diff options
Diffstat (limited to 'dns/message.py')
| -rw-r--r-- | dns/message.py | 915 |
1 files changed, 915 insertions, 0 deletions
diff --git a/dns/message.py b/dns/message.py new file mode 100644 index 0000000..cd746ee --- /dev/null +++ b/dns/message.py @@ -0,0 +1,915 @@ +# Copyright (C) 2001-2004 Nominum, Inc. +# +# Permission to use, copy, modify, and distribute this software and its +# documentation for any purpose with or without fee is hereby granted, +# provided that the above copyright notice and this permission notice +# appear in all copies. +# +# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES +# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF +# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR +# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES +# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN +# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT +# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + +# $Id: message.py,v 1.35 2004/03/19 00:17:27 halley Exp $ + +"""DNS Messages""" + +import cStringIO +import random +import string +import struct +import sys +import time + +import dns.exception +import dns.flags +import dns.name +import dns.opcode +import dns.rcode +import dns.rdata +import dns.rdataclass +import dns.rdatatype +import dns.rrset +import dns.renderer +import dns.tsig + +class ShortHeader(dns.exception.FormError): + """Raised if the DNS packet passed to from_wire() is too short.""" + pass + +class TrailingJunk(dns.exception.FormError): + """Raised if the DNS packet passed to from_wire() has extra junk + at the end of it.""" + pass + +class UnknownHeaderField(dns.exception.DNSException): + """Raised if a header field name is not recognized when converting from + text into a message.""" + pass + +class BadEDNS(dns.exception.FormError): + """Raised if an OPT record occurs somewhere other than the start of + the additional data section.""" + pass + +class BadTSIG(dns.exception.FormError): + """Raised if a TSIG record occurs somewhere other than the end of + the additional data section.""" + pass + +class UnknownTSIGKey(dns.exception.DNSException): + """Raised if we got a TSIG but don't know the key.""" + pass + +class Message(object): + """A DNS message. + + @ivar id: The query id; the default is a randomly chosen id. + @type id: int + @ivar flags: The DNS flags of the message. @see: RFC 1035 for an + explanation of these flags. + @type flags: int + @ivar question: The question section. + @type question: list of dns.rrset.RRset objects + @ivar answer: The answer section. + @type answer: list of dns.rrset.RRset objects + @ivar authority: The authority section. + @type authority: list of dns.rrset.RRset objects + @ivar additional: The additional data section. + @type additional: list of dns.rrset.RRset objects + @ivar edns: The EDNS level to use. The default is -1, no Edns. + @type edns: int + @ivar ednsflags: The EDNS flags + @type ednsflags: long + @ivar payload: The EDNS payload size. The default is 0. + @type payload: int + @ivar keyring: The TSIG keyring to use. The default is None. + @type keyring: dict + @ivar keyname: The TSIG keyname to use. The default is None. + @type keyname: dns.name.Name object + @ivar request_mac: The TSIG MAC of the request message associated with + this message; used when validating TSIG signatures. @see: RFC 2845 for + more information on TSIG fields. + @type request_mac: string + @ivar fudge: TSIG time fudge; default is 300 seconds. + @type fudge: int + @ivar original_id: TSIG original id; defaults to the message's id + @type original_id: int + @ivar tsig_error: TSIG error code; default is 0. + @type tsig_error: int + @ivar other_data: TSIG other data. + @type other_data: string + @ivar mac: The TSIG MAC for this message. + @type mac: string + @ivar xfr: Is the message being used to contain the results of a DNS + zone transfer? The default is False. + @type xfr: bool + @ivar origin: The origin of the zone in messages which are used for + zone transfers or for DNS dynamic updates. The default is None. + @type origin: dns.name.Name object + @ivar tsig_ctx: The TSIG signature context associated with this + message. The default is None. + @type tsig_ctx: hmac.HMAC object + @ivar had_tsig: Did the message decoded from wire format have a TSIG + signature? + @type had_tsig: bool + @ivar multi: Is this message part of a multi-message sequence? The + default is false. This variable is used when validating TSIG signatures + on messages which are part of a zone transfer. + @type multi: bool + @ivar first: Is this message standalone, or the first of a multi + message sequence? This variable is used when validating TSIG signatures + on messages which are part of a zone transfer. + @type first: bool + """ + + def __init__(self, id=None): + if id is None: + self.id = random.randint(0, 65535) + else: + self.id = id + self.flags = 0 + self.question = [] + self.answer = [] + self.authority = [] + self.additional = [] + self.edns = -1 + self.ednsflags = 0 + self.payload = 0 + self.keyring = None + self.keyname = None + self.request_mac = '' + self.other_data = '' + self.tsig_error = 0 + self.fudge = 300 + self.original_id = self.id + self.mac = '' + self.xfr = False + self.origin = None + self.tsig_ctx = None + self.had_tsig = False + self.multi = False + self.first = True + + def __repr__(self): + return '<DNS message, ID ' + `self.id` + '>' + + def __str__(self): + return self.to_text() + + def to_text(self, origin=None, relativize=True, **kw): + """Convert the message to text. + + The I{origin}, I{relativize}, and any other keyword + arguments are passed to the rrset to_wire() method. + + @rtype: string + """ + + s = cStringIO.StringIO() + print >> s, 'id %d' % self.id + print >> s, 'opcode %s' % \ + dns.opcode.to_text(dns.opcode.from_flags(self.flags)) + rc = dns.rcode.from_flags(self.flags, self.ednsflags) + print >> s, 'rcode %s' % dns.rcode.to_text(rc) + print >> s, 'flags %s' % dns.flags.to_text(self.flags) + if self.edns >= 0: + print >> s, 'edns %s' % self.edns + if self.ednsflags != 0: + print >> s, 'eflags %s' % \ + dns.flags.edns_to_text(self.ednsflags) + print >> s, 'payload', self.payload + is_update = dns.opcode.is_update(self.flags) + if is_update: + print >> s, ';ZONE' + else: + print >> s, ';QUESTION' + for rrset in self.question: + print >> s, rrset.to_text(origin, relativize, **kw) + if is_update: + print >> s, ';PREREQ' + else: + print >> s, ';ANSWER' + for rrset in self.answer: + print >> s, rrset.to_text(origin, relativize, **kw) + if is_update: + print >> s, ';UPDATE' + else: + print >> s, ';AUTHORITY' + for rrset in self.authority: + print >> s, rrset.to_text(origin, relativize, **kw) + print >> s, ';ADDITIONAL' + for rrset in self.additional: + print >> s, rrset.to_text(origin, relativize, **kw) + # + # We strip off the final \n so the caller can print the result without + # doing weird things to get around eccentricities in Python print + # formatting + # + return s.getvalue()[:-1] + + def __eq__(self, other): + """Two messages are equal if they have the same content in the + header, question, answer, and authority sections. + @rtype: bool""" + if not isinstance(other, Message): + return False + if self.id != other.id: + return False + if self.flags != other.flags: + return False + for n in self.question: + if n not in other.question: + return False + for n in other.question: + if n not in self.question: + return False + for n in self.answer: + if n not in other.answer: + return False + for n in other.answer: + if n not in self.answer: + return False + for n in self.authority: + if n not in other.authority: + return False + for n in other.authority: + if n not in self.authority: + return False + return True + + def __ne__(self, other): + """Are two messages not equal? + @rtype: bool""" + return not self.__eq__(other) + + def is_response(self, other): + """Is other a response to self? + @rtype: bool""" + if other.flags & dns.flags.QR == 0 or \ + self.id != other.id or \ + dns.opcode.from_flags(self.flags) != \ + dns.opcode.from_flags(other.flags): + return False + if dns.rcode.from_flags(other.flags, other.ednsflags) != \ + dns.rcode.NOERROR: + return True + if dns.opcode.is_update(self.flags): + return True + for n in self.question: + if n not in other.question: + return False + for n in other.question: + if n not in self.question: + return False + return True + + def find_rrset(self, section, name, rdclass, rdtype, + covers=dns.rdatatype.NONE, deleting=None, create=False, + force_unique=False): + """Find the RRset with the given attributes in the specified section. + + @param section: the section of the message to look in, e.g. + self.answer. + @type section: list of dns.rrset.RRset objects + @param name: the name of the RRset + @type name: dns.name.Name object + @param rdclass: the class of the RRset + @type rdclass: int + @param rdtype: the type of the RRset + @type rdtype: int + @param covers: the covers value of the RRset + @type covers: int + @param deleting: the deleting value of the RRset + @type deleting: int + @param create: If True, create the RRset if it is not found. + The created RRset is appended to I{section}. + @type create: bool + @param force_unique: If True and create is also True, create a + new RRset regardless of whether a matching RRset exists already. + @type force_unique: bool + @raises KeyError: the RRset was not found and create was False + @rtype: dns.rrset.RRset object""" + + if not force_unique: + for rrset in section: + if rrset.match(name, rdclass, rdtype, covers, deleting): + return rrset + if not create: + raise KeyError + rrset = dns.rrset.RRset(name, rdclass, rdtype, covers, deleting) + section.append(rrset) + return rrset + + def get_rrset(self, section, name, rdclass, rdtype, + covers=dns.rdatatype.NONE, deleting=None, create=False, + force_unique=False): + """Get the RRset with the given attributes in the specified section. + + If the RRset is not found, None is returned. + + @param section: the section of the message to look in, e.g. + self.answer. + @type section: list of dns.rrset.RRset objects + @param name: the name of the RRset + @type name: dns.name.Name object + @param rdclass: the class of the RRset + @type rdclass: int + @param rdtype: the type of the RRset + @type rdtype: int + @param covers: the covers value of the RRset + @type covers: int + @param deleting: the deleting value of the RRset + @type deleting: int + @param create: If True, create the RRset if it is not found. + The created RRset is appended to I{section}. + @type create: bool + @param force_unique: If True and create is also True, create a + new RRset regardless of whether a matching RRset exists already. + @type force_unique: bool + @rtype: dns.rrset.RRset object or None""" + + try: + rrset = self.find_rrset(section, name, rdclass, rdtype, covers, + deleting, create, force_unique) + except KeyError: + rrset = None + return rrset + + def to_wire(self, origin=None, max_size=65535, **kw): + """Return a string containing the message in DNS compressed wire + format. + + Additional keyword arguments are passed to the rrset to_wire() + method. + + @param origin: The origin to be appended to any relative names. + @type origin: dns.name.Name object + @param max_size: The maximum size of the wire format output. + @type max_size: int + @raises dns.exception.TooBig: max_size was exceeded + @rtype: string + """ + + r = dns.renderer.Renderer(self.id, self.flags, max_size, origin) + for rrset in self.question: + r.add_question(rrset.name, rrset.rdtype, rrset.rdclass) + for rrset in self.answer: + r.add_rrset(dns.renderer.ANSWER, rrset, **kw) + for rrset in self.authority: + r.add_rrset(dns.renderer.AUTHORITY, rrset, **kw) + if self.edns >= 0: + r.add_edns(self.edns, self.ednsflags, self.payload) + for rrset in self.additional: + r.add_rrset(dns.renderer.ADDITIONAL, rrset, **kw) + r.write_header() + if not self.keyname is None: + r.add_tsig(self.keyname, self.keyring[self.keyname], + self.fudge, self.original_id, self.tsig_error, + self.other_data, self.request_mac) + self.mac = r.mac + return r.get_wire() + + def use_tsig(self, keyring, keyname=None, fudge=300, original_id=None, + tsig_error=0, other_data=''): + """When sending, a TSIG signature using the specified keyring + and keyname should be added. + + @param keyring: The TSIG keyring to use; defaults to None. + @type keyring: dict + @param keyname: The name of the TSIG key to use; defaults to None. + The key must be defined in the keyring. If a keyring is specified + but a keyname is not, then the key used will be the first key in the + keyring. Note that the order of keys in a dictionary is not defined, + so applications should supply a keyname when a keyring is used, unless + they know the keyring contains only one key. + @type keyname: dns.name.Name or string + @param fudge: TSIG time fudge; default is 300 seconds. + @type fudge: int + @param original_id: TSIG original id; defaults to the message's id + @type original_id: int + @param tsig_error: TSIG error code; default is 0. + @type tsig_error: int + @param other_data: TSIG other data. + @type other_data: string + """ + + self.keyring = keyring + if keyname is None: + self.keyname = self.keyring.keys()[0] + else: + if isinstance(keyname, str): + keyname = dns.name.from_text(keyname) + self.keyname = keyname + self.fudge = fudge + if original_id is None: + self.original_id = self.id + else: + self.original_id = original_id + self.tsig_error = tsig_error + self.other_data = other_data + + def use_edns(self, edns, ednsflags, payload): + """Configure EDNS behavior. + @param edns: The EDNS level to use. Specifying None or -1 means + 'do not use EDNS'. + @type edns: int or None + @param ednsflags: EDNS flag values. + @type ednsflags: int + @param payload: The EDNS sender's payload field, which is the maximum + size of UDP datagram the sender can handle. + @type payload: int + @see: RFC 2671 + """ + if edns is None: + edns = -1 + self.edns = edns + self.ednsflags = ednsflags + self.payload = payload + + def rcode(self): + """Return the rcode. + @rtype: int + """ + return dns.rcode.from_flags(self.flags, self.ednsflags) + + def set_rcode(self, rcode): + """Set the rcode. + @param rcode: the rcode + @type rcode: int + """ + (value, evalue) = dns.rcode.to_flags(rcode) + self.flags &= 0xFFF0 + self.flags |= value + self.ednsflags &= 0xFF000000L + self.ednsflags |= evalue + if self.ednsflags != 0 and self.edns < 0: + self.edns = 0 + +class _WireReader(object): + """Wire format reader. + + @ivar wire: the wire-format message. + @type wire: string + @ivar message: The message object being built + @type message: dns.message.Message object + @ivar current: When building a message object from wire format, this + variable contains the offset from the beginning of wire of the next octet + to be read. + @type current: int + @ivar updating: Is the message a dynamic update? + @type updating: bool + @ivar zone_rdclass: The class of the zone in messages which are + DNS dynamic updates. + @type zone_rdclass: int + """ + + def __init__(self, wire, message, question_only=False): + self.wire = wire + self.message = message + self.current = 0 + self.updating = False + self.zone_rdclass = dns.rdataclass.IN + self.question_only = question_only + + def _get_question(self, qcount): + """Read the next I{qcount} records from the wire data and add them to + the question section. + @param qcount: the number of questions in the message + @type qcount: int""" + + if self.updating and qcount > 1: + raise dns.exception.FormError + + for i in xrange(0, qcount): + (qname, used) = dns.name.from_wire(self.wire, self.current) + if not self.message.origin is None: + qname = qname.relativize(self.message.origin) + self.current = self.current + used + (rdtype, rdclass) = \ + struct.unpack('!HH', + self.wire[self.current:self.current + 4]) + self.current = self.current + 4 + self.message.find_rrset(self.message.question, qname, + rdclass, rdtype, create=True, + force_unique=True) + if self.updating: + self.zone_rdclass = rdclass + + def _get_section(self, section, count): + """Read the next I{count} records from the wire data and add them to + the specified section. + @param section: the section of the message to which to add records + @type section: list of dns.rrset.RRset objects + @param count: the number of records to read + @type count: int""" + + if self.updating: + force_unique = True + else: + force_unique = False + seen_opt = False + for i in xrange(0, count): + rr_start = self.current + (name, used) = dns.name.from_wire(self.wire, self.current) + if not self.message.origin is None: + name = name.relativize(self.message.origin) + self.current = self.current + used + (rdtype, rdclass, ttl, rdlen) = \ + struct.unpack('!HHIH', + self.wire[self.current:self.current + 10]) + self.current = self.current + 10 + if rdtype == dns.rdatatype.OPT: + if not section is self.message.additional or seen_opt: + raise BadEDNS + self.message.payload = rdclass + self.message.ednsflags = ttl + self.message.edns = (ttl & 0xff0000) >> 16 + seen_opt = True + elif rdtype == dns.rdatatype.TSIG: + if not (section is self.message.additional and + i == (count - 1)): + raise BadTSIG + if self.message.keyring is None: + raise UnknownTSIGKey, 'got signed message without keyring' + secret = self.message.keyring.get(name) + if secret is None: + raise UnknownTSIGKey, "key '%s' unknown" % name + self.message.tsig_ctx = \ + dns.tsig.validate(self.wire, + name, + secret, + int(time.time()), + self.message.request_mac, + rr_start, + self.current, + rdlen, + self.message.tsig_ctx, + self.message.multi, + self.message.first) + self.message.had_tsig = True + else: + if ttl < 0: + ttl = 0 + if self.updating and \ + (rdclass == dns.rdataclass.ANY or + rdclass == dns.rdataclass.NONE): + deleting = rdclass + rdclass = self.zone_rdclass + else: + deleting = None + if deleting == dns.rdataclass.ANY: + covers = dns.rdatatype.NONE + rd = None + else: + rd = dns.rdata.from_wire(rdclass, rdtype, self.wire, + self.current, rdlen, + self.message.origin) + covers = rd.covers() + if self.message.xfr and rdtype == dns.rdatatype.SOA: + force_unique = True + rrset = self.message.find_rrset(section, name, + rdclass, rdtype, covers, + deleting, True, force_unique) + if not rd is None: + rrset.add(rd, ttl) + self.current = self.current + rdlen + + def read(self): + """Read a wire format DNS message and build a dns.message.Message + object.""" + + l = len(self.wire) + if l < 12: + raise ShortHeader + (self.message.id, self.message.flags, qcount, ancount, + aucount, adcount) = struct.unpack('!HHHHHH', self.wire[:12]) + self.current = 12 + if dns.opcode.is_update(self.message.flags): + self.updating = True + self._get_question(qcount) + if self.question_only: + return + self._get_section(self.message.answer, ancount) + self._get_section(self.message.authority, aucount) + self._get_section(self.message.additional, adcount) + if self.current != l: + raise TrailingJunk + if self.message.multi and self.message.tsig_ctx and \ + not self.message.had_tsig: + self.message.tsig_ctx.update(self.wire) + + +def from_wire(wire, keyring=None, request_mac='', xfr=False, origin=None, + tsig_ctx = None, multi = False, first = True, + question_only = False): + """Convert a DNS wire format message into a message + object. + + @param keyring: The keyring to use if the message is signed. + @type keyring: dict + @param request_mac: If the message is a response to a TSIG-signed request, + I{request_mac} should be set to the MAC of that request. + @type request_mac: string + @param xfr: Is this message part of a zone transfer? + @type xfr: bool + @param origin: If the message is part of a zone transfer, I{origin} + should be the origin name of the zone. + @type origin: dns.name.Name object + @param tsig_ctx: The ongoing TSIG context, used when validating zone + transfers. + @type tsig_ctx: hmac.HMAC object + @param multi: Is this message part of a multiple message sequence? + @type multi: bool + @param first: Is this message standalone, or the first of a multi + message sequence? + @type first: bool + @param question_only: Read only up to the end of the question section? + @type question_only: bool + @raises ShortHeader: The message is less than 12 octets long. + @raises TrailingJunk: There were octets in the message past the end + of the proper DNS message. + @raises BadEDNS: An OPT record was in the wrong section, or occurred more + than once. + @raises BadTSIG: A TSIG record was not the last record of the additional + data section. + @rtype: dns.message.Message object""" + + m = Message(id=0) + m.keyring = keyring + m.request_mac = request_mac + m.xfr = xfr + m.origin = origin + m.tsig_ctx = tsig_ctx + m.multi = multi + m.first = first + + reader = _WireReader(wire, m, question_only) + reader.read() + + return m + + +class _TextReader(object): + """Text format reader. + + @ivar tok: the tokenizer + @type tok: dns.tokenizer.Tokenizer object + @ivar message: The message object being built + @type message: dns.message.Message object + @ivar updating: Is the message a dynamic update? + @type updating: bool + @ivar zone_rdclass: The class of the zone in messages which are + DNS dynamic updates. + @type zone_rdclass: int + @ivar last_name: The most recently read name when building a message object + from text format. + @type last_name: dns.name.Name object + """ + + def __init__(self, text, message): + self.message = message + self.tok = dns.tokenizer.Tokenizer(text) + self.last_name = None + self.zone_rdclass = dns.rdataclass.IN + self.updating = False + + def _header_line(self, section): + """Process one line from the text format header section.""" + + (ttype, what) = self.tok.get() + if what == 'id': + self.message.id = self.tok.get_int() + elif what == 'flags': + while True: + token = self.tok.get() + if token[0] != dns.tokenizer.IDENTIFIER: + self.tok.unget(token) + break + self.message.flags = self.message.flags | \ + dns.flags.from_text(token[1]) + if dns.opcode.is_update(self.message.flags): + self.updating = True + elif what == 'edns': + self.message.edns = self.tok.get_int() + self.message.ednsflags = self.message.ednsflags | \ + (self.message.edns << 16) + elif what == 'eflags': + if self.message.edns < 0: + self.message.edns = 0 + while True: + token = self.tok.get() + if token[0] != dns.tokenizer.IDENTIFIER: + self.tok.unget(token) + break + self.message.ednsflags = self.message.ednsflags | \ + dns.flags.edns_from_text(token[1]) + elif what == 'payload': + self.message.payload = self.tok.get_int() + if self.message.edns < 0: + self.message.edns = 0 + elif what == 'opcode': + text = self.tok.get_string() + self.message.flags = self.message.flags | \ + dns.opcode.to_flags(dns.opcode.from_text(text)) + elif what == 'rcode': + text = self.tok.get_string() + self.message.set_rcode(dns.rcode.from_text(text)) + else: + raise UnknownHeaderField + self.tok.get_eol() + + def _question_line(self, section): + """Process one line from the text format question section.""" + + token = self.tok.get(want_leading = True) + if token[0] != dns.tokenizer.WHITESPACE: + self.last_name = dns.name.from_text(token[1], None) + name = self.last_name + token = self.tok.get() + if token[0] != dns.tokenizer.IDENTIFIER: + raise dns.exception.SyntaxError + # Class + try: + rdclass = dns.rdataclass.from_text(token[1]) + token = self.tok.get() + if token[0] != dns.tokenizer.IDENTIFIER: + raise dns.exception.SyntaxError + except dns.exception.SyntaxError: + raise dns.exception.SyntaxError + except: + rdclass = dns.rdataclass.IN + # Type + rdtype = dns.rdatatype.from_text(token[1]) + self.message.find_rrset(self.message.question, name, + rdclass, rdtype, create=True, + force_unique=True) + if self.updating: + self.zone_rdclass = rdclass + self.tok.get_eol() + + def _rr_line(self, section): + """Process one line from the text format answer, authority, or + additional data sections. + """ + + deleting = None + # Name + token = self.tok.get(want_leading = True) + if token[0] != dns.tokenizer.WHITESPACE: + self.last_name = dns.name.from_text(token[1], None) + name = self.last_name + token = self.tok.get() + if token[0] != dns.tokenizer.IDENTIFIER: + raise dns.exception.SyntaxError + # TTL + try: + ttl = int(token[1], 0) + token = self.tok.get() + if token[0] != dns.tokenizer.IDENTIFIER: + raise dns.exception.SyntaxError + except dns.exception.SyntaxError: + raise dns.exception.SyntaxError + except: + ttl = 0 + # Class + try: + rdclass = dns.rdataclass.from_text(token[1]) + token = self.tok.get() + if token[0] != dns.tokenizer.IDENTIFIER: + raise dns.exception.SyntaxError + if rdclass == dns.rdataclass.ANY or rdclass == dns.rdataclass.NONE: + deleting = rdclass + rdclass = self.zone_rdclass + except dns.exception.SyntaxError: + raise dns.exception.SyntaxError + except: + rdclass = dns.rdataclass.IN + # Type + rdtype = dns.rdatatype.from_text(token[1]) + token = self.tok.get() + if token[0] != dns.tokenizer.EOL and token[0] != dns.tokenizer.EOF: + self.tok.unget(token) + rd = dns.rdata.from_text(rdclass, rdtype, self.tok, None) + covers = rd.covers() + else: + rd = None + covers = dns.rdatatype.NONE + rrset = self.message.find_rrset(section, name, + rdclass, rdtype, covers, + deleting, True, self.updating) + if not rd is None: + rrset.add(rd, ttl) + + def read(self): + """Read a text format DNS message and build a dns.message.Message + object.""" + + line_method = self._header_line + section = None + while 1: + token = self.tok.get(True, True) + if token[0] == dns.tokenizer.EOL or token[0] == dns.tokenizer.EOF: + break + if token[0] == dns.tokenizer.COMMENT: + u = token[1].upper() + if u == 'HEADER': + line_method = self._header_line + elif u == 'QUESTION' or u == 'ZONE': + line_method = self._question_line + section = self.message.question + elif u == 'ANSWER' or u == 'PREREQ': + line_method = self._rr_line + section = self.message.answer + elif u == 'AUTHORITY' or u == 'UPDATE': + line_method = self._rr_line + section = self.message.authority + elif u == 'ADDITIONAL': + line_method = self._rr_line + section = self.message.additional + self.tok.get_eol() + continue + self.tok.unget(token) + line_method(section) + + +def from_text(text): + """Convert the text format message into a message object. + + @param text: The text format message. + @type text: string + @raises UnknownHeaderField: + @raises dns.exception.SyntaxError: + @rtype: dns.message.Message object""" + + # 'text' can also be a file, but we don't publish that fact + # since it's an implementation detail. The official file + # interface is from_file(). + + m = Message() + + reader = _TextReader(text, m) + reader.read() + + return m + +def from_file(f): + """Read the next text format message from the specified file. + + @param f: file or string. If I{f} is a string, it is treated + as the name of a file to open. + @raises UnknownHeaderField: + @raises dns.exception.SyntaxError: + @rtype: dns.message.Message object""" + + if sys.hexversion >= 0x02030000: + # allow Unicode filenames; turn on universal newline support + str_type = basestring + opts = 'rU' + else: + str_type = str + opts = 'r' + if isinstance(f, str_type): + f = file(f, opts) + want_close = True + else: + want_close = False + + try: + m = from_text(f) + finally: + if want_close: + f.close() + return m + +def make_query(qname, rdtype, rdclass = dns.rdataclass.IN): + """Make a query message. + + The query name, type, and class may all be specified either + as objects of the appropriate type, or as strings. + + The query will have a randomly choosen query id, and its DNS flags + will be set to dns.flags.RD. + + @param qname: The query name. + @type qname: dns.name.Name object or string + @param rdtype: The desired rdata type. + @type rdtype: int + @param rdclass: The desired rdata class; the default is class IN. + @type rdclass: int + @rtype: dns.message.Message object""" + + if isinstance(qname, str): + qname = dns.name.from_text(qname) + if isinstance(rdtype, str): + rdtype = dns.rdatatype.from_text(rdtype) + if isinstance(rdclass, str): + rdclass = dns.rdataclass.from_text(rdclass) + m = Message() + m.flags |= dns.flags.RD + m.find_rrset(m.question, qname, rdclass, rdtype, create=True, + force_unique=True) + return m |