2 files changed, 34 insertions(+), 16 deletions(-)

M doc/guix.texi
M gnu/system/nss.scm

@@ 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}.
 @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
 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

@@ 27,6 27,7 @@
             name-service
 
             lookup-specification
+            mdns-host-lookup-nss
 
             %default-nss
             %mdns-host-lookup-nss


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