Class DNSStrField

scapy/layers/dns.py:335–381

Special StrField that handles DNS encoding/decoding. It will also handle DNS decompression. (may be StrLenField if a length_from is passed),

class DNSStrField(StrLenField):
    """
    Special StrField that handles DNS encoding/decoding.
    It will also handle DNS decompression.
    (may be StrLenField if a length_from is passed),
    """
    def any2i(self, pkt, x):
        if x and isinstance(x, list):
            return [self.h2i(pkt, y) for y in x]
        return super(DNSStrField, self).any2i(pkt, x)

    def h2i(self, pkt, x):
        # Setting a DNSStrField manually (h2i) means any current compression will break
        if (
            pkt and
            isinstance(pkt.parent, DNSCompressedPacket) and
            pkt.parent.raw_packet_cache
        ):
            pkt.parent.clear_cache()
        if not x:
            return b"."
        x = bytes_encode(x)
        if x[-1:] != b"." and not _is_ptr(x):
            return x + b"."
        return x

    def i2m(self, pkt, x):
        return dns_encode(x, check_built=True)

    def i2len(self, pkt, x):
        return len(self.i2m(pkt, x))

    def get_full(self, pkt):
        while pkt and not isinstance(pkt, DNSCompressedPacket):
            pkt = pkt.parent or pkt.underlayer
        if not pkt:
            return None
        return pkt.get_full()

    def getfield(self, pkt, s):
        remain = b""
        if self.length_from:
            remain, s = super(DNSStrField, self).getfield(pkt, s)
        # Decode the compressed DNS message
        decoded, left = dns_get_str(s, full=self.get_full(pkt))
        # returns (remaining, decoded)
        return left + remain, decoded


class DNSTextField(StrLenField):