man page update for daemonization options.

...MacOS X seems to default (in /etc/syslog.conf) to not logging daemon.info
anywhere.  That kind of defeats the purpose, I think.

client.py

@@ -1,9 +1,98 @@
-import struct, socket, select, errno, re
+import struct, socket, select, errno, re, signal
 import compat.ssubprocess as ssubprocess
-import helpers, ssnet, ssh
+import helpers, ssnet, ssh, ssyslog
 from ssnet import SockWrapper, Handler, Proxy, Mux, MuxWrapper
 from helpers import *
 
+_extra_fd = os.open('/dev/null', os.O_RDONLY)
+
+def _islocal(ip):
+    sock = socket.socket()
+    try:
+        try:
+            sock.bind((ip, 0))
+        except socket.error, e:
+            if e.args[0] == errno.EADDRNOTAVAIL:
+                return False  # not a local IP
+            else:
+                raise
+    finally:
+        sock.close()
+    return True  # it's a local IP, or there would have been an error
+
+
+def got_signal(signum, frame):
+    log('exiting on signal %d\n' % signum)
+    sys.exit(1)
+
+
+_pidname = None
+def check_daemon(pidfile):
+    global _pidname
+    _pidname = os.path.abspath(pidfile)
+    try:
+        oldpid = open(_pidname).read(1024)
+    except IOError, e:
+        if e.errno == errno.ENOENT:
+            return  # no pidfile, ok
+        else:
+            raise Fatal("can't read %s: %s" % (_pidname, e))
+    if not oldpid:
+        os.unlink(_pidname)
+        return  # invalid pidfile, ok
+    oldpid = int(oldpid.strip() or 0)
+    if oldpid <= 0:
+        os.unlink(_pidname)
+        return  # invalid pidfile, ok
+    try:
+        os.kill(oldpid, 0)
+    except OSError, e:
+        if e.errno == errno.ESRCH:
+            os.unlink(_pidname)
+            return  # outdated pidfile, ok
+        elif e.errno == errno.EPERM:
+            pass
+        else:
+            raise
+    raise Fatal("%s: sshuttle is already running (pid=%d)"
+                % (_pidname, oldpid))
+
+
+def daemonize():
+    if os.fork():
+        os._exit(0)
+    os.setsid()
+    if os.fork():
+        os._exit(0)
+
+    outfd = os.open(_pidname, os.O_WRONLY|os.O_CREAT|os.O_EXCL, 0666)
+    try:
+        os.write(outfd, '%d\n' % os.getpid())
+    finally:
+        os.close(outfd)
+    os.chdir("/")
+
+    # Normal exit when killed, or try/finally won't work and the pidfile won't
+    # be deleted.
+    signal.signal(signal.SIGTERM, got_signal)
+    
+    si = open('/dev/null', 'r+')
+    os.dup2(si.fileno(), 0)
+    os.dup2(si.fileno(), 1)
+    si.close()
+
+    ssyslog.stderr_to_syslog()
+
+
+def daemon_cleanup():
+    try:
+        os.unlink(_pidname)
+    except OSError, e:
+        if e.errno == errno.ENOENT:
+            pass
+        else:
+            raise
+
 
 def original_dst(sock):
     try:
@@ -30,6 +119,8 @@ class FirewallClient:
         argvbase = ([sys.argv[0]] +
                     ['-v'] * (helpers.verbose or 0) +
                     ['--firewall', str(port)])
+        if ssyslog._p:
+            argvbase += ['--syslog']
         argv_tries = [
             ['sudo', '-p', '[local sudo] Password: '] + argvbase,
             ['su', '-c', ' '.join(argvbase)],
@@ -98,25 +189,34 @@ class FirewallClient:
             raise Fatal('cleanup: %r returned %d' % (self.argv, rv))
 
 
-def _main(listener, fw, ssh_cmd, remotename, python, seed_hosts, auto_nets):
+def _main(listener, fw, ssh_cmd, remotename, python, seed_hosts, auto_nets,
+          syslog, daemon):
     handlers = []
     if helpers.verbose >= 1:
         helpers.logprefix = 'c : '
     else:
         helpers.logprefix = 'client: '
     debug1('connecting to server...\n')
+
     try:
-        (serverproc, serversock) = ssh.connect(ssh_cmd, remotename, python)
+        (serverproc, serversock) = ssh.connect(ssh_cmd, remotename, python,
+                        stderr=ssyslog._p and ssyslog._p.stdin)
     except socket.error, e:
-        if e.errno == errno.EPIPE:
-            raise Fatal("failed to establish ssh session")
+        if e.args[0] == errno.EPIPE:
+            raise Fatal("failed to establish ssh session (1)")
         else:
             raise
     mux = Mux(serversock, serversock)
     handlers.append(mux)
 
     expected = 'SSHUTTLE0001'
-    initstring = serversock.recv(len(expected))
+    try:
+        initstring = serversock.recv(len(expected))
+    except socket.error, e:
+        if e.args[0] == errno.ECONNRESET:
+            raise Fatal("failed to establish ssh session (2)")
+        else:
+            raise
     
     rv = serverproc.poll()
     if rv:
@@ -126,6 +226,12 @@ def _main(listener, fw, ssh_cmd, remotename, python, seed_hosts, auto_nets):
         raise Fatal('expected server init string %r; got %r'
                         % (expected, initstring))
     debug1('connected.\n')
+    if daemon:
+        daemonize()
+        log('daemonizing (%s).\n' % _pidname)
+    elif syslog:
+        debug1('switching to syslog.\n')
+        ssyslog.stderr_to_syslog()
 
     def onroutes(routestr):
         if auto_nets:
@@ -153,11 +259,26 @@ def _main(listener, fw, ssh_cmd, remotename, python, seed_hosts, auto_nets):
     mux.got_host_list = onhostlist
 
     def onaccept():
-        sock,srcip = listener.accept()
+        global _extra_fd
+        try:
+            sock,srcip = listener.accept()
+        except socket.error, e:
+            if e.args[0] in [errno.EMFILE, errno.ENFILE]:
+                debug1('Rejected incoming connection: too many open files!\n')
+                # free up an fd so we can eat the connection
+                os.close(_extra_fd)
+                try:
+                    sock,srcip = listener.accept()
+                    sock.close()
+                finally:
+                    _extra_fd = os.open('/dev/null', os.O_RDONLY)
+                return
+            else:
+                raise
         dstip = original_dst(sock)
-        debug1('Accept: %r:%r -> %r:%r.\n' % (srcip[0],srcip[1],
-                                           dstip[0],dstip[1]))
-        if dstip == listener.getsockname():
+        debug1('Accept: %s:%r -> %s:%r.\n' % (srcip[0],srcip[1],
+                                              dstip[0],dstip[1]))
+        if dstip[1] == listener.getsockname()[1] and _islocal(dstip[0]):
             debug1("-- ignored: that's my address!\n")
             sock.close()
             return
@@ -182,7 +303,15 @@ def _main(listener, fw, ssh_cmd, remotename, python, seed_hosts, auto_nets):
 
 
 def main(listenip, ssh_cmd, remotename, python, seed_hosts, auto_nets,
-         subnets_include, subnets_exclude):
+         subnets_include, subnets_exclude, syslog, daemon, pidfile):
+    if syslog:
+        ssyslog.start_syslog()
+    if daemon:
+        try:
+            check_daemon(pidfile)
+        except Fatal, e:
+            log("%s\n" % e)
+            return 5
     debug1('Starting sshuttle proxy.\n')
     listener = socket.socket()
     listener.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
@@ -213,6 +342,13 @@ def main(listenip, ssh_cmd, remotename, python, seed_hosts, auto_nets,
     
     try:
         return _main(listener, fw, ssh_cmd, remotename,
-                     python, seed_hosts, auto_nets)
+                     python, seed_hosts, auto_nets, syslog, daemon)
     finally:
-        fw.done()
+        try:
+            if daemon:
+                # it's not our child anymore; can't waitpid
+                fw.p.returncode = 0
+            fw.done()
+        finally:
+            if daemon:
+                daemon_cleanup()

firewall.py

@@ -1,6 +1,6 @@
 import re, errno
 import compat.ssubprocess as ssubprocess
-import helpers
+import helpers, ssyslog
 from helpers import *
 
 
@@ -216,7 +216,7 @@ def restore_etc_hosts(port):
 # exit.  In case that fails, it's not the end of the world; future runs will
 # supercede it in the transproxy list, at least, so the leftover rules
 # are hopefully harmless.
-def main(port):
+def main(port, syslog):
     assert(port > 0)
     assert(port <= 65535)
 
@@ -235,6 +235,10 @@ def main(port):
     # can read from it.
     os.dup2(1, 0)
 
+    if syslog:
+        ssyslog.start_syslog()
+        ssyslog.stderr_to_syslog()
+
     debug1('firewall manager ready.\n')
     sys.stdout.write('READY\n')
     sys.stdout.flush()

main.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 import sys, os, re
 import helpers, options, client, server, firewall, hostwatch
+import compat.ssubprocess as ssubprocess
 from helpers import *
 
 
@@ -46,18 +47,22 @@ def parse_ipport(s):
 
 optspec = """
 sshuttle [-l [ip:]port] [-r [username@]sshserver[:port]] <subnets...>
-sshuttle --firewall <port> <subnets...>
 sshuttle --server
+sshuttle --firewall <port> <subnets...>
+sshuttle --hostwatch
 --
-l,listen=  transproxy to this ip address and port number [0.0.0.0:0]
+l,listen=  transproxy to this ip address and port number [127.0.0.1:0]
 H,auto-hosts scan for remote hostnames and update local /etc/hosts
 N,auto-nets  automatically determine subnets to route
-python= specify the name/path of the python interpreter on the remote server [python]
+python=    path to python interpreter on the remote server [python]
 r,remote=  ssh hostname (and optional username) of remote sshuttle server
 x,exclude= exclude this subnet (can be used more than once)
 v,verbose  increase debug message verbosity
 e,ssh-cmd= the command to use to connect to the remote [ssh]
 seed-hosts= with -H, use these hostnames for initial scan (comma-separated)
+D,daemon   run in the background as a daemon
+syslog     send log messages to syslog (default if you use --daemon)
+pidfile=   pidfile name (only if using --daemon) [./sshuttle.pid]
 server     (internal use only)
 firewall   (internal use only)
 hostwatch  (internal use only)
@@ -65,6 +70,8 @@ hostwatch  (internal use only)
 o = options.Options('sshuttle', optspec)
 (opt, flags, extra) = o.parse(sys.argv[1:])
 
+if opt.daemon:
+    opt.syslog = 1
 helpers.verbose = opt.verbose
 
 try:
@@ -75,7 +82,7 @@ try:
     elif opt.firewall:
         if len(extra) != 1:
             o.fatal('exactly one argument expected')
-        sys.exit(firewall.main(int(extra[0])))
+        sys.exit(firewall.main(int(extra[0]), opt.syslog))
     elif opt.hostwatch:
         sys.exit(hostwatch.hw_main(extra))
     else:
@@ -104,7 +111,8 @@ try:
                              sh,
                              opt.auto_nets,
                              parse_subnets(includes),
-                             parse_subnets(excludes)))
+                             parse_subnets(excludes),
+                             opt.syslog, opt.daemon, opt.pidfile))
 except Fatal, e:
     log('fatal: %s\n' % e)
     sys.exit(99)

server.py

@@ -166,6 +166,7 @@ def main():
 
     while mux.ok:
         if hw.pid:
+            assert(hw.pid > 0)
             (rpid, rv) = os.waitpid(hw.pid, os.WNOHANG)
             if rpid:
                 raise Fatal('hostwatch exited unexpectedly: code 0x%04x\n' % rv)

ssh.py

@@ -21,7 +21,7 @@ def empackage(z, filename):
     return '%s\n%d\n%s' % (basename,len(content), content)
 
 
-def connect(ssh_cmd, rhostport, python):
+def connect(ssh_cmd, rhostport, python, stderr):
     main_exe = sys.argv[0]
     portl = []
 
@@ -87,7 +87,7 @@ def connect(ssh_cmd, rhostport, python):
     s1.close()
     debug2('executing: %r\n' % argv)
     p = ssubprocess.Popen(argv, stdin=s1a, stdout=s1b, preexec_fn=setup,
-                         close_fds=True)
+                          close_fds=True, stderr=stderr)
     os.close(s1a)
     os.close(s1b)
     s2.sendall(content)

sshuttle.md

@@ -1,6 +1,6 @@
-% sshuttle(8) Sshuttle 0.42
+% sshuttle(8) Sshuttle 0.44
 % Avery Pennarun <apenwarr@gmail.com>
-% 2010-11-09
+% 2010-12-31
 
 # NAME
 
@@ -41,7 +41,13 @@ entire subnet to the VPN.
 -l, --listen=*[ip:]port*
 :   use this ip address and port number as the transparent
     proxy port.  By default sshuttle finds an available
-    port automatically, so you don't need to override it.
+    port automatically and listens on IP 127.0.0.1
+    (localhost), so you don't need to override it, and
+    connections are only proxied from the local machine,
+    not from outside machines.  If you want to accept
+    connections from other machines on your network (ie. to
+    run sshuttle on a router) try enabling IP Forwarding in
+    your kernel, then using `--listen 0.0.0.0:0`. 
 
 -H, --auto-hosts
 :   scan for remote hostnames and update the local /etc/hosts
@@ -103,6 +109,20 @@ entire subnet to the VPN.
     if you use this option to give it a few names to start
     from.
     
+-D, --daemon
+:   automatically fork into the background after connecting
+    to the remote server.  Implies `--syslog`.
+    
+--syslog
+:   after connecting, send all log messages to the
+    `syslog`(3) service instead of stderr.  This is
+    implicit if you use `--daemon`.
+    
+--pidfile=*pidfilename*
+:   when using `--daemon`, save sshuttle's pid to
+    *pidfilename*.  The default is `sshuttle.pid` in the
+    current directory.
+
 --server
 :   (internal use only) run the sshuttle server on
     stdin/stdout.  This is what the client runs on
@@ -139,8 +159,8 @@ Test locally by proxying all local connections, without using ssh:
      s:   192.168.42.0/24
     c : connected.
     firewall manager: starting transproxy.
-    c : Accept: '192.168.42.106':50035 -> '192.168.42.121':139.
-    c : Accept: '192.168.42.121':47523 -> '77.141.99.22':443.
+    c : Accept: 192.168.42.106:50035 -> 192.168.42.121:139.
+    c : Accept: 192.168.42.121:47523 -> 77.141.99.22:443.
         ...etc...
     ^C
     firewall manager: undoing changes.
@@ -166,7 +186,7 @@ and subnet guessing:
     hostwatch: Found: testbox1: 1.2.3.4
     hostwatch: Found: mytest2: 5.6.7.8
     hostwatch: Found: domaincontroller: 99.1.2.3
-    c : Accept: '192.168.42.121':60554 -> '77.141.99.22':22.
+    c : Accept: 192.168.42.121:60554 -> 77.141.99.22:22.
     ^C
     firewall manager: undoing changes.
     c : Keyboard interrupt: exiting.

ssnet.py

@@ -15,7 +15,7 @@ CMD_EXIT = 0x4200
 CMD_PING = 0x4201
 CMD_PONG = 0x4202
 CMD_CONNECT = 0x4203
-# CMD_CLOSE = 0x4204   # never used - removed
+CMD_STOP_SENDING = 0x4204
 CMD_EOF = 0x4205
 CMD_DATA = 0x4206
 CMD_ROUTES = 0x4207
@@ -27,6 +27,7 @@ cmd_to_name = {
     CMD_PING: 'PING',
     CMD_PONG: 'PONG',
     CMD_CONNECT: 'CONNECT',
+    CMD_STOP_SENDING: 'STOP_SENDING',
     CMD_EOF: 'EOF',
     CMD_DATA: 'DATA',
     CMD_ROUTES: 'ROUTES',
@@ -106,6 +107,8 @@ class SockWrapper:
     def seterr(self, e):
         if not self.exc:
             self.exc = e
+        self.nowrite()
+        self.noread()
 
     def try_connect(self):
         if self.connect_to and self.shut_write:
@@ -162,8 +165,6 @@ class SockWrapper:
         except OSError, e:
             # unexpected error... stream is dead
             self.seterr(e)
-            self.nowrite()
-            self.noread()
             return 0
         
     def write(self, buf):
@@ -231,6 +232,11 @@ class Proxy(Handler):
         self.wrap2 = wrap2
 
     def pre_select(self, r, w, x):
+        if self.wrap1.shut_read: self.wrap2.nowrite()
+        if self.wrap1.shut_write: self.wrap2.noread()
+        if self.wrap2.shut_read: self.wrap1.nowrite()
+        if self.wrap2.shut_write: self.wrap1.noread()
+        
         if self.wrap1.connect_to:
             _add(w, self.wrap1.rsock)
         elif self.wrap1.buf:
@@ -430,6 +436,7 @@ class MuxWrapper(SockWrapper):
     def noread(self):
         if not self.shut_read:
             self.shut_read = True
+            self.mux.send(self.channel, CMD_STOP_SENDING, '')
             self.maybe_close()
 
     def nowrite(self):
@@ -464,6 +471,8 @@ class MuxWrapper(SockWrapper):
     def got_packet(self, cmd, data):
         if cmd == CMD_EOF:
             self.noread()
+        elif cmd == CMD_STOP_SENDING:
+            self.nowrite()
         elif cmd == CMD_DATA:
             self.buf.append(data)
         else:

ssyslog.py

@@ -0,0 +1,16 @@
+import sys, os
+from compat import ssubprocess
+
+
+_p = None
+def start_syslog():
+    global _p
+    _p = ssubprocess.Popen(['logger',
+                            '-p', 'daemon.notice',
+                            '-t', 'sshuttle'], stdin=ssubprocess.PIPE)
+
+
+def stderr_to_syslog():
+    sys.stdout.flush()
+    sys.stderr.flush()
+    os.dup2(_p.stdin.fileno(), 2)