[smokeping-users] One bad IPv6 FQDN causes all fping6 hosts to not be monitored

[Steven Bytnar]

Hi,

I'm using smokeping 2.4.2 with socket6 and fping6 2.4b2_to.
Try adding this entry to etc/config in a fping6 probe section:
---------------------------------------
++++ ipv6-google-cn

menu = ipv6.google.cn
title =ipv6.google.cn (China)
host = ipv6.google.cn
---------------------------------------

Smokeping reports:

% smokeping --nodaemon --debug
WARNING: Hostname 'ipv6.google.cn' does currently not resolve to an IPv6 address
WARNING: Hostname 'ipv6.google.cn' does currently not resolve to an IPv4 address
WARNING: Hostname 'ipv6.google.cn' does currently not resolve to an IPv6 or IPv4 address

But smokeping still passes ipv6.google.cn to fping6, which results in
fping6 not running.

% /opt/local/sbin/fping6 -v
/opt/local/sbin/fping6: Version 2.4b2_to $Date: 2002/01/16 00:33:42 $
/opt/local/sbin/fping6: comments to noc at zerohype.com
% /opt/local/sbin/fping6 -C 20 -q -B1 -r1 -i10 ipv6.google.com ::1 ipv6.beijing2008.cn ipv6.google.cn
fping6: nodename nor servname provided, or not known


Note that ipv6.google.cn did once resolve to an AAAA, but now resolves
to a CNAME that doesn't resolve.

% host ipv6.google.cn
ipv6.google.cn is an alias for ipv6cn.l.google.com.
% host ipv6cn.l.google.com
% host AAAA ipv6cn.l.google.com
host: couldn't get address for 'ipv6cn.l.google.com': not found
% nslookup -type=AAAA ipv6cn.l.google.com
Server:		192.168.2.1
Address:	192.168.2.1#53

Non-authoritative answer:
*** Can't find ipv6cn.l.google.com: No answer

Authoritative answers can be found from:
l.google.com
	origin = a.l.google.com
	mail addr = dns-admin.google.com
	serial = 1365087
	refresh = 900
	retry = 900
	expire = 1800
	minimum = 60


Would it make sense to change smokeping or to change fping6 to be more tolerant
of hostnames that don't resolve? This situation could apply to almost any
probe though.
If a FQDN is specified and it can't be looked up when smokeping starts,
I would expect:
1) a warning be logged. (A warning is already provided.)
2) a bad FQDN should not affect monitoring other valid hosts.
3) that at some point in the future when the FQDN does become valid,
smokeping would start providing monitoring data for that host without
requiring the sysadmin to restart smokeping.

--Steve