web100srv sometimes fails to retreive packet pair timing results from the fork()'d child

What steps will reproduce the problem?
Sometimes the ndt server will fail to retrieve packet pair results during 
both/either the C2S or S2C test.

This is to do with an IPC timing issue, a throughput test forks into the 
init_pkttrace() code which will start capturing packets via pcap_loop(). This 
then calls the given callback function (print_speed) when it captures a packet, 
as part of this code check_signal_flags() is called in order to break the loop 
if the global variable sig1/sig2 is set. Now the parent tries to break the loop 
by sending signal SIGUSR1/2 which makes the signal handler set the 
corresponding global variable sig1/2.

This often works fine, however only if pcap_loop receives a packet after 
SIGUSR1/2 is sent.

It's quite possible pcap_loop wont process a packet due to it's filter removing 
all unrelated packets and SIGUSR1/2 actually doesn't get sent until after the 
sending/receiving finishes. So unless there are packets buffered packet pair 
results fail to make it back to the parent and the pcap fork() child will hang 
until killed by its alarm.

What version of the product are you using? On what operating system?
Current version on svn r796 . Linux Debian Wheezy.

Please provide any additional information below.
Fix attached

Original issue reported on code.google.com by rsanger...@gmail.com on 13 Jan 2013 at 9:16

Attachments:

FixMissingResults.diff

evristzam / ndt

web100srv sometimes fails to retreive packet pair timing results from the fork()'d child #71