
 				switch(get_local_packet(cfd, &packet, buffers + i)) {
 					case GET_PACKET_EOF:
 						syslog(LOG_INFO, "client %d fd %d EOF\n", i, cfd);
 						goto end_of_connection;
 					case GET_PACKET_ERROR:
 						syslog_perror("read");
 						goto end_of_connection;
 					case GET_PACKET_SHORT_READ:
 						syslog(LOG_INFO, "client %d fd %d short read\n", i, cfd);
 						goto end_of_connection;
 					case GET_PACKET_TOO_LARGE:
 						syslog(LOG_WARNING, "client %d fd %d packet too large (%u bytes)\n",
 							i, cfd, (unsigned int)packet);
 						goto end_of_connection;
 					case GET_PACKET_OUT_OF_MEMORY:
 						syslog(LOG_WARNING, "client %d fd %d out of memory (allocating %u bytes)\n",
 							i, cfd, (unsigned int)packet);
 						goto end_of_connection;
 					case GET_PACKET_INCOMPLETE:
 						syslog(LOG_INFO, "client %d fd %d incomplete packet received, read %zu bytes, total %zu bytes; will continue later\n",
 							i, cfd, buffers[i].read_length, buffers[i].total_length);
 						continue;
 					case 0:
 						break;
 					default:
 						syslog(LOG_WARNING, "client %d fd %d unknown error\n", i, cfd);
 						//abort();
 						goto end_of_connection;
 				}
 				switch(packet->type) {
 					case SSHOUT_LOCAL_LOGIN:
 						user_online(i, packet->data, packet->data + USER_NAME_MAX_LENGTH, online_users_indexes + i, client_fds);
 						break;
 					case SSHOUT_LOCAL_POST_MESSAGE:
 						if(online_users_indexes[i] == -1) {
 							syslog(LOG_NOTICE, "client %d fd %d posting message without login", i, cfd);
 							break;
 						}
 						dispatch_message(online_users + online_users_indexes[i], (struct local_message *)packet->data, client_fds);
 						break;
 					case SSHOUT_LOCAL_GET_ONLINE_USERS:
 						if(send_online_users(i, cfd) < 0) {
 						//	syslog(LOG_NOTICE, "client %d fd %d send_online_users failed, disconnecting", i, cfd);
 						//	goto end_of_connection;
 						}
 						break;
 					default:
 						syslog(LOG_NOTICE, "client %d fd %d unknown packet type %d",
 							i, cfd, packet->type);
 						break;
 				}
 				free(packet);
 				continue;
 end_of_connection:
 				user_offline(i, client_fds);
 				close(cfd);
 				FD_CLR(cfd, &fdset);
 				have_client_fd_closed = 1;
 				client_fds[i] = -1;
 				free(buffers[i].buffer);
 				buffers[i].buffer = NULL;
 				online_users_indexes[i] = -1;
 			}
 		}
 		if(have_client_fd_closed) {
 			max_fd = fd;
 			for(i=0; i<FD_SETSIZE; i++) if(client_fds[i] > max_fd) max_fd = client_fds[i];
 		}
 	}
 }
	/* Secure Shout Host Oriented Unified Talk
	* Copyright 2015-2018 Rivoreo
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License as published by the
	* Free Software Foundation, either version 3 of the License, or (at your
	* option) any later version.
	*
	* This program 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 General Public License for
	* more details.
	*/

	#if defined __sun && defined __SVR4
	#define HAVE_GETPEERUCRED
	#endif

	#define _GNU_SOURCE
	#include "common.h"
	#include <sys/socket.h>
	#include <sys/un.h>
	#include <sys/stat.h>
	#include <unistd.h>
	#include "syncrw.h"
	#include <syslog.h>
	#include <string.h>
	#include <stdlib.h>
	#include <fcntl.h>
	#include <stdio.h>
	#include <errno.h>
	#include "file-helpers.h"
	#include <signal.h>
	#ifdef HAVE_UPDWTMPX
	#include <utmpx.h>
	#ifdef HAVE_GETPEERUCRED
	#include <ucred.h>
	#endif
	#endif

	static struct local_online_user online_users[FD_SETSIZE];

	static void syslog_perror(const char *ident) {
	int e = errno;
	syslog(LOG_ERR, "%s: %s (%d)", ident, strerror(e), e);
	}

	static void broadcast_user_state(const char user_name, int on, const int client_fds) {
	unsigned int i = 0;
	size_t packet_len = sizeof(struct local_packet) + USER_NAME_MAX_LENGTH;
	struct local_packet *packet = malloc(packet_len);
	if(!packet) {
	syslog(LOG_ERR, "broadcast_user_state: out of memory");
	return;
	}
	packet->length = packet_len - sizeof packet->length;
	packet->type = on ? SSHOUT_LOCAL_USER_ONLINE : SSHOUT_LOCAL_USER_OFFLINE;
	strncpy(packet->data, user_name, USER_NAME_MAX_LENGTH);
	do {
	if(online_users[i].id == -1) continue;
	while(write(client_fds[online_users[i].id], packet, packet_len) < 0) {
	if(errno == EINTR) continue;
	syslog_perror("broadcast_user_state: write");
	break;
	}
	} while(++i < sizeof online_users / sizeof *online_users);
	free(packet);
	}

	#ifdef HAVE_UPDWTMPX
	static pid_t get_pid_from_unix_socket(int fd) {
	#ifdef SO_PEERCRED
	struct ucred ucred;
	socklen_t len = sizeof ucred;
	if(getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &len) < 0) return -1;
	return ucred.pid;
	#elif defined HAVE_GETPEERUCRED
	ucred_t *ucred = NULL;
	if(getpeerucred(fd, &ucred) < 0) return -1;
	pid_t r = ucred_getpid(ucred);
	ucred_free(ucred);
	return r;
	#else
	return -1;
	#endif
	}
	#endif

	static int user_online(int id, const char user_name, const char host_name, int index, const int client_fds) {
	int found_dup = 0;
	unsigned int i = 0;
	while(online_users[i].id != -1) {
	if(!found_dup && strcmp(online_users[i].user_name, user_name) == 0) found_dup = 1;
	if(++i >= sizeof online_users / sizeof *online_users) {
	syslog(LOG_WARNING, "cannot let user '%s' from %s login: too many users\n", user_name, host_name);
	return -1;
	}
	}
	struct local_online_user *p = online_users + i;
	p->id = id;
	strncpy(p->user_name, user_name, sizeof p->user_name);
	strncpy(p->host_name, host_name, sizeof p->host_name);
	*index = i;
	while(!found_dup && ++i < sizeof online_users / sizeof *online_users) {
	if(online_users[i].id != -1 && strcmp(online_users[i].user_name, user_name) == 0) found_dup = 1;
	}
	syslog(LOG_INFO, "user %s login from %s id %d dup %d", user_name, host_name, id, found_dup);
	#ifdef HAVE_UPDWTMPX
	if(access("wtmpx", W_OK) == 0) {
	struct timeval tv;
	if(gettimeofday(&tv, NULL) == 0) {
	pid_t pid = get_pid_from_unix_socket(client_fds[id]);
	struct utmpx utx = {
	.ut_type = USER_PROCESS,
	.ut_pid = pid == -1 ? id : pid,
	.ut_tv.tv_sec = tv.tv_sec,
	.ut_tv.tv_usec = tv.tv_usec
	};
	snprintf(utx.ut_line, sizeof utx.ut_line, "%d", id);
	strncpy(utx.ut_user, user_name, sizeof utx.ut_user);
	strncpy(utx.ut_host, host_name, sizeof utx.ut_host);
	updwtmpx("wtmpx", &utx);
	}
	}
	#endif
	if(!found_dup) broadcast_user_state(user_name, 1, client_fds);
	return 0;
	}

	static void user_offline(int id, const int *client_fds) {
	int found_dup = 0;
	unsigned int i = 0;
	while(online_users[i].id != id) {
	if(++i >= sizeof online_users / sizeof *online_users) return;
	}
	const char *user_name = online_users[i].user_name;
	#ifdef HAVE_UPDWTMPX
	const char *host_name = online_users[i].host_name;
	#endif
	online_users[i].id = -1;
	i = 0;
	while(i < sizeof online_users / sizeof *online_users) {
	if(online_users[i].id != -1 && strcmp(online_users[i].user_name, user_name) == 0) {
	found_dup = 1;
	break;
	}
	i++;
	}
	if(!found_dup) broadcast_user_state(user_name, 0, client_fds);
	syslog(LOG_INFO, "user %s logout id %d dup %d", user_name, id, found_dup);
	#ifdef HAVE_UPDWTMPX
	if(access("wtmpx", W_OK) == 0) {
	struct timeval tv;
	if(gettimeofday(&tv, NULL) == 0) {
	pid_t pid = get_pid_from_unix_socket(client_fds[id]);
	struct utmpx utx = {
	.ut_type = DEAD_PROCESS,
	.ut_pid = pid == -1 ? id : pid,
	.ut_tv.tv_sec = tv.tv_sec,
	.ut_tv.tv_usec = tv.tv_usec
	};
	snprintf(utx.ut_line, sizeof utx.ut_line, "%d", id);
	strncpy(utx.ut_user, user_name, sizeof utx.ut_user);
	strncpy(utx.ut_host, host_name, sizeof utx.ut_host);
	updwtmpx("wtmpx", &utx);
	}
	}
	#endif
	}

	static int send_online_users(int receiver_id, int receiver_fd) {
	int r = 0;
	unsigned int i = 0, count = 0;
	do {
	if(online_users[i].id != -1) count++;
	} while(++i < sizeof online_users / sizeof *online_users);
	size_t packet_length = sizeof(struct local_packet) + sizeof(struct local_online_users_info) + sizeof(struct local_online_user) * count;
	struct local_packet *packet = malloc(packet_length);
	if(!packet) {
	syslog(LOG_ERR, "send_online_users: out of memory");
	return 0; // XXX
	}
	packet->length = packet_length - sizeof packet->length;
	packet->type = SSHOUT_LOCAL_ONLINE_USERS_INFO;
	struct local_online_users_info info = (struct local_online_users_info )packet->data;
	info->your_id = receiver_id;
	info->count = count;
	i = 0;
	for(i = 0; i < sizeof online_users / sizeof *online_users && count > 0; i++) {
	if(online_users[i].id == -1) continue;
	count--;
	memcpy(info->user + count, online_users + i, sizeof(struct local_online_user));
	}
	if(sync_write(receiver_fd, packet, packet_length) < 0) {
	syslog_perror("send_online_users: write");
	r = -1;
	}
	free(packet);
	return r;
	}

	static int dispatch_message(const struct local_online_user sender, const struct local_message msg, const int *client_fds) {
	int r = 0;
	unsigned int i = 0;
	int found = 0;
	int is_broadcast = strcmp(msg->msg_to, GLOBAL_NAME) == 0 \|\| strcmp(msg->msg_to, "*") == 0;
	size_t packet_len = sizeof(struct local_packet) + sizeof(struct local_message) + msg->msg_length;
	struct local_packet *packet = malloc(packet_len);
	if(!packet) {
	syslog(LOG_ERR, "dispatch_message: out of memory");
	return -1;
	}
	packet->length = packet_len - sizeof packet->length;
	packet->type = SSHOUT_LOCAL_DISPATCH_MESSAGE;
	memcpy(packet->data, msg, sizeof(struct local_message) + msg->msg_length);
	strncpy(((struct local_message *)packet->data)->msg_from, sender->user_name, USER_NAME_MAX_LENGTH);
	do {
	if(online_users[i].id == -1) continue;
	if(!is_broadcast && strcmp(online_users[i].user_name, msg->msg_to)) {
	// Not the target user, but we also need to send the message back to sender
	if(strcmp(online_users[i].user_name, sender->user_name)) continue;
	} else found = 1;
	if(sync_write(client_fds[online_users[i].id], packet, packet_len) < 0) {
	//syslog(LOG_WARNING, "i = %d, id = %d, fd = %d", i, online_users[i].id, client_fds[online_users[i].id]);
	syslog_perror("dispatch_message: write");
	r = -1;
	}
	} while(++i < sizeof online_users / sizeof *online_users);
	free(packet);
	if(!found) {
	packet_len = sizeof(struct local_packet) + USER_NAME_MAX_LENGTH;
	packet = malloc(packet_len);
	if(!packet) {
	syslog(LOG_ERR, "dispatch_message: out of memory");
	return -1;
	}
	packet->length = packet_len - sizeof packet->length;
	packet->type = SSHOUT_LOCAL_USER_NOT_FOUND;
	strncpy(packet->data, msg->msg_to, USER_NAME_MAX_LENGTH);
	while(write(client_fds[sender->id], packet, packet_len) < 0) {
	if(errno == EINTR) continue;
	syslog_perror("dispatch_message: write");
	r = -1;
	break;
	}
	}
	return r;
	}

	int server_mode(const struct sockaddr_un *socket_addr) {
	static const struct timeval timeout = { .tv_sec = 2 };

	FILE *pid_file = fopen("sshoutd.pid", "r");
	if(pid_file) {
	char buffer[16];
	if(fgetline(pid_file, buffer, sizeof buffer) > 0) {
	int pid = atoi(buffer);
	if(pid > 0 && kill(pid, 0) == 0) {
	fprintf(stderr, "Another server process %d is running\n", pid);
	return 1;
	}
	}
	fclose(pid_file);
	}
	pid_file = fopen("sshoutd.pid", "w");
	if(!pid_file) {
	perror("sshoutd.pid");
	return 1;
	}
	if(fprintf(pid_file, "%d\n", (int)getpid()) < 0) {
	perror("fprintf");
	return 1;
	}
	if(fclose(pid_file) == EOF) {
	perror("fclose");
	return 1;
	}
	signal(SIGPIPE, SIG_IGN);
	int fd = socket(AF_UNIX, SOCK_STREAM, 0);
	if(fd == -1) {
	perror("socket");
	return 1;
	}
	//if(fcntl(fd, F_SETFL, O_NONBLOCK) < 0) syslog_perror("fcntl");
	unlink(socket_addr->sun_path);
	if(bind(fd, (struct sockaddr *)socket_addr, sizeof(struct sockaddr_un)) < 0) {
	perror(socket_addr->sun_path);
	close(fd);
	return 1;
	}
	if(chmod(socket_addr->sun_path, 0600) < 0) {
	perror(socket_addr->sun_path);
	close(fd);
	unlink(socket_addr->sun_path);
	return 1;
	}
	if(listen(fd, 64) < 0) {
	perror("listen");
	close(fd);
	unlink(socket_addr->sun_path);
	return 1;
	}

	openlog("sshoutd", LOG_PID, LOG_DAEMON);

	fd_set fdset;
	FD_ZERO(&fdset);
	FD_SET(fd, &fdset);
	int max_fd = fd;

	int client_fds[FD_SETSIZE];
	struct private_buffer buffers[FD_SETSIZE];
	int online_users_indexes[FD_SETSIZE];
	int i;
	for(i=0; i<FD_SETSIZE; i++) {
	client_fds[i] = -1;
	buffers[i].buffer = NULL;
	online_users[i].id = -1;
	online_users_indexes[i] = -1;
	}

	while(1) {
	int have_client_fd_closed = 0;
	fd_set rfdset = fdset;
	int n = select(max_fd + 1, &rfdset, NULL, NULL, NULL);
	if(n < 0) {
	if(errno == EINTR) continue;
	syslog_perror("select");
	sleep(2);
	continue;
	}
	if(FD_ISSET(fd, &rfdset)) {
	struct sockaddr_un client_addr;
	socklen_t addr_len = sizeof client_addr;
	int cfd;
	do {
	cfd = accept(fd, (struct sockaddr *)&client_addr, &addr_len);
	} while(cfd == -1 && errno == EINTR);
	if(cfd == -1) {
	syslog_perror("accept");
	if(errno == EMFILE && n < 2) sleep(1);
	} else {
	syslog(LOG_INFO, "client fd %d\n", cfd);
	if(setsockopt(cfd, SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof timeout) < 0) syslog_perror("setsockopt");
	if(setsockopt(cfd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof timeout) < 0) syslog_perror("setsockopt");
	i = 0;
	while(1) {
	if(i >= FD_SETSIZE) {
	syslog(LOG_WARNING, "cannot add fd %d to set, too many clients\n", cfd);
	close(cfd);
	break;
	}
	if(client_fds[i] == -1) {
	client_fds[i] = cfd;
	FD_SET(cfd, &fdset);
	if(cfd > max_fd) max_fd = cfd;
	syslog(LOG_INFO, "client %d fd %d\n", i, cfd);
	break;
	}
	i++;
	}
	}
	n--;
	}
	for(i=0; n && i<FD_SETSIZE; i++) {
	int cfd = client_fds[i];
	if(cfd == -1) continue;
	if(FD_ISSET(cfd, &rfdset)) {
	n--;
	struct local_packet *packet;
	switch(get_local_packet(cfd, &packet, buffers + i)) {
	case GET_PACKET_EOF:
	syslog(LOG_INFO, "client %d fd %d EOF\n", i, cfd);
	goto end_of_connection;
	case GET_PACKET_ERROR:
	syslog_perror("read");
	goto end_of_connection;
	case GET_PACKET_SHORT_READ:
	syslog(LOG_INFO, "client %d fd %d short read\n", i, cfd);
	goto end_of_connection;
	case GET_PACKET_TOO_LARGE:
	syslog(LOG_WARNING, "client %d fd %d packet too large (%u bytes)\n",
	i, cfd, (unsigned int)packet);
	goto end_of_connection;
	case GET_PACKET_OUT_OF_MEMORY:
	syslog(LOG_WARNING, "client %d fd %d out of memory (allocating %u bytes)\n",
	i, cfd, (unsigned int)packet);
	goto end_of_connection;
	case GET_PACKET_INCOMPLETE:
	syslog(LOG_INFO, "client %d fd %d incomplete packet received, read %zu bytes, total %zu bytes; will continue later\n",
	i, cfd, buffers[i].read_length, buffers[i].total_length);
	continue;
	case 0:
	break;
	default:
	syslog(LOG_WARNING, "client %d fd %d unknown error\n", i, cfd);
	//abort();
	goto end_of_connection;
	}
	switch(packet->type) {
	case SSHOUT_LOCAL_LOGIN:
	user_online(i, packet->data, packet->data + USER_NAME_MAX_LENGTH, online_users_indexes + i, client_fds);
	break;
	case SSHOUT_LOCAL_POST_MESSAGE:
	if(online_users_indexes[i] == -1) {
	syslog(LOG_NOTICE, "client %d fd %d posting message without login", i, cfd);
	break;
	}
	dispatch_message(online_users + online_users_indexes[i], (struct local_message *)packet->data, client_fds);
	break;
	case SSHOUT_LOCAL_GET_ONLINE_USERS:
	if(send_online_users(i, cfd) < 0) {
	// syslog(LOG_NOTICE, "client %d fd %d send_online_users failed, disconnecting", i, cfd);
	// goto end_of_connection;
	}
	break;
	default:
	syslog(LOG_NOTICE, "client %d fd %d unknown packet type %d",
	i, cfd, packet->type);
	break;
	}
	free(packet);
	continue;
	end_of_connection:
	user_offline(i, client_fds);
	close(cfd);
	FD_CLR(cfd, &fdset);
	have_client_fd_closed = 1;
	client_fds[i] = -1;
	free(buffers[i].buffer);
	buffers[i].buffer = NULL;
	online_users_indexes[i] = -1;
	}
	}
	if(have_client_fd_closed) {
	max_fd = fd;
	for(i=0; i<FD_SETSIZE; i++) if(client_fds[i] > max_fd) max_fd = client_fds[i];
	}
	}
	}