Arch Linux

jmj

Member

Registered: 2023-12-10

Posts: 7

[SOLVED] UDP broadcast broken on 6.16.2

Sending a UDP broadcast doesn't work after upgrading to 6.16.2. It works fine in 6.16.1.

Computer 1 on LAN:

socat -u udp-recv:50000,reuseaddr -

Computer 2 on LAN running kernel 6.16.2:

echo "test" | socat - udp-datagram:255.255.255.255:50000,broadcast

The message "test" is not received on Computer 1.

Anyone else getting this problem?

Edit: Solved in 6.16.5

Last edited by jmj (2025-09-06 13:26:32)

manueljben

Member

Registered: 2020-10-22

Posts: 4

Re: [SOLVED] UDP broadcast broken on 6.16.2

I just installed kernel 6.16.2 and suddenly noticed I was having random/intermittent network issues. Running a simple "curl https://google.com" for example, allowed me to connect to Google 2 or 3 times out of 5, and the rest would give me a "network unreachable" error which is quite weird.

Going back to kernel 6.16.1 solved the problem. There's definitely something wrong/rotten with the network in 6.16.2. I tried to file a bug report, but since the accounts are disabled, I couldn't register to file a report, so I gave up...

loqs

Member

Registered: 2014-03-06

Posts: 18,628

Re: [SOLVED] UDP broadcast broken on 6.16.2

I tried to file a bug report, but since the accounts are disabled, I couldn't register to file a report, so I gave up...

Follow the instruction on the red banner at the top https://gitlab.archlinux.org/archlinux to register.

rodrigorc

Member

Registered: 2025-08-23

Posts: 2

Re: [SOLVED] UDP broadcast broken on 6.16.2

I just noticed a similar problem: some network connections fail randomly.

Unplugging the ethernet cable and plugging it again seems to temporarily solve the issue.

As does setting the link down and up again with `ip link set`.

As does `systemctl restart systemd-networkd`.

Last edited by rodrigorc (2025-08-23 17:02:48)

Sn0wCrack

Member

Registered: 2025-05-08

Posts: 3

Re: [SOLVED] UDP broadcast broken on 6.16.2

Having a similar issue as well. Same as rodrigorc, changing the network conditions (re-connecting, VPN, etc.) or just trying again repeatedly seems to resolve the issue.

loqs

Member

Registered: 2014-03-06

Posts: 18,628

Re: [SOLVED] UDP broadcast broken on 6.16.2

https://lore.kernel.org/regressions/202 … ecast.net/

rodrigorc

Member

Registered: 2025-08-23

Posts: 2

Re: [SOLVED] UDP broadcast broken on 6.16.2

Thanks @loqs. I had just arrived to 9e30ecf23b1b, after some hard bisecting... Funny thing is that I'm only getting the symptoms when the nvidia binary driver is loaded...

Anyway... just reverting 9e30ecf23b1b fixed the issue for my case.

I'm building with the linked patch now, just in case... and it works perfectly!

Last edited by rodrigorc (2025-08-24 16:08:54)

Sn0wCrack

Member

Registered: 2025-05-08

Posts: 3

Re: [SOLVED] UDP broadcast broken on 6.16.2

Just in case anyone is wondering where upstream is at, a v3 patch was made here: https://lore.kernel.org/regressions/202 … gmail.com/

It has been applied to netdev/net as of 3-4 days ago.

Hopefully will be applied in the next release.

gromit

Administrator

From: Germany

Registered: 2024-02-10

Posts: 1,312

Website

Re: [SOLVED] UDP broadcast broken on 6.16.2

You can also open a bug report here and ask for it to be backported/cherry-picked into the arch patchset: https://gitlab.archlinux.org/archlinux/ … x/-/issues

loqs

Member

Registered: 2014-03-06

Posts: 18,628

Re: [SOLVED] UDP broadcast broken on 6.16.2

You can also open a bug report

https://gitlab.archlinux.org/archlinux/ … issues/154

gromit

Administrator

From: Germany

Registered: 2024-02-10

Posts: 1,312

Website

Re: [SOLVED] UDP broadcast broken on 6.16.2

Ah great! I forgot that there already is an open issue and that this one is queued for inclusion with the next stable kernel