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由 Chuck Lever 提交于
Since commit ec88f28d in 2009, checking if the user-specified flavor is in the server's flavor list has been the source of a few noticeable regressions (now fixed), but there is one that is still vexing. An NFS server can list AUTH_NULL in its flavor list, which suggests a client should try to mount the server with the flavor of the client's choice, but the server will squash all accesses. In some cases, our client fails to mount a server because of this check, when the mount could have proceeded successfully. Skip this check if the user has specified "sec=" on the mount command line. But do consult the server-provided flavor list to choose a security flavor if no sec= option is specified on the mount command. If a server lists Kerberos pseudoflavors before "sys" in its export options, our client now chooses Kerberos over AUTH_UNIX for mount points, when no security flavor is specified by the mount command. This could be surprising to some administrators or users, who would then need to have Kerberos credentials to access the export. Or, a client administrator may not have enabled rpc.gssd. In this case, auth_rpcgss.ko might still be loadable, which is enough for the new logic to choose Kerberos over AUTH_UNIX. But the mount would fail since no GSS context can be created without rpc.gssd running. To retain the use of AUTH_UNIX by default: o The server administrator can ensure that "sys" is listed before Kerberos flavors in its export security options (see exports(5)), o The client administrator can explicitly specify "sec=sys" on its mount command line (see nfs(5)), o The client administrator can use "Sec=sys" in an appropriate section of /etc/nfsmount.conf (see nfsmount.conf(5)), or o The client administrator can blacklist auth_rpcgss.ko. Signed-off-by: NChuck Lever <chuck.lever@oracle.com> Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
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