[LU-18808] Allow LNDs to discover custom metadata via pings

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Severity: 3
• Assignee: Tim Day
• Reporter: Tim Day

Description

The EFA LND needs to be able to automatically discover remote EFA NIs GID and manager QP data by first performing a handshake using LNET pings over TCP. This allows EFA to resolve hardware addresses without relying large NID support and without needing the GID to be provided externally.

The metadata for all remote NIs for a particular node are passed via the LNET ping REPLY packet. Since a node will only send its own NIs metadata, a handshake must be performed with each node in a cluster.

We define a new LNET callback lnd_get_nid_metadata to enable LNet to query the LND for NID related metadata to send alongside the ping REPLY. Of course, this is implemented by the EFA LND to transmit the GIDs and manager QP data for local NIs.

Issue Links

• is related to: LU-18977 Introduce AWS EFA LND