Re: TCP_KEEPALIVE for Linux NFS client?

[Calum Mackay <calum.mackay@xxxxxxxxxx>]

On 22/11/2023 11:10 pm, Cedric Blancher wrote:
> On Thu, 23 Nov 2023 at 00:03, Calum Mackay <calum.mackay@xxxxxxxxxx> wrote:
> > hi Ced,
> >
> > On 22/11/2023 10:48 pm, Cedric Blancher wrote:
> > > On Mon, 20 Nov 2023 at 03:57, Olga Kornievskaia <aglo@xxxxxxxxx> wrote:
> > > > Hi Ced,
> > > >
> > > > Why do you think it doesn't use it? Have you looked at a network trace
> > > > of an idle connection? I seem to recall seeing keep-alive being used.
> > >
> > > Well, I don't see a setsockopt(TCP_KEEPALIVE) in the libtirpc code?
> >
> > We have this, in the kernel RPC code:
> >
> >          https://elixir.bootlin.com/linux/latest/source/net/sunrpc/xprtsock.c#L2257
> >
> > which might be it.
>
> Yay, But how does the kernel get the fd from libtirpc?
>
> Also, how can I turn this:
>
> /* TCP Keepalive options */
> sock_set_keepalive(sock->sk);
> tcp_sock_set_keepidle(sock->sk, keepidle);
> tcp_sock_set_keepintvl(sock->sk, keepidle);
> tcp_sock_set_keepcnt(sock->sk, keepcnt);
>
> /* TCP user timeout (see RFC5482) */
> tcp_sock_set_user_timeout(sock->sk, timeo);
>
> into setsockopt() from userland code? Does the BSD socket library have
> such options?

What's the userland aspect here? For NFS, the kernel RPC code owns the 
socket, and sets the sock options.

You can see whether TCP keepalive is enabled, with the final column of 
netstat output:

getz $ netstat -neopa | grep :2049
…
tcp        0      0 192.168.254.2:49802     192.168.254.7:2049 
TIME_WAIT   0          0          -                    timewait (37.52/0/0)
tcp        0      0 192.168.254.2:722       192.168.254.7:2049 
TIME_WAIT   0          0          -                    timewait (37.52/0/0)
tcp        0      0 192.168.254.2:979       192.168.254.7:2049 
ESTABLISHED 0          35214      -                    keepalive (8.47/0/0)

cheers,
calum.

> Ced
>
> > cheers,
> > calum.
> >
> > > Ced
> > >
> > > > On Fri, Nov 17, 2023 at 8:02 PM Cedric Blancher
> > > > <cedric.blancher@xxxxxxxxx> wrote:
> > > > > Good morning!
> > > > >
> > > > > Why does the Linux NFS client not use TCP_KEEPALIVE for its TCP
> > > > > connections? What are the pro and cons of using that for NFS TCP
> > > > > connections?
> > > > >
> > > > > Ced
> > > > > --
> > > > > Cedric Blancher <cedric.blancher@xxxxxxxxx>
> > > > > [https://plus.google.com/u/0/+CedricBlancher/]
> > > > > Institute Pasteur
> >
> > --
> > Calum Mackay
> > Linux Kernel Engineering
> > Oracle Linux and Virtualisation

--
Calum Mackay
Linux Kernel Engineering
Oracle Linux and Virtualisation

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