avahi: ping can't resolve hostname, but nslookup can

ping tells me that it can't resolve some hostname ("ping: unknown host domain.company.local") in a URL but when I use host or nslookup on the same computer on the command line, the resolutions works fine (i.e. it's fast and reliable).

What could be causing this?

More testing: Firefox, wget and ping have the same problem. Pinging the IP address works.

OS: Linux (Ubuntu 13.04)

EDIT My /etc/resolv.conf reads:

nameserver 127.0.1.1
search domain.company.local

netstat reports:

Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.1.1:53            0.0.0.0:*               LISTEN      -               

so something is running on this port (nslookup also reports it uses 127.0.1.1 as DNS server).

There is no /etc/*inetd.conf, so I'm not sure which application serves this port.

It seems that dnsmasq is used:

/usr/sbin/dnsmasq --no-resolv --keep-in-foreground --no-hosts --bind-interfaces
   --pid-file=/var/run/NetworkManager/dnsmasq.pid --listen-address=127.0.1.1
   --conf-file=/var/run/NetworkManager/dnsmasq.conf --cache-size=0 --proxy-dnssec
   --enable-dbus=org.freedesktop.NetworkManager.dnsmasq
   --conf-dir=/etc/NetworkManager/dnsmasq.d

All the config files and folders are empty. Since nslookup says it uses 127.0.1.1#53 my guess is that dnsmasq works even without a configuration. But how does it know which parent DNS to query?

EDIT2 Disabling dnsmasq as suggested by harrymc didn't help. So I ran strace ping which gave me this odd output (just the interesting parts):

open("/etc/host.conf", O_RDONLY|O_CLOEXEC) = 4
read(4, "127.0.0.1\tlocalhost\n#127.0.1.1\ta"..., 4096) = 613
...
open("/lib/libnss_mdns4_minimal.so.2", O_RDONLY|O_CLOEXEC) = 4
read(4, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\0\f\0\0\0\0\0\0"..., 832) = 832
...
mmap(NULL, 2105560, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 4, 0) = 0x7f7829b00000
...
socket(PF_FILE, SOCK_STREAM, 0)         = 4
fcntl(4, F_GETFD)                       = 0
fcntl(4, F_SETFD, FD_CLOEXEC)           = 0
connect(4, {sa_family=AF_FILE, path="/var/run/avahi-daemon/socket"}, 110) = 0
fcntl(4, F_GETFL)                       = 0x2 (flags O_RDWR)
fstat(4, {st_mode=S_IFSOCK|0777, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f782a4f8000
lseek(4, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)
write(4, "RESOLVE-HOSTNAME-IPV4 domain.com"..., 44) = 44
read(4, "-15 Timeout reached\n", 4096)  = 20

So ping looks in /etc/hosts which makes sense. Then it loads and mmap()s /lib/libnss_mdns4_minimal.so.2 which makes sense as well.

But then it talks to avahi!?

Which led me to this forum post: ping doesn't make a dns request.

My /etc/nsswitch.conf also contains this line:

hosts:          files mdns4_minimal [NOTFOUND=return] dns mdns4

If I ping a working address, I see that the process also loads /lib/libnss_mdns4_minimal.so.2 but then, it does a DNS query via port 53.

So my guess is now that /lib/libnss_mdns4_minimal.so.2 is somehow noticing that the IP address ends with .local and not with .com and then the [NOTFOUND=return] is triggered.

How do I fix this?

Solution 1:

As described in detail in this blog post, you need to edit /etc/avahi/avahi-daemon.conf:

[server]
domain-name=.alocal

This binds the daemon to the domain .alocal instead of the default .local.

and restart the daemon with:

sudo service avahi-daemon restart

Note from the blog post:

You may need to flush the DNS,mDNS and resolver cache, as well as restart your web browsers to clear their internal cache.

After that, ping and nslookup started to agree.

Thanks to harrymc for getting me on the right track.

Solution 2:

Modifying /etc/nsswitch.conf and replacing:

hosts:          files mdns4_minimal [NOTFOUND=return] dns mdns4

by:

hosts:          files dns

worked for me.

Solution 3:

Easy thing to do: Edit /etc/default/avahi-daemon

Change the line:

AVAHI_DAEMON_DETECT_LOCAL=1

to

AVAHI_DAEMON_DETECT_LOCAL=0

Restart the avahi-daemon, or kill it.

I don't like Avahi, and I don't use any of its features. If you want to truly disable avahi, modify /etc/init/avahi-daemon.conf, similar to the following:

start on (never 
          and filesystem
      and started dbus)
stop on stopping dbus

Solution 4:

it seems .local address can't be access in ubuntu.

a solution is to edit /etc/nsswitch.conf and change this line :

hosts:          files mdns4_minimal [NOTFOUND=return] dns

by this :

hosts:          files dns