The Net::DNS::RR is the base class for DNS Resource Record (RR) objects. A RR is a pack of data that represents resources for a DNS zone. The form in which this data is shows can be drawed as follow:
"name ttl class type data"
The name is the name of the resource, like an canonical name for an A record (internet ip address). The ttl is the time to live, expressed in seconds. type and class are respectively the type of resource (A for ip addresses, NS for nameservers, and so on) and the class, which is almost always IN, the Internet class. At the end, data is the value associated to the name for that particular type of resource record. An example:
# A record for IP address "www.example.com 86400 IN A 172.16.100.1" # NS record for name server "www.example.com 86400 IN NS ns.example.com"
A new RR object can be created in 2 ways: passing a string such the ones above, or specifying each field as the pair of an hash. See the Net::DNS::RR.new method for details.
Create a new instance of Net::DNS::RR class, or an instance of any of the subclass of the appropriate type.
Argument can be a string or an hash. With a sting, we can pass a RR resource record in the canonical format:
a = Net::DNS::RR.new("foo.example.com. 86400 A 10.1.2.3") mx = Net::DNS::RR.new("example.com. 7200 MX 10 mailhost.example.com.") cname = Net::DNS::RR.new("www.example.com 300 IN CNAME www1.example.com") txt = Net::DNS::RR.new('baz.example.com 3600 HS TXT "text record"')
Incidentally, a, mx, cname and txt objects will be instances of respectively Net::DNS::RR::A, Net::DNS::RR::MX, Net::DNS::RR::CNAME and Net::DNS::RR::TXT classes.
The name and RR data are required; all other informations are optional. If omitted, the TTL defaults to 10800, type default to A and the RR class defaults to IN. Omitting the optional fields is useful for creating the empty RDATA sections required for certain dynamic update operations. All names must be fully qualified. The trailing dot (.) is optional.
The preferred method is however passing an hash with keys and values:
rr = Net::DNS::RR.new( :name => "foo.example.com", :ttl => 86400, :cls => "IN", :type => "A", :address => "10.1.2.3" ) rr = Net::DNS::RR.new( :name => "foo.example.com", :rdata => "10.1.2.3" )
Name and data are required; all the others fields are optionals like we've seen before. The data field can be specified either with the right name of the resource (:address in the example above) or with the generic key :rdata. Consult documentation to find the exact name for the resource in each subclass.
# File lib/net/dns/rr.rb, line 109 def initialize(arg) instance = case arg when String new_from_string(arg) when Hash new_from_hash(arg) else raise ArgumentError, "Invalid argument, must be a RR string or an hash of values" end if @type.to_s == "ANY" @cls = Net::DNS::RR::Classes.new("IN") end build_pack set_type instance end
Return a new RR object of the correct type (like Net::DNS::RR::A if the type is A) from a binary string, usually obtained from network stream.
This method is used when parsing a binary packet by the Packet class.
# File lib/net/dns/rr.rb, line 136 def RR.parse(data) o = allocate obj, offset = o.send(:new_from_binary, data, 0) obj end
Same as RR.parse, but takes an entire packet binary data to perform name expansion. Default when analizing a packet just received from a network stream.
Return an instance of appropriate class and the offset pointing at the end of the data parsed.
# File lib/net/dns/rr.rb, line 149 def RR.parse_packet(data, offset) o = allocate o.send(:new_from_binary, data, offset) end
Class accessor
# File lib/net/dns/rr.rb, line 168 def cls @cls.to_s end
Return the RR object in binary data format, suitable for using in network streams, with names compressed. Must pass as arguments the offset inside the packet and an hash of compressed names.
This method is to be used in other classes and is not intended for user space programs.
TO FIX in one of the future releases
# File lib/net/dns/rr.rb, line 204 def comp_data(offset,compnames) str, offset, names = dn_comp(@name, offset, compnames) str += [@type.to_i, @cls.to_i, ttl, @rdlength].pack("n2 N n") offset += Net::DNS::RRFIXEDSZ [str, offset, names] end
Return the RR object in binary data format, suitable for using in network streams.
raw_data = rr.data puts "RR is #{raw_data.size} bytes long"
# File lib/net/dns/rr.rb, line 189 def data str = pack_name(@name) str + [@type.to_i, @cls.to_i, ttl, @rdlength].pack("n2 N n") + get_data end
Returns a human readable representation of this record. The value is always a String.
mx = Net::DNS::RR.new("example.com. 7200 MX 10 mailhost.example.com.") #=> example.com. 7200 IN MX 10 mailhost.example.com.
# File lib/net/dns/rr.rb, line 218 def inspect to_s end
Data belonging to that appropriate class, not to be used (use real accessors instead)
# File lib/net/dns/rr.rb, line 179 def rdata @rdata end
Returns an Array with all the attributes for this record.
mx = Net::DNS::RR.new("example.com. 7200 MX 10 mailhost.example.com.") mx.to_a #=> ["example.com.", 7200, "IN", "MX", "10 mailhost.example.com."]
# File lib/net/dns/rr.rb, line 243 def to_a [name, ttl, cls.to_s, type.to_s, value] end
Returns a String representation of this record.
mx = Net::DNS::RR.new("example.com. 7200 MX 10 mailhost.example.com.") mx.to_s #=> "example.com. 7200 IN MX 10 mailhost.example.com."
# File lib/net/dns/rr.rb, line 228 def to_s items = to_a.map { |e| e.to_s } if @name.size < 24 items.pack("A24 A8 A8 A8 A*") else items.join(" ") end.to_s end
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