Re: HEADS UP: NFS changes coming into CURRENT early February

On Tue, Jan 21, 2025 at 10:27 PM Gleb Smirnoff <glebius@freebsd.org> wrote:
>
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>
>   Hi,
>
> TLDR version:
> users of NFS with Kerberos (e.g. running gssd(8)) as well as users of NFS with
> TLS (e.g. running rpc.tlsclntd(8) or rpc.tlsservd(8)) as well as users of
> network lock manager (e.g. having 'options NFSLOCKD' and running rpcbind(8))
> are affected.  You would need to recompile & reinstall both the world and the
> kernel together.  Of course this is what you'd normally do when you track
> FreeBSD CURRENT, but better be warned.  I will post hashes of the specific
> revisions that break API/ABI when they are pushed.
>
> Longer version:
> last year I tried to check-in a new implementation of unix(4) SOCK_STREAM and
> SOCK_SEQPACKET in d80a97def9a1, but was forced to back it out due to several
> kernel side abusers of a unix(4) socket.  The most difficult ones are the NFS
> related RPC services, that act as RPC clients talking to an RPC servers in
> userland.  Since it is impossible to fully emulate a userland process
> connection to a unix(4) socket they need to work with the socket internal
> structures bypassing all the normal KPIs and conventions.  Of course they
> didn't tolerate the new implementation that totally eliminated intermediate
> buffer on the sending side.
>
> While the original motivation for the upcoming changes is the fact that I want
> to go forward with the new unix/stream and unix/seqpacket, I also tried to make
> kernel to userland RPC better.  You judge if I succeeded or not :) Here are
> some highlights:
>
> - Code footprint both in kernel clients and in userland daemons is reduced.
>   Example: gssd:    1 file changed, 5 insertions(+), 64 deletions(-)
>            kgssapi: 1 file changed, 26 insertions(+), 78 deletions(-)
>                     4 files changed, 1 insertion(+), 11 deletions(-)
> - You can easily see all RPC calls from kernel to userland with genl(1):
>   # genl monitor rpcnl
> - The new transport is multithreaded in kernel by default, so kernel clients
>   can send a bunch of RPCs without any serialization and if the userland
>   figures out how to parallelize their execution, such parallelization would
>   happen.  Note: new rpc.tlsservd(8) will use threads.
> - One ad-hoc single program syscall is removed - gssd_syscall.  Note:
>   rpctls syscall remains, but I have some ideas on how to improve that, too.
>   Not at this step though.
> - All sleeps of kernel RPC calls are now in single place, and they all have
>   timeouts.  I believe NFS services are now much more resilient to hangs.
>   A deadlock when NFS kernel thread is blocked on unix socket buffer, and
>   the socket can't go away because its application is blocked in some other
>   syscall is no longer possible.
>
> The code is posted on phabricator, reviews D48547 through D48552.
> Reviewers are very welcome!
>
> I share my branch on Github. It is usually rebased on today's CURRENT:
>
> https://github.com/glebius/FreeBSD/commits/gss-netlink/
>
> Early testers are very welcome!
Good work getting all this committed!

You might want to put an entry in UPDATING noting that the daemons
need to be upgraded with the kernel.

Thanks for all your work on this, rick

>
> --
> Gleb Smirnoff
>