Add 'sshuttle --hostwatch' subcommand.

This tries to discover local hostnames and prints them to stdout.  Will be
used by the server for auto-hostname tracking.

helpers.py

@@ -16,6 +16,10 @@ def debug2(s):
     if verbose >= 2:
         log(s)
 
+def debug3(s):
+    if verbose >= 3:
+        log(s)
+
 
 class Fatal(Exception):
     pass

hostwatch.py

+import subprocess, time, socket, re, select
+if not globals().get('skip_imports'):
+    import helpers
+    from helpers import *
+
+POLL_TIME = 60*15
+
+
+_nmb_ok = True
+_smb_ok = True
+hostnames = {}
+queue = {}
+null = open('/dev/null', 'rb+')
+
+
+def _is_ip(s):
+    return re.match(r'\d+\.\d+\.\d+\.\d+$', s)
+
+
+def found_host(hostname, ip):
+    hostname = re.sub(r'\..*', '', hostname)
+    hostname = re.sub(r'[^-\w]', '_', hostname)
+    if ip.startswith('127.') or hostname == 'localhost':
+        return
+    oldip = hostnames.get(hostname)
+    if oldip != ip:
+        hostnames[hostname] = ip
+        debug1('Found: %s: %s\n' % (hostname, ip))
+        sys.stdout.write('%s,%s\n' % (hostname, ip))
+
+
+def _check_etc_hosts():
+    debug1(' > hosts\n')
+    for line in open('/etc/hosts'):
+        line = re.sub(r'#.*', '', line)
+        words = line.strip().split()
+        if not words:
+            continue
+        ip = words[0]
+        names = words[1:]
+        if _is_ip(ip):
+            debug2('<    %s %r\n' % (ip, names))
+            for n in names:
+                check_host(n)
+                found_host(n, ip)
+
+
+def _check_revdns(ip):
+    debug1(' > rev: %s\n' % ip)
+    try:
+        r = socket.gethostbyaddr(ip)
+        debug3('<    %s\n' % r[0])
+        check_host(r[0])
+        found_host(r[0], ip)
+    except socket.herror, e:
+        pass
+
+
+def _check_dns(hostname):
+    debug1(' > dns: %s\n' % hostname)
+    try:
+        ip = socket.gethostbyname(hostname)
+        debug3('<    %s\n' % ip)
+        check_host(ip)
+        found_host(hostname, ip)
+    except socket.gaierror, e:
+        pass
+
+
+def _check_smb(hostname):
+    global _smb_ok
+    if not _smb_ok:
+        return
+    argv = ['smbclient', '-U', '%', '-L', hostname]
+    debug2(' > smb: %s\n' % hostname)
+    try:
+        p = subprocess.Popen(argv, stdout=subprocess.PIPE, stderr=null)
+        lines = p.stdout.readlines()
+        p.wait()
+    except OSError, e:
+        log('%r failed: %r\n' % (argv, e))
+        _smb_ok = False
+        return
+
+    lines.reverse()
+
+    # junk at top
+    while lines:
+        line = lines.pop().strip()
+        if re.match(r'Server\s+', line):
+            break
+
+    # server list section:
+    #    Server   Comment
+    #    ------   -------
+    while lines:
+        line = lines.pop().strip()
+        if not line or re.match(r'-+\s+-+', line):
+            continue
+        if re.match(r'Workgroup\s+Master', line):
+            break
+        words = line.split()
+        hostname = words[0].lower()
+        debug3('<    %s\n' % hostname)
+        check_host(hostname)
+
+    # workgroup list section:
+    #   Workgroup  Master
+    #   ---------  ------
+    while lines:
+        line = lines.pop().strip()
+        if re.match(r'-+\s+', line):
+            continue
+        if not line:
+            break
+        words = line.split()
+        (workgroup, hostname) = (words[0].lower(), words[1].lower())
+        debug3('<    group(%s) -> %s\n' % (workgroup, hostname))
+        check_host(hostname)
+        check_workgroup(workgroup)
+
+    if lines:
+        assert(0)
+
+
+def _check_nmb(hostname, is_workgroup, is_master):
+    global _nmb_ok
+    if not _nmb_ok:
+        return
+    argv = ['nmblookup'] + ['-M']*is_master + ['--', hostname]
+    debug2(' > n%d%d: %s\n' % (is_workgroup, is_master, hostname))
+    try:
+        p = subprocess.Popen(argv, stdout=subprocess.PIPE, stderr=null)
+        lines = p.stdout.readlines()
+        rv = p.wait()
+    except OSError, e:
+        log('%r failed: %r\n' % (argv, e))
+        _nmb_ok = False
+        return
+    if rv:
+        log('%r returned %d\n' % (argv, rv))
+        return
+    for line in lines:
+        m = re.match(r'(\d+\.\d+\.\d+\.\d+) (\w+)<\w\w>\n', line)
+        if m:
+            g = m.groups()
+            (ip, name) = (g[0], g[1].lower())
+            debug3('<    %s -> %s\n' % (name, ip))
+            if is_workgroup:
+                _enqueue(_check_smb, ip)
+            else:
+                found_host(name, ip)
+                check_host(name)
+
+
+def check_host(hostname):
+    if _is_ip(hostname):
+        _enqueue(_check_revdns, hostname)
+    else:
+        _enqueue(_check_dns, hostname)
+    _enqueue(_check_smb, hostname)
+    _enqueue(_check_nmb, hostname, False, False)
+
+
+def check_workgroup(hostname):
+    _enqueue(_check_nmb, hostname, True, False)
+    _enqueue(_check_nmb, hostname, True, True)
+
+
+def _enqueue(op, *args):
+    t = (op,args)
+    if queue.get(t) == None:
+        queue[t] = 0
+
+
+def _stdin_still_ok(timeout):
+    r,w,x = select.select([sys.stdin.fileno()], [], [], timeout)
+    if r:
+        b = os.read(sys.stdin.fileno(), 4096)
+        if not b:
+            return False
+    return True
+
+
+def hw_main(seed_hosts):
+    if helpers.verbose >= 2:
+        helpers.logprefix = 'HH: '
+    else:
+        helpers.logprefix = 'hostwatch: '
+        
+    _enqueue(_check_etc_hosts)
+    check_host('localhost')
+    check_host(socket.gethostname())
+    check_workgroup('workgroup')
+    check_workgroup('-')
+    for h in seed_hosts:
+        check_host(h)
+
+    while 1:
+        now = time.time()
+        for t,last_polled in queue.items():
+            if not _stdin_still_ok(0):
+                break
+            if now - last_polled > POLL_TIME:
+                (op,args) = t
+                queue[t] = time.time()
+                op(*args)
+            try:
+                sys.stdout.flush()
+            except IOError:
+                break
+                
+        # FIXME: use a smarter timeout based on oldest last_polled
+        if not _stdin_still_ok(1):
+            break

main.py

 #!/usr/bin/env python
 import sys, os, re
-import helpers, options, client, server, firewall
+import helpers, options, client, server, firewall, hostwatch
 from helpers import *
 
 
@@ -56,6 +56,7 @@ v,verbose  increase debug message verbosity
 noserver   don't use a separate server process (mostly for debugging)
 server     [internal use only]
 firewall   [internal use only]
+hostwatch  [internal use only]
 """
 o = options.Options('sshuttle', optspec)
 (opt, flags, extra) = o.parse(sys.argv[1:])
@@ -64,11 +65,15 @@ helpers.verbose = opt.verbose
 
 try:
     if opt.server:
+        if len(extra) != 0:
+            o.fatal('no arguments expected')
         sys.exit(server.main())
     elif opt.firewall:
         if len(extra) != 1:
             o.fatal('exactly one argument expected')
         sys.exit(firewall.main(int(extra[0])))
+    elif opt.hostwatch:
+        sys.exit(hostwatch.hw_main(extra))
     else:
         if len(extra) < 1 and not opt.auto_nets:
             o.fatal('at least one subnet (or -N) expected')