Re: [PATCH] showmount: try v3 before falling back to v1

[Steve Dickson <SteveD@redhat.com>]

On 01/05/2010 12:31 PM, Chuck Lever wrote:
> 
> On Jan 4, 2010, at 8:34 PM, Dan McGee wrote:
> 
>> A lot of people don't have anything below v3 enabled, so showmount is
>> completely unusable. Try v3 {tcp, udp} first; if they don't work, fall
>> back
>> to v1 {tcp, udp}; if those don't work then just fail as before.
> 
> I don't see any immediate problems with this.
> 
Well I do have a bz request that we stop using the lower mount
version so we can move away from NFSv2 support... so here is
my version of this patch... 

Comments??

steved.


Author: Steve Dickson <steved@redhat.com>
Date:   Tue Jan 5 13:29:07 2010 -0500

    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.
    
    Signed-off-by: Steve Dickson <steved@redhat.com>

diff --git a/utils/showmount/showmount.c b/utils/showmount/showmount.c
index 418e8b9..17224a6 100644
--- a/utils/showmount/showmount.c
+++ b/utils/showmount/showmount.c
@@ -85,22 +85,29 @@ static const char *nfs_sm_pgmtbl[] = {
 	NULL,
 };
 
+static const int mount_vers[] = {
+	MOUNTVERS_NFSV3,
+	MOUNTVERS_POSIX,
+	MOUNTVERS,
+};
+static const int max_vers = (sizeof(mount_vers)/sizeof(mount_vers[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, int vers)
 {
 	rpcprog_t program = nfs_getrpcbyname(MOUNTPROG, nfs_sm_pgmtbl);
 	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;
 
@@ -122,7 +129,7 @@ int main(int argc, char **argv)
 	mountlist list;
 	int i;
 	int n;
-	int maxlen;
+	int maxlen, vers=0;
 	char **dumpv;
 
 	program_name = argv[0];
@@ -185,7 +192,8 @@ int main(int argc, char **argv)
 		break;
 	}
 
-	mclient = nfs_get_mount_client(hostname);
+again:
+	mclient = nfs_get_mount_client(hostname, mount_vers[vers]);
 	mclient->cl_auth = authunix_create_default();
 	total_timeout.tv_sec = TOTAL_TIMEOUT;
 	total_timeout.tv_usec = 0;
@@ -197,6 +205,10 @@ 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)
+				goto again;
+		}
 		if (clnt_stat != RPC_SUCCESS) {
 			clnt_perror(mclient, "rpc mount export");
 			clnt_destroy(mclient);
@@ -232,6 +244,10 @@ 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)
+			goto again;
+	}
 	if (clnt_stat != RPC_SUCCESS) {
 		clnt_perror(mclient, "rpc mount dump");
 		clnt_destroy(mclient);