As per another question, I'm using hping--icmp-ts to send the ICMP time stamp requests to debug asymmetric routes.

It seems like my OpenBSD box generates time stamp replies by default without any issues when being hping'ed from OS X, per tcpdump on OpenBSD:

17:27:43.220109 osx.example.net > openbsd.example.net : icmp: time stamp request
17:27:43.220138 openbsd.example.net > osx.example.net: icmp: time stamp reply

However, my OS X 10.8, when being hping'ed from OpenBSD, doesn't seem to generate any replies, and, according to its own tcpdump, it doesn't look like this is related to any external firewalls, since the local tcpdump doesn't reveal any replies being generated, unless I'm misunderstading the tcpdump readings, or, more specifically, lack thereof:

20:26:47.330517 IP openbsd.example.net > osx.example.net: ICMP time stamp query id 14881 seq 0, length 20

It'd be more convenient to hping my OS X laptop from my OpenBSD server, than the other way around; how do I make OS X work here?

% sysctl net | fgrep icmp
% sudo sysctl -w net.inet.icmp.timestamp=1
net.inet.icmp.timestamp: 0 -> 1
  • That seems a once off solution (which might be enough to debug). Could you add how to make this permanent on OS X ? – Hennes Nov 26 '13 at 1:02
  • @Hennes, probably sudo sh -c "echo net.inet.icmp.timestamp=1 >> /etc/sysctl.conf", but I cannot test right now to ensure it works. – cnst Nov 26 '13 at 1:08

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