320 lines
12 KiB
Scheme
320 lines
12 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (guix ssh)
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#:use-module (guix store)
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#:use-module (guix i18n)
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#:use-module (ssh session)
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#:use-module (ssh auth)
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#:use-module (ssh key)
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#:use-module (ssh channel)
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#:use-module (ssh popen)
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#:use-module (ssh session)
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#:use-module (ssh dist)
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#:use-module (ssh dist node)
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#:use-module (srfi srfi-11)
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#:use-module (srfi srfi-34)
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#:use-module (srfi srfi-35)
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#:use-module (ice-9 match)
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#:use-module (ice-9 binary-ports)
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#:export (open-ssh-session
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remote-daemon-channel
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connect-to-remote-daemon
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send-files
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retrieve-files
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remote-store-host
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file-retrieval-port))
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;;; Commentary:
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;;;
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;;; This module provides tools to support communication with remote stores
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;;; over SSH, using Guile-SSH.
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;;;
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;;; Code:
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(define %compression
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"zlib@openssh.com,zlib")
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(define* (open-ssh-session host #:key user port
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(compression %compression))
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"Open an SSH session for HOST and return it. When USER and PORT are #f, use
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default values or whatever '~/.ssh/config' specifies; otherwise use them.
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Throw an error on failure."
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(let ((session (make-session #:user user
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#:host host
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#:port port
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#:timeout 10 ;seconds
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;; #:log-verbosity 'protocol
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;; We need lightweight compression when
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;; exchanging full archives.
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#:compression compression
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#:compression-level 3)))
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;; Honor ~/.ssh/config.
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(session-parse-config! session)
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(match (connect! session)
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('ok
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;; Use public key authentication, via the SSH agent if it's available.
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(match (userauth-public-key/auto! session)
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('success
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session)
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(x
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(disconnect! session)
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(raise (condition
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(&message
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(message (format #f (G_ "SSH authentication failed for '~a': ~a~%")
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host (get-error session)))))))))
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(x
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;; Connection failed or timeout expired.
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(raise (condition
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(&message
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(message (format #f (G_ "SSH connection to '~a' failed: ~a~%")
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host (get-error session))))))))))
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(define* (remote-daemon-channel session
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#:optional
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(socket-name
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"/var/guix/daemon-socket/socket"))
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"Return an input/output port (an SSH channel) to the daemon at SESSION."
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(define redirect
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;; Code run in SESSION to redirect the remote process' stdin/stdout to the
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;; daemon's socket, à la socat. The SSH protocol supports forwarding to
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;; Unix-domain sockets but libssh doesn't have an API for that, hence this
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;; hack.
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`(begin
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(use-modules (ice-9 match) (rnrs io ports))
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(let ((sock (socket AF_UNIX SOCK_STREAM 0))
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(stdin (current-input-port))
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(stdout (current-output-port)))
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(setvbuf stdin _IONBF)
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(setvbuf stdout _IONBF)
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(connect sock AF_UNIX ,socket-name)
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(let loop ()
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(match (select (list stdin sock) '() (list stdin stdout sock))
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((reads writes ())
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(when (memq stdin reads)
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(match (get-bytevector-some stdin)
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((? eof-object?)
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(primitive-exit 0))
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(bv
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(put-bytevector sock bv))))
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(when (memq sock reads)
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(match (get-bytevector-some sock)
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((? eof-object?)
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(primitive-exit 0))
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(bv
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(put-bytevector stdout bv))))
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(loop))
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(_
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(primitive-exit 1)))))))
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(open-remote-pipe* session OPEN_BOTH
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;; Sort-of shell-quote REDIRECT.
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"guile" "-c"
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(object->string
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(object->string redirect))))
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(define* (connect-to-remote-daemon session
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#:optional
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(socket-name
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"/var/guix/daemon-socket/socket"))
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"Connect to the remote build daemon listening on SOCKET-NAME over SESSION,
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an SSH session. Return a <nix-server> object."
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(open-connection #:port (remote-daemon-channel session)))
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(define (store-import-channel session)
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"Return an output port to which archives to be exported to SESSION's store
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can be written."
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;; Using the 'import-paths' RPC on a remote store would be slow because it
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;; makes a round trip every time 32 KiB have been transferred. This
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;; procedure instead opens a separate channel to use the remote
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;; 'import-paths' procedure, which consumes all the data in a single round
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;; trip. This optimizes the successful case at the expense of error
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;; conditions: errors can only be reported once all the input has been
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;; consumed.
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(define import
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`(begin
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(use-modules (guix) (srfi srfi-34)
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(rnrs io ports) (rnrs bytevectors))
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(define (consume-input port)
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(let ((bv (make-bytevector 32768)))
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(let loop ()
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(let ((n (get-bytevector-n! port bv 0
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(bytevector-length bv))))
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(unless (eof-object? n)
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(loop))))))
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;; Upon completion, write an sexp that denotes the status.
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(write
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(catch #t
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(lambda ()
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(guard (c ((nix-protocol-error? c)
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;; Consume all the input since the only time we can
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;; report the error is after everything has been
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;; consumed.
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(consume-input (current-input-port))
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(list 'protocol-error (nix-protocol-error-message c))))
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(with-store store
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(setvbuf (current-input-port) _IONBF)
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(import-paths store (current-input-port))
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'(success))))
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(lambda args
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(cons 'error args))))))
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(open-remote-pipe session
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(string-join
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`("guile" "-c"
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,(object->string (object->string import))))
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OPEN_BOTH))
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(define* (store-export-channel session files
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#:key recursive?)
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"Return an input port from which an export of FILES from SESSION's store can
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be read. When RECURSIVE? is true, the closure of FILES is exported."
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;; Same as above: this is more efficient than calling 'export-paths' on a
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;; remote store.
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(define export
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`(begin
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(use-modules (guix))
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(with-store store
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(setvbuf (current-output-port) _IONBF)
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;; FIXME: Exceptions are silently swallowed. We should report them
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;; somehow.
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(export-paths store ',files (current-output-port)
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#:recursive? ,recursive?))))
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(open-remote-input-pipe session
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(string-join
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`("guile" "-c"
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,(object->string
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(object->string export))))))
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(define* (send-files local files remote
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#:key
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recursive?
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(log-port (current-error-port)))
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"Send the subset of FILES from LOCAL (a local store) that's missing to
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REMOTE, a remote store. When RECURSIVE? is true, send the closure of FILES.
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Return the list of store items actually sent."
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;; Compute the subset of FILES missing on SESSION and send them.
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(let* ((files (if recursive? (requisites local files) files))
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(session (channel-get-session (nix-server-socket remote)))
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(node (make-node session))
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(missing (node-eval node
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`(begin
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(use-modules (guix)
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(srfi srfi-1) (srfi srfi-26))
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(with-store store
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(remove (cut valid-path? store <>)
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',files)))))
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(count (length missing))
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(port (store-import-channel session)))
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(format log-port (N_ "sending ~a store item to '~a'...~%"
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"sending ~a store items to '~a'...~%" count)
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count (session-get session 'host))
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;; Send MISSING in topological order.
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(export-paths local missing port)
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;; Tell the remote process that we're done. (In theory the end-of-archive
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;; mark of 'export-paths' would be enough, but in practice it's not.)
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(channel-send-eof port)
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;; Wait for completion of the remote process and read the status sexp from
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;; PORT.
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(let* ((result (false-if-exception (read port)))
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(status (zero? (channel-get-exit-status port))))
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(close-port port)
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(match result
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(('success . _)
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missing)
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(('protocol-error message)
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(raise (condition
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(&nix-protocol-error (message message) (status 42)))))
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(('error key args ...)
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(raise (condition
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(&nix-protocol-error
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(message (call-with-output-string
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(lambda (port)
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(print-exception port #f key args))))
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(status 43)))))
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(_
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(raise (condition
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(&nix-protocol-error
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(message "unknown error while sending files over SSH")
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(status 44)))))))))
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(define (remote-store-session remote)
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"Return the SSH channel beneath REMOTE, a remote store as returned by
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'connect-to-remote-daemon', or #f."
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(channel-get-session (nix-server-socket remote)))
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(define (remote-store-host remote)
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"Return the name of the host REMOTE is connected to, where REMOTE is a
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remote store as returned by 'connect-to-remote-daemon'."
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(match (remote-store-session remote)
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(#f #f)
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((? session? session)
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(session-get session 'host))))
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(define* (file-retrieval-port files remote
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#:key recursive?)
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"Return an input port from which to retrieve FILES (a list of store items)
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from REMOTE, along with the number of items to retrieve (lower than or equal
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to the length of FILES.)"
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(values (store-export-channel (remote-store-session remote) files
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#:recursive? recursive?)
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(length files))) ;XXX: inaccurate when RECURSIVE? is true
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(define* (retrieve-files local files remote
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#:key recursive? (log-port (current-error-port)))
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"Retrieve FILES from REMOTE and import them using the 'import-paths' RPC on
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LOCAL. When RECURSIVE? is true, retrieve the closure of FILES."
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(let-values (((port count)
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(file-retrieval-port files remote
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#:recursive? recursive?)))
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(format #t (N_ "retrieving ~a store item from '~a'...~%"
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"retrieving ~a store items from '~a'...~%" count)
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count (remote-store-host remote))
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(when (eof-object? (lookahead-u8 port))
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;; The failure could be because one of the requested store items is not
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;; valid on REMOTE, or because Guile or Guix is improperly installed.
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;; TODO: Improve error reporting.
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(raise (condition
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(&message
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(message
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(format #f
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(G_ "failed to retrieve store items from '~a'")
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(remote-store-host remote)))))))
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(let ((result (import-paths local port)))
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(close-port port)
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result)))
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;;; ssh.scm ends here
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