Hi Philip,
On 14/03/2017 15:45, Philip Homburg wrote: > Hi John, > > On 2017/03/14 14:49 , John wrote: >> feature request, when preforming DNS queries over TCP would it be >> possible for the probe to differentiate between a timeout and a TCP >> Reset. Currently the result just records the following when it gets a >> reset[1]. >> >> `error.timeout: 5000` > > I'll create a ticket for that. I have no idea about the ETA at the moment. Awesome thanks, no need for ETA just wanted to get it on the radar >> A similar feature to record ICMP prohibited for udp queries would also >> be useful but likely much harder. > > I wonder if the retry option would help here. The second send should get > an error from the kernel if the previous one resulted in an error ICMP. > > Actually getting the ICMP is possibly too hard, but a send error may > help a bit. But it requires some experimenting to see if this approach > would work. a bit to low level, kernel, socket programing for me but a quick google produces this if it helps """ Normally, UDP pretty much ignores ICMP errors, so if you want to see them, you need to open a raw socket to receive all ICMP packets and look for ones relevant to your socket. On Linux, at least, an alternative is to set the IP_RECVERR socket option. If you do that, you can do a recvmsg with the MSG_ERRQUEUE flag set to get any ICMP (or other) errors associated with your socket. This has the advantage of not requiring elevated privileges or a second socket. """ http://stackoverflow.com/questions/23118113/c-sockets-send-udp-and-process-icmp-reply-from-router Thanks
