relay: fix many bugs with nick collision handling, and add flood prevention for fixing nicks

Closes #85. Nick collisions caused by internal clients are handled fine now, including the following cases:
- Abusing spawnClient to create a user with the same nick as a relay client, but with a lower TS.
- When both an UID (e.g. 42XAAAAAA) and a tagged UID (_42XAAAAAA) exist on the same network (the two will both try to take the same nick of _42XAAAAAA/net over the relay).

The case where changing NICK from a long cut-off nick to another long cut-off nick is also mitigated. somelongnick/net won't show nick changes to somelongnic//net if the old and new nicks have give the same normalized relay nick.

This introduces a new dependency, expiringdict, from https://pypi.python.org/pypi/expiringdict/1.1.2, which is used as a cache for flood prevention.

README.md

@@ -14,6 +14,7 @@ Dependencies currently include:
 
 * Python 3.4+
 * PyYAML (`pip install pyyaml` or `apt-get install python3-yaml`)
+* *For the relay plugin only*: expiringdict (`pip install expiringdict`/`apt-get install python3-expiringdict`)
 
 #### Supported IRCds
 
@@ -23,7 +24,7 @@ Dependencies currently include:
 
 ### Installation
 
-1) Rename `config.yml.example` to `config.yml` and configure your instance there. Not all options are properly implemented yet, and the configuration schema isn't finalized yet - this means your configuration may break in an update!
+1) Rename `config.yml.example` to `config.yml` and configure your instance there. Not all options are properly implemented yet, and the configuration schema isn't finalized yet - this means that your configuration may break in an update!
 
 2) Run `main.py` from the command line.
 

plugins/relay.py

@@ -8,6 +8,8 @@ import threading
 import string
 from collections import defaultdict
 
+from expiringdict import ExpiringDict
+
 import utils
 from log import log
 from conf import confname
@@ -19,6 +21,7 @@ dbname += '.db'
 
 relayusers = defaultdict(dict)
 spawnlocks = defaultdict(threading.Lock)
+savecache = ExpiringDict(max_len=5, max_age_seconds=10)
 
 def relayWhoisHandlers(irc, target):
     user = irc.users[target]
@@ -31,41 +34,46 @@ def relayWhoisHandlers(irc, target):
                                                      remotenick)]
 utils.whois_handlers.append(relayWhoisHandlers)
 
-def normalizeNick(irc, netname, nick, separator=None, oldnick=''):
+def normalizeNick(irc, netname, nick, separator=None, uid=''):
     separator = separator or irc.serverdata.get('separator') or "/"
     log.debug('(%s) normalizeNick: using %r as separator.', irc.name, separator)
     orig_nick = nick
     protoname = irc.proto.__name__
     maxnicklen = irc.maxnicklen
     if not protoname.startswith(('insp', 'unreal')):
-        # Charybdis doesn't allow / in usernames, and will quit with
+        # Charybdis doesn't allow / in usernames, and will SQUIT with
-        # a protocol violation if there is one.
+        # a protocol violation if it sees one.
         separator = separator.replace('/', '|')
         nick = nick.replace('/', '|')
     if nick.startswith(tuple(string.digits)):
         # On TS6 IRCds, nicks that start with 0-9 are only allowed if
         # they match the UID of the originating server. Otherwise, you'll
-        # get nasty protocol violations!
+        # get nasty protocol violation SQUITs!
         nick = '_' + nick
     tagnicks = True
 
     suffix = separator + netname
     nick = nick[:maxnicklen]
-    # Maximum allowed length of a nickname.
+    # Maximum allowed length of a nickname, minus the obligatory /network tag.
     allowedlength = maxnicklen - len(suffix)
-    # If a nick is too long, the real nick portion must be cut off, but the
-    # /network suffix must remain the same.
 
+    # If a nick is too long, the real nick portion will be cut off, but the
+    # /network suffix MUST remain the same.
     nick = nick[:allowedlength]
     nick += suffix
-    # FIXME: factorize
+
-    while utils.nickToUid(irc, nick) or utils.nickToUid(irc, oldnick) and not \
+    # The nick we want exists? Darn, create another one then.
-            isRelayClient(irc, utils.nickToUid(irc, nick)):
-        # The nick we want exists? Darn, create another one then, but only if
-        # the target isn't an internal client!
     # Increase the separator length by 1 if the user was already tagged,
     # but couldn't be created due to a nick conflict.
     # This can happen when someone steals a relay user's nick.
+
+    # However, if the user is changing from, say, a long, cut-off nick to another long,
+    # cut-off nick, we don't need to check for duplicates and tag the nick twice.
+
+    # somecutoffnick/net would otherwise be erroneous NICK'ed to somecutoffnic//net,
+    # even though there would be no collision because the old and new nicks are from
+    # the same client.
+    while utils.nickToUid(irc, nick) and utils.nickToUid(irc, nick) != uid:
         new_sep = separator + separator[-1]
         log.debug('(%s) normalizeNick: nick %r is in use; using %r as new_sep.', irc.name, nick, new_sep)
         nick = normalizeNick(irc, netname, orig_nick, separator=new_sep)
@@ -271,7 +279,7 @@ utils.add_hook(handle_squit, 'SQUIT')
 def handle_nick(irc, numeric, command, args):
     for netname, user in relayusers[(irc.name, numeric)].items():
         remoteirc = utils.networkobjects[netname]
-        newnick = normalizeNick(remoteirc, irc.name, args['newnick'])
+        newnick = normalizeNick(remoteirc, irc.name, args['newnick'], uid=user)
         if remoteirc.users[user].nick != newnick:
             remoteirc.proto.nickClient(remoteirc, user, newnick)
 utils.add_hook(handle_nick, 'NICK')
@@ -912,8 +920,18 @@ def handle_save(irc, numeric, command, args):
         remotenet, remoteuser = realuser
         remoteirc = utils.networkobjects[remotenet]
         nick = remoteirc.users[remoteuser].nick
-        newnick = normalizeNick(irc, remotenet, nick, oldnick=args['oldnick'])
+        # Limit how many times we can attempt to fix our nick, to prevent
+        # floods and such.
+        if savecache.setdefault(target, 0) <= 5:
+            newnick = normalizeNick(irc, remotenet, nick)
+            log.info('(%s) SAVE received for relay client %r (%s), fixing nick to %s',
+                      irc.name, target, nick, newnick)
             irc.proto.nickClient(irc, target, newnick)
+        else:
+            log.warning('(%s) SAVE received for relay client %r (%s), not '
+                        'fixing nick again due to 5 failed attempts in '
+                        'the last 10 seconds!',  irc.name, target, nick)
+        savecache[target] += 1
     else:
         # Somebody else on the network (not a PyLink client) had a nick collision;
         # relay this as a nick change appropriately.