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Use length field when dns-query is using TCP

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* net/dns.el (dns-write): Correct spelling in docstring.
(dns-read): Add optional tcp-p parameter, skip 2-byte length field
if non-nil.
(dns-query): Tell dns-read and dns-write if we're using TCP.
This commit is contained in:
Robert Pluim 2020-04-03 17:37:01 +02:00
parent 8d95e75eb6
commit 23b04ef0e7
1 changed files with 17 additions and 13 deletions
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30
lisp/net/dns.el
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@ -138,7 +138,7 @@ updated. Set this variable to t to disable the check.")
(defun dns-write (spec &optional tcp-p)
"Write a DNS packet according to SPEC.
If TCP-P, the first two bytes of the package with be the length field."
If TCP-P, the first two bytes of the packet will be the length field."
(with-temp-buffer
(set-buffer-multibyte nil)
(dns-write-bytes (dns-get 'id spec) 2)
@ -189,13 +189,15 @@ If TCP-P, the first two bytes of the package with be the length field."
(dns-write-bytes (buffer-size) 2))
(buffer-string)))
(defun dns-read (packet)
(defun dns-read (packet &optional tcp-p)
(with-temp-buffer
(set-buffer-multibyte nil)
(let ((spec nil)
queries answers authorities additionals)
(insert packet)
(goto-char (point-min))
;; When using TCP we have a 2 byte length field to ignore.
(goto-char (+ (point-min)
(if tcp-p 2 0)))
(push (list 'id (dns-read-bytes 2)) spec)
(let ((byte (dns-read-bytes 1)))
(push (list 'response-p (if (zerop (logand byte (ash 1 7))) nil t))
@ -407,23 +409,25 @@ If REVERSEP, look up an IP address."
nil)
(with-temp-buffer
(set-buffer-multibyte nil)
(let ((process (condition-case ()
(dns-make-network-process (car dns-servers))
(error
(message
"dns: Got an error while trying to talk to %s"
(car dns-servers))
nil)))
(let* ((process (condition-case ()
(dns-make-network-process (car dns-servers))
(error
(message
"dns: Got an error while trying to talk to %s"
(car dns-servers))
nil)))
(step 100)
(times (* dns-timeout 1000))
(id (random 65000)))
(id (random 65000))
(tcp-p (and process (not (process-contact process :type)))))
(when process
(process-send-string
process
(dns-write `((id ,id)
(opcode query)
(queries ((,name (type ,type))))
(recursion-desired-p t))))
(recursion-desired-p t))
tcp-p))
(while (and (zerop (buffer-size))
(> times 0))
(let ((step-sec (/ step 1000.0)))
@ -436,7 +440,7 @@ If REVERSEP, look up an IP address."
(when (and (>= (buffer-size) 2)
;; We had a time-out.
(> times 0))
(let ((result (dns-read (buffer-string))))
(let ((result (dns-read (buffer-string) tcp-p)))
(if fullp
result
(let ((answer (car (dns-get 'answers result))))