scenario.py 31.1 KB
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from abc import ABC
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import binascii
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import calendar
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from datetime import datetime
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import logging
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import os
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import posixpath
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import random
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import socket
import struct
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import time
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from typing import Optional
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import dns.dnssec
import dns.message
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import dns.name
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import dns.rcode
import dns.rrset
import dns.tsigkeyring
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import pydnstest.augwrap
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import pydnstest.matchpart
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import pydnstest.mock_client
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def str2bool(v):
    """ Return conversion of JSON-ish string value to boolean. """
    return v.lower() in ('yes', 'true', 'on', '1')


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# Global statistics
g_rtt = 0.0
g_nqueries = 0

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class DNSBlob(ABC):
    def to_wire(self) -> bytes:
        raise NotImplementedError

    def __str__(self) -> str:
        return '<DNSBlob>'


class DNSMessage(DNSBlob):
    def __init__(self, message: dns.message.Message) -> None:
        assert message is not None
        self.message = message

    def to_wire(self) -> bytes:
        return self.message.to_wire(max_size=65535)

    def __str__(self) -> str:
        return str(self.message)


class DNSReply(DNSMessage):
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    def __init__(
                self,
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                message: dns.message.Message,
                query: Optional[dns.message.Message] = None,
                copy_id: bool = False,
                copy_query: bool = False
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            ) -> None:
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        super().__init__(message)
        if copy_id or copy_query:
            if query is None:
                raise ValueError("query must be provided to adjust copy_id/copy_query")
            self.adjust_reply(query, copy_id, copy_query)
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    def adjust_reply(
                self,
                query: dns.message.Message,
                copy_id: bool = True,
                copy_query: bool = True
            ) -> None:
        answer = dns.message.from_wire(self.message.to_wire(),
                                       xfr=self.message.xfr,
                                       one_rr_per_rrset=True)
        answer.use_edns(query.edns, query.ednsflags, options=self.message.options)
        if copy_id:
            answer.id = query.id
            # Copy letter-case if the template has QD
            if answer.question:
                answer.question[0].name = query.question[0].name
        if copy_query:
            answer.question = query.question
        # Re-set, as the EDNS might have reset the ext-rcode
        answer.set_rcode(self.message.rcode())
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        # sanity check: adjusted answer should be almost the same
        assert len(answer.answer) == len(self.message.answer)
        assert len(answer.authority) == len(self.message.authority)
        assert len(answer.additional) == len(self.message.additional)
        self.message = answer
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class DNSReplyRaw(DNSBlob):
    def __init__(
                self,
                wire: bytes,
                query: Optional[dns.message.Message] = None,
                copy_id: bool = False
            ) -> None:
        assert wire is not None
        self.wire = wire
        if copy_id:
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            if query is None:
                raise ValueError("query must be provided to adjust copy_id")
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            self.adjust_reply(query, copy_id)

    def adjust_reply(
                self,
                query: dns.message.Message,
                copy_id: bool = True
            ) -> None:
        if copy_id:
            if len(self.wire) < 2:
                raise ValueError(
                    'wire data must contain at least 2 bytes to adjust query id')
            raw_answer = bytearray(self.wire)
            struct.pack_into('!H', raw_answer, 0, query.id)
            self.wire = bytes(raw_answer)

    def to_wire(self) -> bytes:
        return self.wire

    def __str__(self) -> str:
        return '<DNSReplyRaw>'


class DNSReplyServfail(DNSMessage):
    def __init__(self, query: dns.message.Message) -> None:
        message = dns.message.make_response(query)
        message.set_rcode(dns.rcode.SERVFAIL)
        super().__init__(message)
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class Entry:
    """
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    Data entry represents scripted message and extra metadata,
    notably match criteria and reply adjustments.
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    """

    # Globals
    default_ttl = 3600
    default_cls = 'IN'
    default_rc = 'NOERROR'

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    def __init__(self, node):
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        """ Initialize data entry. """
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        self.node = node
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        self.origin = '.'
        self.message = dns.message.Message()
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        self.message.use_edns(edns=0, payload=4096)
        self.fired = 0
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        # RAW
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        self.raw_data = self.process_raw()
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        # MATCH
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        self.match_fields = self.process_match()
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        # FLAGS
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        self.process_reply_line()
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        # ADJUST
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        self.adjust_fields = {m.value for m in node.match("/adjust")}
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        # MANDATORY
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        try:
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            self.mandatory = list(node.match("/mandatory"))[0]
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        except (KeyError, IndexError):
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            self.mandatory = None
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        # TSIG
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        self.process_tsig()

        # SECTIONS & RECORDS
        self.sections = self.process_sections()

    def process_raw(self):
        try:
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            return binascii.unhexlify(self.node["/raw"].value)
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        except KeyError:
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            return None
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    def process_match(self):
        try:
            self.node["/match_present"]
        except KeyError:
            return None

        fields = set(m.value for m in self.node.match("/match"))

        if 'all' in fields:
            fields.remove("all")
            fields |= set(["opcode", "qtype", "qname", "flags",
                           "rcode", "answer", "authority", "additional"])

        if 'question' in fields:
            fields.remove("question")
            fields |= set(["qtype", "qname"])

        return fields

    def process_reply_line(self):
        """Extracts flags, rcode and opcode from given node and adjust dns message accordingly"""
        self.fields = [f.value for f in self.node.match("/reply")]
        if 'DO' in self.fields:
            self.message.want_dnssec(True)
        opcode = self.get_opcode(fields=self.fields)
        rcode = self.get_rcode(fields=self.fields)
        self.message.flags = self.get_flags(fields=self.fields)
        if rcode is not None:
            self.message.set_rcode(rcode)
        if opcode is not None:
            self.message.set_opcode(opcode)

    def process_tsig(self):
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        try:
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            tsig = list(self.node.match("/tsig"))[0]
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            tsig_keyname = tsig["/keyname"].value
            tsig_secret = tsig["/secret"].value
            keyring = dns.tsigkeyring.from_text({tsig_keyname: tsig_secret})
            self.message.use_tsig(keyring=keyring, keyname=tsig_keyname)
        except (KeyError, IndexError):
            pass

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    def process_sections(self):
        sections = set()
        for section in self.node.match("/section/*"):
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            section_name = posixpath.basename(section.path)
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            sections.add(section_name)
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            for record in section.match("/record"):
                owner = record['/domain'].value
                if not owner.endswith("."):
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                    owner += self.origin
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                try:
                    ttl = dns.ttl.from_text(record['/ttl'].value)
                except KeyError:
                    ttl = self.default_ttl
                try:
                    rdclass = dns.rdataclass.from_text(record['/class'].value)
                except KeyError:
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                    rdclass = dns.rdataclass.from_text(self.default_cls)
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                rdtype = dns.rdatatype.from_text(record['/type'].value)
                rr = dns.rrset.from_text(owner, ttl, rdclass, rdtype)
                if section_name != "question":
                    rd = record['/data'].value.split()
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                    if rd:
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                        if rdtype == dns.rdatatype.DS:
                            rd[1] = str(dns.dnssec.algorithm_from_text(rd[1]))
                        rd = dns.rdata.from_text(rr.rdclass, rr.rdtype, ' '.join(
                            rd), origin=dns.name.from_text(self.origin), relativize=False)
                    rr.add(rd)
                if section_name == 'question':
                    if rr.rdtype == dns.rdatatype.AXFR:
                        self.message.xfr = True
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                    self.message.question.append(rr)
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                elif section_name == 'answer':
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                    self.message.answer.append(rr)
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                elif section_name == 'authority':
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                    self.message.authority.append(rr)
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                elif section_name == 'additional':
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                    self.message.additional.append(rr)
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        return sections
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    def __str__(self):
        txt = 'ENTRY_BEGIN\n'
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        if self.raw_data is None:
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            txt += 'MATCH {0}\n'.format(' '.join(self.match_fields))
        txt += 'ADJUST {0}\n'.format(' '.join(self.adjust_fields))
        txt += 'REPLY {rcode} {flags}\n'.format(
            rcode=dns.rcode.to_text(self.message.rcode()),
            flags=' '.join([dns.flags.to_text(self.message.flags),
                            dns.flags.edns_to_text(self.message.ednsflags)])
        )
        for sect_name in ['question', 'answer', 'authority', 'additional']:
            sect = getattr(self.message, sect_name)
            if not sect:
                continue
            txt += 'SECTION {n}\n'.format(n=sect_name.upper())
            for rr in sect:
                txt += str(rr)
                txt += '\n'
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        if self.raw_data is not None:
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            txt += 'RAW\n'
            if self.raw_data:
                txt += binascii.hexlify(self.raw_data)
            else:
                txt += 'NULL'
            txt += '\n'
        txt += 'ENTRY_END\n'
        return txt

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    @classmethod
    def get_flags(cls, fields):
        """From `fields` extracts and returns flags"""
        flags = []
        for code in fields:
            try:
                dns.flags.from_text(code)  # throws KeyError on failure
                flags.append(code)
            except KeyError:
                pass
        return dns.flags.from_text(' '.join(flags))

    @classmethod
    def get_rcode(cls, fields):
        """
        From `fields` extracts and returns rcode.
        Throws `ValueError` if there are more then one rcodes
        """
        rcodes = []
        for code in fields:
            try:
                rcodes.append(dns.rcode.from_text(code))
            except dns.rcode.UnknownRcode:
                pass
        if len(rcodes) > 1:
            raise ValueError("Parse failed, too many rcode values.", rcodes)
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        if not rcodes:
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            return None
        return rcodes[0]

    @classmethod
    def get_opcode(cls, fields):
        """
        From `fields` extracts and returns opcode.
        Throws `ValueError` if there are more then one opcodes
        """
        opcodes = []
        for code in fields:
            try:
                opcodes.append(dns.opcode.from_text(code))
            except dns.opcode.UnknownOpcode:
                pass
        if len(opcodes) > 1:
            raise ValueError("Parse failed, too many opcode values.")
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        if not opcodes:
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            return None
        return opcodes[0]

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    def match(self, msg):
        """ Compare scripted reply to given message based on match criteria. """
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        for code in self.match_fields:
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            try:
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                pydnstest.matchpart.match_part(self.message, msg, code)
            except pydnstest.matchpart.DataMismatch as ex:
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                errstr = '%s in the response:\n%s' % (str(ex), msg.to_text())
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                # TODO: cisla radku
                raise ValueError("%s, \"%s\": %s" % (self.node.span, code, errstr))
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    def cmp_raw(self, raw_value):
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        assert self.raw_data is not None
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        expected = None
        if self.raw_data is not None:
            expected = binascii.hexlify(self.raw_data)
        got = None
        if raw_value is not None:
            got = binascii.hexlify(raw_value)
        if expected != got:
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            raise ValueError("raw message comparsion failed: expected %s got %s" % (expected, got))
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    def reply(self, query) -> Optional[DNSBlob]:
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        if 'do_not_answer' in self.adjust_fields:
            return None
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        if self.raw_data is not None:
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            copy_id = 'raw_data' in self.adjust_fields
            assert self.raw_data is not None
            return DNSReplyRaw(self.raw_data, query, copy_id)
        copy_id = 'copy_id' in self.adjust_fields
        copy_query = 'copy_query' in self.adjust_fields
        return DNSReply(self.message, query, copy_id, copy_query)
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    def set_edns(self, fields):
        """ Set EDNS version and bufsize. """
        version = 0
        bufsize = 4096
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        if fields and fields[0].isdigit():
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            version = int(fields.pop(0))
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        if fields and fields[0].isdigit():
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            bufsize = int(fields.pop(0))
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        if bufsize == 0:
            self.message.use_edns(False)
            return
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        opts = []
        for v in fields:
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            k, v = tuple(v.split('=')) if '=' in v else (v, True)
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            if k.lower() == 'nsid':
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                opts.append(dns.edns.GenericOption(dns.edns.NSID, '' if v is True else v))
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            if k.lower() == 'subnet':
                net = v.split('/')
                subnet_addr = net[0]
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                family = socket.AF_INET6 if ':' in subnet_addr else socket.AF_INET
                addr = socket.inet_pton(family, subnet_addr)
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                prefix = len(addr) * 8
                if len(net) > 1:
                    prefix = int(net[1])
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                addr = addr[0: (prefix + 7) / 8]
                if prefix % 8 != 0:  # Mask the last byte
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                    addr = addr[:-1] + chr(ord(addr[-1]) & 0xFF << (8 - prefix % 8))
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                opts.append(dns.edns.GenericOption(8, struct.pack(
                    "!HBB", 1 if family == socket.AF_INET else 2, prefix, 0) + addr))
        self.message.use_edns(edns=version, payload=bufsize, options=opts)
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class Range:
    """
    Range represents a set of scripted queries valid for given step range.
    """
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    log = logging.getLogger('pydnstest.scenario.Range')
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    def __init__(self, node):
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        """ Initialize reply range. """
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        self.node = node
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        self.a = int(node['/from'].value)
        self.b = int(node['/to'].value)
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        assert self.a <= self.b
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        address = node["/address"].value
        self.addresses = {address} if address is not None else set()
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        self.addresses |= {a.value for a in node.match("/address/*")}
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        self.stored = [Entry(n) for n in node.match("/entry")]
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        self.args = {}
        self.received = 0
        self.sent = 0

    def __del__(self):
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        self.log.info('[ RANGE %d-%d ] %s received: %d sent: %d',
                      self.a, self.b, self.addresses, self.received, self.sent)
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    def __str__(self):
        txt = '\nRANGE_BEGIN {a} {b}\n'.format(a=self.a, b=self.b)
        for addr in self.addresses:
            txt += '        ADDRESS {0}\n'.format(addr)

        for entry in self.stored:
            txt += '\n'
            txt += str(entry)
        txt += 'RANGE_END\n\n'
        return txt
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    def eligible(self, ident, address):
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        """ Return true if this range is eligible for fetching reply. """
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        if self.a <= ident <= self.b:
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            return (None is address
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                    or set() == self.addresses
                    or address in self.addresses)
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        return False

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    def reply(self, query: dns.message.Message) -> Optional[DNSBlob]:
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        """Get answer for given query (adjusted if needed)."""
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        self.received += 1
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        for candidate in self.stored:
            try:
                candidate.match(query)
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                resp = candidate.reply(query)
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                # Probabilistic loss
                if 'LOSS' in self.args:
                    if random.random() < float(self.args['LOSS']):
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                        return DNSReplyServfail(query)
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                self.sent += 1
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                candidate.fired += 1
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                return resp
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            except ValueError:
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                pass
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        return DNSReplyServfail(query)
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class StepLogger(logging.LoggerAdapter):  # pylint: disable=too-few-public-methods
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    """
    Prepent Step identification before each log message.
    """
    def process(self, msg, kwargs):
        return '[STEP %s %s] %s' % (self.extra['id'], self.extra['type'], msg), kwargs


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class Step:
    """
    Step represents one scripted action in a given moment,
    each step has an order identifier, type and optionally data entry.
    """
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    require_data = ['QUERY', 'CHECK_ANSWER', 'REPLY']
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    def __init__(self, node):
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        """ Initialize single scenario step. """
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        self.node = node
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        self.id = int(node.value)
        self.type = node["/type"].value
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        self.log = StepLogger(logging.getLogger('pydnstest.scenario.Step'),
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                              {'id': self.id, 'type': self.type})
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        try:
            self.delay = int(node["/timestamp"].value)
        except KeyError:
            pass
        self.data = [Entry(n) for n in node.match("/entry")]
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        self.queries = []
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        self.has_data = self.type in Step.require_data
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        self.answer = None
        self.raw_answer = None
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        self.repeat_if_fail = 0
        self.pause_if_fail = 0
        self.next_if_fail = -1
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    def __str__(self):
        txt = '\nSTEP {i} {t}'.format(i=self.id, t=self.type)
        if self.repeat_if_fail:
            txt += ' REPEAT {v}'.format(v=self.repeat_if_fail)
        elif self.pause_if_fail:
            txt += ' PAUSE {v}'.format(v=self.pause_if_fail)
        elif self.next_if_fail != -1:
            txt += ' NEXT {v}'.format(v=self.next_if_fail)
        # if self.args:
        #     txt += ' '
        #     txt += ' '.join(self.args)
        txt += '\n'

        for data in self.data:
            # from IPython.core.debugger import Tracer
            # Tracer()()
            txt += str(data)
        return txt
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    def play(self, ctx):
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        """ Play one step from a scenario. """
        if self.type == 'QUERY':
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            self.log.info('')
            self.log.debug(self.data[0].message.to_text())
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            # Parse QUERY-specific parameters
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            choice, tcp = None, False
            return self.__query(ctx, tcp=tcp, choice=choice)
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        elif self.type == 'CHECK_OUT_QUERY':  # ignore
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            self.log.info('')
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            return None
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        elif self.type == 'CHECK_ANSWER' or self.type == 'ANSWER':
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            self.log.info('')
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            return self.__check_answer(ctx)
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        elif self.type == 'TIME_PASSES ELAPSE':
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            self.log.info('')
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            return self.__time_passes()
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        elif self.type == 'REPLY' or self.type == 'MOCK':
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            self.log.info('')
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            return None
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        else:
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            raise NotImplementedError('step %03d type %s unsupported' % (self.id, self.type))
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    def __check_answer(self, ctx):
        """ Compare answer from previously resolved query. """
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        if not self.data:
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            raise ValueError("response definition required")
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        expected = self.data[0]
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        if expected.raw_data is not None:
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            self.log.debug("raw answer: %s", ctx.last_raw_answer.to_text())
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            expected.cmp_raw(ctx.last_raw_answer)
        else:
            if ctx.last_answer is None:
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                raise ValueError("no answer from preceding query")
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            self.log.debug("answer: %s", ctx.last_answer.to_text())
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            expected.match(ctx.last_answer)

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    def __query(self, ctx, tcp=False, choice=None):
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        """
        Send query and wait for an answer (if the query is not RAW).

        The received answer is stored in self.answer and ctx.last_answer.
        """
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        if not self.data:
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            raise ValueError("query definition required")
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        if self.data[0].raw_data is not None:
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            data_to_wire = self.data[0].raw_data
        else:
            # Don't use a message copy as the EDNS data portion is not copied.
            data_to_wire = self.data[0].message.to_wire()
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        if choice is None or not choice:
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            choice = list(ctx.client.keys())[0]
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        if choice not in ctx.client:
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            raise ValueError('step %03d invalid QUERY target: %s' % (self.id, choice))
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        tstart = datetime.now()
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        # Send query and wait for answer
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        answer = None
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        sock = pydnstest.mock_client.setup_socket(ctx.client[choice][0],
                                                  ctx.client[choice][1],
                                                  tcp)
        pydnstest.mock_client.send_query(sock, data_to_wire)
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        if self.data[0].raw_data is None:
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            answer = pydnstest.mock_client.get_answer(sock)

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        # Track RTT
        rtt = (datetime.now() - tstart).total_seconds() * 1000
        global g_rtt, g_nqueries
        g_nqueries += 1
        g_rtt += rtt
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        # Remember last answer for checking later
        self.raw_answer = answer
        ctx.last_raw_answer = answer
        if self.raw_answer is not None:
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            self.answer = dns.message.from_wire(self.raw_answer, one_rr_per_rrset=True)
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        else:
            self.answer = None
        ctx.last_answer = self.answer

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    def __time_passes(self):
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        """ Modify system time. """
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        file_old = os.environ["FAKETIME_TIMESTAMP_FILE"]
        file_next = os.environ["FAKETIME_TIMESTAMP_FILE"] + ".next"
        with open(file_old, 'r') as time_file:
            line = time_file.readline().strip()
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        t = time.mktime(datetime.strptime(line, '@%Y-%m-%d %H:%M:%S').timetuple())
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        t += self.delay
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        with open(file_next, 'w') as time_file:
            time_file.write(datetime.fromtimestamp(t).strftime('@%Y-%m-%d %H:%M:%S') + "\n")
            time_file.flush()
        os.replace(file_next, file_old)
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class Scenario:
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    log = logging.getLogger('pydnstest.scenatio.Scenario')
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    def __init__(self, node, filename):
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        """ Initialize scenario with description. """
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        self.node = node
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        self.info = node.value
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        self.file = filename
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        self.ranges = [Range(n) for n in node.match("/range")]
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        self.current_range = None
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        self.steps = [Step(n) for n in node.match("/step")]
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        self.current_step = None
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        self.client = {}
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    def __str__(self):
        txt = 'SCENARIO_BEGIN'
        if self.info:
            txt += ' {0}'.format(self.info)
        txt += '\n'
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        for range_ in self.ranges:
            txt += str(range_)
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        for step in self.steps:
            txt += str(step)
        txt += "\nSCENARIO_END"
        return txt

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    def reply(self, query: dns.message.Message, address=None) -> Optional[DNSBlob]:
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        """Generate answer packet for given query."""
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        current_step_id = self.current_step.id
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        # Unknown address, select any match
        # TODO: workaround until the server supports stub zones
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        all_addresses = set()  # type: ignore
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        for rng in self.ranges:
            all_addresses.update(rng.addresses)
        if address not in all_addresses:
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            address = None
        # Find current valid query response range
        for rng in self.ranges:
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            if rng.eligible(current_step_id, address):
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                self.current_range = rng
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                return rng.reply(query)
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        # Find any prescripted one-shot replies
        for step in self.steps:
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            if step.id < current_step_id or step.type != 'REPLY':
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                continue
            try:
                candidate = step.data[0]
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                candidate.match(query)
                step.data.remove(candidate)
                return candidate.reply(query)
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            except (IndexError, ValueError):
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                pass
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        return DNSReplyServfail(query)
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    def play(self, paddr):
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        """ Play given scenario. """
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        # Store test subject => address mapping
        self.client = paddr
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        step = None
        i = 0
        while i < len(self.steps):
            step = self.steps[i]
            self.current_step = step
            try:
                step.play(self)
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            except ValueError as ex:
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                if step.repeat_if_fail > 0:
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                    self.log.info("[play] step %d: exception - '%s', retrying step %d (%d left)",
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                                  step.id, ex, step.next_if_fail, step.repeat_if_fail)
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                    step.repeat_if_fail -= 1
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                    if step.pause_if_fail > 0:
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                        time.sleep(step.pause_if_fail)
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                    if step.next_if_fail != -1:
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                        next_steps = [j for j in range(len(self.steps)) if self.steps[
                            j].id == step.next_if_fail]
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                        if not next_steps:
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                            raise ValueError('step %d: wrong NEXT value "%d"' %
                                             (step.id, step.next_if_fail))
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                        next_step = next_steps[0]
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                        if next_step < len(self.steps):
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                            i = next_step
                        else:
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                            raise ValueError('step %d: Can''t branch to NEXT value "%d"' %
                                             (step.id, step.next_if_fail))
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                    continue
                else:
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                    raise ValueError('%s step %d %s' % (self.file, step.id, str(ex)))
            i += 1
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        for r in self.ranges:
            for e in r.stored:
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                if e.mandatory and e.fired == 0:
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                    # TODO: cisla radku
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                    raise ValueError('Mandatory section at %s not fired' % e.mandatory.span)
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def get_next(file_in, skip_empty=True):
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    """ Return next token from the input stream. """
    while True:
        line = file_in.readline()
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        if not line:
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            return False
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        quoted, escaped = False, False
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        for i, char in enumerate(line):
            if char == '\\':
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                escaped = not escaped
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            if not escaped and char == '"':
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                quoted = not quoted
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            if char == ';' and not quoted:
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                line = line[0:i]
                break
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            if char != '\\':
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                escaped = False
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        tokens = ' '.join(line.strip().split()).split()
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        if not tokens:
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            if skip_empty:
                continue
            else:
                return '', []
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        op = tokens.pop(0)
        return op, tokens

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def parse_config(scn_cfg, qmin, installdir):  # FIXME: pylint: disable=too-many-statements
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    """
    Transform scene config (key, value) pairs into dict filled with defaults.
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    Returns tuple:
      context dict: {Jinja2 variable: value}
      trust anchor dict: {domain: [TA lines for particular domain]}
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    """
    # defaults
    do_not_query_localhost = True
    harden_glue = True
    sockfamily = 0  # auto-select value for socket.getaddrinfo
    trust_anchor_list = []
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    trust_anchor_files = {}
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    negative_ta_list = []
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    stub_addr = None
    override_timestamp = None

    features = {}
    feature_list_delimiter = ';'
    feature_pair_delimiter = '='

    for k, v in scn_cfg:
        # Enable selectively for some tests
        if k == 'do-not-query-localhost':
            do_not_query_localhost = str2bool(v)
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        elif k == 'domain-insecure':
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            negative_ta_list.append(v)
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        elif k == 'harden-glue':
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            harden_glue = str2bool(v)
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        elif k == 'query-minimization':
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            qmin = str2bool(v)
        elif k == 'trust-anchor':
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            trust_anchor = v.strip('"\'')
            trust_anchor_list.append(trust_anchor)
            domain = dns.name.from_text(trust_anchor.split()[0]).canonicalize()
            if domain not in trust_anchor_files:
                trust_anchor_files[domain] = []
            trust_anchor_files[domain].append(trust_anchor)
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        elif k == 'val-override-timestamp':
            override_timestamp_str = v.strip('"\'')
            override_timestamp = int(override_timestamp_str)
        elif k == 'val-override-date':
            override_date_str = v.strip('"\'')
            ovr_yr = override_date_str[0:4]
            ovr_mnt = override_date_str[4:6]
            ovr_day = override_date_str[6:8]
            ovr_hr = override_date_str[8:10]
            ovr_min = override_date_str[10:12]
            ovr_sec = override_date_str[12:]
            override_date_str_arg = '{0} {1} {2} {3} {4} {5}'.format(
                ovr_yr, ovr_mnt, ovr_day, ovr_hr, ovr_min, ovr_sec)
            override_date = time.strptime(override_date_str_arg, "%Y %m %d %H %M %S")
            override_timestamp = calendar.timegm(override_date)
        elif k == 'stub-addr':
            stub_addr = v.strip('"\'')
        elif k == 'features':
            feature_list = v.split(feature_list_delimiter)
            try:
                for f_item in feature_list:
                    if f_item.find(feature_pair_delimiter) != -1:
                        f_key, f_value = [x.strip()
                                          for x
                                          in f_item.split(feature_pair_delimiter, 1)]
                    else:
                        f_key = f_item.strip()
                        f_value = ""
                    features[f_key] = f_value
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            except KeyError as ex:
                raise KeyError("can't parse features (%s) in config section (%s)" % (v, str(ex)))
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        elif k == 'feature-list':
            try:
                f_key, f_value = [x.strip() for x in v.split(feature_pair_delimiter, 1)]
                if f_key not in features:
                    features[f_key] = []
                f_value = f_value.replace("{{INSTALL_DIR}}", installdir)
                features[f_key].append(f_value)
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            except KeyError as ex:
                raise KeyError("can't parse feature-list (%s) in config section (%s)"
                               % (v, str(ex)))
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        elif k == 'force-ipv6' and v.upper() == 'TRUE':
            sockfamily = socket.AF_INET6
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        else:
            raise NotImplementedError('unsupported CONFIG key "%s"' % k)
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    ctx = {
        "DO_NOT_QUERY_LOCALHOST": str(do_not_query_localhost).lower(),
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        "NEGATIVE_TRUST_ANCHORS": negative_ta_list,
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        "FEATURES": features,
        "HARDEN_GLUE": str(harden_glue).lower(),
        "INSTALL_DIR": installdir,
        "QMIN": str(qmin).lower(),
        "TRUST_ANCHORS": trust_anchor_list,
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        "TRUST_ANCHOR_FILES": trust_anchor_files.keys()
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    }
    if stub_addr:
        ctx['ROOT_ADDR'] = stub_addr
        # determine and verify socket family for specified root address
        gai = socket.getaddrinfo(stub_addr, 53, sockfamily, 0,
                                 socket.IPPROTO_UDP, socket.AI_NUMERICHOST)
        assert len(gai) == 1
        sockfamily = gai[0][0]
    if not sockfamily:
        sockfamily = socket.AF_INET  # default to IPv4
    ctx['_SOCKET_FAMILY'] = sockfamily
    if override_timestamp:
        ctx['_OVERRIDE_TIMESTAMP'] = override_timestamp
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    return (ctx, trust_anchor_files)
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def parse_file(path):
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    """ Parse scenario from a file. """
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    aug = pydnstest.augwrap.AugeasWrapper(
        confpath=path, lens='Deckard', loadpath=os.path.dirname(__file__))
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    node = aug.tree
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    config = []
    for line in [c.value for c in node.match("/config/*")]:
        if line:
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            if not line.startswith(';'):
                if '#' in line:
                    line = line[0:line.index('#')]
                # Break to key-value pairs
                # e.g.: ['minimization', 'on']
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                kv = [x.strip() for x in line.split(':', 1)]
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                if len(kv) >= 2:
                    config.append(kv)
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    scenario = Scenario(node["/scenario"], posixpath.basename(node.path))
    return scenario, config