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nss: Allow selecting IP protocol for mDNS lookups.

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* gnu/system/nss.scm (mdns-host-lookup-nss): New procedure.
* doc/guix.texi (Name Service Switch): Document it.

Change-Id: Ie4ff4aab6bf41eb2cec69b78a8427594b20bc954
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
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Sergey Trofimov 2025-10-06 16:57:06 +02:00 • committed by Ludovic Courtès
parent 9da40e7bc3
commit a16d6225ee
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2 changed files with 34 additions and 16 deletions
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9
doc/guix.texi
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@ -46289,6 +46289,15 @@ This is the name service switch configuration with support for host name
lookup over multicast DNS (mDNS) for host names ending in @code{.local}. lookup over multicast DNS (mDNS) for host names ending in @code{.local}.
@end defvar @end defvar
Furthermore, mDNS lookups could be restricted to IPv4 or IPv6 protocols
using the procedure @code{mdns-host-lookup-nss}.
@deffn {Procedure} mdns-host-lookup-nss @
[#:ipv6? #t] [#:ipv4? #t]
Return a @code{name-service-switch} object with mDNS lookup restricted
to specified protocols.
@end deffn
The reference for name service switch configuration is given below. It The reference for name service switch configuration is given below. It
is a direct mapping of the configuration file format of the C library , so is a direct mapping of the configuration file format of the C library , so
please refer to the C library manual for more information (@pxref{NSS please refer to the C library manual for more information (@pxref{NSS

41
gnu/system/nss.scm
View file

@ -27,6 +27,7 @@
name-service name-service
lookup-specification lookup-specification
mdns-host-lookup-nss
%default-nss %default-nss
%mdns-host-lookup-nss %mdns-host-lookup-nss
@ -152,26 +153,34 @@
;; Default NSS configuration. ;; Default NSS configuration.
(name-service-switch)) (name-service-switch))
(define %mdns-host-lookup-nss (define* (mdns-host-lookup-nss #:key (ipv6? #t) (ipv4? #t))
(name-service-switch (let ((flavour (cond
(hosts (list %files ;first, check /etc/hosts ((and ipv6? ipv4?) "mdns")
(ipv6? "mdns6")
(ipv4? "mdns4")
(#t (error "No protocols enabled for mDNS lookups.")))))
(name-service-switch
(hosts (list %files ;first, check /etc/hosts
;; If the above did not succeed, try with 'mdns_minimal'. ;; If the above did not succeed, try with 'mdns_minimal'.
(name-service (name-service
(name "mdns_minimal") (name (string-append flavour "_minimal"))
;; 'mdns_minimal' is authoritative for '.local'. When it ;; 'mdns_minimal' is authoritative for '.local'. When it
;; returns "not found", no need to try the next methods. ;; returns "not found", no need to try the next methods.
(reaction (lookup-specification (reaction (lookup-specification
(not-found => return)))) (not-found => return))))
;; Then fall back to DNS. ;; Then fall back to DNS.
(name-service (name-service
(name "dns")) (name "dns"))
;; Finally, try with the "full" 'mdns'. ;; Finally, try with the "full" 'mdns'.
(name-service (name-service
(name "mdns")))))) (name flavour)))))))
(define %mdns-host-lookup-nss (mdns-host-lookup-nss))
;;; ;;;