X-Git-Url: http://dolda2000.com/gitweb/?p=ldd.git;a=blobdiff_plain;f=ldd%2Fresolver.py;fp=ldd%2Fresolver.py;h=9189b34e31efa478d4fb24b15897119ddc15b4ea;hp=0000000000000000000000000000000000000000;hb=769e7ed964e3720cf25825dd5390af5fb0bf4851;hpb=2e783944bffb349dff8667dab0ba0c48b21c9504 diff --git a/ldd/resolver.py b/ldd/resolver.py new file mode 100644 index 0000000..9189b34 --- /dev/null +++ b/ldd/resolver.py @@ -0,0 +1,301 @@ +# ldd - DNS implementation in Python +# Copyright (C) 2006 Fredrik Tolf +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 2 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program; if not, write to the Free Software +# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + +import socket +import select +import time +import random + +import proto +import rec +import dn + +class error(Exception): + def __init__(self, text): + self.text = text + + def __str__(self): + return self.text + +class servfail(error): + def __init__(self): + error.__init__(self, "SERVFAIL") + +class unreachable(error): + def __init__(self, server): + error.__init__(self, "could not reach server: " + str(server)) + +def resolvecnames(pkt, res = None): + if res is None: res = default + for q in pkt.qlist: + cnrr = pkt.getanswer(q.name, rec.rtypebyname("CNAME")) + if cnrr is not None: + if pkt.getanswer(cnrr.data["priname"], q.rtype) is None: + try: + resp = res.squery(cnrr.data["priname"], q.rtype) + except error: + continue + if resp is None: + continue + anrr = resp.getanswer(cnrr.data["priname"], q.rtype) + if anrr is None: + continue + pkt.addan(anrr) + +def resolveadditional(pkt, rr, res = None): + if res is None: res = default + for name in rr.data: + if isinstance(rr.data[name], dn.domainname): + for rtype in ["A", "AAAA"]: + if pkt.getanswer(rr.data[name], rtype) is not None: + continue + try: + resp = res.squery(rr.data[name], rtype) + except error: + continue + if resp is None: + continue + anrr = resp.getanswer(rr.data[name], rtype) + if anrr is None: + continue + pkt.addad(anrr) + +def extractaddrinfo(packet, name): + ret = [] + for rr in packet.anlist + packet.adlist: + if rr.head.name == name: + if rr.head.istype("A"): + ret += [(socket.AF_INET, socket.inet_ntop(socket.AF_INET, rr.data["address"]))] + elif rr.head.istype("AAAA"): + ret += [(socket.AF_INET6, socket.inet_ntop(socket.AF_INET6, rr.data["address"]))] + return ret + +def resolve(packet, nameserver, recurse, retries = 3, timeout = 2000, hops = 0, cnameres = None, verbose = False, visited = None): + if cnameres is None: cnameres = default + if visited is None: visited = set() + visited |= set([nameserver]) + sk = socket.socket(nameserver[0], socket.SOCK_DGRAM) + sk.bind(("", 0)) + for i in range(retries): + sk.sendto(packet.encode(), nameserver[1:]) + p = select.poll() + p.register(sk.fileno(), select.POLLIN) + fds = p.poll(timeout) + if (sk.fileno(), select.POLLIN) in fds: + break + else: + raise unreachable(nameserver) + ret = sk.recv(65536) + sk.close() + try: + resp = proto.decodepacket(ret) + except proto.malformedpacket, inst: + raise error(str(inst)) + if resp.qid != packet.qid: + raise error("got response with wrong qid(?!)") + if "resp" not in resp.flags: + raise error("got query in response") + if resp.rescode != 0: + if resp.rescode == proto.SERVFAIL: + raise servfail() + if resp.rescode == proto.NXDOMAIN: + return resp + raise error("non-successful response (" + str(resp.rescode) + ")") + if recurse: + resolvecnames(resp, cnameres) + if not recurse or resp.hasanswers(): + return resp + if not resp.hasanswers() and "auth" in resp.flags: + return resp + if hops > 30: + raise error("too many levels deep") + for rr in resp.aulist: + if verbose: + print (hops * " ") + "Checking " + str(rr) + if rr.head.istype("NS"): + if verbose: + print (hops * " ") + "Will try " + str(rr) + ai = extractaddrinfo(resp, rr.data["nsname"]) + if len(ai) == 0: + if verbose: + print (hops * " ") + "Resolving nameservers for " + str(rr.data["nsname"]) + resolveadditional(resp, rr) + ai = extractaddrinfo(resp, rr.data["nsname"]) + for ns in ai: + ns += (53,) + if ns in visited: + if verbose: + print (hops * " ") + "Will not try " + str(ns) + " again" + continue + if verbose: + print (hops * " ") + "Trying " + str(ns) + try: + resp2 = resolve(packet, ns, recurse, retries, timeout, hops + 1, verbose = verbose, visited = visited) + except unreachable: + if verbose: + print (hops * " ") + "Could not reach " + str(ns) + continue + if verbose: + if resp2 is None: + print (hops * " ") + "Got None" + else: + if "auth" in resp2.flags: + austr = "Auth" + else: + austr = "Nonauth" + print (hops * " ") + "Got " + str(resp2.hasanswers()) + " (" + austr + ")" + if resp2 is not None and resp2.hasanswers(): + return resp2 + if resp2 is not None and not resp2.hasanswers() and "auth" in resp2.flags: + return resp2 + return None + +class resolver: + def __init__(self, nameserver, recurse, nsrecurse = True, retries = 3, timeout = 2000, verbose = False): + self.nameserver = nameserver + self.recurse = recurse + self.nsrecurse = nsrecurse + self.retries = retries + self.timeout = timeout + self.verbose = verbose + + def resolve(self, packet): + return resolve(packet, self.nameserver, self.recurse, self.retries, self.timeout, verbose = self.verbose) + + def squery(self, name, rtype): + packet = proto.packet() + try: + if self.nsrecurse: packet.setflags(["recurse"]) + except AttributeError: pass + packet.addq(rec.rrhead(name, rtype)) + return self.resolve(packet) + +class multiresolver(resolver): + def __init__(self, resolvers): + self.rl = [{"res": res, "qs": []} for res in resolvers] + self.lastclean = int(time.time()) + + def clean(self): + now = int(time.time()) + if now - self.lastclean < 60: + return + self.lastclean = now + for r in self.rl: + nl = [] + for q in r["qs"]: + if now - q["time"] < 1800: + nl += [q] + r["qs"] = nl + + def resolve(self, packet): + self.clean() + l = [] + ts = 0 + for r in self.rl: + if len(r["qs"]) < 1: + score = 1.0 + else: + score = float(sum([q["s"] for q in r["qs"]])) / len(r["qs"]) + l += [(score, r)] + ts += score + c = random.random() * ts + for score, r in l: + c -= score + if c <= 0: + break + else: + assert(False) + try: + res = r["res"].resolve(packet) + except error: + r["qs"] = r["qs"][:10] + [{"time": int(time.time()), "s": 0}] + raise + r["qs"] = r["qs"][:10] + [{"time": int(time.time()), "s": 1}] + return res + +class sysresolver(resolver): + def __init__(self, conffile = "/etc/resolv.conf"): + nslist = [] + prelist = [] + a = open(conffile, "r") + for line in (l.strip() for l in a): + p = line.find(" ") + if p >= 0: + c = line[:p] + line = line[p + 1:] + if c == "nameserver": + try: + socket.inet_pton(socket.AF_INET, line) + except socket.error: pass + else: + nslist += [(socket.AF_INET, line, 53)] + try: + socket.inet_pton(socket.AF_INET6, line) + except socket.error: pass + else: + nslist += [(socket.AF_INET6, line, 53)] + if c == "domain" or c == "search": # How do these differ? + prelist += line.split() + a.close() + rl = [] + for ns in nslist: + rl += [resolver(ns, False, True)] + self.resolver = multiresolver(rl) + self.prelist = [] + for prefix in prelist: + pp = dn.fromstring(prefix) + pp.rooted = True + self.prelist += [pp] + + def resolve(self, packet): + res = self.resolver.resolve(packet) + return res + + def squery(self, name, rtype): + if type(name) == str: + name = dn.fromstring(name) + if not name.rooted: + namelist = [name + prefix for prefix in self.prelist] + [name + dn.fromstring(".")] + else: + namelist = [name] + for name in namelist: + packet = proto.packet() + packet.setflags(["recurse"]) + packet.addq(rec.rrhead(name, rtype)) + res = self.resolve(packet) + if res.rescode == 0: + break + return res + +sysres = sysresolver() +rootresolvers = {"a": resolver((socket.AF_INET, "198.41.0.4", 53), True, False), + "b": resolver((socket.AF_INET, "192.228.79.201", 53), True, False), + "c": resolver((socket.AF_INET, "192.33.4.12", 53), True, False), + "d": resolver((socket.AF_INET, "128.8.10.90", 53), True, False), + "e": resolver((socket.AF_INET, "192.203.230.10", 53), True, False), + "f": resolver((socket.AF_INET, "192.5.5.241", 53), True, False), + "g": resolver((socket.AF_INET, "192.112.36.4", 53), True, False), + "h": resolver((socket.AF_INET, "128.63.2.53", 53), True, False), + "i": resolver((socket.AF_INET, "192.36.148.17", 53), True, False), + "j": resolver((socket.AF_INET, "192.58.128.30", 53), True, False), + "k": resolver((socket.AF_INET, "193.0.14.129", 53), True, False), + "l": resolver((socket.AF_INET, "198.32.64.12", 53), True, False), + "m": resolver((socket.AF_INET, "202.12.27.33", 53), True, False) + } +rootres = multiresolver(rootresolvers.values()) + +default = sysres