[LEDE-DEV] [PATCH] dnsmasq: manage resolv.conf iff when listening on 127.0.0.1#53

[Hans Dedecker]

On Wed, Jun 7, 2017 at 12:07 PM, Paul Oranje <por at xs4all.nl> wrote:
> 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, resolvfile is now set irrespective of the value of noresolv.
>
> Fixes (partially) FS#785
>
> Signed-off-by: Paul Oranje <por at 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.
> When no instance of dnsmasq has been configured to listen on 127.0.0.1#53 then
> resolv.conf is not touched.
>
> 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#4454a  has been submitted to make sure it always manages
> resov.conf when it owns localhost:domain.
>
> Background:
> This patch has been discussed with Hans Dedecker and Eric Luerhsen and replaces
> an earlier patch that is hereby retracted:
>         dnsmasq: write resolv.conf also when noresolv = 1
>
> Paul
>
> ---
>  .../network/services/dnsmasq/files/dnsmasq.init    | 60 +++++++++++++---------
>  1 file changed, 35 insertions(+), 25 deletions(-)
>
> diff --git a/package/network/services/dnsmasq/files/dnsmasq.init b/package/network/services/dnsmasq/files/dnsmasq.init
> index 62a3169c67..cab3d2843c 100644
> --- a/package/network/services/dnsmasq/files/dnsmasq.init
> +++ b/package/network/services/dnsmasq/files/dnsmasq.init
> @@ -695,6 +695,21 @@ dhcp_relay_add() {
>         fi
>  }
>
> +dnsmasq_ismain()
> +{
> +       local cfg="$1"
> +       local port notinterfaces
> +
> +       config_get port "$cfg" port "53"
> +       [ $port = "53" ] || return 1
Any reason why a dnsmasq instance has to be bound on port 53 to be
considered as main instance ? If port is not 0 it can be considered as
a dnsmasq main instance as a dnat rule can rewrite the udp destination
port
> +
> +       config_get notinterfaces "$cfg" notinterface ""
> +       [ -n $notinterfaces -a list_contains $notinterfaces "loopback" ] || return 1
Has this been tested ?
Following error is thrown "sh: loopback: unknown operand" when doing
dnsmasq restart
> +
> +       # dnsmasq instance is designated to listen on 127.0.0.1#53.
> +       return 0
> +}
> +
>  dnsmasq_start()
>  {
>         local cfg="$1" disabled resolvfile user_dhcpscript
> @@ -839,14 +854,10 @@ dnsmasq_start()
>         [ -n "$leasefile" -a \! -e "$leasefile" ] && touch "$leasefile"
>         config_get_bool cachelocal "$cfg" cachelocal 1
>
> -       config_get_bool noresolv "$cfg" noresolv 0
> -       if [ "$noresolv" != "1" ]; then
> -               config_get resolvfile "$cfg" resolvfile "/tmp/resolv.conf.auto"
> -               # So jail doesn't complain if file missing
> -               [ -n "$resolvfile" -a \! -e "$resolvfile" ] && touch "$resolvfile"
> -       fi
> -
> -       [ -n "$resolvfile" ] && xappend "--resolv-file=$resolvfile"
> +       config_get resolvfile "$cfg" resolvfile "/tmp/resolv.conf.auto"
> +       xappend "--resolv-file=$resolvfile"
> +       # So jail doesn't complain if file missing
> +       [ \! -e "$resolvfile" ] && touch "$resolvfile"
>
>         config_get hostsfile "$cfg" dhcphostsfile
>         [ -e "$hostsfile" ] && xappend "--dhcp-hostsfile=$hostsfile"
> @@ -959,16 +970,6 @@ 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
> @@ -986,20 +987,29 @@ dnsmasq_start()
>         procd_add_jail_mount_rw /var/run/dnsmasq/ $leasefile
>
>         procd_close_instance
> +
> +
> +       # write /tmp/resolve.conf only for main instance
> +       dnsmasq_ismain $cfg && {
> +               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
> +       }
>  }
>
>  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
> -               }
> +       dnsmasq_ismain $cfg && {
> +               [ -f /tmp/resolv.conf ] && rm -f /tmp/resolv.conf
> +               ln -s /tmp/resolv.conf.auto /tmp/resolv.conf
>         }
>
>         rm -f ${BASEDHCPSTAMPFILE}.${cfg}.*.dhcp
> --
> 2.13.0
>
Increase PKG_RELEASE as well in the package Makefile

Hans