OpenVPN / OpenVPN/openvpn3

Unable to set tun-mtu with openvpn2

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Dominant language
C++
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Description

Hi,
I followed this help page of the openvpn2 command and discovered that I can set --tun-mtu 1360. I tried that and the client did not complain about the argument, but the tun0 device is created using the default mtu of 1500.
I've also found this issue: https://codeberg.org/OpenVPN/openvpn3-linux/issues/92 this is likely what I'm running into, but it was closed a couple of month ago, stating that this is a problem with the core library. Thats why I opened this issue here.

Is this expected behavior?

Thanks and kind regards,
BerriJ

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with docs/man/openvpn2.1.rst and reproduce the command using --tun-mtu 1360, then compare the resulting tun0 MTU with the requested value. Read linked issue 92 for the core-library context; done means either tun0 uses 1360 or the expected behavior is clearly documented and the discrepancy is explained.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
networking, security
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
45/100

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