[Bug 1203430] [NEW] dnsmasq doesn't listen on a given 127.* listen-address if bind-dynamic, interface and except-interface options are given

[Thomas Hood]

Public bug reported:

If I start dnsmasq as follows

    dnsmasq  --conf-file= --resolv-file=/tmp/r.conf --bind-dynamic --listen-address=127.0.3.1
    echo "nameserver 192.168.1.254" > /tmp/r.conf

then I can resolve a name, e.g., "www.microsoft.com", with dig.

    dig @127.0.3.1 www.microsoft.com

And I can still resolve names with that "dig" command if I start dnsmasq
as follows (with "--interface=eth0").

    dnsmasq  --conf-file=  --resolv-file=/tmp/r.conf --bind-dynamic --listen-address=127.0.3.1 --interface=eth0
    echo "nameserver 192.168.1.254" > /tmp/r.conf

However, I can't resolve anything if I start dnsmasq as follows (with
"--except-interface=lo").

    dnsmasq --conf-file= --resolv-file=/tmp/r.conf --bind-dynamic --listen-address=127.0.3.1 --interface=eth0 --except-interface=lo
    echo "nameserver 192.168.1.254" > /tmp/r.conf

Dnsmasq just doesn't respond even though it's supposedly listening at
127.0.3.1.

> # netstat -nlp | grep :53
> tcp        0      0 127.0.3.1:53            0.0.0.0:*               LISTEN      5887/dnsmasq    
> tcp        0      0 192.168.1.20:53         0.0.0.0:*               LISTEN      5887/dnsmasq    
> tcp6       0      0 fe80::f2de:f1ff:fe6b:53 :::*                    LISTEN      5887/dnsmasq    
> udp        0      0 0.0.0.0:5353            0.0.0.0:*                           768/avahi-daemon: r
> udp        0      0 127.0.3.1:53            0.0.0.0:*                           5887/dnsmasq    
> udp        0      0 192.168.1.20:53         0.0.0.0:*                           5887/dnsmasq    
> udp6       0      0 :::5353                 :::*                                768/avahi-daemon: r
> udp6       0      0 fe80::f2de:f1ff:fe6b:53 :::*                                5887/dnsmasq    


If I start dnsmasq as above but with "--bind-interfaces" instead of "--bind-dynamic" then the "dig" command works.

Additional info:

> # ifconfig
> eth0      Link encap:Ethernet  HWaddr f0:de:f1:6b:22:bf  
>           inet addr:192.168.1.20  Bcast:192.168.1.255  Mask:255.255.255.0
>           inet6 addr: fe80::f2de:f1ff:fe6b:22bf/64 Scope:Link
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:124343 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:59204 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:56834893 (56.8 MB)  TX bytes:8614172 (8.6 MB)
>           Interrupt:20 Memory:f2500000-f2520000
>
> lo        Link encap:Local Loopback  
>           inet addr:127.0.0.1  Mask:255.0.0.0
>           inet6 addr: ::1/128 Scope:Host
>           UP LOOPBACK RUNNING  MTU:65536  Metric:1
>           RX packets:806 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:806 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:0
>           RX bytes:220819 (220.8 KB)  TX bytes:220819 (220.8 KB)


Dnsmasq version: 2.65-1ubuntu1

** Affects: dnsmasq (Ubuntu)
     Importance: Undecided
         Status: New

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Title:
  dnsmasq doesn't listen on a given 127.* listen-address if bind-
  dynamic, interface and except-interface options are given

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