gnu: isc-dhcp: Patch dhclient to support resolvconf.

* gnu/packages/patches/dhclient-script-resolvconf-support.patch: New patch.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/admin.scm (isc-dhcp): Patch dhclient-script and update wrapper.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/packages/admin.scm

@@ -1572,7 +1572,9 @@ connection alive.")
                                     version "/dhcp-" version ".tar.gz"))
                 (sha256
                  (base32
-                  "1ivkvhhvqxap6c51cli7pa6xn76ngxri1zbl45ishz4ranxidi0a"))))
+                  "1ivkvhhvqxap6c51cli7pa6xn76ngxri1zbl45ishz4ranxidi0a"))
+                (patches (search-patches
+                           "dhclient-script-resolvconf-support.patch"))))
       (build-system gnu-build-system)
       (arguments
        `(#:parallel-build? #f
@@ -1666,12 +1668,13 @@ connection alive.")
              (lambda* (#:key inputs outputs #:allow-other-keys)
                ;; Install the dhclient script for GNU/Linux and make sure
                ;; if finds all the programs it needs.
-               (let* ((out       (assoc-ref outputs "out"))
+               (let* ((out        (assoc-ref outputs "out"))
-                      (libexec   (string-append out "/libexec"))
+                      (libexec    (string-append out "/libexec"))
-                      (coreutils (assoc-ref inputs "coreutils*"))
+                      (coreutils  (assoc-ref inputs "coreutils*"))
-                      (inetutils (assoc-ref inputs "inetutils"))
+                      (inetutils  (assoc-ref inputs "inetutils"))
-                      (grep      (assoc-ref inputs "grep*"))
+                      (grep       (assoc-ref inputs "grep*"))
-                      (sed       (assoc-ref inputs "sed*"))
+                      (resolvconf (assoc-ref inputs "resolvconf*"))
+                      (sed        (assoc-ref inputs "sed*"))
                       (debianutils (assoc-ref inputs "debianutils")))
                  (substitute* "client/scripts/linux"
                    (("/sbin/ip")
@@ -1687,7 +1690,8 @@ connection alive.")
                      ,(map (lambda (dir)
                              (string-append dir "/bin:"
                                             dir "/sbin"))
-                           (list inetutils coreutils grep sed debianutils))))))))))
+                           (list inetutils coreutils grep sed resolvconf
+                                 debianutils))))))))))
 
       (native-inputs
        (list config perl file))
@@ -1716,6 +1720,7 @@ connection alive.")
 
                 ("coreutils*" ,coreutils)
                 ("grep*" ,grep)
+                ("resolvconf*" ,openresolv)
                 ("sed*" ,sed)))
 
       (home-page "https://www.isc.org/dhcp/")

gnu/packages/patches/dhclient-script-resolvconf-support.patch

@@ -0,0 +1,58 @@
+Implement resolvconf support
+
+Due to the potential for multiple sources contenting for /etc/resolv.conf
+control, this patch replaces direct file munging with resolvconf indirection.
+
+--- a/client/scripts/linux	1970-01-01 09:00:01.000000000 +0900
++++ b/client/scripts/linux	1970-01-01 09:00:01.000000000 +0900
+@@ -36,11 +36,11 @@
+ # This updated version mostly follows Debian script by Andrew Pollock et al.
+ make_resolv_conf() {
+     local new_resolv_conf
++    new_resolv_conf=$(mktemp)
+ 
+     # DHCPv4
+     if [ -n "$new_domain_search" ] || [ -n "$new_domain_name" ] ||
+-       [ -n "$new_domain_name_servers" ]; then
+-        new_resolv_conf=/etc/resolv.conf.dhclient-new
++        [ -n "$new_domain_name_servers" ]; then
+         rm -f $new_resolv_conf
+ 
+         if [ -n "$new_domain_name" ]; then
+@@ -70,17 +70,12 @@
+                 echo nameserver $nameserver >>$new_resolv_conf
+             done
+         else # keep 'old' nameservers
+-            sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p /etc/resolv.conf >>$new_resolv_conf
++            resolvconf -l "$interface.dhcp" | sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p >>$new_resolv_conf
+         fi
+ 
+-	if [ -f /etc/resolv.conf ]; then
+-	    chown --reference=/etc/resolv.conf $new_resolv_conf
+-	    chmod --reference=/etc/resolv.conf $new_resolv_conf
+-	fi
+-        mv -f $new_resolv_conf /etc/resolv.conf
++        resolvconf -a "$interface.dhpc" <"$new_resolv_conf"
+     # DHCPv6
+     elif [ -n "$new_dhcp6_domain_search" ] || [ -n "$new_dhcp6_name_servers" ]; then
+-        new_resolv_conf=/etc/resolv.conf.dhclient-new
+         rm -f $new_resolv_conf
+ 
+         if [ -n "$new_dhcp6_domain_search" ]; then
+@@ -97,14 +92,10 @@
+                 echo nameserver $nameserver >>$new_resolv_conf
+             done
+         else # keep 'old' nameservers
+-            sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p /etc/resolv.conf >>$new_resolv_conf
++            resolvconf -l "$interface.dhcp6" | sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p >>$new_resolv_conf
+         fi
+ 
+-	if [ -f /etc/resolv.conf ]; then
+-            chown --reference=/etc/resolv.conf $new_resolv_conf
+-            chmod --reference=/etc/resolv.conf $new_resolv_conf
+-	fi
+-        mv -f $new_resolv_conf /etc/resolv.conf
++        resolvconf -a "$interface.dhpc6" <"$new_resolv_conf"
+     fi
+ }
+