Thanks for your reply.
I think I have a good enough understanding of LNET itself. My question was more
about how LNET is being used by Lustre itself.
LNET will established connections only if asked for by upper layers.
When I was talking about client and server, I was talking about how Lustre was
using it.
As far as I understood, Lustre server only contact clients when they need to
send LDLM callbacks.
They do so through the socket already opened by the client (reverse import).
What happened if the socket is closed is what I'm not sure. I though the server
is rather waiting for the client to reconnect and if not, is more or less
evicting it.
Could it be possible that the server in this case opens the connection itself
without waiting for the client to reconnect?
Aurélien
Le 18/02/2020 05:42, « NeilBrown » <ne...@suse.com> a écrit :
LNet is a peer-to-peer protocol, it has no concept of client and server.
If one host needs to send a message to another but doesn't already have
a connection, it creates a new connection.
I don't yet know enough specifics of the lustre protocol to be certain
of the circumstances when a lustre server will need to initiate a message
to a client, but I imagine that recalling a lock might be one.
I think you should assume that any LNet node might receive a connection
from any other LNet node (for which they share an LNet network), and
that the connection could come from any port between 512 and 1023
(LNET_ACCEPTOR_MIN_PORT to LNET_ACCEPTOR_MAX_PORT).
NeilBrown
On Mon, Feb 17 2020, Degremont, Aurelien wrote:
> Hi all,
>
> From what I've understood so far, LNET listens on port 988 by default and
peers connect to it using 1021-1023 TCP ports as source ports.
> At Lustre level, servers listen on 988 and clients connect to them using
the same source ports 1021-1023.
> So only accepting connections to port 988 on server side sounded pretty
safe to me. However, I've seen connections from 1021-1023 to 988, from server
hosts to client hosts sometimes.
> I can't understand what mechanism could trigger these connections. Did I
miss something?
>
> Thanks
>
> Aurélien
>
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