Re: kern/53166: NFS default to UDP; it should really default to TCP

[Jason Thorpe <thorpej%me.com@localhost>]

> On Apr 8, 2018, at 7:05 AM, Christos Zoulas <christos%zoulas.com@localhost> wrote:
> 
> Did this (the default change request) came up because you are trying to
> boot over wifi and it is lossy because of the fragmentation? Or there
> was another reason? I thought that the boot code has been changed to do
> rsize=wsize=1024 for that reason…

This particular system (an RPI) boots on local micro SD, but I’m using an NFS export from my iMac to host pkgsrc, and a few other odds and ends during development of the project the RPI will reside in.  I noticed the NFS connection (over WiFi with urtwn) was slightly flaky, and it was then I noticed that it was running over UDP.  Changing it to TCP addressed the issue I was seeing (and Wireshark running on the server shows the occasional dropped packet or duplicate ACK that TCP quickly recovers from).

Yes, I could just remember to use the mount option all the time, but I thought the default should be more sensible because basically there’s no reason to not use TCP these days.

I only changed the sense of the NFS_BOOT_* option as a matter of consistency.  I did not change the standalone NFS code because I think the standalone code only supports UDP, and it indeed uses a really small read size to avoid problems with fragmentation.

—thorpej