source: trunk/instant_messenger/socket/proxy.c @ 165

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <stdarg.h>
#include <syslog.h>
#include <fcntl.h>
#include <semaphore.h>
#include <sys/ipc.h>
#include <sys/shm.h>

// Buffer size, in bytes, used for copying in the Cat() function.
const size_t BUF_SIZE = 4096;

// Global variables
char g_program_name[100];       // Initialised from argv[0] in ParseArgs()

// structs
struct accept
{
        int newfd;
        struct sockaddr_in sa;
        struct in_addr jabber_addr;
        unsigned short jabber_port;
};

/*struct client
{
        unsigned char * user;
        unsigned char * key;
        int jabber;
        int shmid;
        struct client * next,
                                  * previous;
};*/
struct client
{
        char * user;
        int client_fd;
        int jabber_fd;
        int keep_alive;
        int connectionType; // 0 = read/write; 1 = read; -1 = write;
        time_t last_action;
        struct client * next;
        struct client * previous;
};

struct cat
{
        int in_fd,
                out_fd;
        int jabber,
                keep_alive;
        struct client * client;
        int connectionType;
};

struct client * clients = (struct client *)NULL;

pthread_mutex_t mutexsum;

// Typedef for a signal handler function.
typedef void (* signal_handler_t) (int);

// Prototypes for functions in this file.
void ParseArgs (int, char **, struct in_addr *, unsigned short *, struct in_addr *, unsigned short *);
void Initialise (void);
void sig_child (int);
int CreateServerSocket (struct in_addr, unsigned short);
void Daemonise (void);
void MainLoop (int, struct in_addr, unsigned short);
struct accept * AcceptClientConnection (int);
void VerifyClient(void *);
struct client * Handshake(int);
int ConnectToServer (struct in_addr, unsigned short);
void Reading (void * info);
void Writing (void * info);
int NameToAddr (const char *, struct in_addr *);
int NameToPort (const char *, unsigned short *, const char *);
#ifdef __GNUC__
        void quit (const char *, ...) __attribute__ ((format (printf, 1, 2)));
        void pbomb (const char *, ...) __attribute__ ((format (printf, 1, 2)));
        void hbomb (const char *, ...) __attribute__ ((format (printf, 1, 2)));
#else
        void quit (const char *, ...);
        void pbomb (const char *, ...);
        void hbomb (const char *, ...);
#endif
void set_signal_handler (int, signal_handler_t);

int main (int argc, char ** argv)
{
        struct in_addr remote_addr,
                                   local_addr;
        unsigned short remote_port,
                                   local_port;
        int listen_fd;

        ParseArgs (argc, argv, &remote_addr, &remote_port, &local_addr, &local_port);

        Initialise ();

        // Create server socket before becoming a daemon so
        // there is still a chance to print an error message.
        listen_fd = CreateServerSocket (local_addr, local_port);
        if ( listen_fd < 0 )
                pbomb ("Unable to create server socket");

        //Daemonise ();

        MainLoop (listen_fd, remote_addr, remote_port); // never returns

        exit (EXIT_SUCCESS);
}

// ParseArgs()
// Parse the command line arguments to extract the remote
// and local adresses and port numbers, ra, rp, la & lp.
// Exit the program gracefully upon error.
void ParseArgs (int argc, char ** argv, struct in_addr * ra, unsigned short * rp, struct in_addr * la, unsigned short * lp)
{
        // argv[0] = program name
        // argv[1] = remote_addr
        // argv[2] = remote_port
        // argv[3] = local_addr (optional)
        // argv[4] = local_port (optional)

        char * p = strrchr (argv[0], '/');

        strncpy (g_program_name, (p == NULL) ? argv[0] : p + 1, sizeof (g_program_name) - 1);

        if ( (argc < 3) || (argc > 5) )
        {
                fprintf (stderr, "usage: %s remote_addr remote_port [local_addr] [local_port]\n", argv[0]);
                exit (EXIT_FAILURE);
        }

        if ( NameToAddr (argv[1], ra) )
                hbomb ("Unable to resolve \"%s\" to an ip address", argv[1]);

        if ( NameToPort (argv[2], rp, "tcp") )
                quit ("Unable to resolve \"%s\" to a port number", argv[2]);

        if ( argc < 4 )
                la->s_addr = htonl (INADDR_ANY);
        else
                if ( NameToAddr (argv[3], la) )
                        hbomb ("Unable to resolve \"%s\" to an ip address", argv[3]);

        if ( argc < 5 )
                memcpy (lp, rp, sizeof (*lp));
        else
                if ( NameToPort (argv[4], lp, "tcp") )
                        quit ("Unable to resolve \"%s\" to a port number", argv[4]);
}

// Initialise()
// Setup syslog, signal handlers, and other intialisation.
void Initialise (void)
{
        openlog (g_program_name, LOG_PID, LOG_USER);
        syslog (LOG_INFO, "%s started", g_program_name);

        chdir ("/"); // Change working directory to the root.

        umask (0); // Clear our file mode creation mask

        //set_signal_handler (SIGCHLD, sig_child);

        //signal (SIGPIPE, SIG_IGN);
}

// sig_child()
// Handles SIGCHLD from exiting child processes.
void sig_child (int signo)
{
        pid_t pid;

        (void) signo; // suppress compiler warning

        for ( ; ; )
        {
                write(1, "SIG\n", sizeof("SIG\n"));
                pid = waitpid (WAIT_ANY, NULL, WNOHANG);

                if ( pid > 0 )
                        syslog (LOG_INFO, "Caught SIGCHLD from pid %d", pid);
                else
                        break;
        }
        write(1, "SIG...\n", sizeof("SIG...\n"));

        if ( (pid < 0) && (errno != ECHILD) )
                syslog (LOG_ERR, "waitpid(): %m"), exit (EXIT_FAILURE);

        return;
}

// CreateServerSocket()
// Create a socket, bind it to the specified address
// and port, and set it to listen for client connections.
// Returns < 0 on failure to bind, bombs on error otherwise,
// returns the fd of the new socket on success.
int CreateServerSocket (struct in_addr addr, unsigned short port)
{
        int err,
                fd;
        const int on = 1;
        struct sockaddr_in sa;

        // Create a socket and get its descriptor.
        fd = socket (AF_INET, SOCK_STREAM, 0);
        if ( fd < 0 )
                syslog (LOG_ERR, "socket(): %m"), exit (EXIT_FAILURE);

        // Set SO_REUSEADDR socket option
        if ( setsockopt (fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof (on)) < 0 )
                syslog (LOG_ERR, "setsockopt(fd%d, SO_REUSEADDR): %m", fd);

        // Load a sa structure with the specified address and port
        sa.sin_family = AF_INET;
        sa.sin_port = htons (port);
        //sa.sin_addr = addr;
        sa.sin_addr.s_addr = htonl(INADDR_ANY);
        memset (sa.sin_zero, 0, sizeof (sa.sin_zero));

        // Bind our socket to the address and port specified
        err = bind (fd, (struct sockaddr *) &sa, sizeof (sa));
        if ( err < 0 )
        {
                syslog (LOG_ERR, "bind(): %m");
                return err;
        }

        // Tell socket to listen and queue up to 5 incoming connections.
        if ( listen (fd, 5) < 0 )
                syslog (LOG_ERR, "listen(): %m"), exit (EXIT_FAILURE);

        return fd;
}

// Daemonise()
// Put the program in the background, set PPID=1, create a
// new session and process group, without a controlling tty.
void Daemonise (void)
{
        pid_t pid;

        // Close stdin, stdout & stderr
        // @TODO:
        //              open /dev/null and dup the fd to stdin, stdout & stderr
        //              close(STDIN_FILENO);
        //              close(STDOUT_FILENO);
        //              close(STDERR_FILENO);

        syslog (LOG_INFO, "%s daemonising", g_program_name);

        // Fork the process to put it in the background.

        pid = fork ();
        if ( pid == -1 )
                syslog (LOG_ERR, "fork(): %m"), exit (EXIT_FAILURE);

        // parent terminates here, so shell thinks the command is done.
        if ( pid )
                exit (0);

        syslog (LOG_INFO, "%s in background", g_program_name);

        // 1st child continues to run in the background with PPID=1

        // Become leader of a new session and a new process group,
        // with no controlling tty.
        setsid ();

        // Fork again to guarantee the process will
        // not be able to aquire a controlling tty.

        // signal (SIGHUP, SIG_IGN);
        // required according to Stevens' UNP2 p333

        pid = fork ();
        if (pid == -1)
                syslog (LOG_ERR, "fork(): %m"), exit (EXIT_FAILURE);

        if ( pid ) // 1st child terminates
                exit (0);

        // 2nd child continues, no longer a session or group leader

        syslog (LOG_INFO, "%s daemonised", g_program_name);
}

// MainLoop()
// Classic concurrent server model.
// Wait for a client to connect, fork a child process
// to do the business with the client, parent process
// continues to wait for the next connection.
// This function does not return.
void MainLoop (int listen_fd, struct in_addr rem_addr, unsigned short rem_port)
{
        struct accept * accept;
        pthread_t accept_thread,
                          clear_list_thread;

        pthread_mutex_init(&mutexsum, NULL);

        //pthread_create(&clear_list_thread, NULL, (void *) &ClearList, (void *)NULL );

        for ( ; ; )
        {
                accept = AcceptClientConnection (listen_fd);
                accept->jabber_addr = rem_addr;
                accept->jabber_port = rem_port;

                pthread_create(&accept_thread, NULL, (void *) &VerifyClient, (void *) accept);
        }
        pthread_mutex_destroy(&mutexsum);
        pthread_exit(NULL);
}

// AcceptClientConnection()
// waits for a tcp connect to the socket listen_fd, which
// must already be bound and set to listen on a local port.
// Bombs on error, returns the fd of the new socket on success.
//int AcceptClientConnection (int listen_fd)
struct accept * AcceptClientConnection (int listen_fd)
{
        int newfd;
        struct sockaddr_in sa;
        socklen_t socklen;

        syslog (LOG_INFO, "AcceptClientConnection(fd%d)", listen_fd);

        // Accept the connection and create a new socket for it.
        socklen = sizeof (sa);
        memset (&sa, 0, socklen);
        do
        {
                newfd = accept (listen_fd, (struct sockaddr *) &sa, &socklen);
        }
        while ( (newfd < 0) && (errno == EINTR) );

        syslog (LOG_INFO, "Accepted client connection on new socket fd%d", newfd);

        if ( newfd < 0 )
                syslog (LOG_ERR, "accept(): %m"), exit (EXIT_FAILURE);

        if ( socklen != sizeof (sa) )
                syslog (LOG_ERR, "accept() screwed up!"), exit (EXIT_FAILURE);

        //return (newfd);

        struct accept * new_accept = (struct accept *) malloc(sizeof(struct accept));
        new_accept->newfd = newfd;
        new_accept->sa = sa;

        return (new_accept);
}

void VerifyClient(void * accept)
{
        int jabber_fd = (int)NULL,
                connectionType = 0;
        struct accept * client = (struct accept *) accept;
        struct client * user = (struct client *)NULL;
        struct cat * info;
        pthread_t cat_thread;

        /*FILE *file;
        char line[80];
        char *ips[20];
        int cont;
        int j;*/

        unsigned int addr = 0;
        char buf[250];
        addr = ntohl(client->sa.sin_addr.s_addr);
        sprintf(buf,"%d.%d.%d.%d",
                        (addr >> 24)  , (addr >> 16) & 0xFF ,
                        (addr >> 8) & 0xFF ,  addr & 0xFF);
        printf("\nNew connection: %s\n", buf);

        /*if(!(file = fopen("/etc/socket_im/hosts","r")))
        {
                printf("Impossível abrir o arquivo hosts \n");
                exit(1);
        }

        fgets(line, 80, file);
        while(!feof(file))
        {
                ips[cont] = malloc(sizeof(char)*17);
                line[strlen(line) - 1 ] = '\0';
                strcpy(ips[cont], line);
                fgets(line, 80, file);
                cont++;
        }

        fclose(file);

        for( j = 0; j < cont; j++)
        {
                if( strcmp( buf, ips[j] ) == 0)
                {
                        user = Handshake(client->newfd);
                        jabber_fd = user->jabber_fd;
                        connectionType = user->connectionType;
                        break;
                }
        }*/

        if ( strcmp(buf, "10.15.20.42") == 0 )//|| strcmp(buf, "10.15.20.202") == 0 || strcmp(buf, "10.15.20.145") == 0 )
        {
                user = Handshake(client->newfd);
                jabber_fd = user->jabber_fd;
                connectionType = user->connectionType;
        }

        if ( jabber_fd == (int)NULL )
        {
                jabber_fd = ConnectToServer(client->jabber_addr, client->jabber_port);

                if ( user != (struct client *)NULL )
                        user->jabber_fd = jabber_fd;
        }

        info = (struct cat *) malloc(sizeof(struct cat));

        info->in_fd = jabber_fd;
        info->out_fd = client->newfd;
        info->jabber = (int)NULL;
        info->keep_alive = (int)NULL;
        info->client = user;
        info->connectionType = connectionType;

        if ( !connectionType )
        {
                pthread_create(&cat_thread, NULL, (void *) &Reading, (void *)info );
                pthread_create(&cat_thread, NULL, (void *) &Writing, (void *)info );
        }
        else
        {
                if ( connectionType == 1 )
                        pthread_create(&cat_thread, NULL, (void *) &Reading, (void *)info );
                else
                        pthread_create(&cat_thread, NULL, (void *) &Writing, (void *)info );
        }

        pthread_exit(0);
}

struct client * Handshake(int newfd)
{
        float is_new_client;// = (float) NULL;
        int bytes_rcvd,
                bytes_sent,
                connectionType,
                i;

        unsigned char * const buf = (char *) malloc (sizeof(char) * 5);
        char * user = (char *) malloc(128 * sizeof(char)),
                 * pass = (char *) malloc(128 * sizeof(char)),
                 * type = (char *) malloc(128 * sizeof(char));

        //struct client * clients = (struct client *)NULL;
        struct client * new_client = (struct client *)NULL;

        bzero(buf, 5);
        sprintf(buf, "user");
        for ( i = 0; i < sizeof(buf); i += bytes_sent )
        {
                bytes_sent = send (newfd, buf + i, sizeof(buf) - i, 0);

                if ( bytes_sent < 0 )
                        break;
        }

        bzero(user, 128);
        if ( (bytes_rcvd = recv (newfd, user, 128, 0)) < 1 )
        {
                printf("USER....: %s", user);
                shutdown(newfd, SHUT_RDWR);
                close(newfd);
                pthread_exit(0);
        }

        bzero(buf, 5);
        sprintf(buf, "pass");
        for ( i = 0; i < sizeof(buf); i += bytes_sent )
        {
                bytes_sent = send (newfd, buf + i, sizeof(buf) - i, 0);

                if ( bytes_sent < 0 )
                        break;
        }

        bzero(pass, 128);
        if ( (bytes_rcvd = recv (newfd, pass, 128, 0)) < 1 )
        {
                printf("PASS....: %s", pass);
                shutdown(newfd, SHUT_RDWR);
                close(newfd);
                pthread_exit(0);
        }

        bzero(buf, 5);
        sprintf(buf, "type");
        for ( i = 0; i < sizeof(buf); i += bytes_sent )
        {
                bytes_sent = send (newfd, buf + i, sizeof(buf) - i, 0);

                if ( bytes_sent < 0 )
                        break;
        }

        bzero(type, 128);
        if ( (bytes_rcvd = recv (newfd, type, 128, 0)) < 1 )
        {
                printf("TYPE....: %s", type);
                shutdown(newfd, SHUT_RDWR);
                close(newfd);
                pthread_exit(0);
        }

        pthread_mutex_lock (&mutexsum);
        if ( clients == (struct client *)NULL )
        {
                clients = (struct client *) malloc(sizeof(struct client));

                new_client = clients;
                new_client->previous = (struct client *)NULL;
                is_new_client = 1;
        }
        else
        {
                new_client = clients;
                while ( ((is_new_client = (float)strcmp(new_client->user, user)) != 0) && (new_client->next != (struct client *)NULL) )
                        new_client = new_client->next;
        }

        if ( is_new_client != 0 )
        {
                new_client->next = (struct client *) malloc(sizeof(struct client));
                new_client->next->previous = new_client;
                new_client = new_client->next;
                new_client->user = user;
                new_client->jabber_fd = (int)NULL;
                new_client->keep_alive = 1;
                new_client->next = (struct client *)NULL;
        }

        bzero(buf, 5);
        if ( is_new_client != 0 || new_client->jabber_fd == (int)NULL  )
                sprintf(buf, "new");
        else
                sprintf(buf, "rec");

        send (newfd, buf, 3, 0);

        new_client->client_fd = newfd;
        new_client->last_action = time(NULL);
        new_client->connectionType = 0;
        pthread_mutex_unlock(&mutexsum);

        if ( strcmp(type, "read") == 0 )
                new_client->connectionType = 1;
        else
                if ( strcmp(type, "write") == 0 )
                        new_client->connectionType = 2;

        return new_client;
}

// ConnectToServer()
// attempts a tcp connect to the server specified
// by addr and port.  Bombs on failure to connect,
// returns the fd of the new socket on success.
int ConnectToServer (struct in_addr addr, unsigned short port)
{
        // TODO: have a timeout for connect() - see Unix socket FAQ 6.2

        int fd, err;
        struct sockaddr_in sa;

        // Create a socket and get its descriptor.
        fd = socket (AF_INET, SOCK_STREAM, 0);

        if ( fd < 0 )
                syslog (LOG_ERR, "socket(): %m"), exit (EXIT_FAILURE);

        sa.sin_family = AF_INET;
        sa.sin_port = htons (port);
        sa.sin_addr = addr;
        memset (sa.sin_zero, 0, sizeof (sa.sin_zero));

        err = connect (fd, (struct sockaddr *) &sa, sizeof (sa));
        if (err < 0)
        {
                syslog (LOG_ERR, "Unable to connect socket fd%d to server: %m", fd);
                exit (EXIT_FAILURE);
        }

        syslog (LOG_INFO, "Connected socket fd%d to server", fd);

        return fd;
}

// Cat()
// read data from in_fd and write it to out_fd until
// the connection is closed by one of the peers.
// Data is copied using a dynamically allocated buffer.
void Reading (void * info)
{
        unsigned char * const buf = (char *) malloc (sizeof(char) * BUF_SIZE);
        int bytes_rcvd,
                bytes_sent = (int) NULL,
                i;

        struct cat * user = (struct cat *) info;
        int in_fd = user->in_fd,
                out_fd = user->out_fd;

        syslog (LOG_INFO, "Reading(fd%d, fd%d)", in_fd, out_fd);

        // @TODO: verificar alocacao buffer
        //if ( buf == NULL )
        //      syslog (LOG_ERR, "malloc(): %m"), exit (EXIT_FAILURE);

        do
        {
                bzero(buf, BUF_SIZE);
                bytes_rcvd = recv (in_fd, buf, BUF_SIZE, 0);

                // descomentar para ver oq esta passado de informacao
                //puts(buf);

                for ( i = 0; i < bytes_rcvd; i += bytes_sent )
                {
                        bytes_sent = send (out_fd, buf + i, bytes_rcvd - i, 0);

                        if ( bytes_sent < 0 )
                                break;
                }
        }
        while ( (bytes_rcvd > 0) && (bytes_sent > 0) );

        //if ( (bytes_rcvd < 0) && (errno != ECONNRESET) )
        //      syslog (LOG_ERR, "recv(): %m"), exit (EXIT_FAILURE);

        //if ( (bytes_sent < 0) && (errno != EPIPE) )
        //      syslog (LOG_ERR, "send(): %m"), exit (EXIT_FAILURE);

        free (buf);
        //shutdown (user->out_fd, SHUT_RDWR);
        close (user->out_fd);
        close (user->out_fd);
        pthread_exit(0);
}

void Writing (void * info)
{
        unsigned char * const buf = (char *) malloc (sizeof(char) * BUF_SIZE);
        int bytes_rcvd,
                bytes_sent = (int) NULL,
                i;

        struct cat * user = (struct cat *) info;
        int in_fd = user->out_fd,
                out_fd = user->in_fd;

        syslog (LOG_INFO, "Writing(fd%d, fd%d)", in_fd, out_fd);

        // @TODO: verificar alocacao buffer
        //if ( buf == NULL )
        //      syslog (LOG_ERR, "malloc(): %m"), exit (EXIT_FAILURE);

        do
        {
                bzero(buf, BUF_SIZE);
                bytes_rcvd = recv (in_fd, buf, BUF_SIZE, 0);

                // descomentar para ver oq esta passado de informacao
                //puts(buf);

                for ( i = 0; i < bytes_rcvd; i += bytes_sent )
                {
                        bytes_sent = send (out_fd, buf + i, bytes_rcvd - i, 0);

                        if ( bytes_sent < 0 )
                                break;
                }
        }
        while ( (bytes_rcvd > 0) && (bytes_sent > 0) );

        //if ( (bytes_rcvd < 0) && (errno != ECONNRESET) )
        //      syslog (LOG_ERR, "recv(): %m"), exit (EXIT_FAILURE);

        //if ( (bytes_sent < 0) && (errno != EPIPE) )
        //      syslog (LOG_ERR, "send(): %m"), exit (EXIT_FAILURE);

        free (buf);
        //shutdown (user->out_fd, SHUT_RDWR);
        close (user->out_fd);
        close (user->out_fd);
        pthread_exit(0);
}

// NameToAddress()
// Convert name to an ip address.
// Returns 0 on success, -1 on failure.
int NameToAddr (const char * name, struct in_addr * p_inaddr)
{
        struct hostent * he;

        // First, attempt to convert from string ip format
        // TODO: use inet_aton() instead
        p_inaddr->s_addr = inet_addr (name);
        if ( p_inaddr->s_addr != -1U ) // Success
                return 0;

        // Next, attempt to read from /etc/hosts or do a DNS lookup
        he = gethostbyname (name);
        if ( he != NULL ) // Success
        {
                memcpy (p_inaddr, he->h_addr, sizeof (struct in_addr));
                return 0;
        }

        return -1; // Failed to resolve name to an ip address
}

// NameToPort()
// Convert name to a port number. Name can either be a port name
// (in which case proto must also be set to either "tcp" or "udp")
// or name can be the ascii representation of the port number.
// Returns 0 on success, -1 on failure.
int NameToPort (const char * name, unsigned short * port, const char * proto)
{
        unsigned long lport;
        char * errpos;
        struct servent * se;

        // First, attempt to convert string to integer
        lport = strtoul (name, &errpos, 0);
        if ( (*errpos == 0) && (lport <= 65535) ) // Success
        {
                *port = lport;
                return 0;
        }

        // Next, attempt to read the string from /etc/services
        se = getservbyname (name, proto);
        if ( se != NULL) // Success
        {
                *port = ntohs (se->s_port);
                return 0;
        }

        return -1; // Failed to resolve port name to a number
}

// quit()
// Print an error message to stderr
// and syslog, then exit the program.
void quit (const char * fmt, ...) // quit with msg
{
        va_list ap;

        fflush (stdout);

        fprintf (stderr, "%s: ", g_program_name);

        va_start (ap, fmt);
        vfprintf (stderr, fmt, ap);
        va_end (ap);

        fputc ('\n', stderr);

        syslog (LOG_ERR, "I quit!");

        exit (EXIT_FAILURE);
}

// pbomb()
// Print an error message to stderr
// and syslog, then exit the program.
// pbomb() additionally include the
// string representation of errno.
void pbomb (const char * fmt, ...) // bomb with perror
{
        va_list ap;
        int errno_save = errno;
        char buf[100];

        fflush (stdout);

        fprintf (stderr, "%s: ", g_program_name);

        va_start (ap, fmt);
        vsnprintf (buf, sizeof (buf), fmt, ap);
        va_end (ap);

        errno = errno_save;
        perror (buf);

        syslog (LOG_ERR, "Bang!: %s: %m", buf);

        exit (EXIT_FAILURE);
}

// hbomb()
// Print an error message to stderr
// and syslog, then exit the program.
// hbomb() additionally include the
// string representation of h_errno.
void hbomb (const char * fmt, ...) // bomb with herror
{
        va_list ap;
        int h_errno_save = h_errno;
        char buf[100];

        fflush (stdout);

        fprintf (stderr, "%s: ", g_program_name);

        va_start (ap, fmt);
        vsnprintf (buf, sizeof (buf), fmt, ap);
        va_end (ap);

        h_errno = h_errno_save;
        herror (buf);

        syslog (LOG_ERR, "Bang!: %s: %s", buf, hstrerror (h_errno));

        exit (EXIT_FAILURE);
}

// set_signal_handler()
// Sets a signal handler function.
// Similar to signal() but this method
// is more portable between platforms.
void set_signal_handler (int signum, signal_handler_t sa_handler_func)
{
        struct sigaction act;

        act.sa_handler = sa_handler_func;
        sigemptyset (&(act.sa_mask));
        act.sa_flags = 0;

        if ( sigaction (signum, &act, NULL) < 0 )
        {
                syslog (LOG_ERR, "Error setting handler for signal %d: %m", signum);
                exit (EXIT_FAILURE);
        }
}