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Chuck Lever authored
NFSv4.0 clients must send endpoint information for their callback service to NFSv4.0 servers during their first contact with a server. Traditionally on Linux, user space provides the callback endpoint IP address via the "clientaddr=" mount option. During an NFSv4 migration event, it is possible that an FSID may be migrated to a destination server that is accessible via a different source IP address than the source server was. The client must update callback endpoint information on the destination server so that it can maintain leases and allow delegation. Without a new "clientaddr=" option from user space, however, the kernel itself must construct an appropriate IP address for the callback update. Provide an API in the RPC client for upper layer RPC consumers to acquire a source address for a remote. The mechanism used by the mount.nfs command is copied: set up a connected UDP socket to the designated remote, then scrape the source address off the socket. We are careful to select the correct network namespace when setting up the temporary UDP socket. Signed-off-by:
Chuck Lever <chuck.lever@oracle.com> Signed-off-by:
Trond Myklebust <Trond.Myklebust@netapp.com>
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