Using iperf-2.0.5-11.el6.x86_64: Using moderately high-speed interfaces, e.g. 1Gigabit, it is possible to overflow the 32-bit packet counter within iperf causing the test to "prematurely" finish. At 1Gbps, using full-sized UDP packets, it's possible to reach a 2^31 signed 32-bit Integer counter wrap within about 6 hours. This makes it difficult to use iperf to soak test a system for an extended period, even more so if the interface runs at 10Gbps or more. Looking at the source code, it's apparent that recent code changes have partially fixed this issue by ensuring that several variables, including Total Byte Counts, have been modified to use 64Bit unsigned integers, but the problem still remains for the Total Packet Count and potentially some other counters. The code logic appears to use a signed 32bit integer as both a Packet Count and a Packet ID which is embedded within the Packet, with the special case of ID == -1 used to signal "end of test". Ideally, I would imagine that the code should use a 64-bit unsigned integer for the Packet Count/ID, with a separate flag indicating "end-of-test". To reproduce the problem, run a 1Gbps UDP test between two iperfs for at least 7 hours ==~ 25000 seconds. ( or run for longer at slower speeds to trigger the same 32-bit wrap ). FWIW, iperf3 seems to have the same issue, but I'm not using that at present due to the lack of multicast support.
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