Package: avahi-daemon
Version: 0.6.27-2
Severity: normal
Hi,
I have more info.
I was seeing a very annoying problem where openssh sshd would not
allow logins:
$ ssh-nomux pyke
<120 seconds pass, the sshd connection timeout>
Connection closed by 192.168.100.200
After a while searching for this, I found that sshd would hang here:
Dec 20 23:53:00 pyke sshd[30251]: debug3: Trying to reverse map address
192.168.100.188.
and that using "-o UseDNS=no" to sshd would work around the no-login
problem.
Now to the avahi part:
I also found that gethostbyaddr() would hang and never return
(after leaving it going overnight):
$ python -c 'import socket ; print socket.gethostbyaddr("192.168.100.188")'
It is correlated with this dbus error:
$ avahi-resolve -a 192.168.100.188
Failed to create client object: An unexpected D-Bus error occured
If avahi isn't running at all, we get this error instead and there is
*not* a problem with gethostbyaddr():
$ avahi-resolve -a 192.168.100.188
Failed to create client object: Daemon not running
Attempting to invoke-rc.d avahi restart/stop does not work - I have to
kill it. It also gets into some sort of a bad state where
"invoke-rc.d avahi-daemon start" won't cleanly start it again.
Here are straces on the avahi-daemon processes when they are hung
(when not hung, the first process waits at poll() and the second
waits at read()):
<process: avahi-daemon: running [pyke.local]>
select(13, NULL, [12], NULL, NULL
<process: avahi-daemon: chroot helper>
read(4,
A C-c at the console results in more strace output but it hangs again
at a select() call again.
I see this in the output of avahi-daemon --debug, but there are many
lines like this and they they go on for a while before it hangs:
Invalid response packet from host 128.59.x.y.
Invalid response packet from host 128.59.z.w.
Here is a gdb backtrace from when it is hung (retrived from gdb --args
avahi-daemon --debug, there are two avahi processes so I'm not sure if
this is the most useful output):
#0 0x00007ffff686b8b3 in select () from /lib/libc.so.6
#1 0x00007ffff79c3093 in avahi_wait_for_write (fd=<value optimized out>)
at fdutil.c:66
#2 0x00007ffff79b5a2c in sendmsg_loop (fd=12, msg=0x7fffffffe3f0,
flags=<value optimized out>) at socket.c:463
#3 0x00007ffff79b5ebe in avahi_send_dns_packet_ipv6 (fd=12, interface=3,
p=0x7fc7f0, src_address=0x63ae7c, dst_address=0x0,
dst_port=<value optimized out>) at socket.c:623
#4 0x00007ffff79a93dc in avahi_interface_send_packet_unicast (i=0x63ae40,
p=0x7fc7f0, a=0x0, port=0) at iface.c:601
#5 0x00007ffff79b7d04 in append_known_answers_and_send (
e=<value optimized out>, data=<value optimized out>) at query-sched.c:269
#6 elapse_callback (e=<value optimized out>, data=<value optimized out>)
at query-sched.c:310
#7 0x00007ffff79a8890 in expiration_event (timeout=<value optimized out>,
userdata=0x623ad0) at timeeventq.c:94
#8 0x00007ffff7bda8f0 in avahi_simple_poll_dispatch (s=0x622810)
at simple-watch.c:570
#9 0x0000000000408f33 in run_server (argc=<value optimized out>,
argv=<value optimized out>) at main.c:1219
#10 main (argc=<value optimized out>, argv=<value optimized out>)
at main.c:1637
This happens intermittently, so it may be avahi-daemon getting into a
bad state caused by network traffic. However, it *is* reproducible if
I leave the daemon running for a few hours, so give me tasks and I can
get more debugging information.
This is effectively a possible DOS (including DOS of ssh) from IPs
which don't have rDNS set up. Workarounds are UseDNS=no for sshd or
sshing from an IP with a valid rDNS.
Let me know if there is anything more I can do.
Thanks,
- richard
-- System Information:
Debian Release: squeeze/sid
APT prefers testing
APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Kernel: Linux 2.6.32-5-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages avahi-daemon depends on:
ii adduser 3.112+nmu2 add and remove users and groups
ii bind9-host [host] 1:9.7.2.dfsg.P3-1 Version of 'host' bundled with BIN
ii dbus 1.2.24-3 simple interprocess messaging syst
ii libavahi-common3 0.6.27-2 Avahi common library
ii libavahi-core7 0.6.27-2 Avahi's embeddable mDNS/DNS-SD lib
ii libc6 2.11.2-7 Embedded GNU C Library: Shared lib
ii libcap2 1:2.19-3 support for getting/setting POSIX.
ii libdaemon0 0.14-2 lightweight C library for daemons
ii libdbus-1-3 1.2.24-3 simple interprocess messaging syst
ii libexpat1 2.0.1-7 XML parsing C library - runtime li
ii lsb-base 3.2-23.1 Linux Standard Base 3.2 init scrip
Versions of packages avahi-daemon recommends:
ii libnss-mdns 0.10-3.1 NSS module for Multicast DNS name
Versions of packages avahi-daemon suggests:
pn avahi-autoipd <none> (no description available)
-- no debconf information
--
To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org
with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
