Re: Diagnosing virtual machine network issues

On 7/30/24 16:11, Alex Arslan wrote:
> 
>> Can you provide more context?  I'm not seeing earlier messages anywhere in my email folders.  Is this a Qemu issue?
> 
> The original message is from just over a month ago, archived here:
> https://lists.freebsd.org/archives/freebsd-hackers/2024-June/003378.html
> Basically, we have FreeBSD 13.2 VMs running under KVM on a Linux machine.
> Some code is using libcurl to make a request to an invalid domain and is
> testing that the error is a resolution failure. This test passes on all
> platforms except specifically in these FreeBSD VMs; I can't reproduce
> locally on FreeBSD. That made me think that there's an issue with how the
> VM was set up, prompting the original message and discussion. Then what
> I recently found was that we set a 30-second timeout for the libcurl
> request, which FreeBSD hits in the VM, as it evidently spends a full
> 30 seconds attempting to resolve the host, while e.g. Linux reports a
> resolution failure immediately.
> 
>> Coincidentally, I'm experimenting with FreeBSD under Qemu on my Mac Mini M1 and seeing about 93 mbits/sec in iperf, regardless of the NIC configured.  ( VM to bare metal host )  Bare metal to bare metal shows 930 mbits/sec.
> 
> 
> That's interesting, can you show how you did that? I'm not familiar with
> iperf (or most things in the realm of networking). Do you know why it's
> so much slower?

Typical use is very simple:

One one machine: iperf -s
On the other: iperf -c hostname-of-1st-machine

The iperf man page shows other options if you want to fine-tune.

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