With this patch the dnsmasq init script manages resolv.conf if and only if
when dnsmasq will listen on 127.0.0.1#53 (is main resolver instance).
Also adds ::1 to the resolver file.

For unbound a likewise patch exists (PR#4454).
Fixes (combined with the unbound PR) FS#785

Signed-off-by: Paul Oranje <p...@xs4all.nl>
---
The intended invariant is that resolv.conf is managed whenever a resolver
listens on 127.0.0.1#53. Besides dnsmasq, unbound can take that role as well 
(but only when dnsmasq is not already listens on 127.0.0.1#53).
When no instance of dnsmasq has been configured to listen on 127.0.0.1#53 then
resolv.conf is not touched by dnsmasq.

Currently unbound handles resolv.conf also, but leaves it to dnsmasq whenever
that will run, even when no dnsmasq instance will listen on localhost:53. So
for unbound PR#4454  has been submitted to make sure it always manages
resov.conf when it owns localhost:domain.


Tests performed:

- with/without unbound, dhcp linkages none and dnsmasq
- dnsmasq listens on #53, not #53 (dnsmasq takes precedence when also on #53)
- listen on localhost, not localhost
- noresolv false and true
- one/multiple dnsmasq instances (useless combinations are omitted in testing)

single dnsmasq instance
    standard setup
==> dnsmasq manages resolv.conf

two dnsmasq instances, each serving another LAN
    both dnsmasq on #53
    dnsmasq-2 notinterface loopback
==> dnsmasq-1 manages resolv.conf

two dnsmasq unstances and unbound (dhcp_link: none, one dnsmasq behind ubound)
    both dnsmasq on #53
    dnsmasq-2 on #53, notinterface loopback
        noresolv true and server 127.0.0.1#1053
    unbound on #1053
==> dnsmasq-1 manages resolv.conf

two dnsmasq instances and unbound (dhcp_link: dnsmasq)
    dnsmasq-1 on #1053, noresolv true
    dnsmasq-2 on #2053, noresolv true
    unbound on #53
        forward LAN1 to 127.0.0.1#1053, forward LAN2 to 127.0.0.1#2053
==> unbound manages resolv.conf

on init stops resolv.conf is reset to the auto resolvfile.


History:
v1 -> v2        corrected synxtax error
                increased PKG_RELEASE
v2              reverted with commit 8180bbac7c237a31bd6e06c63e342c72342b7303
v3              corected errors, setup/teardown routines and thoroughly tested

Paul


 package/network/services/dnsmasq/Makefile          |  2 +-
 .../network/services/dnsmasq/files/dnsmasq.init    | 79 +++++++++++++++-------
 2 files changed, 55 insertions(+), 26 deletions(-)

diff --git a/package/network/services/dnsmasq/Makefile 
b/package/network/services/dnsmasq/Makefile
index f9ab13aef0..35ac6b2891 100644
--- a/package/network/services/dnsmasq/Makefile
+++ b/package/network/services/dnsmasq/Makefile
@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=dnsmasq
 PKG_VERSION:=2.77
-PKG_RELEASE:=3
+PKG_RELEASE:=4
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
 PKG_SOURCE_URL:=http://thekelleys.org.uk/dnsmasq/
diff --git a/package/network/services/dnsmasq/files/dnsmasq.init 
b/package/network/services/dnsmasq/files/dnsmasq.init
index d5177ecb0c..2a4d7b2239 100644
--- a/package/network/services/dnsmasq/files/dnsmasq.init
+++ b/package/network/services/dnsmasq/files/dnsmasq.init
@@ -707,9 +707,51 @@ dhcp_relay_add() {
        fi
 }
 
+_resolv_setup()
+{
+       local cfg="$1"
+       local port notinterfaces
+
+       config_get port "$cfg" port "53"
+       [ $port = "53" ] || return
+
+       config_get notinterfaces "$cfg" notinterface ""
+       [ -n "$notinterfaces" ] && list_contains notinterfaces "loopback" && 
return
+
+       # dnsmasq instance is designated to listen on 127.0.0.1#53.
+       # rewrite /tmp/resolv.conf
+       rm -f /tmp/resolv.conf
+       {
+               echo "# /tmp/resolv.conf generated by dnsmasq $cfg $( date )"
+               [ $ADD_LOCAL_DOMAIN -eq 1 ] && [ -n "$DOMAIN" ] && {
+                       echo "search $DOMAIN"
+               }
+               DNS_SERVERS="$DNS_SERVERS 127.0.0.1 ::1"
+               for DNS_SERVER in $DNS_SERVERS ; do
+                       echo "nameserver $DNS_SERVER"
+               done
+       } > /tmp/resolv.conf
+
+       return
+}
+
+_resolv_teardown()
+{
+       cfg="$1"
+
+       case $( cat /tmp/resolv.conf ) in
+       *"generated by dnsmasq $cfg"*)
+               # resolv.conf was written by this instance,
+               # reset /tmp/resolv.conf to default.
+               [ -f /tmp/resolv.conf ] && rm -f /tmp/resolv.conf
+               ln -s /tmp/resolv.conf.auto /tmp/resolv.conf
+               ;;
+       esac
+}
+
 dnsmasq_start()
 {
-       local cfg="$1" disabled resolvfile user_dhcpscript
+       local cfg="$1" disabled noresolv resolvfile user_dhcpscript
 
        config_get_bool disabled "$cfg" disabled 0
        [ "$disabled" -gt 0 ] && return 0
@@ -785,7 +827,6 @@ dnsmasq_start()
        append_bool "$cfg" nonegcache "--no-negcache"
        append_bool "$cfg" strictorder "--strict-order"
        append_bool "$cfg" logqueries "--log-queries=extra"
-       append_bool "$cfg" noresolv "--no-resolv"
        append_bool "$cfg" localise_queries "--localise-queries"
        append_bool "$cfg" readethers "--read-ethers"
        append_bool "$cfg" dbus "--enable-dbus"
@@ -854,14 +895,15 @@ dnsmasq_start()
        config_get_bool cachelocal "$cfg" cachelocal 1
 
        config_get_bool noresolv "$cfg" noresolv 0
-       if [ "$noresolv" != "1" ]; then
+       if [ "$noresolv" = "1" ]; then
+               xappend "--no-resolv"
+       else
                config_get resolvfile "$cfg" resolvfile "/tmp/resolv.conf.auto"
+               xappend "--resolv-file=$resolvfile"
                # So jail doesn't complain if file missing
-               [ -n "$resolvfile" -a \! -e "$resolvfile" ] && touch 
"$resolvfile"
+               [ -e "$resolvfile" ] && touch "$resolvfile"
        fi
 
-       [ -n "$resolvfile" ] && xappend "--resolv-file=$resolvfile"
-
        config_get hostsfile "$cfg" dhcphostsfile
        [ -e "$hostsfile" ] && xappend "--dhcp-hostsfile=$hostsfile"
 
@@ -973,16 +1015,6 @@ dnsmasq_start()
        echo >> $CONFIGFILE_TMP
        mv -f $CONFIGFILE_TMP $CONFIGFILE
 
-       [ "$resolvfile" = "/tmp/resolv.conf.auto" ] && {
-               rm -f /tmp/resolv.conf
-               [ $ADD_LOCAL_DOMAIN -eq 1 ] && [ -n "$DOMAIN" ] && {
-                       echo "search $DOMAIN" >> /tmp/resolv.conf
-               }
-               DNS_SERVERS="$DNS_SERVERS 127.0.0.1"
-               for DNS_SERVER in $DNS_SERVERS ; do
-                       echo "nameserver $DNS_SERVER" >> /tmp/resolv.conf
-               done
-       }
 
        procd_open_instance $cfg
        procd_set_param command $PROG -C $CONFIGFILE -k -x 
/var/run/dnsmasq/dnsmasq."${cfg}".pid
@@ -1000,21 +1032,18 @@ dnsmasq_start()
        procd_add_jail_mount_rw /var/run/dnsmasq/ $leasefile
 
        procd_close_instance
+
+
+       # rewrite /tmp/resolv.conf only for main instance
+       _resolv_setup $cfg
 }
 
 dnsmasq_stop()
 {
        local cfg="$1"
 
-       config_get resolvfile "$cfg" "resolvfile"
-
-       #relink /tmp/resolve.conf only for main instance
-       [ "$resolvfile" = "/tmp/resolv.conf.auto" ] && {
-               [ -f /tmp/resolv.conf ] && {
-                       rm -f /tmp/resolv.conf
-                       ln -s "$resolvfile" /tmp/resolv.conf
-               }
-       }
+       #relink /tmp/resolv.conf only for main instance
+       _resolv_teardown $cfg
 
        rm -f ${BASEDHCPSTAMPFILE}.${cfg}.*.dhcp
 }
-- 
2.13.1


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