showmount: Try the highest mount version then fall back to lower ones

Showmount should try the highest mount version first then fall
back to the lower ones when the server returns a RPC_PROGVERSMISMATCH
error. The idea being not using the lower mount versions will begin
the process of moving away from NFSv2 support.

Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Steve Dickson <steved@redhat.com>

diff --git a/utils/showmount/showmount.c b/utils/showmount/showmount.c
index 418e8b9e4f9d3d233dda3a241f1fa69e2d58582d..f567093c7dafd8a6afa34ab894ed028b8833984c 100644 (file)
--- a/utils/showmount/showmount.c
+++ b/utils/showmount/showmount.c
@@ -78,29 +78,36 @@ static void usage(FILE *fp, int n)
        exit(n);
 }
 
-static const char *nfs_sm_pgmtbl[] = {
+static const char *mount_pgm_tbl[] = {
        "showmount",
        "mount",
        "mountd",
        NULL,
 };
 
+static const rpcvers_t mount_vers_tbl[] = {
+       MOUNTVERS_NFSV3,
+       MOUNTVERS_POSIX,
+       MOUNTVERS,
+};
+static const unsigned int max_vers_tblsz = 
+       (sizeof(mount_vers_tbl)/sizeof(mount_vers_tbl[0]));
+
 /*
  * Generate an RPC client handle connected to the mountd service
  * at @hostname, or die trying.
  *
  * Supports both AF_INET and AF_INET6 server addresses.
  */
-static CLIENT *nfs_get_mount_client(const char *hostname)
+static CLIENT *nfs_get_mount_client(const char *hostname, rpcvers_t vers)
 {
-       rpcprog_t program = nfs_getrpcbyname(MOUNTPROG, nfs_sm_pgmtbl);
+       rpcprog_t program = nfs_getrpcbyname(MOUNTPROG, mount_pgm_tbl);
        CLIENT *client;
 
-       client = clnt_create(hostname, program, MOUNTVERS, "tcp");
+       client = clnt_create(hostname, program, vers, "tcp");
        if (client)
                return client;
-
-       client = clnt_create(hostname, program, MOUNTVERS, "udp");
+       client = clnt_create(hostname, program, vers, "udp");
        if (client)
                return client;
 
@@ -123,6 +130,7 @@ int main(int argc, char **argv)
        int i;
        int n;
        int maxlen;
+       int unsigned vers=0;
        char **dumpv;
 
        program_name = argv[0];
@@ -185,11 +193,12 @@ int main(int argc, char **argv)
                break;
        }
 
-       mclient = nfs_get_mount_client(hostname);
+       mclient = nfs_get_mount_client(hostname, mount_vers_tbl[vers]);
        mclient->cl_auth = authunix_create_default();
        total_timeout.tv_sec = TOTAL_TIMEOUT;
        total_timeout.tv_usec = 0;
 
+again:
        if (eflag) {
                memset(&exportlist, '\0', sizeof(exportlist));
 
@@ -197,6 +206,13 @@ int main(int argc, char **argv)
                        (xdrproc_t) xdr_void, NULL,
                        (xdrproc_t) xdr_exports, (caddr_t) &exportlist,
                        total_timeout);
+               if (clnt_stat == RPC_PROGVERSMISMATCH) {
+                       if (++vers <  max_vers_tblsz) {
+                               (void)CLNT_CONTROL(mclient, CLSET_VERS, 
+                                       (void *)&mount_vers_tbl[vers]);
+                               goto again;
+                               }
+               }
                if (clnt_stat != RPC_SUCCESS) {
                        clnt_perror(mclient, "rpc mount export");
                        clnt_destroy(mclient);
@@ -232,6 +248,13 @@ int main(int argc, char **argv)
                (xdrproc_t) xdr_void, NULL,
                (xdrproc_t) xdr_mountlist, (caddr_t) &dumplist,
                total_timeout);
+       if (clnt_stat == RPC_PROGVERSMISMATCH) {
+               if (++vers <  max_vers_tblsz) {
+                       (void)CLNT_CONTROL(mclient, CLSET_VERS, 
+                               (void *)&mount_vers_tbl[vers]);
+                       goto again;
+               }
+       }
        if (clnt_stat != RPC_SUCCESS) {
                clnt_perror(mclient, "rpc mount dump");
                clnt_destroy(mclient);