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Diffstat (limited to 'lisp/dns/message.lisp')
| -rw-r--r-- | lisp/dns/message.lisp | 299 |
1 files changed, 29 insertions, 270 deletions
diff --git a/lisp/dns/message.lisp b/lisp/dns/message.lisp index 079e971c7e..0eedbe6601 100644 --- a/lisp/dns/message.lisp +++ b/lisp/dns/message.lisp @@ -1,152 +1,5 @@ (in-package :dns) -;; 3. DOMAIN NAME SPACE AND RR DEFINITIONS 10 -;; 3.1. Name space definitions 10 -;; 3.2. RR definitions 11 -;; 3.2.1. Format 11 -;; 3.2.2. TYPE values 12 -;; 3.2.3. QTYPE values 12 -;; 3.2.4. CLASS values 13 -;; 3.2.5. QCLASS values 13 -;; 3.3. Standard RRs 13 -;; 3.3.1. CNAME RDATA format 14 -;; 3.3.2. HINFO RDATA format 14 -;; 3.3.3. MB RDATA format (EXPERIMENTAL) 14 -;; 3.3.4. MD RDATA format (Obsolete) 15 -;; 3.3.5. MF RDATA format (Obsolete) 15 -;; 3.3.6. MG RDATA format (EXPERIMENTAL) 16 -;; 3.3.7. MINFO RDATA format (EXPERIMENTAL) 16 -;; 3.3.8. MR RDATA format (EXPERIMENTAL) 17 -;; 3.3.9. MX RDATA format 17 -;; 3.3.10. NULL RDATA format (EXPERIMENTAL) 17 -;; 3.3.11. NS RDATA format 18 -;; 3.3.12. PTR RDATA format 18 -;; 3.3.13. SOA RDATA format 19 -;; 3.3.14. TXT RDATA format 20 -;; 3.4. ARPA Internet specific RRs 20 -;; 3.4.1. A RDATA format 20 -;; 3.4.2. WKS RDATA format 21 -;; 3.5. IN-ADDR.ARPA domain 22 -;; 3.6. Defining new types, classes, and special namespaces 24 -;; 4. MESSAGES 25 -;; 4.1. Format 25 -;; 4.1.1. Header section format 26 -;; 4.1.2. Question section format 28 -;; 4.1.3. Resource record format 29 -;; 4.1.4. Message compression 30 -;; 4.2. Transport 32 -;; 4.2.1. UDP usage 32 -;; 4.2.2. TCP usage 32 -;; 5. MASTER FILES 33 -;; 5.1. Format 33 -;; 5.2. Use of master files to define zones 35 -;; 5.3. Master file example 36 -;; 6. NAME SERVER IMPLEMENTATION 37 -;; 6.1. Architecture 37 -;; 6.1.1. Control 37 -;; 6.1.2. Database 37 -;; 6.1.3. Time 39 -;; 6.2. Standard query processing 39 -;; 6.3. Zone refresh and reload processing 39 -;; 6.4. Inverse queries (Optional) 40 -;; 6.4.1. The contents of inverse queries and responses 40 -;; 6.4.2. Inverse query and response example 41 -;; 6.4.3. Inverse query processing 42 -;; 6.5. Completion queries and responses 42 -;; 7. RESOLVER IMPLEMENTATION 43 -;; 7.1. Transforming a user request into a query 43 -;; 7.2. Sending the queries 44 -;; 7.3. Processing responses 46 -;; 7.4. Using the cache 47 -;; 8. MAIL SUPPORT 47 -;; 8.1. Mail exchange binding 48 -;; 8.2. Mailbox binding (Experimental) 48 -;; 9. REFERENCES and BIBLIOGRAPHY 50 -;; Index 54 - -;; 2.3.4. Size limits -;; Various objects and parameters in the DNS have size limits. They are -;; listed below. Some could be easily changed, others are more -;; fundamental. -;; labels 63 octets or less -;; names 255 octets or less -;; TTL positive values of a signed 32 bit number. -;; UDP messages 512 octets or less - -;; 3. DOMAIN NAME SPACE AND RR DEFINITIONS - -;; Domain names in messages are expressed in terms of a sequence of labels. -;; Each label is represented as a one octet length field followed by that -;; number of octets. Since every domain name ends with the null label of -;; the root, a domain name is terminated by a length byte of zero. The -;; high order two bits of every length octet must be zero, and the -;; remaining six bits of the length field limit the label to 63 octets or -;; less. - -;; To simplify implementations, the total length of a domain name (i.e., -;; label octets and label length octets) is restricted to 255 octets or -;; less. - -;; Although labels can contain any 8 bit values in octets that make up a -;; label, it is strongly recommended that labels follow the preferred -;; syntax described elsewhere in this memo, which is compatible with -;; existing host naming conventions. Name servers and resolvers must -;; compare labels in a case-insensitive manner (i.e., A=a), assuming ASCII -;; with zero parity. Non-alphabetic codes must match exactly. - -;; 3.2. RR definitions - -;; 3.2.1. Format - -;; All RRs have the same top level format shown below: - -;; 1 1 1 1 1 1 -;; 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; | | -;; / / -;; / NAME / -;; | | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; | TYPE | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; | CLASS | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; | TTL | -;; | | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; | RDLENGTH | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--| -;; / RDATA / -;; / / -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - - -;; where: - -;; NAME an owner name, i.e., the name of the node to which this -;; resource record pertains. - -;; TYPE two octets containing one of the RR TYPE codes. - -;; CLASS two octets containing one of the RR CLASS codes. - -;; TTL a 32 bit signed integer that specifies the time interval -;; that the resource record may be cached before the source -;; of the information should again be consulted. Zero -;; values are interpreted to mean that the RR can only be -;; used for the transaction in progress, and should not be -;; cached. For example, SOA records are always distributed -;; with a zero TTL to prohibit caching. Zero values can -;; also be used for extremely volatile data. - -;; RDLENGTH an unsigned 16 bit integer that specifies the length in -;; octets of the RDATA field. - -;; RDATA 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. - ;; 3.2.2. TYPE values ;; TYPE fields are used in resource records. Note that these types are a @@ -734,26 +587,38 @@ (declaim (ftype (function (stream) (values qname integer)) read-qname)) (defun read-qname (stream) "Reads a DNS QNAME from STREAM." - (let ((start-at (+ 1 (file-position stream)))) - (iter (for byte in-stream stream using #'read-byte) - ;; Total size is needed, count for each iteration byte, plus its - ;; own value. - (sum (+ 1 byte) into size) - - (until (equal byte 0)) + (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 either a length-byte or the final - ;; terminating byte. + ;; 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)) @@ -797,18 +662,9 @@ ;; 4.1.3. Resource record format (defbinary dns-rr (:byte-order :big-endian) - ;; magic number indicating a pointer response - ;; - ;; TODO(tazjin): This could theoretically be a QNAME, but - ;; Google DNS doesn't do that. For compatibility it is - ;; still sensible to add support for it. - (magic 3 :type (magic :value 3 :actual-type (unsigned-byte 2))) - - ;; a domain name to which this resource record pertains. - (name nil :type (pointer :data-type (custom :lisp-type qname - :reader #'read-qname - :writer #'write-qname) - :pointer-type (unsigned-byte 14))) + (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 @@ -843,109 +699,12 @@ ;; the question for the name server (question #() :type (simple-array dns-question ((dns-header-qdcount header)))) - ;; RRs answering the question + ;; ;; 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) + ;; ;; ;; RRs pointing toward an authority + (authority #() :type (simple-array dns-rr ((dns-header-nscount header)))) ;; ;; RRs holding additional information - ;; (additional) - ) - -;; 4.1.4. Message compression - -;; In order to reduce the size of messages, the domain system utilizes a -;; compression scheme which eliminates the repetition of domain names in a -;; message. In this scheme, an entire domain name or a list of labels at -;; the end of a domain name is replaced with a pointer to a prior occurance -;; of the same name. - -;; The pointer takes the form of a two octet sequence: - -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; | 1 1| OFFSET | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - -;; The first two bits are ones. This allows a pointer to be distinguished -;; from a label, since the label must begin with two zero bits because -;; labels are restricted to 63 octets or less. (The 10 and 01 combinations -;; are reserved for future use.) The OFFSET field specifies an offset from -;; the start of the message (i.e., the first octet of the ID field in the -;; domain header). A zero offset specifies the first byte of the ID field, -;; etc. - -;; The compression scheme allows a domain name in a message to be -;; represented as either: - -;; - a sequence of labels ending in a zero octet - -;; - a pointer - -;; - a sequence of labels ending with a pointer - -;; Pointers can only be used for occurances of a domain name where the -;; format is not class specific. If this were not the case, a name server -;; or resolver would be required to know the format of all RRs it handled. -;; As yet, there are no such cases, but they may occur in future RDATA -;; formats. - -;; If a domain name is contained in a part of the message subject to a -;; length field (such as the RDATA section of an RR), and compression is -;; used, the length of the compressed name is used in the length -;; calculation, rather than the length of the expanded name. - -;; Programs are free to avoid using pointers in messages they generate, -;; although this will reduce datagram capacity, and may cause truncation. -;; However all programs are required to understand arriving messages that -;; contain pointers. - -;; For example, a datagram might need to use the domain names F.ISI.ARPA, -;; FOO.F.ISI.ARPA, ARPA, and the root. Ignoring the other fields of the -;; message, these domain names might be represented as: - -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 20 | 1 | F | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 22 | 3 | I | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 24 | S | I | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 26 | 4 | A | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 28 | R | P | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 30 | A | 0 | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 40 | 3 | F | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 42 | O | O | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 44 | 1 1| 20 | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 64 | 1 1| 26 | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ -;; 92 | 0 | | -;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - -;; The domain name for F.ISI.ARPA is shown at offset 20. The domain name -;; FOO.F.ISI.ARPA is shown at offset 40; this definition uses a pointer to -;; concatenate a label for FOO to the previously defined F.ISI.ARPA. The -;; domain name ARPA is defined at offset 64 using a pointer to the ARPA -;; component of the name F.ISI.ARPA at 20; note that this pointer relies on -;; ARPA being the last label in the string at 20. The root domain name is -;; defined by a single octet of zeros at 92; the root domain name has no -;; labels. - -;; 4.2. Transport -;; Messages sent over TCP connections use server port 53 (decimal). The -;; message is prefixed with a two byte length field which gives the message -;; length, excluding the two byte length field. This length field allows -;; the low-level processing to assemble a complete message before beginning -;; to parse it. + (additional #() :type (simple-array dns-rr ((dns-header-arcount header))))) |