Retr - column in tcp result not showing

[citytoast]

Hey,

I'm doing some troubleshooting (probably because of some old and too long cables) and while using -u I can see the package loss.
But when doing tcp the "Retr" column wont show, neither on the client nor on the server.

I'm using the latest Windows build (https://github.com/ar51an/iperf3-win-builds).

Anyone knows why? I tried using -V but still didn't show.

Client:

Server:

[davidBar-On]

The retransmissions information is taken from the TCP Info, but iperf3 does not support Windows TCP info as shown by the has_tcpinfo() code below. This may be just because iperf3 is not supported officially by iperf3. To add the support, CygWin should support TCP Info. At least in the past there were issues with this, but it may be that now CygWin doe support TCP info. If this is the case, then maybe the support can be added.

iperf/src/tcp_info.c

Lines 60 to 68 in 28976ad

	int
	has_tcpinfo(void)
	{
	#if (defined(linux) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)) \
	&& defined(TCP_INFO)
	return 1;
	#else
	return 0;
	#endif

[bucweat]

So I guess this also explains why the Retr columns are missing in MacOS also? Installed from homebrew, here is version info.

iperf3 --version
iperf 3.20 (cJSON 1.7.15)
Darwin charlies-MacBook-Pro.local 24.6.0 Darwin Kernel Version 24.6.0: Wed Nov  5 21:30:23 PST 2025; root:xnu-11417.140.69.705.2~1/RELEASE_X86_64 x86_64
Optional features available: sendfile / zerocopy, authentication, support IPv4 don't fragment, POSIX threads

I would think, with Linux roots, that MacOS would have tcpinfo.

[davidBar-On]

I would think, with Linux roots, that MacOS would have tcpinfo.

Actually, issue #1411 from 2022 already mentions this. Per this issue, tcpinfo support on MacOs is relatively new and probably this is the reason it was not included in iperf3 originally, but it seems that it can be added now.

[bmah888]

The tcpinfo structure differs between different OSs (this is definitely true between FreeBSD and Linux). So someone seeking to add support for tcpinfo to a Windows build would need to verify that the needed members of that structure are present, have the same semantics, etc.

Also, the macOS kernel isn't Linux based...it's roughly based on Mach (and BSD?).

[bucweat]

See #2008 I gave it a try... Google AI helped --> https://share.google/aimode/X4qqnAUdSpUR58Wni