DNS Resolution

def query(qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN, tcp=False, source=None, 
          raise_on_no_answer=True, source_port=0, lifetime=None):
    """
    Query using the default resolver.
    
    Args:
        qname (str or dns.name.Name): Domain name to query
        rdtype (str or int): Record type (default 'A')
        rdclass (str or int): Record class (default 'IN')
        tcp (bool): Use TCP instead of UDP
        source (str): Source IP address
        raise_on_no_answer (bool): Raise exception if no answer
        source_port (int): Source port number
        lifetime (float): Total query lifetime in seconds
        
    Returns:
        dns.resolver.Answer: Query result with sequence-like access
    """

def zone_for_name(name, rdclass='IN', tcp=False, resolver=None):
    """
    Find the zone containing the specified name.
    
    Args:
        name (str or dns.name.Name): Domain name
        rdclass (str or int): Record class (default 'IN')
        tcp (bool): Use TCP instead of UDP
        resolver (dns.resolver.Resolver): Custom resolver
        
    Returns:
        dns.name.Name: Zone name containing the specified name
    """

def get_default_resolver():
    """
    Get the default resolver instance.
    
    Returns:
        dns.resolver.Resolver: Default resolver
    """

def reset_default_resolver():
    """Re-initialize the default resolver from system configuration."""

def override_system_resolver(resolver=None):
    """
    Override system DNS resolution functions.
    
    Args:
        resolver (dns.resolver.Resolver): Custom resolver or None for default
    """

def restore_system_resolver():
    """Restore original system DNS resolution functions."""

class Resolver:
    """
    A DNS resolver with configurable options.
    
    Attributes:
        nameservers (list): List of nameserver IP addresses
        port (int): Default port for queries (default 53)
        timeout (float): Timeout for individual queries
        lifetime (float): Total timeout for all queries
        search (list): Search domains for relative names
        domain (dns.name.Name): Local domain name
        ndots (int): Minimum dots for absolute name treatment
        rotate (bool): Rotate through nameservers
        cache (dns.resolver.Cache): Answer cache
        flags (int): Query flags
        edns (int): EDNS version (-1 to disable)
        ednsflags (int): EDNS flags
        payload (int): EDNS payload size
        keyring (dict): TSIG keyring
        keyname (dns.name.Name): TSIG key name
        keyalgorithm (dns.name.Name): TSIG algorithm
    """
    
    def __init__(self, filename='/etc/resolv.conf', configure=True):
        """
        Initialize resolver.
        
        Args:
            filename (str): Configuration file path
            configure (bool): Configure from system settings
        """
    
    def query(self, qname, rdtype='A', rdclass='IN', tcp=False, source=None,
              raise_on_no_answer=True, source_port=0):
        """
        Query using this resolver instance.
        
        Returns:
            dns.resolver.Answer: Query result
        """
    
    def read_resolv_conf(self, f):
        """
        Read configuration from resolv.conf format file.
        
        Args:
            f (file-like): File to read from
        """
    
    def use_tsig(self, keyring, keyname=None, algorithm=dns.tsig.default_algorithm):
        """
        Configure TSIG authentication for queries.
        
        Args:
            keyring (dict): TSIG keyring mapping key names to key values
            keyname (dns.name.Name): TSIG key name (optional, uses first key if None)
            algorithm (dns.name.Name): TSIG algorithm (default: HMAC-MD5)
        """

class Answer:
    """
    DNS query answer with sequence-like access to resource records.
    
    Attributes:
        qname (dns.name.Name): Query name
        rdtype (int): Record type queried
        rdclass (int): Record class queried  
        response (dns.message.Message): Full DNS response
        rrset (dns.rrset.RRset): Answer resource record set
        canonical_name (dns.name.Name): Canonical name after CNAME following
        expiration (float): Answer expiration time
    """
    
    def __iter__(self):
        """Iterate over resource records in the answer."""
    
    def __len__(self):
        """Return number of resource records."""
    
    def __getitem__(self, index):
        """Get resource record by index."""

class Cache:
    """
    Simple thread-safe DNS answer cache.
    
    Args:
        cleaning_interval (float): Cache cleaning interval in seconds
    """
    
    def get(self, key):
        """Get cached answer for key."""
    
    def put(self, key, value):
        """Store answer in cache."""
    
    def flush(self, key=None):
        """Remove items from cache."""

class LRUCache(Cache):
    """
    Bounded least-recently-used DNS answer cache.
    
    Args:
        max_size (int): Maximum cache entries (default 100000)
    """

import dns.resolver

# Simple A record lookup
result = dns.resolver.query('example.com', 'A')
for rdata in result:
    print(f"IP: {rdata.address}")

# MX record lookup
mx_result = dns.resolver.query('example.com', 'MX')
for rdata in mx_result:
    print(f"Mail server: {rdata.exchange}, priority: {rdata.preference}")

# TXT record lookup
txt_result = dns.resolver.query('example.com', 'TXT')
for rdata in txt_result:
    print(f"TXT: {rdata.strings}")

import dns.resolver

# Create custom resolver
resolver = dns.resolver.Resolver()
resolver.nameservers = ['8.8.8.8', '8.8.4.4']  # Google DNS
resolver.timeout = 10
resolver.lifetime = 30

# Query using custom resolver
result = resolver.query('example.com', 'AAAA')
for rdata in result:
    print(f"IPv6: {rdata.address}")

# Configure search domains
resolver.search = [dns.name.from_text('example.com')]
resolver.domain = dns.name.from_text('example.com')

import dns.resolver
import dns.exception

try:
    result = dns.resolver.query('nonexistent.example.com', 'A')
except dns.resolver.NXDOMAIN as e:
    print(f"Domain does not exist: {e}")
except dns.resolver.NoAnswer as e:
    print(f"No answer for query: {e}")
except dns.resolver.Timeout as e:
    print(f"Query timed out: {e}")
except dns.exception.DNSException as e:
    print(f"DNS error occurred: {e}")

class NXDOMAIN(DNSException):
    """The query name does not exist."""

class YXDOMAIN(DNSException):
    """The query name is too long after DNAME substitution."""

class NoAnswer(DNSException):
    """The DNS response does not contain an answer to the question."""

class NoNameservers(DNSException):
    """All nameservers failed to answer the query."""

class NotAbsolute(DNSException):
    """An absolute domain name is required but was not provided."""

class NoRootSOA(DNSException):
    """There is no SOA RR at the DNS root name."""

class NoMetaqueries(DNSException):
    """DNS metaqueries are not allowed."""