| Class | Dnsruby::Resolver |
| In: |
lib/dnsruby/resolver.rb
|
| Parent: | Object |
Dnsruby::Resolver is a DNS stub resolver. This class performs queries with retries across multiple nameservers. The system configured resolvers are used by default.
The retry policy is a combination of the Net::DNS and dnsjava approach, and has the option of :
complete, but in which the total time per query round is split between the number of nameservers targetted for the first round. and total time for query round is doubled for each query round
Note that, if a total timeout is specified, then that will apply regardless of the retry policy (i.e. it may cut retries short).
Note also that these timeouts are distinct from the SingleResolver‘s packet_timeout
Timeouts apply to the initial query and response. If DNSSEC validation is to be performed, then additional queries may be required (these are performed automatically by Dnsruby). Each additional query will be performed with its own timeouts. So, even with a query_timeout of 5 seconds, a response which required extensive validation may take several times that long. (Future versions of Dnsruby may expose finer-grained events for client tracking of responses and validation)
These methods raise an exception or return a response message with rcode==NOERROR
There are "!" versions of these two methods that return an array [response, error] instead of raising an error on failure. They can be called as follows: response, error = resolver.send_message!(...) response, error = resolver.query!(...) If the request succeeds, response will contain the Dnsruby::Message response and error will be nil. If the request fails, response will be nil and error will contain the error raised.
These methods use a response queue to return the response and the error
Dnsruby runs a pure Ruby event loop to handle I/O in a single thread. Support for EventMachine has been deprecated.
| DefaultQueryTimeout | = | 0 |
| DefaultPacketTimeout | = | 5 |
| DefaultRetryTimes | = | 1 |
| DefaultRetryDelay | = | 5 |
| DefaultPipeLiningMaxQueries | = | 5 |
| DefaultPort | = | 53 |
| DefaultDnssec | = | false |
| AbsoluteMinDnssecUdpSize | = | 1220 |
| MinDnssecUdpSize | = | 4096 |
| DefaultUDPSize | = | MinDnssecUdpSize |
| config | [R] | The current Config |
| dnssec | [R] | Use DNSSEC for this Resolver |
| do_caching | [R] | Does this Resolver cache answers, and attempt to retrieve answer from the cache? |
| do_caching | [RW] | Defines whether we will cache responses, or pass every request to the upstream resolver. This is only really useful when querying authoritative servers (as the upstream recursive resolver is likely to cache) |
| do_validation | [RW] | Defines whether validation is performed by default on this Resolver when the query method is called. Note that send_message and send_async expect a Message object to be passed in, which is already configured to the callers requirements. |
| ignore_truncation | [R] | Should truncation be ignored? i.e. the TC bit is ignored and thus the resolver will not requery over TCP if TC is set |
| no_tcp | [R] | If no_tcp==true, then ONLY UDP will be used as a transport. This should not generally be used, but is provided as a debugging aid. |
| packet_timeout | [R] | The timeout for any individual packet. This is the timeout used by SingleResolver |
| port | [R] | The port to send queries to on the resolver |
| query_timeout | [RW] | Note that this timeout represents the total time a query may run for - multiple packets can be sent to multiple nameservers in this time. This is distinct from the SingleResolver per-packet timeout The query_timeout is not required - it will default to 0, which means "do not use query_timeout". If this is the case then the timeout will be dictated by the retry_times and retry_delay attributes |
| recurse | [R] | Should the Recursion Desired bit be set? |
| retry_delay | [RW] | The query will be tried across nameservers retry_times times, with a delay of retry_delay seconds between each retry. The first time round, retry_delay will be divided by the number of nameservers being targetted, and a new nameserver will be queried with the resultant delay. |
| retry_times | [RW] | The query will be tried across nameservers retry_times times, with a delay of retry_delay seconds between each retry. The first time round, retry_delay will be divided by the number of nameservers being targetted, and a new nameserver will be queried with the resultant delay. |
| src_address | [R] | The source address to send queries from for IPv4 |
| src_address6 | [R] | The source address to send queries from for IPv6 |
| tcp_pipelining | [R] | If tcp_pipelining==true, then we reuse the TCP connection |
| tcp_pipelining_max_queries | [R] | How many times (number of messages) to reuse the pipelining connection before closing, :infinite for infinite number of requests per connection |
| tsig | [R] | |
| udp_size | [R] | The maximum UDP size to be used |
| use_tcp | [R] | Should TCP be used as a transport rather than UDP? If use_tcp==true, then ONLY TCP will be used as a transport. |
Create a new Resolver object. If no parameters are passed in, then the default system configuration will be used. Otherwise, a Hash may be passed in with the following optional elements :
Can be a single Integer or a Range or an Array If an invalid port is selected (one reserved by IANA), then an ArgumentError will be raised. "0" means "any valid port" - this is only a viable option if it is the only port in the list. An ArgumentError will be raised if "0" is added to an existing set of source ports.
res.add_src_port(60000)
res.add_src_port([60001,60005,60010])
res.add_src_port(60015..60115)
— @TODO@ Should really auto-generate these methods. Also, any way to tie them up with SingleResolver RDoc? ++
Query for a name. If a valid Message is received, then it is returned to the caller. Otherwise an exception (a Dnsruby::ResolvError or Dnsruby::ResolvTimeout) is raised.
require 'dnsruby'
res = Dnsruby::Resolver.new
response = res.query('example.com') # defaults to Types.A, Classes.IN
response = res.query('example.com', Types.MX)
response = res.query('208.77.188.166') # IPv4 address so PTR query will be made
response = res.query('208.77.188.166', Types.PTR)
Like query, but does not raise an error when an error occurs. Instead, it returns it. @return a 2 element array: [response, error]
Sends a message with send_plain_message. Effectively a wrapper around send_plain_message, but adds the ability to configure whether an error will be raised or returned if it occurs.
@param message the message to send to the DNS server @param error_strategy :return to return [response, error] (default),
:raise to return response only, or raise an error if one occurs
Asynchronously send a Message to the server. The send can be done using just Dnsruby. Support for EventMachine has been deprecated.
A client_queue is supplied by the client, along with an optional client_query_id to identify the response. The client_query_id is generated, if not supplied, and returned to the client. When the response is known, a tuple of (query_id, response_message, exception) will be added to the client_queue.
The query is sent synchronously in the caller‘s thread. The select thread is then used to listen for and process the response (up to pushing it to the client_queue). The client thread is then used to retrieve the response and deal with it.
Takes :
Returns :
generated if it is not passed in by the client
id = res.send_async(msg, queue) NOT SUPPORTED : id = res.send_async(msg, queue, use_tcp) id = res.send_async(msg, queue, id) id = res.send_async(msg, queue, id, use_tcp)
require 'dnsruby'
res = Dnsruby::Resolver.newsend
query_id = 10 # can be any object you like
query_queue = Queue.new
res.send_async(Message.new('example.com', Types.MX), query_queue, query_id)
query_id_2 = res.send_async(Message.new('example.com', Types.A), query_queue)
# ...do a load of other stuff here...
2.times do
response_id, response, exception = query_queue.pop
# You can check the ID to see which query has been answered
if exception == nil
# deal with good response
else
# deal with problem
end
end
Send a message, and wait for the response. If a valid Message is received, then it is returned to the caller. Otherwise an exception (a Dnsruby::ResolvError or Dnsruby::ResolvTimeout) is raised.
send_async is called internally.
example :
require 'dnsruby'
include Dnsruby
res = Dnsruby::Resolver.new
begin
response = res.send_message(Message.new('example.com', Types.MX))
rescue ResolvError
# ...
rescue ResolvTimeout
# ...
end
Like send_message, but does not raise an error when an error occurs. Instead, it returns it. @return a 2 element array: [response, error]
This method takes a Message (supplied by the client), and sends it to the configured nameservers. No changes are made to the Message before it is sent (TSIG signatures will be applied if configured on the Resolver). Retries are handled as the Resolver is configured to do. Incoming responses to the query are not cached or validated (although TCP fallback will be performed if the TC bit is set and the (Single)Resolver has ignore_truncation set to false). Note that the Message is left untouched - this means that no OPT records are added, even if the UDP transport for the server is specified at more than 512 bytes. If it is desired to use EDNS for this packet, then you should call the Dnsruby::PacketSender#prepare_for_dnssec(msg), or Dnsruby::PacketSender#add_opt_rr(msg) The return value from this method is the [response, error] tuple. Either of these values may be nil - it is up to the client to check.
example :
require 'dnsruby'
include Dnsruby
res = Dnsruby::Resolver.new
response, error = res.send_plain_message(Message.new('example.com', Types.MX))
if error
print "Error returned : #{error}\n"
else
process_response(response)
end
The source port to send queries from Returns either a single Integer or an Array e.g. ‘0’, or ’[60001, 60002, 60007]’
Defaults to 0 - random port
Can be a single Integer or a Range or an Array If an invalid port is selected (one reserved by IANA), then an ArgumentError will be raised.
res.src_port=0
res.src_port=[60001,60005,60010]
res.src_port=60015..60115
Sets the TSIG to sign outgoing messages with. Pass in either a Dnsruby::RR::TSIG, or a key_name and key (or just a key) Pass in nil to stop tsig signing.