refactor(lisp/dns): Split package into multiple files
Adds a package definition file and moves the current client into client.lisp Note that the client is not working at all at this commit as this is a work-in-progress snapshot.
This commit is contained in:
Vincent Ambo
parent
29e1de2fd2
commit
09621f5371
4 changed files with 182 additions and 31 deletions
173
lisp/dns/client.lisp
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173
lisp/dns/client.lisp
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;; Implementation of a DoH-client, see RFC 8484 (DNS Queries over
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;; HTTPS (DoH))
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(in-package #:dns)
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;; The DoH client is configured with a URI Template [RFC6570]
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(defvar *doh-base-url* "https://dns.google/dns-query"
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"Base URL of the service providing DNS-over-HTTP(S). Defaults to the
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Google-hosted API.")
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(defun lookup-generic (name type)
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(multiple-value-bind (stream)
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(drakma:http-request *doh-base-url*
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:decode-content t
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:want-stream t
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:parameters `(("type" . ,type)
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("name" . ,name)
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("ct" . "application/dns-message")))
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(read-binary 'dns-message stream)))
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(defun lookup-txt (name)
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"Look up the TXT records at NAME."
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(lookup-generic name "TXT"))
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(defun lookup-mx (name)
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"Look up the MX records at NAME."
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(lookup-generic name "MX"))
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;; The URI Template defined in this document is processed without any
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;; variables when the HTTP method is POST. When the HTTP method is GET,
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;; the single variable "dns" is defined as the content of the DNS
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;; request (as described in Section 6), encoded with base64url
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;; [RFC4648].
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;; When using the POST method, the DNS query is included as the message
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;; body of the HTTP request, and the Content-Type request header field
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;; indicates the media type of the message. POSTed requests are
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;; generally smaller than their GET equivalents.
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;; Using the GET method is friendlier to many HTTP cache
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;; implementations.
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;; The DoH client SHOULD include an HTTP Accept request header field to
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;; indicate what type of content can be understood in response.
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;; Irrespective of the value of the Accept request header field, the
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;; client MUST be prepared to process "application/dns-message" (as
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;; described in Section 6) responses but MAY also process other DNS-
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;; related media types it receives.
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;; In order to maximize HTTP cache friendliness, DoH clients using media
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;; formats that include the ID field from the DNS message header, such
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;; as "application/dns-message", SHOULD use a DNS ID of 0 in every DNS
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;; request. HTTP correlates the request and response, thus eliminating
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;; the need for the ID in a media type such as "application/dns-
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;; message". The use of a varying DNS ID can cause semantically
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;; equivalent DNS queries to be cached separately.
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;; DoH clients can use HTTP/2 padding and compression [RFC7540] in the
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;; same way that other HTTP/2 clients use (or don't use) them.
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;; 4.1.1. HTTP Request Examples
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;; These examples use HTTP/2-style formatting from [RFC7540].
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;; These examples use a DoH service with a URI Template of
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;; "https://dnsserver.example.net/dns-query{?dns}" to resolve IN A
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;; records.
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;; The requests are represented as bodies with media type "application/
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;; dns-message".
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;; The first example request uses GET to request "www.example.com".
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;; :method = GET
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;; :scheme = https
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;; :authority = dnsserver.example.net
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;; :path = /dns-query?dns=AAABAAABAAAAAAAAA3d3dwdleGFtcGxlA2NvbQAAAQAB
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;; accept = application/dns-message
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;; Finally, a GET-based query for "a.62characterlabel-makes-base64url-
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;; distinct-from-standard-base64.example.com" is shown as an example to
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;; emphasize that the encoding alphabet of base64url is different than
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;; regular base64 and that padding is omitted.
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;; The only response type defined in this document is "application/dns-
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;; message", but it is possible that other response formats will be
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;; defined in the future. A DoH server MUST be able to process
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;; "application/dns-message" request messages.
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;; Each DNS request-response pair is mapped to one HTTP exchange.
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;; DNS response codes indicate either success or failure for the DNS
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;; query. A successful HTTP response with a 2xx status code (see
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;; Section 6.3 of [RFC7231]) is used for any valid DNS response,
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;; HTTP responses with non-successful HTTP status codes do not contain
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;; replies to the original DNS question in the HTTP request. DoH
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;; clients need to use the same semantic processing of non-successful
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;; HTTP status codes as other HTTP clients.
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;; 4.2.2. HTTP Response Example
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;; This is an example response for a query for the IN AAAA records for
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;; "www.example.com" with recursion turned on. The response bears one
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;; answer record with an address of 2001:db8:abcd:12:1:2:3:4 and a TTL
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;; of 3709 seconds.
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;; :status = 200
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;; content-type = application/dns-message
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;; content-length = 61
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;; cache-control = max-age=3709
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;; <61 bytes represented by the following hex encoding>
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;; 00 00 81 80 00 01 00 01 00 00 00 00 03 77 77 77
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;; 07 65 78 61 6d 70 6c 65 03 63 6f 6d 00 00 1c 00
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;; 01 c0 0c 00 1c 00 01 00 00 0e 7d 00 10 20 01 0d
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;; b8 ab cd 00 12 00 01 00 02 00 03 00 04
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;; This protocol MUST be used with the https URI scheme [RFC7230].
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;; In particular, DoH servers SHOULD assign an explicit HTTP freshness
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;; lifetime (see Section 4.2 of [RFC7234]) so that the DoH client is
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;; more likely to use fresh DNS data. This requirement is due to HTTP
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;; caches being able to assign their own heuristic freshness (such as
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;; that described in Section 4.2.2 of [RFC7234]), which would take
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;; control of the cache contents out of the hands of the DoH server.
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;; The assigned freshness lifetime of a DoH HTTP response MUST be less
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;; than or equal to the smallest TTL in the Answer section of the DNS
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;; response. A freshness lifetime equal to the smallest TTL in the
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;; Answer section is RECOMMENDED. For example, if a HTTP response
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;; carries three RRsets with TTLs of 30, 600, and 300, the HTTP
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;; freshness lifetime should be 30 seconds (which could be specified as
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;; "Cache-Control: max-age=30"). This requirement helps prevent expired
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;; RRsets in messages in an HTTP cache from unintentionally being
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;; served.
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;; If the DNS response has no records in the Answer section, and the DNS
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;; response has an SOA record in the Authority section, the response
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;; freshness lifetime MUST NOT be greater than the MINIMUM field from
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;; that SOA record (see [RFC2308]).
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;; DoH clients MUST account for the Age response header field's value
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;; [RFC7234] when calculating the DNS TTL of a response. For example,
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;; if an RRset is received with a DNS TTL of 600, but the Age header
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;; field indicates that the response has been cached for 250 seconds,
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;; the remaining lifetime of the RRset is 350 seconds. This requirement
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;; applies to both DoH client HTTP caches and DoH client DNS caches.
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;; Those features were introduced to HTTP in HTTP/2 [RFC7540].
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;; Earlier versions of HTTP are capable of conveying the semantic
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;; requirements of DoH but may result in very poor performance.
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;; In order to maximize interoperability, DoH clients and DoH servers
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;; MUST support the "application/dns-message" media type.
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;; The data payload for the "application/dns-message" media type is a
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;; single message of the DNS on-the-wire format defined in Section 4.2.1
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;; of [RFC1035], which in turn refers to the full wire format defined in
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;; Section 4.1 of that RFC.
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;; This media type restricts the maximum size of the DNS message to
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;; 65535 bytes.
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;; When using the GET method, the data payload for this media type MUST
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;; be encoded with base64url [RFC4648] and then provided as a variable
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;; named "dns" to the URI Template expansion. Padding characters for
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;; base64url MUST NOT be included.
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;; When using the POST method, the data payload for this media type MUST
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;; NOT be encoded and is used directly as the HTTP message body.
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@ -4,12 +4,15 @@ pkgs.nix.buildLisp.library {
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name = "dns";
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name = "dns";
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deps = with pkgs.third_party.lisp; [
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deps = with pkgs.third_party.lisp; [
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drakma
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lisp-binary
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iterate
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alexandria
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alexandria
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cl-json
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cl-json
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drakma
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];
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];
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srcs = [
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srcs = [
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./resolver.lisp
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./package.lisp
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./client.lisp
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];
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];
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}
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}
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4
lisp/dns/package.lisp
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4
lisp/dns/package.lisp
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@ -0,0 +1,4 @@
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(defpackage #:dns
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(:documentation "Simple DNS resolver in Common Lisp")
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(:use #:cl #:iterate #:lisp-binary)
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(:export #:lookup-txt #:lookup-mx))
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;; Initial implementation is a simple client for
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;; https://developers.google.com/speed/public-dns/docs/doh/json
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(defpackage #:dns
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(:documentation "Simple DNS resolver in Common Lisp")
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(:use #:cl)
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(:export #:lookup-txt #:lookup-mx))
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(defvar *doh-base-url* "https://dns.google/resolve"
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"Base URL of the service providing DNS-over-HTTP(S). Defaults to the
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Google-hosted API.")
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(defun lookup-generic (name type)
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(multiple-value-bind (body)
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(drakma:http-request *doh-base-url*
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:decode-content t
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:want-stream t
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:parameters `(("type" . ,type)
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("name" . ,name)
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("ct" . "application/x-javascript")))
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(cl-json:decode-json body)))
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(defun lookup-txt (name)
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"Look up the TXT records at NAME."
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(lookup-generic name "TXT"))
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(defun lookup-mx (name)
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"Look up the MX records at NAME."
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(lookup-generic name "MX"))
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Loading…
Reference in a new issue