(in-package :dns) ;; 3.2.2. TYPE values ;; TYPE fields are used in resource records. Note that these types are a ;; subset of QTYPEs. ;; TYPE value and meaning ;; A 1 a host address ;; NS 2 an authoritative name server ;; MD 3 a mail destination (Obsolete - use MX) ;; MF 4 a mail forwarder (Obsolete - use MX) ;; CNAME 5 the canonical name for an alias ;; SOA 6 marks the start of a zone of authority ;; MB 7 a mailbox domain name (EXPERIMENTAL) ;; MG 8 a mail group member (EXPERIMENTAL) ;; MR 9 a mail rename domain name (EXPERIMENTAL) ;; NULL 10 a null RR (EXPERIMENTAL) ;; WKS 11 a well known service description ;; PTR 12 a domain name pointer ;; HINFO 13 host information ;; MINFO 14 mailbox or mail list information ;; MX 15 mail exchange ;; TXT 16 text strings ;; 3.2.3. QTYPE values ;; QTYPE fields appear in the question part of a query. QTYPES are a ;; superset of TYPEs, hence all TYPEs are valid QTYPEs. In addition, the ;; following QTYPEs are defined: ;; AXFR 252 A request for a transfer of an entire zone ;; MAILB 253 A request for mailbox-related records (MB, MG or MR) ;; MAILA 254 A request for mail agent RRs (Obsolete - see MX) ;; * 255 A request for all records ;; 3.2.4. CLASS values ;; CLASS fields appear in resource records. The following CLASS mnemonics ;; and values are defined: ;; IN 1 the Internet ;; CS 2 the CSNET class (Obsolete - used only for examples in ;; some obsolete RFCs) ;; CH 3 the CHAOS class ;; HS 4 Hesiod [Dyer 87] ;; 3.2.5. QCLASS values ;; QCLASS fields appear in the question section of a query. QCLASS values ;; are a superset of CLASS values; every CLASS is a valid QCLASS. In ;; addition to CLASS values, the following QCLASSes are defined: ;; * 255 any class ;; 3.3. Standard RRs ;; The following RR definitions are expected to occur, at least ;; potentially, in all classes. In particular, NS, SOA, CNAME, and PTR ;; will be used in all classes, and have the same format in all classes. ;; Because their RDATA format is known, all domain names in the RDATA ;; section of these RRs may be compressed. ;; is a domain name represented as a series of labels, and ;; terminated by a label with zero length. is a single ;; length octet followed by that number of characters. ;; is treated as binary information, and can be up to 256 characters in ;; length (including the length octet). ;; 3.3.1. CNAME RDATA format ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; / CNAME / ;; / / ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; where: ;; CNAME A which specifies the canonical or primary ;; name for the owner. The owner name is an alias. ;; CNAME RRs cause no additional section processing, but name servers may ;; choose to restart the query at the canonical name in certain cases. See ;; the description of name server logic in [RFC-1034] for details. ;; 3.3.11. NS RDATA format ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; / NSDNAME / ;; / / ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; where: ;; NSDNAME A which specifies a host which should be ;; authoritative for the specified class and domain. ;; NS records cause both the usual additional section processing to locate ;; a type A record, and, when used in a referral, a special search of the ;; zone in which they reside for glue information. ;; The NS RR states that the named host should be expected to have a zone ;; starting at owner name of the specified class. Note that the class may ;; not indicate the protocol family which should be used to communicate ;; with the host, although it is typically a strong hint. For example, ;; hosts which are name servers for either Internet (IN) or Hesiod (HS) ;; class information are normally queried using IN class protocols. ;; 3.3.12. PTR RDATA format ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; / PTRDNAME / ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; where: ;; PTRDNAME A which points to some location in the ;; domain name space. ;; PTR records cause no additional section processing. These RRs are used ;; in special domains to point to some other location in the domain space. ;; These records are simple data, and don't imply any special processing ;; similar to that performed by CNAME, which identifies aliases. See the ;; description of the IN-ADDR.ARPA domain for an example. ;; 3.3.13. SOA RDATA format ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; / MNAME / ;; / / ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; / RNAME / ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; | SERIAL | ;; | | ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; | REFRESH | ;; | | ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; | RETRY | ;; | | ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; | EXPIRE | ;; | | ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; | MINIMUM | ;; | | ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; where: ;; MNAME The of the name server that was the ;; original or primary source of data for this zone. ;; RNAME A which specifies the mailbox of the ;; person responsible for this zone. ;; SERIAL The unsigned 32 bit version number of the original copy ;; of the zone. Zone transfers preserve this value. This ;; value wraps and should be compared using sequence space ;; arithmetic. ;; REFRESH A 32 bit time interval before the zone should be ;; refreshed. ;; RETRY A 32 bit time interval that should elapse before a ;; failed refresh should be retried. ;; EXPIRE A 32 bit time value that specifies the upper limit on ;; the time interval that can elapse before the zone is no ;; longer authoritative. ;; MINIMUM The unsigned 32 bit minimum TTL field that should be ;; exported with any RR from this zone. ;; SOA records cause no additional section processing. ;; All times are in units of seconds. ;; Most of these fields are pertinent only for name server maintenance ;; operations. However, MINIMUM is used in all query operations that ;; retrieve RRs from a zone. Whenever a RR is sent in a response to a ;; query, the TTL field is set to the maximum of the TTL field from the RR ;; and the MINIMUM field in the appropriate SOA. Thus MINIMUM is a lower ;; bound on the TTL field for all RRs in a zone. Note that this use of ;; MINIMUM should occur when the RRs are copied into the response and not ;; when the zone is loaded from a master file or via a zone transfer. The ;; reason for this provison is to allow future dynamic update facilities to ;; change the SOA RR with known semantics. ;; 3.3.14. TXT RDATA format ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; / TXT-DATA / ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; where: ;; TXT-DATA One or more s. ;; TXT RRs are used to hold descriptive text. The semantics of the text ;; depends on the domain where it is found. ;; 3.4. Internet specific RRs ;; 3.4.1. A RDATA format ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; | ADDRESS | ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; where: ;; ADDRESS A 32 bit Internet address. ;; Hosts that have multiple Internet addresses will have multiple A ;; records. ;; A records cause no additional section processing. The RDATA section of ;; an A line in a master file is an Internet address expressed as four ;; decimal numbers separated by dots without any imbedded spaces (e.g., ;; "10.2.0.52" or "192.0.5.6"). ;; 3.4.2. WKS RDATA format ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; | ADDRESS | ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; | PROTOCOL | | ;; +--+--+--+--+--+--+--+--+ | ;; | | ;; / / ;; / / ;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ ;; where: ;; ADDRESS An 32 bit Internet address ;; PROTOCOL An 8 bit IP protocol number ;; A variable length bit map. The bit map must be a ;; multiple of 8 bits long. ;; The WKS record is used to describe the well known services supported by ;; a particular protocol on a particular internet address. The PROTOCOL ;; field specifies an IP protocol number, and the bit map has one bit per ;; port of the specified protocol. The first bit corresponds to port 0, ;; the second to port 1, etc. If the bit map does not include a bit for a ;; protocol of interest, that bit is assumed zero. The appropriate values ;; and mnemonics for ports and protocols are specified in [RFC-1010]. ;; For example, if PROTOCOL=TCP (6), the 26th bit corresponds to TCP port ;; 25 (SMTP). If this bit is set, a SMTP server should be listening on TCP ;; port 25; if zero, SMTP service is not supported on the specified ;; address. ;; The purpose of WKS RRs is to provide availability information for ;; servers for TCP and UDP. If a server supports both TCP and UDP, or has ;; multiple Internet addresses, then multiple WKS RRs are used. ;; WKS RRs cause no additional section processing. ;; In master files, both ports and protocols are expressed using mnemonics ;; or decimal numbers. ;; 3.5. IN-ADDR.ARPA domain ;; The Internet uses a special domain to support gateway location and ;; Internet address to host mapping. Other classes may employ a similar ;; strategy in other domains. The intent of this domain is to provide a ;; guaranteed method to perform host address to host name mapping, and to ;; facilitate queries to locate all gateways on a particular network in the ;; Internet. ;; Note that both of these services are similar to functions that could be ;; performed by inverse queries; the difference is that this part of the ;; domain name space is structured according to address, and hence can ;; guarantee that the appropriate data can be located without an exhaustive ;; search of the domain space. ;; The domain begins at IN-ADDR.ARPA and has a substructure which follows ;; the Internet addressing structure. ;; Domain names in the IN-ADDR.ARPA domain are defined to have up to four ;; labels in addition to the IN-ADDR.ARPA suffix. Each label represents ;; one octet of an Internet address, and is expressed as a character string ;; for a decimal value in the range 0-255 (with leading zeros omitted ;; except in the case of a zero octet which is represented by a single ;; zero). ;; Host addresses are represented by domain names that have all four labels ;; specified. Thus data for Internet address 10.2.0.52 is located at ;; domain name 52.0.2.10.IN-ADDR.ARPA. The reversal, though awkward to ;; read, allows zones to be delegated which are exactly one network of ;; address space. For example, 10.IN-ADDR.ARPA can be a zone containing ;; data for the ARPANET, while 26.IN-ADDR.ARPA can be a separate zone for ;; MILNET. Address nodes are used to hold pointers to primary host names ;; in the normal domain space. ;; Network numbers correspond to some non-terminal nodes at various depths ;; in the IN-ADDR.ARPA domain, since Internet network numbers are either 1, ;; 2, or 3 octets. Network nodes are used to hold pointers to the primary ;; host names of gateways attached to that network. Since a gateway is, by ;; definition, on more than one network, it will typically have two or more ;; network nodes which point at it. Gateways will also have host level ;; pointers at their fully qualified addresses. ;; Both the gateway pointers at network nodes and the normal host pointers ;; at full address nodes use the PTR RR to point back to the primary domain ;; names of the corresponding hosts. ;; For example, the IN-ADDR.ARPA domain will contain information about the ;; ISI gateway between net 10 and 26, an MIT gateway from net 10 to MIT's ;; net 18, and hosts A.ISI.EDU and MULTICS.MIT.EDU. Assuming that ISI ;; gateway has addresses 10.2.0.22 and 26.0.0.103, and a name MILNET- ;; GW.ISI.EDU, and the MIT gateway has addresses 10.0.0.77 and 18.10.0.4 ;; and a name GW.LCS.MIT.EDU, the domain database would contain: ;; 10.IN-ADDR.ARPA. PTR MILNET-GW.ISI.EDU. ;; 10.IN-ADDR.ARPA. PTR GW.LCS.MIT.EDU. ;; 18.IN-ADDR.ARPA. PTR GW.LCS.MIT.EDU. ;; 26.IN-ADDR.ARPA. PTR MILNET-GW.ISI.EDU. ;; 22.0.2.10.IN-ADDR.ARPA. PTR MILNET-GW.ISI.EDU. ;; 103.0.0.26.IN-ADDR.ARPA. PTR MILNET-GW.ISI.EDU. ;; 77.0.0.10.IN-ADDR.ARPA. PTR GW.LCS.MIT.EDU. ;; 4.0.10.18.IN-ADDR.ARPA. PTR GW.LCS.MIT.EDU. ;; 103.0.3.26.IN-ADDR.ARPA. PTR A.ISI.EDU. ;; 6.0.0.10.IN-ADDR.ARPA. PTR MULTICS.MIT.EDU. ;; Thus a program which wanted to locate gateways on net 10 would originate ;; a query of the form QTYPE=PTR, QCLASS=IN, QNAME=10.IN-ADDR.ARPA. It ;; would receive two RRs in response: ;; 10.IN-ADDR.ARPA. PTR MILNET-GW.ISI.EDU. ;; 10.IN-ADDR.ARPA. PTR GW.LCS.MIT.EDU. ;; The program could then originate QTYPE=A, QCLASS=IN queries for MILNET- ;; GW.ISI.EDU. and GW.LCS.MIT.EDU. to discover the Internet addresses of ;; these gateways. ;; A resolver which wanted to find the host name corresponding to Internet ;; host address 10.0.0.6 would pursue a query of the form QTYPE=PTR, ;; QCLASS=IN, QNAME=6.0.0.10.IN-ADDR.ARPA, and would receive: ;; 6.0.0.10.IN-ADDR.ARPA. PTR MULTICS.MIT.EDU. ;; Several cautions apply to the use of these services: ;; - Since the IN-ADDR.ARPA special domain and the normal domain ;; for a particular host or gateway will be in different zones, ;; the possibility exists that that the data may be inconsistent. ;; - Gateways will often have two names in separate domains, only ;; one of which can be primary. ;; - Systems that use the domain database to initialize their ;; routing tables must start with enough gateway information to ;; guarantee that they can access the appropriate name server. ;; - The gateway data only reflects the existence of a gateway in a ;; manner equivalent to the current HOSTS.TXT file. It doesn't ;; replace the dynamic availability information from GGP or EGP. ;; 3.6. Defining new types, classes, and special namespaces ;; The previously defined types and classes are the ones in use as of the ;; date of this memo. New definitions should be expected. This section ;; makes some recommendations to designers considering additions to the ;; existing facilities. The mailing list NAMEDROPPERS@SRI-NIC.ARPA is the ;; forum where general discussion of design issues takes place. ;; In general, a new type is appropriate when new information is to be ;; added to the database about an existing object, or we need new data ;; formats for some totally new object. Designers should attempt to define ;; types and their RDATA formats that are generally applicable to all ;; classes, and which avoid duplication of information. New classes are ;; appropriate when the DNS is to be used for a new protocol, etc which ;; requires new class-specific data formats, or when a copy of the existing ;; name space is desired, but a separate management domain is necessary. ;; New types and classes need mnemonics for master files; the format of the ;; master files requires that the mnemonics for type and class be disjoint. ;; TYPE and CLASS values must be a proper subset of QTYPEs and QCLASSes ;; respectively. ;; The present system uses multiple RRs to represent multiple values of a ;; type rather than storing multiple values in the RDATA section of a ;; single RR. This is less efficient for most applications, but does keep ;; RRs shorter. The multiple RRs assumption is incorporated in some ;; experimental work on dynamic update methods. ;; The present system attempts to minimize the duplication of data in the ;; database in order to insure consistency. Thus, in order to find the ;; address of the host for a mail exchange, you map the mail domain name to ;; a host name, then the host name to addresses, rather than a direct ;; mapping to host address. This approach is preferred because it avoids ;; the opportunity for inconsistency. ;; In defining a new type of data, multiple RR types should not be used to ;; create an ordering between entries or express different formats for ;; equivalent bindings, instead this information should be carried in the ;; body of the RR and a single type used. This policy avoids problems with ;; caching multiple types and defining QTYPEs to match multiple types. ;; For example, the original form of mail exchange binding used two RR ;; types one to represent a "closer" exchange (MD) and one to represent a ;; "less close" exchange (MF). The difficulty is that the presence of one ;; RR type in a cache doesn't convey any information about the other ;; because the query which acquired the cached information might have used ;; a QTYPE of MF, MD, or MAILA (which matched both). The redesigned ;; service used a single type (MX) with a "preference" value in the RDATA ;; section which can order different RRs. However, if any MX RRs are found ;; in the cache, then all should be there. ;; 4. MESSAGES ;; 4.1. Format ;; All communications inside of the domain protocol are carried in a single ;; format called a message. The top level format of message is divided ;; into 5 sections (some of which are empty in certain cases) shown below: ;; The names of the sections after the header are derived from their use in ;; standard queries. The question section contains fields that describe a ;; question to a name server. These fields are a query type (QTYPE), a ;; query class (QCLASS), and a query domain name (QNAME). The last three ;; sections have the same format: a possibly empty list of concatenated ;; resource records (RRs). The answer section contains RRs that answer the ;; question; the authority section contains RRs that point toward an ;; authoritative name server; the additional records section contains RRs ;; which relate to the query, but are not strictly answers for the ;; question. ;; The header section is always present. The header includes fields that ;; specify which of the remaining sections are present, and also specify ;; whether the message is a query or a response, a standard query or some ;; other opcode, etc. ;; 4.1.1. Header section format (defbinary dns-header (:byte-order :big-endian) ;; A 16 bit identifier assigned by the program that ;; generates any kind of query. This identifier is copied ;; the corresponding reply and can be used by the requester ;; to match up replies to outstanding queries. (id 0 :type 16) ;; A one bit field that specifies whether this message is a ;; query (0), or a response (1). (qr 0 :type 1) ;; A four bit field that specifies kind of query in this ;; message. This value is set by the originator of a query ;; and copied into the response. The values are: ;; ;; 0 a standard query (QUERY) ;; 1 an inverse query (IQUERY) ;; 2 a server status request (STATUS) ;; 3-15 reserved for future use (opcode 0 :type 4) ; TODO(tazjin): use define-enum ;; Authoritative Answer - this bit is valid in responses, ;; and specifies that the responding name server is an ;; authority for the domain name in question section. (aa nil :type 1) ;; TrunCation - specifies that this message was truncated ;; due to length greater than that permitted on the ;; transmission channel. (tc nil :type 1) ;; Recursion Desired - this bit may be set in a query and ;; is copied into the response. If RD is set, it directs ;; the name server to pursue the query recursively. ;; Recursive query support is optional. (rd nil :type 1) ;; Recursion Available - this be is set or cleared in a ;; response, and denotes whether recursive query support is ;; available in the name server. (ra nil :type 1) ;; Reserved for future use. Must be zero in all queries and ;; responses. (z 0 :type 3) ;; Response code - this 4 bit field is set as part of ;; responses. The values have the following ;; interpretation: ;; 0 No error condition ;; 1 Format error - The name server was ;; unable to interpret the query. ;; 2 Server failure - The name server was ;; unable to process this query due to a ;; problem with the name server. ;; 3 Name Error - Meaningful only for ;; responses from an authoritative name ;; server, this code signifies that the ;; domain name referenced in the query does ;; not exist. ;; 4 Not Implemented - The name server does ;; not support the requested kind of query. ;; 5 Refused - The name server refuses to ;; perform the specified operation for ;; policy reasons. For example, a name ;; server may not wish to provide the ;; information to the particular requester, ;; or a name server may not wish to perform ;; a particular operation (e.g., zone ;; transfer) for particular data. ;; 6-15 Reserved for future use. (rcode 0 :type 4) ;; an unsigned 16 bit integer specifying the number of ;; entries in the question section. (qdcount 0 :type 16) ;; an unsigned 16 bit integer specifying the number of ;; resource records in the answer section. (ancount 0 :type 16) ;; an unsigned 16 bit integer specifying the number of name ;; server resource records in the authority records ;; section. (nscount 0 :type 16) ;; an unsigned 16 bit integer specifying the number of ;; resource records in the additional records section. (arcount 0 :type 16)) ;; Representation of DNS QNAMEs. ;; ;; A QNAME can be either made up entirely of labels, which is ;; basically a list of strings, or be terminated with a pointer to an ;; offset within the original message. (deftype qname-field () '(or ;; pointer (unsigned-byte 14) ;; label string)) (defstruct qname (start-at 0 :type (unsigned-byte 14)) (names #() :type (vector qname-field))) ;; Domain names in questions and resource records are represented as a ;; sequence of labels, where each label consists of a length octet ;; followed by that number of octets. ;; ;; The domain name terminates with the zero length octet for the null ;; label of the root. Note that this field may be an odd number of ;; octets; no padding is used. (declaim (ftype (function (stream) (values qname integer)) read-qname)) (defun read-qname (stream) "Reads a DNS QNAME from STREAM." (let ((start-at (file-position stream))) (iter (for byte next (read-byte stream)) ;; Each fragment is collected into this byte vector pre-allocated ;; with the correct size. (for fragment = (make-array byte :element-type '(unsigned-byte 8) :fill-pointer 0)) ;; If the bit sequence (1 1) is encountered at the beginning of ;; the fragment, a qname pointer is being read. (let ((byte-copy byte)) (when (equal #b11 (lisp-binary/integer:pop-bits 2 8 byte-copy)) (let ((next (read-byte stream))) (lisp-binary/integer:push-bits byte-copy 8 next) (collect next into fragments result-type vector) (sum 2 into size) (finish)))) ;; Total size is needed, count for each iteration byte, plus its ;; own value. (sum (+ 1 byte) into size) (until (equal byte 0)) ;; On each iteration, this will interpret the current byte as an ;; unsigned integer and read from STREAM an equivalent amount of ;; times to assemble the current fragment. ;; ;; Advancing the stream like this also ensures that the next ;; iteration occurs on a new fragment or the final terminating ;; byte. ;; ;; TODO(tazjin): Use lisp-binary:read-counted-string. (dotimes (_ byte (collect (babel:octets-to-string fragment) into fragments result-type vector)) (vector-push (read-byte stream) fragment)) (finally (return (values (make-qname :start-at start-at :names fragments) size)))))) (declaim (ftype (function (stream qname)) write-qname)) (defun write-qname (stream qname) "Write a DNS qname to STREAM." ;; Write each fragment starting with its (byte-) length, followed by ;; the bytes. (iter (for fragment in-vector (qname-names qname)) (for bytes = (babel:string-to-octets fragment)) (write-byte (length bytes) stream) (iter (for byte in-vector bytes) (write-byte byte stream))) ;; Always finish off the serialisation with a null-byte! (write-byte 0 stream)) ;; 4.1.2. Question section format (defbinary dns-question (:byte-order :big-endian :export t) ;; a domain name represented (qname "" :type (custom :lisp-type qname :reader #'read-qname :writer #'write-qname)) ;; a two octet code which specifies the type of the query. ;; The values for this field include all codes valid for a ;; TYPE field, together with some more general codes which ;; can match more than one type of RR. (qtype 0 :type 16) ;; TODO(tazjin): define type after the RR binary ;; a two octet code that specifies the class of the query. For ;; example, the QCLASS field is IN for the Internet. (qclass 0 :type 16)) ; TODO(tazjin): enum? ;; 4.1.3. Resource record format (define-enum dns-type 2 (:byte-order :big-endian) ;; http://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml (A 1) (NS 2) (CNAME 5) (SOA 6) (PTR 12) (MX 15) (TXT 16) (SRV 33) (AAAA 28) (ANY 255)) ;; (typically wants SOA, MX, NS and MX) (defbinary dns-rr (:byte-order :big-endian :export t) (name nil :type (custom :lisp-type qname :reader #'read-qname :writer #'write-qname)) ;; two octets containing one of the RR type codes. This ;; field specifies the meaning of the data in the RDATA ;; field. (type 0 :type dns-type) ;; two octets which specify the class of the data in the ;; RDATA field. (class 0 :type 16) ; TODO(tazjin): enum ;; a 32 bit unsigned integer that specifies the time ;; interval (in seconds) that the resource record may be ;; cached before it should be discarded. Zero values are ;; interpreted to mean that the RR can only be used for the ;; transaction in progress, and should not be cached. (ttl 0 :type 32) ;; an unsigned 16 bit integer that specifies the length in ;; octets of the RDATA field. (rdlength 0 :type 16) ;; a variable length string of octets that describes the ;; resource. The format of this information varies ;; according to the TYPE and CLASS of the resource record. ;; For example, the if the TYPE is A and the CLASS is IN, ;; the RDATA field is a 4 octet ARPA Internet address. (rdata #() :type (eval (case type ;; TODO(tazjin): Deal with multiple strings in single RRDATA ((TXT) '(counted-string 1)) ((A) '(simple-array (unsigned-byte 8) (4))) (otherwise `(simple-array (unsigned-byte 8) (,rdlength))))))) (defbinary dns-message (:byte-order :big-endian :export t) (header nil :type dns-header) ;; the question for the name server (question #() :type (simple-array dns-question ((dns-header-qdcount header)))) ;; ;; RRs answering the question ;; (answer #() :type (simple-array (unsigned-byte 8) (16))) (answer #() :type (simple-array dns-rr ((dns-header-ancount header)))) ;; ;; ;; RRs pointing toward an authority (authority #() :type (simple-array dns-rr ((dns-header-nscount header)))) ;; ;; RRs holding additional information (additional #() :type (simple-array dns-rr ((dns-header-arcount header)))))