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## dns-response

The class of a DNS response object. When dns-query is called with the decode argument `nil`, the response from the nameserver is returned in its raw form. The response is represented by a `dns-response` object which contains pointers to `dns-rr` objects. It has the following slots and accessors:

- `id`, accessor is dns-response-id. The number of the query for which this is a response. Each query is given a unique number by dns-query so that it can associate responses with queries.
- `flags`, accessor is dns-response-flags. The characteristics of the response are described by a set of flags represented in this slot by a list of keyword symbols. The set of flags can be found in rfc1035, the document describing the DNS specification (see The Allegro CL Domain Naming System Package in dns.htm for a link to rfc1035).
- `flags-value`, accessor is dns-response-flags-value. An integer that is the raw form of the flags value.
- `answer`, accessor is dns-response-answer. A list of `dns-rr` objects which comprise the answer to the query. If there are no answers then that is significant as well as that tells you that what you're asking for either doesn't exist or can't be computed at this time.
- `authority`, accessor is dns-response-authority. DNS permits nameservers to cache information and this is in fact critical to prevent nameserver overloading. What this means though is that the same information can be stored in a large collection of nameservers. However for any piece of information there is always a set of nameservers that are the authoritative nameservers for that information. This field in the dns-response lists the nameservers that are the authority for answering the dns-query that was posed. The nameservers are returned as a list of `dns-rr` objects.
- `additional`, accessor is dns-response-additional. Some queries return answers which would immediately prompt another query. For example a `:type :mx` dns-query to find a mail exchanger for a name returns a set of mail exchanger machine names. After receiving those names the program will almost certainly want to find the IP addresses for those machine names. Thus the DNS system can anticipate the follow up query and can return in the additional slot a list of `dns-rr`'s that would be returned by the followup query. In the `:type :mx` query the additional slot usually contains a list of those mail exchangers machine names and their IP addresses. There is no guarantee that that information will be provided in the additional slot

See dns.htm.

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This page was not revised from the 8.2 page.
Created 2012.5.30.

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