nmap caused network stoppage (or system lockup)

[funkz]

This just happened when I tried to identify a device on my internal network, using the nmap -A command. I'm running FreeBSD 14.1-RELEASE-p3 GENERIC on a headless gateway server between my internal network and the internet.

I ran it inside of screen in an ssh session. As soon as I ran it, the ssh session locked and networking stopped. Pinging, requesting a new IP (DHCP), the box became unresponsive. So I had to go hit the power button and restart it. Any ideas?

root@skunk ~ % nmap -A 10.0.2.56
Starting Nmap 7.94 ( https://nmap.org ) at 2024-08-29 08:54 EST

That was it. Any ideas? I don't know if it took down the whole system or just the network card as I don't have a monitor plugged in (nor video card for that matter).

Here's the point in my /var/log/messages where it happened, you can see the new boot starting.

Aug 29 08:47:09 skunk kernel: re1: promiscuous mode enabled
Aug 29 08:47:15 skunk kernel: re1: promiscuous mode disabled
Aug 29 09:25:36 skunk syslogd: kernel boot file is /boot/kernel/kernel
Aug 29 09:25:36 skunk kernel: ---<<BOOT>>---
Aug 29 09:25:36 skunk kernel: Copyright (c) 1992-2023 The FreeBSD Project.

 

[Alain De Vos]

firewall ?

 

[sko]

What kind of system are you using for that gateway? '-A' is quite extensive and hence ressource hungry, so a small system might be catatonic for a while during scanning.

Also disable all offloading on that realtek NIC - it's usually broken and causes problems in many ways. It might be very likely that the driver and/or firmware will still lock up - it's still a realtek... If possible just dump it and go for mellanox or intel.

 

[funkz]

firewall ?

Yes. The box I ran nmap on has an active pf firewall.

What kind of system are you using for that gateway? '-A' is quite extensive and hence ressource hungry, so a small system might be catatonic for a while during scanning.

Also disable all offloading on that realtek NIC - it's usually broken and causes problems in many ways. It might be very likely that the driver and/or firmware will still lock up - it's still a realtek... If possible just dump it and go for mellanox or intel.

Thanks, that is probably likely what the culprit would be. I hit the power button and it instantly dropped power (powered off), which indicates that it'd hung/shut down. Normally when I press the power button, FreeBSD begins the shutdown process and it takes 10-15 seconds. I wouldn't expect FreeBSD to just hang/kernel fault unless it's a driver issue or some other low-level issue. The machine is not too slow, it's an i5-2500K with 16GB RAM.