diff options
author | Camil Staps | 2016-05-02 15:36:05 +0200 |
---|---|---|
committer | Camil Staps | 2016-05-02 15:36:05 +0200 |
commit | 7120add95d0c5b8a97af861785ec9fe1cfc7eaee (patch) | |
tree | 986d3801536e5d45937ee3d22474bc6eca120819 /project2/proj2_s4498062/dns/domainname.py | |
parent | Assignment 5 (diff) |
dos2unix
Diffstat (limited to 'project2/proj2_s4498062/dns/domainname.py')
-rw-r--r-- | project2/proj2_s4498062/dns/domainname.py | 226 |
1 files changed, 113 insertions, 113 deletions
diff --git a/project2/proj2_s4498062/dns/domainname.py b/project2/proj2_s4498062/dns/domainname.py index 09f98fa..85e14bf 100644 --- a/project2/proj2_s4498062/dns/domainname.py +++ b/project2/proj2_s4498062/dns/domainname.py @@ -1,113 +1,113 @@ -#!/usr/bin/env python2
-
-""" Parsing and composing domain names
-
-This module contains two classes for converting domain names to and from bytes.
-You won't have to use these classes. They're used internally in Message,
-Question, ResourceRecord and RecordData. You can read section 4.1.4 of RFC 1035
-if you want more info.
-"""
-
-import struct
-
-
-class Composer(object):
- def __init__(self):
- self.offsets = dict()
-
- def to_bytes(self, offset, dnames):
- # Convert each domain name in to bytes
- result = b""
- for i, dname in enumerate(dnames):
- # Split domain name into labels
- labels = dname.split(".")
-
- # Determine keys of subdomains in offset dict
- keys = []
- for label in reversed(labels):
- name = label
- if keys:
- name += "." + keys[-1]
- keys.append(name)
- keys.reverse()
-
- # Convert label to bytes
- add_null = True
- for j, label in enumerate(labels):
- if keys[j] in self.offsets:
- offset = self.offsets[keys[j]]
- pointer = (3 << 14) + offset
- result += struct.pack("!H", pointer)
- add_null = False
- offset += 2
- break
- else:
- self.offsets[keys[j]] = offset
- result += struct.pack("!B{}s".format(len(label)),
- len(label),
- label)
- offset += 1 + len(label)
-
- # Add null character at end
- if add_null:
- result += b"\x00"
- offset += 1
-
- return result
-
-
-class Parser(object):
- def __init__(self):
- self.labels = dict()
-
- def from_bytes(self, packet, offset, num):
- begin_offset = offset
- dnames = []
-
- # Read the domain names
- for i in range(num):
- # Read a new domain name
- dname = ""
- prev_offsets = []
- done = False
- while done is False:
- # Read length of next label
- llength = struct.unpack_from("!B", packet, offset)[0]
-
- # Done reading domain when length is zero
- if llength == 0:
- offset += 1
- break
-
- # Compression label
- elif (llength >> 6) == 3:
- new_offset = offset + 2
- target = struct.unpack_from("!H", packet, offset)[0]
- target -= 3 << 14
- label = self.labels[target]
- done = True
-
- # Normal label
- else:
- new_offset = offset + llength + 1
- label = struct.unpack_from("{}s".format(llength),
- packet, offset+1)[0]
-
- # Add label to dictionary
- self.labels[offset] = label
- for prev_offset in prev_offsets:
- self.labels[prev_offset] += "." + label
- prev_offsets.append(offset)
-
- # Update offset
- offset = new_offset
-
- # Append label to domain name
- if len(dname) > 0:
- dname += "."
- dname += label
-
- # Append domain name to list
- dnames.append(dname)
-
- return dnames, offset
+#!/usr/bin/env python2 + +""" Parsing and composing domain names + +This module contains two classes for converting domain names to and from bytes. +You won't have to use these classes. They're used internally in Message, +Question, ResourceRecord and RecordData. You can read section 4.1.4 of RFC 1035 +if you want more info. +""" + +import struct + + +class Composer(object): + def __init__(self): + self.offsets = dict() + + def to_bytes(self, offset, dnames): + # Convert each domain name in to bytes + result = b"" + for i, dname in enumerate(dnames): + # Split domain name into labels + labels = dname.split(".") + + # Determine keys of subdomains in offset dict + keys = [] + for label in reversed(labels): + name = label + if keys: + name += "." + keys[-1] + keys.append(name) + keys.reverse() + + # Convert label to bytes + add_null = True + for j, label in enumerate(labels): + if keys[j] in self.offsets: + offset = self.offsets[keys[j]] + pointer = (3 << 14) + offset + result += struct.pack("!H", pointer) + add_null = False + offset += 2 + break + else: + self.offsets[keys[j]] = offset + result += struct.pack("!B{}s".format(len(label)), + len(label), + label) + offset += 1 + len(label) + + # Add null character at end + if add_null: + result += b"\x00" + offset += 1 + + return result + + +class Parser(object): + def __init__(self): + self.labels = dict() + + def from_bytes(self, packet, offset, num): + begin_offset = offset + dnames = [] + + # Read the domain names + for i in range(num): + # Read a new domain name + dname = "" + prev_offsets = [] + done = False + while done is False: + # Read length of next label + llength = struct.unpack_from("!B", packet, offset)[0] + + # Done reading domain when length is zero + if llength == 0: + offset += 1 + break + + # Compression label + elif (llength >> 6) == 3: + new_offset = offset + 2 + target = struct.unpack_from("!H", packet, offset)[0] + target -= 3 << 14 + label = self.labels[target] + done = True + + # Normal label + else: + new_offset = offset + llength + 1 + label = struct.unpack_from("{}s".format(llength), + packet, offset+1)[0] + + # Add label to dictionary + self.labels[offset] = label + for prev_offset in prev_offsets: + self.labels[prev_offset] += "." + label + prev_offsets.append(offset) + + # Update offset + offset = new_offset + + # Append label to domain name + if len(dname) > 0: + dname += "." + dname += label + + # Append domain name to list + dnames.append(dname) + + return dnames, offset |