`open-network-stream' in `nntp-open-network-stream': strange behaviour

`open-network-stream' in `nntp-open-network-stream': strange behaviour

[Christoph Conrad]

Hi!

Linux 2.2.14, i386, Emacs 20.7.1, latest CVS Oort Gnus.

I have the following problem since a few weeks now, a workaround i found
now is at the end of the mail.

When `open-network-stream' failed ONE time for a given host (cause i am
not online, host overloaded etc.), it fails forever in the same emacs
session. If i restart my Emacs, it works again.

This behaviour is ONLY as described when the hostname is a symbolic name
like "News.CIS.DFN.DE". When i always resolve the name to an ip address
before i give it as argument to `open-network-stream', it works again
after having failed.

I know that this isn't a genuine Gnus problem, it might be a problem of
`open-network-stream' or even my network configuration. Maybe you could
give me a hint. With the workaround below it works as expected.

(defun cc-resolve-address( domain )
  (save-excursion
    (let ((output-buf (generate-new-buffer " *resolve-address*")))
      (unwind-protect
          (progn
            (set-buffer output-buf)
            (and (eq (call-process
                      "/usr/bin/nslookup" nil output-buf nil
                      "-retries=1" domain)
                     0)
                 (> (point-max) 2)
                 (goto-char (point-max))
                 (when (re-search-backward (concat "^Name: [ ]*"
                                                   domain
                                                   "\n"
                                                   "Address: [ ]*\\(.*\\)$")
                                           nil t)
                   (match-string 1))))
        ;; unwind-protect cleanup
        (kill-buffer output-buf)))))

(defun nntp-open-network-stream( buffer )
  (let ( (host nntp-address) )
    (when (not (string-match "[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+"
                             host))
      (setq host (cc-resolve-address host)))
    (if host
        (open-network-stream "nntpd" buffer host nntp-port-number)
      ;; kill buffer due to a possible bug in nntp-open-connection
      (kill-buffer buffer)
      (error "nntp-open-network-stream: couldn't resolve %s" nntp-address))))


Best regards,
cu, -cc-
-- 
=> GNU Emacs Webring @ <http://nav.webring.yahoo.com/hub?ring=emacs> <=
Look Ma, this man can twist his fingers as if they were made of rubber,
isn't that amazing? -- Not really, he's been using emacs for years...!

Re: `open-network-stream' in `nntp-open-network-stream': strange behaviour

[Jake Colman]

How  are you using this fix?  Are you replacing gnus source?  I see exactly
the same bug when accessing my imap server.

>>>>> "CC" == Christoph Conrad <christoph.conrad@gmx.de> writes:

    CC> Hi!  Linux 2.2.14, i386, Emacs 20.7.1, latest CVS Oort Gnus.

    CC> I have the following problem since a few weeks now, a workaround i
    CC> found now is at the end of the mail.

    CC> When `open-network-stream' failed ONE time for a given host (cause i
    CC> am not online, host overloaded etc.), it fails forever in the same
    CC> emacs session. If i restart my Emacs, it works again.

    CC> This behaviour is ONLY as described when the hostname is a symbolic
    CC> name like "News.CIS.DFN.DE". When i always resolve the name to an ip
    CC> address before i give it as argument to `open-network-stream', it
    CC> works again after having failed.

    CC> I know that this isn't a genuine Gnus problem, it might be a problem
    CC> of `open-network-stream' or even my network configuration. Maybe you
    CC> could give me a hint. With the workaround below it works as expected.

    CC> (defun cc-resolve-address( domain )
    CC>   (save-excursion
    CC>     (let ((output-buf (generate-new-buffer " *resolve-address*")))
    CC>       (unwind-protect
    CC>           (progn
    CC>             (set-buffer output-buf) (and (eq (call-process
    CC>                       "/usr/bin/nslookup" nil output-buf nil
    CC>                       "-retries=1" domain)
    CC>                      0)
    CC>                  (> (point-max) 2) (goto-char (point-max)) (when
    CC>                  (re-search-backward (concat "^Name: [ ]*"
    CC>                                                    domain "\n"
    CC>                                                    "Address: [
    CC>                                                    ]*\\(.*\\)$")
    CC>                                            nil t)
    CC>                    (match-string 1))))
    CC>         ;; unwind-protect cleanup
    CC>         (kill-buffer output-buf)))))

    CC> (defun nntp-open-network-stream( buffer )
    CC>   (let ( (host nntp-address) )
    CC>     (when (not (string-match "[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+"
    CC>                              host))
    CC>       (setq host (cc-resolve-address host)))
    CC>     (if host
    CC>         (open-network-stream "nntpd" buffer host nntp-port-number)
    CC>       ;; kill buffer due to a possible bug in nntp-open-connection
    CC>       (kill-buffer buffer) (error "nntp-open-network-stream: couldn't
    CC>       resolve %s" nntp-address))))


    CC> Best regards, cu, -cc- -- => GNU Emacs Webring @
    CC> <http://nav.webring.yahoo.com/hub?ring=emacs> <= Look Ma, this man
    CC> can twist his fingers as if they were made of rubber, isn't that
    CC> amazing? -- Not really, he's been using emacs for years...!

-- 
Jake Colman                     

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                                       E-mail: jcolman@jnc.com
                                          web: http://www.ppllc.com

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Re: `open-network-stream' in `nntp-open-network-stream': strange behaviour

[Christoph Conrad]

Hi Jake,

you wrote:

    > How are you using this fix? Are you replacing gnus source? I see
    > exactly the same bug when accessing my imap server.

I included the two pieces of code into .emacs.gnus.el.
`nntp-open-network-stream' replaces the (simple) original definition
from "nntp.el":

;; original
(defun nntp-open-network-stream (buffer)
  (open-network-stream "nntpd" buffer nntp-address nntp-port-number))

I see in your headers: 
User-Agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.1 (Channel Islands)

If you don't mind about a lot of possibly open " *nntpd" buffers (was
fixed a few days ago in the CVS gnus; you don't see the buffers), you
can also use `cc-resolve-address' with

(defadvice open-network-stream
  ( before nntp-open-network-stream-resolve act )
    (when (not (string-match "[0-9.]+" (ad-get-arg 2)))
      (ad-set-arg 2 (cc-resolve-address nntp-address))))

instead of replacing `nntp-open-network-stream'. This a little bit
cleaner. Please let me know if it solves your problem.

Best regards,
cu, -cc-
-- 
=> GNU Emacs Webring @ <http://www.gnusoftware.com/WebRing/> <=
Look Ma, this man can twist his fingers as if they were made of rubber,
isn't that amazing? -- Not really, he's been using emacs for years...!