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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2020 Mathieu Othacehe <othacehe@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (guix avahi)
#:use-module (guix records)
#:use-module (guix build syscalls)
#:use-module (avahi)
#:use-module (avahi client)
#:use-module (avahi client lookup)
#:use-module (avahi client publish)
#:use-module (srfi srfi-9)
#:use-module (ice-9 threads)
#:export (avahi-service
avahi-service?
avahi-service-name
avahi-service-type
avahi-service-interface
avahi-service-local-address
avahi-service-address
avahi-service-port
avahi-service-txt
avahi-publish-service-thread
avahi-browse-service-thread))
(define-record-type* <avahi-service>
avahi-service make-avahi-service
avahi-service?
(name avahi-service-name)
(type avahi-service-type)
(interface avahi-service-interface)
(local-address avahi-service-local-address)
(address avahi-service-address)
(port avahi-service-port)
(txt avahi-service-txt))
(define never
;; Never true.
(const #f))
(define* (avahi-publish-service-thread name
#:key
type port
(stop-loop? never)
(timeout (if (eq? stop-loop? never)
#f
500))
(txt '()))
"Publish the service TYPE using Avahi, for the given PORT, on all interfaces
and for all protocols. Also, advertise the given TXT record list.
This procedure starts a new thread running the Avahi event loop. It exits
when STOP-LOOP? procedure returns true."
(define client-callback
(lambda (client state)
(when (eq? state client-state/s-running)
(let ((group (make-entry-group client (const #t))))
(apply
add-entry-group-service! group interface/unspecified
protocol/unspecified '()
name type #f #f port txt)
(commit-entry-group group)))))
(call-with-new-thread
(lambda ()
(let* ((poll (make-simple-poll))
(client (make-client (simple-poll poll)
(list
client-flag/ignore-user-config)
client-callback)))
(while (not (stop-loop?))
(if timeout
(iterate-simple-poll poll timeout)
(iterate-simple-poll poll)))))))
(define (interface->ip-address interface)
"Return the local IP address of the given INTERFACE."
(let* ((socket (socket AF_INET SOCK_STREAM 0))
(address (network-interface-address socket interface))
(ip (inet-ntop (sockaddr:fam address)
(sockaddr:addr address))))
(close-port socket)
ip))
(define* (avahi-browse-service-thread proc
#:key
types
(ignore-local? #t)
(family AF_INET)
(stop-loop? never)
(timeout (if (eq? stop-loop? never)
#f
500)))
"Browse services which type is part of the TYPES list, using Avahi. The
search is restricted to services with the given FAMILY. Each time a service
is found or removed, PROC is called and passed as argument the corresponding
AVAHI-SERVICE record. If a service is available on multiple network
interfaces, it will only be reported on the first interface found.
This procedure starts a new thread running the Avahi event loop. It exits
when STOP-LOOP? procedure returns true."
(define %known-hosts
;; Set of Avahi discovered hosts.
(make-hash-table))
(define (service-resolver-callback resolver interface protocol event
service-name service-type domain
host-name address-type address port
txt flags)
;; Handle service resolution events.
(cond ((eq? event resolver-event/found)
;; Add the service if the host is unknown. This means that if a
;; service is available on multiple network interfaces for a single
;; host, only the first interface found will be considered.
(unless (or (hash-ref %known-hosts service-name)
(and ignore-local?
(member lookup-result-flag/local flags)))
(let* ((address (inet-ntop family address))
(local-address (interface->ip-address interface))
(service* (avahi-service
(name service-name)
(type service-type)
(interface interface)
(local-address local-address)
(address address)
(port port)
(txt txt))))
(hash-set! %known-hosts service-name service*)
(proc 'new-service service*))))
((eq? event resolver-event/failure)
;; Failure to resolve the host associated with a service. This
;; usually means that the mDNS record hasn't expired yet but that
;; the host went off-line.
(let ((service (hash-ref %known-hosts service-name)))
(when service
(proc 'remove-service service)
(hash-remove! %known-hosts service-name)))))
(free-service-resolver! resolver))
(define (service-browser-callback browser interface protocol event
service-name service-type
domain flags)
(cond
((eq? event browser-event/new)
(make-service-resolver (service-browser-client browser)
interface protocol
service-name service-type domain
protocol/unspecified '()
service-resolver-callback))
((eq? event browser-event/remove)
(let ((service (hash-ref %known-hosts service-name)))
(when service
(proc 'remove-service service)
(hash-remove! %known-hosts service-name))))))
(define client-callback
(lambda (client state)
(if (eq? state client-state/s-running)
(for-each (lambda (type)
(make-service-browser client
interface/unspecified
protocol/inet
type #f '()
service-browser-callback))
types))))
(let* ((poll (make-simple-poll))
(client (make-client (simple-poll poll)
'() ;; no flags
client-callback)))
(and (client? client)
(while (not (stop-loop?))
(if timeout
(iterate-simple-poll poll timeout)
(iterate-simple-poll poll))))))
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