vmx(4) ignoring MTU changes

[Dustin Marquess]

Just wanted to see if this was known or not before I filed a pr, as I
didn't see any mention of it in the man page. This is on the latest
HEAD build.

Was trying to see if vmx(4) supported jumbo pages when I noticed that
it seems to completely ignore all MTU changes at all:

localhost# ifconfig vmx0 | head -1
vmx0: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
localhost# ifconfig vmx0 mtu 9000
localhost# ifconfig vmx0 | head -1
vmx0: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
localhost# ifconfig vmx0 mtu 576
localhost# ifconfig vmx0 | head -1
vmx0: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500

Thanks!
-Dustin

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[Lloyd Parkes]

Post by Dustin Marquess
Was trying to see if vmx(4) supported jumbo pages when I noticed that

It’s quite possible that vmx(4) doesn’t support jumbo frames for the same reason that vioif doesn’t support jumbo frames, and that is that the programmer porting the driver didn’t know how to handle jumbo frames with mbuf(9). A few years ago I asked on this list if anyone knew how to handle jumbo frames with mbuf(9) and didn’t get a reply.

I tried to RTFM and RTFS but that didn’t work out either.

TFM appears to have been written by a non-native speaker of English (or a computer programmer, same thing). The information in TFM is pretty good, but sometimes the wrong words are used. I’ll try and remember to file a PR with patches. For an API as extensive as mbuf(9), some examples would be really useful and this is the area where TFM is most lacking IMHO.

As for TFS, I think network hardware has got a bit more complicated since I was fooling about with 10Mb/s ethernet…

Cheers,
Lloyd


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