| Index: trunk/udpmcast/udpmcast.py |
| — | — | @@ -0,0 +1,215 @@ |
| | 2 | +#!/usr/bin/python |
| | 3 | +# |
| | 4 | +# udpcast.py |
| | 5 | +# application level udp multicaster/multiplexer |
| | 6 | +# Written on 2005/04/03 by Mark Bergsma <mark@nedworks.org> |
| | 7 | +# |
| | 8 | +# $Id$ |
| | 9 | + |
| | 10 | +import socket, getopt, sys, os, signal, pwd, grp |
| | 11 | + |
| | 12 | +debugging = False |
| | 13 | + |
| | 14 | +def createDaemon(): |
| | 15 | + """ |
| | 16 | + Detach a process from the controlling terminal and run it in the |
| | 17 | + background as a daemon. |
| | 18 | + """ |
| | 19 | + |
| | 20 | + try: |
| | 21 | + # Fork a child process so the parent can exit. This will return control |
| | 22 | + # to the command line or shell. This is required so that the new process |
| | 23 | + # is guaranteed not to be a process group leader. We have this guarantee |
| | 24 | + # because the process GID of the parent is inherited by the child, but |
| | 25 | + # the child gets a new PID, making it impossible for its PID to equal its |
| | 26 | + # PGID. |
| | 27 | + pid = os.fork() |
| | 28 | + except OSError, e: |
| | 29 | + return((e.errno, e.strerror)) # ERROR (return a tuple) |
| | 30 | + |
| | 31 | + if (pid == 0): # The first child. |
| | 32 | + |
| | 33 | + # Next we call os.setsid() to become the session leader of this new |
| | 34 | + # session. The process also becomes the process group leader of the |
| | 35 | + # new process group. Since a controlling terminal is associated with a |
| | 36 | + # session, and this new session has not yet acquired a controlling |
| | 37 | + # terminal our process now has no controlling terminal. This shouldn't |
| | 38 | + # fail, since we're guaranteed that the child is not a process group |
| | 39 | + # leader. |
| | 40 | + os.setsid() |
| | 41 | + |
| | 42 | + # When the first child terminates, all processes in the second child |
| | 43 | + # are sent a SIGHUP, so it's ignored. |
| | 44 | + signal.signal(signal.SIGHUP, signal.SIG_IGN) |
| | 45 | + |
| | 46 | + try: |
| | 47 | + # Fork a second child to prevent zombies. Since the first child is |
| | 48 | + # a session leader without a controlling terminal, it's possible for |
| | 49 | + # it to acquire one by opening a terminal in the future. This second |
| | 50 | + # fork guarantees that the child is no longer a session leader, thus |
| | 51 | + # preventing the daemon from ever acquiring a controlling terminal. |
| | 52 | + pid = os.fork() # Fork a second child. |
| | 53 | + except OSError, e: |
| | 54 | + return((e.errno, e.strerror)) # ERROR (return a tuple) |
| | 55 | + |
| | 56 | + if (pid == 0): # The second child. |
| | 57 | + # Ensure that the daemon doesn't keep any directory in use. Failure |
| | 58 | + # to do this could make a filesystem unmountable. |
| | 59 | + os.chdir("/") |
| | 60 | + # Give the child complete control over permissions. |
| | 61 | + os.umask(0) |
| | 62 | + else: |
| | 63 | + os._exit(0) # Exit parent (the first child) of the second child. |
| | 64 | + else: |
| | 65 | + os._exit(0) # Exit parent of the first child. |
| | 66 | + |
| | 67 | + # Close all open files. Try the system configuration variable, SC_OPEN_MAX, |
| | 68 | + # for the maximum number of open files to close. If it doesn't exist, use |
| | 69 | + # the default value (configurable). |
| | 70 | + try: |
| | 71 | + maxfd = os.sysconf("SC_OPEN_MAX") |
| | 72 | + except (AttributeError, ValueError): |
| | 73 | + maxfd = 256 # default maximum |
| | 74 | + |
| | 75 | + for fd in range(0, maxfd): |
| | 76 | + try: |
| | 77 | + os.close(fd) |
| | 78 | + except OSError: # ERROR (ignore) |
| | 79 | + pass |
| | 80 | + |
| | 81 | + # Redirect the standard file descriptors to /dev/null. |
| | 82 | + os.open("/dev/null", os.O_RDONLY) # standard input (0) |
| | 83 | + os.open("/dev/null", os.O_RDWR) # standard output (1) |
| | 84 | + os.open("/dev/null", os.O_RDWR) # standard error (2) |
| | 85 | + |
| | 86 | + return(0) |
| | 87 | + |
| | 88 | +def debug(msg): |
| | 89 | + global debugging |
| | 90 | + if debugging: |
| | 91 | + print msg; |
| | 92 | + |
| | 93 | +def multicast_diagrams(sock, addrrules): |
| | 94 | + portnr = sock.getsockname()[1]; |
| | 95 | + |
| | 96 | + while 1: |
| | 97 | + diagram, srcaddr = sock.recvfrom(2**14) |
| | 98 | + if not diagram: break |
| | 99 | + |
| | 100 | + try: |
| | 101 | + addresses = addrrules[srcaddr[0]] |
| | 102 | + except KeyError: |
| | 103 | + addresses = addrrules[0] |
| | 104 | + |
| | 105 | + for addr in addresses: |
| | 106 | + try: |
| | 107 | + sock.sendto(diagram, 0, (addr, portnr)) |
| | 108 | + debug('Sent diagram to '+addr+' port '+str(portnr)) |
| | 109 | + except socket.error: |
| | 110 | + debug('Error while sending diagram to '+addr) |
| | 111 | + pass |
| | 112 | + |
| | 113 | +def join_multicast_group(sock, multicast_group): |
| | 114 | + import struct |
| | 115 | + |
| | 116 | + ip_mreq = struct.pack('!4sl', socket.inet_aton(multicast_group), |
| | 117 | + socket.INADDR_ANY) |
| | 118 | + sock.setsockopt(socket.IPPROTO_IP, |
| | 119 | + socket.IP_ADD_MEMBERSHIP, |
| | 120 | + ip_mreq) |
| | 121 | + |
| | 122 | + # We do not want to see our own messages back |
| | 123 | + sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_LOOP, 0) |
| | 124 | + |
| | 125 | +def print_help(): |
| | 126 | + print 'Usage:\n\tudpmcast [ options ] { addresses | forward rules }\n' |
| | 127 | + print 'Options:' |
| | 128 | + print '\t-d\t\tFork into the background (become a daemon)' |
| | 129 | + print '\t-p {portnr}\tUDP port number to listen on (default is 4827)' |
| | 130 | + print '\t-j {mcast addr}\tMulticast group to join on startup' |
| | 131 | + print '\t-u {username}\tChange uid' |
| | 132 | + print '\t-g {group}\tChange group' |
| | 133 | + print '\t-t {ttl}\tSet multicast TTL for outgoing multicast packets' |
| | 134 | + print '\t-v\t\tBe more verbose' |
| | 135 | + |
| | 136 | +if __name__ == '__main__': |
| | 137 | + host = '' |
| | 138 | + portnr = 4827 |
| | 139 | + multicast_group = None |
| | 140 | + multicast_ttl = None |
| | 141 | + daemon = False |
| | 142 | + user = group = None |
| | 143 | + opts = 'dhj:p:vu:g:t:' |
| | 144 | + |
| | 145 | + # Parse options |
| | 146 | + options, arguments = getopt.getopt(sys.argv[1:], opts) |
| | 147 | + if len(arguments) == 0: |
| | 148 | + print_help() |
| | 149 | + sys.exit() |
| | 150 | + else: |
| | 151 | + for option, value in options: |
| | 152 | + if option == '-j': |
| | 153 | + multicast_group = value |
| | 154 | + elif option == '-p': |
| | 155 | + portnr = int(value) |
| | 156 | + elif option == '-h': |
| | 157 | + print_help() |
| | 158 | + sys.exit() |
| | 159 | + elif option == '-d': |
| | 160 | + daemon = True |
| | 161 | + elif option == '-u': |
| | 162 | + user = value |
| | 163 | + elif option == '-g': |
| | 164 | + group = value |
| | 165 | + elif option == '-v': |
| | 166 | + debugging = True |
| | 167 | + elif option == '-t': |
| | 168 | + multicast_ttl = int(value) |
| | 169 | + |
| | 170 | + try: |
| | 171 | + # Change uid and gid |
| | 172 | + try: |
| | 173 | + if group: os.setgid(grp.getgrnam(group).gr_gid) |
| | 174 | + if user: os.setuid(pwd.getpwnam(user).pw_uid) |
| | 175 | + except: |
| | 176 | + print "Error: Could not change uid or gid." |
| | 177 | + sys.exit(-1) |
| | 178 | + |
| | 179 | + # Become a daemon |
| | 180 | + if daemon: |
| | 181 | + createDaemon() |
| | 182 | + |
| | 183 | + # Open the UDP socket |
| | 184 | + sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) |
| | 185 | + sock.bind((host, portnr)) |
| | 186 | + |
| | 187 | + # Set the multicast TTL if requested |
| | 188 | + if multicast_ttl is not None: |
| | 189 | + sock.setsockopt(socket.IPPROTO_IP, |
| | 190 | + socket.IP_MULTICAST_TTL, |
| | 191 | + multicast_ttl) |
| | 192 | + |
| | 193 | + # Join a multicast group if requested |
| | 194 | + if multicast_group is not None: |
| | 195 | + debug('Joining multicast group ' + multicast_group) |
| | 196 | + join_multicast_group(sock, multicast_group) |
| | 197 | + |
| | 198 | + # Parse the argument list |
| | 199 | + addrrules = { 0: [] } |
| | 200 | + for argument in arguments: |
| | 201 | + if argument[0] == '{': |
| | 202 | + # Forward rule |
| | 203 | + addrrules.update(eval(argument)) |
| | 204 | + else: |
| | 205 | + # Default forward |
| | 206 | + addrrules[0].append(argument) |
| | 207 | + |
| | 208 | + debug('Forward rules: ' + str(addrrules)) |
| | 209 | + |
| | 210 | + # Multiplex everything that comes in |
| | 211 | + multicast_diagrams(sock, addrrules) |
| | 212 | + except socket.error, msg: |
| | 213 | + print msg[1]; |
| | 214 | + except KeyboardInterrupt: |
| | 215 | + pass |
| | 216 | + |
| Property changes on: trunk/udpmcast/udpmcast.py |
| ___________________________________________________________________ |
| Added: svn:keywords |
| 1 | 217 | + Author Date Id Revision |
| Added: svn:eol-style |
| 2 | 218 | + native |
| Added: svn:executable |
| 3 | 219 | + * |