Function: tramp-maybe-open-connection
tramp-maybe-open-connection is a byte-compiled function defined in
tramp-sh.el.gz.
Signature
(tramp-maybe-open-connection VEC)
Documentation
Maybe open a connection VEC.
Does not do anything if a connection is already open, but re-opens the connection if a previous connection has died for some reason.
Source Code
;; Defined in /usr/src/emacs/lisp/net/tramp-sh.el.gz
(defun tramp-maybe-open-connection (vec)
"Maybe open a connection VEC.
Does not do anything if a connection is already open, but re-opens the
connection if a previous connection has died for some reason."
;; During completion, don't reopen a new connection.
(unless (tramp-connectable-p vec)
(throw 'non-essential 'non-essential))
(let ((p (tramp-get-connection-process vec))
(process-name (tramp-get-connection-property vec "process-name" nil))
(process-environment (copy-sequence process-environment))
(pos (with-current-buffer (tramp-get-connection-buffer vec) (point))))
;; If Tramp opens the same connection within a short time frame,
;; there is a problem. We shall signal this.
(unless (or (process-live-p p)
(and (processp p) (not non-essential))
(not (tramp-file-name-equal-p
vec (car tramp-current-connection)))
(time-less-p
(time-since (cdr tramp-current-connection))
(or tramp-connection-min-time-diff 0)))
(throw 'suppress 'suppress))
;; If too much time has passed since last command was sent, look
;; whether process is still alive. If it isn't, kill it. When
;; using ssh, it can sometimes happen that the remote end has hung
;; up but the local ssh client doesn't recognize this until it
;; tries to send some data to the remote end. So that's why we
;; try to send a command from time to time, then look again
;; whether the process is really alive.
(condition-case nil
(when (and (time-less-p
60 (time-since
(tramp-get-connection-property p "last-cmd-time" 0)))
(process-live-p p))
(tramp-send-command vec "echo are you awake" t t)
(unless (and (process-live-p p)
(tramp-wait-for-output p 10))
;; The error will be caught locally.
(tramp-error vec 'file-error "Awake did fail")))
(file-error
(tramp-cleanup-connection vec t)
(setq p nil)))
;; New connection must be opened.
(condition-case err
(unless (process-live-p p)
(with-tramp-progress-reporter
vec 3
(if (zerop (length (tramp-file-name-user vec)))
(format "Opening connection %s for %s using %s"
process-name
(tramp-file-name-host vec)
(tramp-file-name-method vec))
(format "Opening connection %s for %s@%s using %s"
process-name
(tramp-file-name-user vec)
(tramp-file-name-host vec)
(tramp-file-name-method vec)))
(catch 'uname-changed
;; Start new process.
(when (and p (processp p))
(delete-process p))
(setenv "TERM" tramp-terminal-type)
(setenv "LC_ALL" (tramp-get-local-locale vec))
(if (stringp tramp-histfile-override)
(setenv "HISTFILE" tramp-histfile-override)
(if tramp-histfile-override
(progn
(setenv "HISTFILE")
(setenv "HISTFILESIZE" "0")
(setenv "HISTSIZE" "0"))))
(setenv "PROMPT_COMMAND")
(setenv "PS1" tramp-initial-end-of-output)
(unless (stringp tramp-encoding-shell)
(tramp-error vec 'file-error "`tramp-encoding-shell' not set"))
(let* ((current-host tramp-system-name)
(target-alist (tramp-compute-multi-hops vec))
;; Needed for `tramp-get-remote-null-device'.
(previous-hop nil)
;; We will apply `tramp-ssh-controlmaster-options'
;; only for the first hop.
(options (tramp-ssh-controlmaster-options vec))
(process-connection-type tramp-process-connection-type)
(process-adaptive-read-buffering nil)
;; There are unfortunate settings for "cmdproxy" on
;; W32 systems.
(process-coding-system-alist nil)
(coding-system-for-read nil)
(extra-args (tramp-get-sh-extra-args tramp-encoding-shell))
;; This must be done in order to avoid our file
;; name handler.
(p (let ((default-directory
tramp-compat-temporary-file-directory))
(apply
#'start-process
(tramp-get-connection-name vec)
(tramp-get-connection-buffer vec)
(append
(list tramp-encoding-shell)
(and extra-args (split-string extra-args))
(and tramp-encoding-command-interactive
(list tramp-encoding-command-interactive)))))))
;; Set sentinel and query flag. Initialize variables.
(set-process-sentinel p #'tramp-process-sentinel)
(process-put p 'vector vec)
(process-put p 'adjust-window-size-function #'ignore)
(set-process-query-on-exit-flag p nil)
(setq tramp-current-connection (cons vec (current-time)))
(tramp-message vec 6 "%s" (string-join (process-command p) " "))
;; Set connection-local variables.
(tramp-set-connection-local-variables vec)
;; Check whether process is alive.
(tramp-barf-if-no-shell-prompt
p 10
"Couldn't find local shell prompt for %s" tramp-encoding-shell)
;; Now do all the connections as specified.
(while target-alist
(let* ((hop (car target-alist))
(l-method (tramp-file-name-method hop))
(l-user (tramp-file-name-user hop))
(l-domain (tramp-file-name-domain hop))
(l-host (tramp-file-name-host hop))
(l-port (tramp-file-name-port hop))
(remote-shell
(tramp-get-method-parameter hop 'tramp-remote-shell))
(extra-args (tramp-get-sh-extra-args remote-shell))
(async-args
(tramp-compat-flatten-tree
(tramp-get-method-parameter hop 'tramp-async-args)))
(connection-timeout
(tramp-get-method-parameter
hop 'tramp-connection-timeout))
(command
(tramp-get-method-parameter hop 'tramp-login-program))
;; We don't create the temporary file. In
;; fact, it is just a prefix for the
;; ControlPath option of ssh; the real
;; temporary file has another name, and it is
;; created and protected by ssh. It is also
;; removed by ssh when the connection is
;; closed. The temporary file name is cached
;; in the main connection process, therefore
;; we cannot use `tramp-get-connection-process'.
(tmpfile
(with-tramp-connection-property
(tramp-get-process vec) "temp-file"
(tramp-compat-make-temp-name)))
r-shell)
;; Check, whether there is a restricted shell.
(dolist (elt tramp-restricted-shell-hosts-alist)
(when (string-match-p elt current-host)
(setq r-shell t)))
(setq current-host l-host)
;; Set password prompt vector.
(tramp-set-connection-property
p "password-vector"
(make-tramp-file-name
:method l-method :user l-user :domain l-domain
:host l-host :port l-port))
;; Set session timeout.
(when (tramp-get-method-parameter
hop 'tramp-session-timeout)
(tramp-set-connection-property
p "session-timeout"
(tramp-get-method-parameter
hop 'tramp-session-timeout)))
;; Replace `login-args' place holders.
(setq
command
(mapconcat
#'identity
(append
;; We do not want to see the trailing local
;; prompt in `start-file-process'.
(unless r-shell '("exec"))
`(,command)
;; Add arguments for asynchronous processes.
(when process-name async-args)
(tramp-expand-args
hop 'tramp-login-args
?h (or l-host "") ?u (or l-user "") ?p (or l-port "")
?c (format-spec options (format-spec-make ?t tmpfile))
?n (concat
"2>" (tramp-get-remote-null-device previous-hop))
?l (concat remote-shell " " extra-args " -i"))
;; A restricted shell does not allow "exec".
(when r-shell '("&&" "exit" "||" "exit")))
" "))
;; Send the command.
(tramp-message vec 3 "Sending command `%s'" command)
(tramp-send-command vec command t t)
(tramp-process-actions
p vec
(min
pos (with-current-buffer (process-buffer p) (point-max)))
tramp-actions-before-shell
(or connection-timeout tramp-connection-timeout))
(tramp-message
vec 3 "Found remote shell prompt on `%s'" l-host)
;; Next hop.
(setq options ""
target-alist (cdr target-alist)
previous-hop hop)))
;; Activate session timeout.
(when (tramp-get-connection-property p "session-timeout" nil)
(run-at-time
(tramp-get-connection-property p "session-timeout" nil) nil
#'tramp-timeout-session vec))
;; Make initial shell settings.
(tramp-open-connection-setup-interactive-shell p vec)
;; Mark it as connected.
(tramp-set-connection-property p "connected" t)))))
;; Cleanup, and propagate the signal.
((error quit)
(tramp-cleanup-connection vec t)
(signal (car err) (cdr err))))))