Add libnss-resolve package

Protect nss removal with a refcount, to not disable nss module until all
instances have been removed.

Closes: #798905

debian/changelog

@@ -32,6 +32,9 @@ systemd (227-3) UNRELEASED; urgency=medium
   * Re-add bits which call SELinux in systemd-user pam service.
     (Closes: #804565)
 
+  [ Felipe Sateler ]
+  * Add libnss-resolve package. (Closes: #798905)
+
  -- Martin Pitt <mpitt@debian.org>  Tue, 13 Oct 2015 11:03:21 +0200
 
 systemd (227-2) unstable; urgency=medium

debian/control

@@ -204,6 +204,22 @@ Description: nss module to resolve hostnames for local container instances
  .
  Installing this package automatically adds mymachines to /etc/nsswitch.conf.
 
+Package: libnss-resolve
+Architecture: linux-any
+Multi-Arch: same
+Replaces: systemd (<< 227-3)
+Breaks: systemd (<< 227-3)
+Section: admin
+Priority: extra
+Pre-Depends: ${misc:Pre-Depends}
+Depends: ${shlibs:Depends}, ${misc:Depends}, systemd
+Description: nss module to resolve names via systemd-resolved
+ nss-resolve is a plugin for the GNU Name Service Switch (NSS) functionality
+ of the GNU C Library (glibc) providing DNS and LLMNR resolution to programs via
+ the systemd-resolved daemon (provided in the systemd package).
+ .
+ Installing this package automatically adds resolve to /etc/nsswitch.conf.
+
 Package: libsystemd0
 Architecture: linux-any
 Multi-Arch: same

debian/libnss-resolve.install

@@ -0,0 +1,3 @@
+lib/*/libnss_resolve*.so.*
+usr/share/man/man8/libnss_resolve.so.2.8
+usr/share/man/man8/nss-resolve.8

debian/libnss-resolve.postinst

@@ -0,0 +1,42 @@
+#!/bin/sh
+set -e
+
+# This code was taken from libnss-myhostname
+
+# try to insert resolve entries to the "hosts" line in /etc/nsswitch.conf to
+# automatically enable libnss-resolve support; do not change the
+# configuration if the "hosts" line already references some resolve lookups
+insert_nss_entry() {
+    echo "Checking NSS setup..."
+    # abort if /etc/nsswitch.conf does not exist
+    if ! [ -e /etc/nsswitch.conf ]; then
+        echo "Could not find /etc/nsswitch.conf."
+        return
+    fi
+    perl -i -pe '
+        sub insert {
+            my $line = shift;
+            # this also splits on tab
+            my @bits=split(" ", $line);
+            # do not break configuration if the "hosts" line already references
+            # resolve
+            if (grep { $_ eq "resolve"} @bits) {
+                return $line;
+            }
+            # add resolve before dns
+            return join " ", map {
+	        $_ eq "dns" ? ("resolve", "$_") : $_
+            } @bits;
+        }
+        s/^(hosts:\s+)(.*)/$1.insert($2)/e;
+    ' /etc/nsswitch.conf
+}
+
+if [ "$1" = configure ] && [ -z "$2" ]; then
+    echo "First installation detected..."
+    # first install: setup the recommended configuration (unless
+    # nsswitch.conf already contains resolve entries)
+    insert_nss_entry
+fi
+
+#DEBHELPER#

debian/libnss-resolve.postrm

@@ -0,0 +1,32 @@
+#!/bin/sh
+set -e
+
+# This code was taken from libnss-myhostname
+remove_nss_entry() {
+    refcount=$(dpkg-query -f '${db:Status-Abbrev} ${binary:Package}\n' \
+        -W libnss-resolve | grep '^i' | wc -l)
+    if [ "$refcount" -gt 0 ] ; then
+        # there are other instances, do nothing
+        return
+    fi
+    echo "Checking NSS setup..."
+    # abort if /etc/nsswitch.conf does not exist
+    if ! [ -e /etc/nsswitch.conf ]; then
+        echo "Could not find /etc/nsswitch.conf."
+        return
+    fi
+    perl -i -pe '
+        sub remove {
+            my $s=shift;
+            $s=~s/\s+\Qresolve\E//g;
+            return $s;
+        }
+        s/^(hosts:)(.*)/$1.remove($2)/e;
+    ' /etc/nsswitch.conf
+}
+
+if [ "$1" = remove ]; then
+    remove_nss_entry
+fi
+
+#DEBHELPER#

debian/rules

@@ -168,9 +168,6 @@ override_dh_install:
 ifeq (, $(filter noudeb, $(DEB_BUILD_PROFILES)))
 	dh_install -pudev-udeb -plibudev1-udeb --sourcedir=debian/install/udeb
 endif
-	# still needs to mature a bit, and packaging
-	rm -f debian/install/*/usr/lib/*/libnss_resolve*
-
 	# fix location of NSS modules
 	cd debian/install/deb/; for f in usr/lib/*/libnss_*; do mv $$f $${f#usr/}; done