[151] | 1 | #include "server.h" |
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| 2 | |
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| 3 | int main (int argc, char ** argv) |
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| 4 | { |
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| 5 | struct in_addr remote_addr, |
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| 6 | local_addr; |
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| 7 | unsigned short remote_port, |
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| 8 | local_port; |
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| 9 | int listen_fd; |
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| 10 | |
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| 11 | ParseArgs (argc, argv, &remote_addr, &remote_port, &local_addr, &local_port); |
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| 12 | |
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| 13 | Initialise (); |
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| 14 | |
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| 15 | // Create server socket before becoming a daemon so |
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| 16 | // there is still a chance to print an error message. |
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| 17 | listen_fd = CreateServerSocket (local_addr, local_port); |
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| 18 | if ( listen_fd < 0 ) |
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| 19 | pbomb ("Unable to create server socket"); |
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| 20 | |
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| 21 | //Daemonise (); |
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| 22 | |
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| 23 | MainLoop (listen_fd, remote_addr, remote_port); // never returns |
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| 24 | |
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| 25 | exit (EXIT_SUCCESS); |
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| 26 | } |
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| 27 | |
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| 28 | // ParseArgs() |
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| 29 | // Parse the command line arguments to extract the remote |
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| 30 | // and local adresses and port numbers, ra, rp, la & lp. |
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| 31 | // Exit the program gracefully upon error. |
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| 32 | void ParseArgs (int argc, char ** argv, struct in_addr * ra, unsigned short * rp, struct in_addr * la, unsigned short * lp) |
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| 33 | { |
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| 34 | // argv[0] = program name |
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| 35 | // argv[1] = remote_addr |
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| 36 | // argv[2] = remote_port |
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| 37 | // argv[3] = local_addr (optional) |
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| 38 | // argv[4] = local_port (optional) |
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| 39 | |
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| 40 | char * p = strrchr (argv[0], '/'); |
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| 41 | |
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| 42 | strncpy (g_program_name, (p == NULL) ? argv[0] : p + 1, sizeof (g_program_name) - 1); |
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| 43 | |
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| 44 | if ( (argc < 3) || (argc > 5) ) |
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| 45 | { |
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| 46 | fprintf (stderr, "usage: %s remote_addr remote_port [local_addr] [local_port]\n", argv[0]); |
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| 47 | exit (EXIT_FAILURE); |
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| 48 | } |
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| 49 | |
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| 50 | if ( NameToAddr (argv[1], ra) ) |
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| 51 | hbomb ("Unable to resolve \"%s\" to an ip address", argv[1]); |
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| 52 | |
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| 53 | if ( NameToPort (argv[2], rp, "tcp") ) |
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| 54 | quit ("Unable to resolve \"%s\" to a port number", argv[2]); |
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| 55 | |
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| 56 | if ( argc < 4 ) |
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| 57 | la->s_addr = htonl (INADDR_ANY); |
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| 58 | else |
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| 59 | if ( NameToAddr (argv[3], la) ) |
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| 60 | hbomb ("Unable to resolve \"%s\" to an ip address", argv[3]); |
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| 61 | |
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| 62 | if ( argc < 5 ) |
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| 63 | memcpy (lp, rp, sizeof (*lp)); |
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| 64 | else |
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| 65 | if ( NameToPort (argv[4], lp, "tcp") ) |
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| 66 | quit ("Unable to resolve \"%s\" to a port number", argv[4]); |
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| 67 | } |
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| 68 | |
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| 69 | // Initialise() |
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| 70 | // Setup syslog, signal handlers, and other intialisation. |
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| 71 | void Initialise (void) |
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| 72 | { |
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| 73 | openlog (g_program_name, LOG_PID, LOG_USER); |
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| 74 | syslog (LOG_INFO, "%s started", g_program_name); |
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| 75 | |
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| 76 | chdir ("/"); // Change working directory to the root. |
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| 77 | |
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| 78 | umask (0); // Clear our file mode creation mask |
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| 79 | |
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| 80 | set_signal_handler (SIGCHLD, sig_child); |
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| 81 | |
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| 82 | signal (SIGPIPE, SIG_IGN); |
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| 83 | } |
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| 84 | |
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| 85 | // sig_child() |
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| 86 | // Handles SIGCHLD from exiting child processes. |
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| 87 | void sig_child (int signo) |
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| 88 | { |
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| 89 | pid_t pid; |
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| 90 | |
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| 91 | (void) signo; // suppress compiler warning |
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| 92 | |
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| 93 | for ( ; ; ) |
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| 94 | { |
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| 95 | write(1, "SIG\n", sizeof("SIG\n")); |
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| 96 | pid = waitpid (WAIT_ANY, NULL, WNOHANG); |
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| 97 | |
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| 98 | if ( pid > 0 ) |
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| 99 | syslog (LOG_INFO, "Caught SIGCHLD from pid %d", pid); |
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| 100 | else |
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| 101 | break; |
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| 102 | } |
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| 103 | write(1, "SIG...\n", sizeof("SIG...\n")); |
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| 104 | |
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| 105 | if ( (pid < 0) && (errno != ECHILD) ) |
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| 106 | syslog (LOG_ERR, "waitpid(): %m"), exit (EXIT_FAILURE); |
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| 107 | |
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| 108 | return; |
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| 109 | } |
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| 110 | |
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| 111 | // CreateServerSocket() |
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| 112 | // Create a socket, bind it to the specified address |
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| 113 | // and port, and set it to listen for client connections. |
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| 114 | // Returns < 0 on failure to bind, bombs on error otherwise, |
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| 115 | // returns the fd of the new socket on success. |
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| 116 | int CreateServerSocket (struct in_addr addr, unsigned short port) |
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| 117 | { |
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| 118 | int err, |
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| 119 | fd; |
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| 120 | const int on = 1; |
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| 121 | struct sockaddr_in sa; |
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| 122 | |
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| 123 | // Create a socket and get its descriptor. |
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| 124 | fd = socket (AF_INET, SOCK_STREAM, 0); |
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| 125 | if ( fd < 0 ) |
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| 126 | syslog (LOG_ERR, "socket(): %m"), exit (EXIT_FAILURE); |
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| 127 | |
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| 128 | // Set SO_REUSEADDR socket option |
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| 129 | if ( setsockopt (fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof (on)) < 0 ) |
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| 130 | syslog (LOG_ERR, "setsockopt(fd%d, SO_REUSEADDR): %m", fd); |
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| 131 | |
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| 132 | // Load a sa structure with the specified address and port |
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| 133 | sa.sin_family = AF_INET; |
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| 134 | sa.sin_port = htons (port); |
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| 135 | sa.sin_addr = addr; |
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| 136 | memset (sa.sin_zero, 0, sizeof (sa.sin_zero)); |
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| 137 | |
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| 138 | // Bind our socket to the address and port specified |
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| 139 | err = bind (fd, (struct sockaddr *) &sa, sizeof (sa)); |
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| 140 | if ( err < 0 ) |
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| 141 | { |
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| 142 | syslog (LOG_ERR, "bind(): %m"); |
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| 143 | return err; |
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| 144 | } |
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| 145 | |
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| 146 | // Tell socket to listen and queue up to 5 incoming connections. |
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| 147 | if ( listen (fd, 5) < 0 ) |
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| 148 | syslog (LOG_ERR, "listen(): %m"), exit (EXIT_FAILURE); |
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| 149 | |
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| 150 | return fd; |
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| 151 | } |
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| 152 | |
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| 153 | // Daemonise() |
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| 154 | // Put the program in the background, set PPID=1, create a |
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| 155 | // new session and process group, without a controlling tty. |
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| 156 | void Daemonise (void) |
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| 157 | { |
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| 158 | pid_t pid; |
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| 159 | |
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| 160 | // Close stdin, stdout & stderr |
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| 161 | // TODO: |
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| 162 | // open /dev/null and dup the fd to stdin, stdout & stderr |
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| 163 | // close(STDIN_FILENO); |
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| 164 | // close(STDOUT_FILENO); |
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| 165 | // close(STDERR_FILENO); |
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| 166 | |
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| 167 | syslog (LOG_INFO, "%s daemonising", g_program_name); |
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| 168 | |
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| 169 | // Fork the process to put it in the background. |
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| 170 | |
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| 171 | pid = fork (); |
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| 172 | if ( pid == -1 ) |
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| 173 | syslog (LOG_ERR, "fork(): %m"), exit (EXIT_FAILURE); |
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| 174 | |
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| 175 | // parent terminates here, so shell thinks the command is done. |
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| 176 | if ( pid ) |
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| 177 | exit (0); |
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| 178 | |
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| 179 | syslog (LOG_INFO, "%s in background", g_program_name); |
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| 180 | |
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| 181 | // 1st child continues to run in the background with PPID=1 |
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| 182 | |
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| 183 | // Become leader of a new session and a new process group, |
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| 184 | // with no controlling tty. |
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| 185 | setsid (); |
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| 186 | |
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| 187 | // Fork again to guarantee the process will |
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| 188 | // not be able to aquire a controlling tty. |
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| 189 | |
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| 190 | // signal (SIGHUP, SIG_IGN); |
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| 191 | // required according to Stevens' UNP2 p333 |
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| 192 | |
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| 193 | pid = fork (); |
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| 194 | if (pid == -1) |
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| 195 | syslog (LOG_ERR, "fork(): %m"), exit (EXIT_FAILURE); |
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| 196 | |
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| 197 | if ( pid ) // 1st child terminates |
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| 198 | exit (0); |
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| 199 | |
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| 200 | // 2nd child continues, no longer a session or group leader |
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| 201 | |
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| 202 | syslog (LOG_INFO, "%s daemonised", g_program_name); |
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| 203 | } |
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| 204 | |
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| 205 | // MainLoop() |
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| 206 | // Classic concurrent server model. |
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| 207 | // Wait for a client to connect, fork a child process |
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| 208 | // to do the business with the client, parent process |
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| 209 | // continues to wait for the next connection. |
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| 210 | // This function does not return. |
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| 211 | void MainLoop (int listen_fd, struct in_addr rem_addr, unsigned short rem_port) |
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| 212 | { |
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| 213 | int server_fd, |
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| 214 | client_fd; |
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| 215 | pid_t child_pid; |
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| 216 | |
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| 217 | for ( ; ; ) |
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| 218 | { |
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| 219 | client_fd = AcceptClientConnection (listen_fd); |
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| 220 | |
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| 221 | child_pid = fork (); |
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| 222 | if ( child_pid == -1 ) |
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| 223 | syslog (LOG_ERR, "fork(): %m"), exit (EXIT_FAILURE); |
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| 224 | |
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| 225 | if ( child_pid ) // parent |
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| 226 | { |
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| 227 | close (client_fd); |
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| 228 | |
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| 229 | syslog (LOG_INFO, "Forked child pid %d to deal with client", child_pid); |
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| 230 | |
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| 231 | continue; |
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| 232 | } |
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| 233 | else // child |
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| 234 | { |
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| 235 | close (listen_fd); |
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| 236 | |
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| 237 | server_fd = ConnectToServer (rem_addr, rem_port); |
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| 238 | |
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| 239 | Proxy (server_fd, client_fd); |
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| 240 | |
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| 241 | syslog (LOG_INFO, "exiting"); |
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| 242 | _exit (0); |
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| 243 | } |
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| 244 | } |
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| 245 | } |
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| 246 | |
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| 247 | // Proxy() |
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| 248 | // Copies data between server_fd and client_fd in both directions |
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| 249 | // until one or other peer closes their connection. |
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| 250 | void Proxy (int server_fd, int client_fd) |
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| 251 | { |
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| 252 | pid_t helper_pid; |
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| 253 | |
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| 254 | syslog (LOG_INFO, "Proxy(fd%d, fd%d)", server_fd, client_fd); |
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| 255 | |
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| 256 | signal (SIGCHLD, SIG_IGN); |
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| 257 | |
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| 258 | helper_pid = fork (); |
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| 259 | if ( helper_pid == -1 ) |
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| 260 | syslog (LOG_ERR, "fork(): %m"), exit (EXIT_FAILURE); |
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| 261 | |
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| 262 | if ( helper_pid ) // parent |
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| 263 | { |
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| 264 | syslog (LOG_INFO, "Forked child pid %d to help with proxying", helper_pid); |
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| 265 | |
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| 266 | Cat (server_fd, client_fd); |
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| 267 | |
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| 268 | shutdown (client_fd, 1); |
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| 269 | close (server_fd); |
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| 270 | close (client_fd); |
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| 271 | |
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| 272 | wait (0); // wait for helper to exit |
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| 273 | } |
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| 274 | else // child (helper) |
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| 275 | { |
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| 276 | Cat (client_fd, server_fd); |
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| 277 | |
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| 278 | shutdown (server_fd, 1); |
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| 279 | |
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| 280 | syslog (LOG_INFO, "exiting"); |
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| 281 | exit (0); // helper exits here |
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| 282 | } |
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| 283 | } |
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| 284 | |
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| 285 | // AcceptClientConnection() |
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| 286 | // waits for a tcp connect to the socket listen_fd, which |
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| 287 | // must already be bound and set to listen on a local port. |
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| 288 | // Bombs on error, returns the fd of the new socket on success. |
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| 289 | int AcceptClientConnection (int listen_fd) |
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| 290 | { |
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| 291 | int newfd; |
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| 292 | struct sockaddr_in sa; |
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| 293 | socklen_t socklen; |
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| 294 | |
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| 295 | syslog (LOG_INFO, "AcceptClientConnection(fd%d)", listen_fd); |
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| 296 | |
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| 297 | // Accept the connection and create a new socket for it. |
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| 298 | socklen = sizeof (sa); |
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| 299 | memset (&sa, 0, socklen); |
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| 300 | do |
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| 301 | { |
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| 302 | newfd = accept (listen_fd, (struct sockaddr *) &sa, &socklen); |
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| 303 | } |
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| 304 | while ( (newfd < 0) && (errno == EINTR) ); |
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| 305 | |
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| 306 | syslog (LOG_INFO, "Accepted client connection on new socket fd%d", newfd); |
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| 307 | |
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| 308 | if ( newfd < 0 ) |
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| 309 | syslog (LOG_ERR, "accept(): %m"), exit (EXIT_FAILURE); |
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| 310 | |
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| 311 | if ( socklen != sizeof (sa) ) |
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| 312 | syslog (LOG_ERR, "accept() screwed up!"), exit (EXIT_FAILURE); |
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| 313 | |
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| 314 | return (newfd); |
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| 315 | } |
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| 316 | |
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| 317 | // ConnectToServer() |
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| 318 | // attempts a tcp connect to the server specified |
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| 319 | // by addr and port. Bombs on failure to connect, |
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| 320 | // returns the fd of the new socket on success. |
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| 321 | int ConnectToServer (struct in_addr addr, unsigned short port) |
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| 322 | { |
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| 323 | // TODO: have a timeout for connect() - see Unix socket FAQ 6.2 |
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| 324 | |
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| 325 | int fd, err; |
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| 326 | struct sockaddr_in sa; |
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| 327 | |
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| 328 | // Create a socket and get its descriptor. |
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| 329 | fd = socket (AF_INET, SOCK_STREAM, 0); |
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| 330 | |
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| 331 | if ( fd < 0 ) |
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| 332 | syslog (LOG_ERR, "socket(): %m"), exit (EXIT_FAILURE); |
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| 333 | |
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| 334 | sa.sin_family = AF_INET; |
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| 335 | sa.sin_port = htons (port); |
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| 336 | sa.sin_addr = addr; |
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| 337 | memset (sa.sin_zero, 0, sizeof (sa.sin_zero)); |
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| 338 | |
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| 339 | err = connect (fd, (struct sockaddr *) &sa, sizeof (sa)); |
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| 340 | if (err < 0) |
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| 341 | { |
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| 342 | syslog (LOG_ERR, "Unable to connect socket fd%d to server: %m", fd); |
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| 343 | exit (EXIT_FAILURE); |
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| 344 | } |
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| 345 | |
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| 346 | syslog (LOG_INFO, "Connected socket fd%d to server", fd); |
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| 347 | |
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| 348 | return fd; |
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| 349 | } |
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| 350 | |
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| 351 | // Cat() |
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| 352 | // read data from in_fd and write it to out_fd until |
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| 353 | // the connection is closed by one of the peers. |
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| 354 | // Data is copied using a dynamically allocated buffer. |
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| 355 | void Cat (int in_fd, int out_fd) |
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| 356 | { |
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| 357 | unsigned char * const buf = (char *) malloc (sizeof(char) * BUF_SIZE); |
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| 358 | int bytes_rcvd, |
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| 359 | bytes_sent = (int) NULL, |
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| 360 | i; |
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| 361 | |
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| 362 | syslog (LOG_INFO, "Cat(fd%d, fd%d)", in_fd, out_fd); |
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| 363 | |
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| 364 | if ( buf == NULL ) |
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| 365 | syslog (LOG_ERR, "malloc(): %m"), exit (EXIT_FAILURE); |
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| 366 | |
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| 367 | do |
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| 368 | { |
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| 369 | write(1, "DO\n", sizeof("DO\n")); |
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| 370 | bzero(buf, BUF_SIZE); |
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| 371 | bytes_rcvd = recv (in_fd, buf, BUF_SIZE, 0); |
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| 372 | |
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| 373 | for ( i = 0; i < bytes_rcvd; i += bytes_sent ) |
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| 374 | { |
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| 375 | bytes_sent = send (out_fd, buf + i, bytes_rcvd - i, 0); |
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| 376 | |
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| 377 | if ( bytes_sent < 0 ) |
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| 378 | break; |
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| 379 | } |
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| 380 | write(1, "WHILE\n", sizeof("WHILE\n")); |
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| 381 | } |
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| 382 | while ( (bytes_rcvd > 0) && (bytes_sent > 0) ); |
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| 383 | |
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| 384 | write(1, "...\n", sizeof("...\n")); |
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| 385 | |
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| 386 | if ( (bytes_rcvd < 0) && (errno != ECONNRESET) ) |
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| 387 | syslog (LOG_ERR, "recv(): %m"), exit (EXIT_FAILURE); |
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| 388 | |
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| 389 | if ( (bytes_sent < 0) && (errno != EPIPE) ) |
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| 390 | syslog (LOG_ERR, "send(): %m"), exit (EXIT_FAILURE); |
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| 391 | |
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| 392 | free (buf); |
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| 393 | } |
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| 394 | |
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| 395 | // NameToAddress() |
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| 396 | // Convert name to an ip address. |
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| 397 | // Returns 0 on success, -1 on failure. |
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| 398 | int NameToAddr (const char * name, struct in_addr * p_inaddr) |
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| 399 | { |
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| 400 | struct hostent * he; |
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| 401 | |
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| 402 | // First, attempt to convert from string ip format |
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| 403 | // TODO: use inet_aton() instead |
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| 404 | p_inaddr->s_addr = inet_addr (name); |
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| 405 | if ( p_inaddr->s_addr != -1U ) // Success |
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| 406 | return 0; |
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| 407 | |
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| 408 | // Next, attempt to read from /etc/hosts or do a DNS lookup |
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| 409 | he = gethostbyname (name); |
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| 410 | if ( he != NULL ) // Success |
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| 411 | { |
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| 412 | memcpy (p_inaddr, he->h_addr, sizeof (struct in_addr)); |
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| 413 | return 0; |
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| 414 | } |
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| 415 | |
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| 416 | return -1; // Failed to resolve name to an ip address |
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| 417 | } |
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| 418 | |
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| 419 | // NameToPort() |
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| 420 | // Convert name to a port number. Name can either be a port name |
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| 421 | // (in which case proto must also be set to either "tcp" or "udp") |
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| 422 | // or name can be the ascii representation of the port number. |
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| 423 | // Returns 0 on success, -1 on failure. |
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| 424 | int NameToPort (const char * name, unsigned short * port, const char * proto) |
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| 425 | { |
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| 426 | unsigned long lport; |
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| 427 | char * errpos; |
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| 428 | struct servent * se; |
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| 429 | |
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| 430 | // First, attempt to convert string to integer |
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| 431 | lport = strtoul (name, &errpos, 0); |
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| 432 | if ( (*errpos == 0) && (lport <= 65535) ) // Success |
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| 433 | { |
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| 434 | *port = lport; |
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| 435 | return 0; |
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| 436 | } |
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| 437 | |
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| 438 | // Next, attempt to read the string from /etc/services |
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| 439 | se = getservbyname (name, proto); |
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| 440 | if ( se != NULL) // Success |
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| 441 | { |
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| 442 | *port = ntohs (se->s_port); |
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| 443 | return 0; |
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| 444 | } |
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| 445 | |
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| 446 | return -1; // Failed to resolve port name to a number |
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| 447 | } |
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| 448 | |
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| 449 | // quit() |
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| 450 | // Print an error message to stderr |
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| 451 | // and syslog, then exit the program. |
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| 452 | void quit (const char * fmt, ...) // quit with msg |
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| 453 | { |
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| 454 | va_list ap; |
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| 455 | |
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| 456 | fflush (stdout); |
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| 457 | |
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| 458 | fprintf (stderr, "%s: ", g_program_name); |
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| 459 | |
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| 460 | va_start (ap, fmt); |
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| 461 | vfprintf (stderr, fmt, ap); |
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| 462 | va_end (ap); |
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| 463 | |
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| 464 | fputc ('\n', stderr); |
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| 465 | |
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| 466 | syslog (LOG_ERR, "I quit!"); |
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| 467 | |
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| 468 | exit (EXIT_FAILURE); |
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| 469 | } |
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| 470 | |
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| 471 | // pbomb() |
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| 472 | // Print an error message to stderr |
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| 473 | // and syslog, then exit the program. |
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| 474 | // pbomb() additionally include the |
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| 475 | // string representation of errno. |
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| 476 | void pbomb (const char * fmt, ...) // bomb with perror |
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| 477 | { |
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| 478 | va_list ap; |
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| 479 | int errno_save = errno; |
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| 480 | char buf[100]; |
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| 481 | |
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| 482 | fflush (stdout); |
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| 483 | |
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| 484 | fprintf (stderr, "%s: ", g_program_name); |
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| 485 | |
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| 486 | va_start (ap, fmt); |
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| 487 | vsnprintf (buf, sizeof (buf), fmt, ap); |
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| 488 | va_end (ap); |
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| 489 | |
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| 490 | errno = errno_save; |
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| 491 | perror (buf); |
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| 492 | |
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| 493 | syslog (LOG_ERR, "Bang!: %s: %m", buf); |
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| 494 | |
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| 495 | exit (EXIT_FAILURE); |
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| 496 | } |
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| 497 | |
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| 498 | // hbomb() |
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| 499 | // Print an error message to stderr |
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| 500 | // and syslog, then exit the program. |
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| 501 | // hbomb() additionally include the |
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| 502 | // string representation of h_errno. |
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| 503 | void hbomb (const char * fmt, ...) // bomb with herror |
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| 504 | { |
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| 505 | va_list ap; |
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| 506 | int h_errno_save = h_errno; |
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| 507 | char buf[100]; |
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| 508 | |
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| 509 | fflush (stdout); |
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| 510 | |
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| 511 | fprintf (stderr, "%s: ", g_program_name); |
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| 512 | |
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| 513 | va_start (ap, fmt); |
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| 514 | vsnprintf (buf, sizeof (buf), fmt, ap); |
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| 515 | va_end (ap); |
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| 516 | |
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| 517 | h_errno = h_errno_save; |
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| 518 | herror (buf); |
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| 519 | |
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| 520 | syslog (LOG_ERR, "Bang!: %s: %s", buf, hstrerror (h_errno)); |
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| 521 | |
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| 522 | exit (EXIT_FAILURE); |
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| 523 | } |
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| 524 | |
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| 525 | // set_signal_handler() |
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| 526 | // Sets a signal handler function. |
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| 527 | // Similar to signal() but this method |
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| 528 | // is more portable between platforms. |
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| 529 | void set_signal_handler (int signum, signal_handler_t sa_handler_func) |
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| 530 | { |
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| 531 | struct sigaction act; |
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| 532 | |
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| 533 | act.sa_handler = sa_handler_func; |
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| 534 | sigemptyset (&(act.sa_mask)); |
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| 535 | act.sa_flags = 0; |
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| 536 | |
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| 537 | if ( sigaction (signum, &act, NULL) < 0 ) |
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| 538 | { |
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| 539 | syslog (LOG_ERR, "Error setting handler for signal %d: %m", signum); |
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| 540 | exit (EXIT_FAILURE); |
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| 541 | } |
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| 542 | } |
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