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

The following reply was made to PR kern/53166; it has been noted by GNATS.

From: Jason Thorpe <>
Subject: Re: kern/53166: NFS default to UDP; it should really default to TCP
Date: Sun, 08 Apr 2018 08:00:25 -0700

 > On Apr 8, 2018, at 7:05 AM, Christos Zoulas <> =
 > Did this (the default change request) came up because you are trying =
 > 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 =
 > rsize=3Dwsize=3D1024 for that reason=E2=80=A6
 This particular system (an RPI) boots on local micro SD, but I=E2=80=99m =
 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=E2=80=99=
 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.

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