showmount: try v3 before falling back to v1

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.

Signed-off-by Dan McGee <[email protected]>

---

First (and quick) attempt at a patch here for showmount. Let me know if you see serious problems with it or the approach. It seemed relatively sane to me and fixed my problems after brief testing.

See a report like this for some proof this is an issue in the wild:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=557954

Thanks,

-Dan

utils/showmount/showmount.c | 8 ++++++++

1 files changed, 8 insertions(+), 0 deletions(-)

utils/showmount/showmount.c +8 -0

index 418e8b9..716c06d 100644
@@ -96,6 +96,14 @@ static CLIENT *nfs_get_mount_client(const char  
 *hostname)
 	rpcprog_t program = nfs_getrpcbyname(MOUNTPROG, nfs_sm_pgmtbl);
 	CLIENT *client;
 
+	client = clnt_create(hostname, program, MOUNTVERS_NFSV3, "tcp");
+	if (client)
+		return client;
+
+	client = clnt_create(hostname, program, MOUNTVERS_NFSV3, "udp");
+	if (client)
+		return client;
+
 	client = clnt_create(hostname, program, MOUNTVERS, "tcp");
 	if (client)

		return client;

Signature · 6 lines

1.6.6

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Quoted 4 lines · Dan McGee

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.

Quoted 10 lines · Chuck Lever

Quoted 4 lines · Dan McGee

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 <[email protected]>
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 <[email protected]>

utils/showmount/showmount.c +0 -0

index 418e8b9..17224a6 100644

utils/showmount/showmount.c +2 -2

 {
 	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;

utils/showmount/showmount.c +2 -1

 	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;

utils/showmount/showmount.c +4 -0

 		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);

Quoted 21 lines

Author: Steve Dickson <[email protected]>
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 <[email protected]>

utils/showmount/showmount.c +0 -0

index 418e8b9..17224a6 100644
@@ -85,22 +85,29 @@ static const char *nfs_sm_pgmtbl[] = {
    NULL,
 };
 

utils/showmount/showmount.c static const char *nfs_sm_pgmtbl[] = { · line 88

Quoted 1 line

utils/showmount/showmount.c +1 -0

+static const int mount_vers[] = {

RPC version numbers are rpcvers_t, not int.

The array above this one is called "nfs_sm_pgmtbl"... to be consistent with existing code you should name this one "nfs_sm_verstbl".

utils/showmount/showmount.c static const char *nfs_sm_pgmtbl[] = { · line 93

Quoted 5 lines

utils/showmount/showmount.c +5 -0

+    MOUNTVERS_NFSV3,
+    MOUNTVERS_POSIX,
+    MOUNTVERS,
+};
+static const int max_vers = (sizeof(mount_vers)/sizeof(mount_vers[0]));

Array indices are unsigned.

Calling this "max_vers" suggests it's actually a version number, and not an index into the version array; that's confusing.

The array above this one has a NULL entry as it's final element. To be consistent with existing code, you should copy that logic for this array instead of using a separate "max_vers" variable.

utils/showmount/showmount.c static const char *nfs_sm_pgmtbl[] = { · line 101

Quoted 10 lines

utils/showmount/showmount.c +2 -1

+
 /*
 * 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)

RPC version numbers are rpcvers_t, not int. At the very least, clnt_create(3t) takes an unsigned version number argument.

Quoted 15 lines

utils/showmount/showmount.c +2 -2

 {
    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;
 

utils/showmount/showmount.c int main(int argc, char **argv) · line 132

Quoted 5 lines

utils/showmount/showmount.c +1 -1

@@ -122,7 +129,7 @@ int main(int argc, char **argv)
    mountlist list;
    int i;
    int n;
-    int maxlen;
+    int maxlen, vers=0;

Array indices are unsigned integers.

Calling this "vers" suggests it's actually a version number, and not an index into the version array; that's confusing.

Quoted 19 lines

utils/showmount/showmount.c +3 -1

    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) {

utils/showmount/showmount.c int main(int argc, char **argv) · line 211

Quoted 3 lines

utils/showmount/showmount.c +3 -0

+            if (++vers <  max_vers)
+                goto again;
+        }

clnt_create(3t) should tell you if the requested version number is working; libtirpc's version does a NULLPROC call, for example. It would be simpler to move this check into nfs_get_mount_client(), then you wouldn't need the retry loop here.

But nfs_get_mount_client() already doesn't care why the clnt_create(3t) call fails, it just retries the creation with different parameters if it didn't succeed. Do we really care enough to retry _only_ if the specific RPC version isn't available? We use the same procedure number with the same arguments and the same results for all three protocol versions, yes?

Quoted 5 lines

Quoted 5 lines

Author: Steve Dickson <[email protected]>
Date: =C2=A0 Tue Jan 5 13:29:07 2010 -0500

=C2=A0 =C2=A0showmount: Try the highest mount version then fall bac=

Quoted 2 lines

Quoted 2 lines

=C2=A0 =C2=A0Showmount should try the highest mount version first t=

Quoted 1 line

Quoted 1 line

=C2=A0 =C2=A0back to the lower ones when the server returns a RPC_P=

Quoted 1 line

Quoted 1 line

=C2=A0 =C2=A0error. The idea being not using the lower mount versio=

Quoted 5 lines

utils/showmount/showmoun=

Quoted 5 lines

=C2=A0 =C2=A0the process of moving away from NFSv2 support.

=C2=A0 =C2=A0Signed-off-by: Steve Dickson <[email protected]>

utils/showmount/showmoun= renamed from utils/showmount/showmount.c +0 -0

Quoted 7 lines

Quoted 7 lines

index 418e8b9..17224a6 100644

utils/showmount/showmount.c +0 -0

@@ -85,22 +85,29 @@ static const char *nfs_sm_pgmtbl[] =3D {
 =C2=A0 =C2=A0 NULL,
 };
 

Quoted 3 lines

utils/showmount/showmount.c static const char *nfs_sm_pgmtbl[] =3D { · line 88

Quoted 1 line

utils/showmount/showmount.c +1 -0

+static const int mount_vers[] =3D {

RPC version numbers are rpcvers_t, not int.

True..

Quoted 2 lines

The array above this one is called "nfs_sm_pgmtbl"... to be consiste=

Quoted 7 lines

with existing code you should name this one "nfs_sm_verstbl".

utils/showmount/showmount.c static const char *nfs_sm_pgmtbl[] =3D { · line 93

Quoted 5 lines

utils/showmount/showmount.c +5 -0

+ =C2=A0 =C2=A0MOUNTVERS_NFSV3,
+ =C2=A0 =C2=A0MOUNTVERS_POSIX,
+ =C2=A0 =C2=A0MOUNTVERS,
+};
+static const int max_vers =3D (sizeof(mount_vers)/sizeof(mount_ver=

Quoted 2 lines

Array indices are unsigned.

Sure...

Quoted 2 lines

Calling this "max_vers" suggests it's actually a version number, and=

Quoted 1 line

an index into the version array; that's confusing.

Its pretty simple code.. don't see this confusion.... but.. It changed to =C2=A0mount_vers_tbl

Quoted 2 lines

The array above this one has a NULL entry as it's final element. =C2=

Quoted 1 line

consistent with existing code, you should copy that logic for this a=

Quoted 1 line

instead of using a separate "max_vers" variable.

Having the NULL messes up the sizeof calculations

Quoted 4 lines

Quoted 4 lines

utils/showmount/showmount.c +1 -0

+
 /*

=C2=A0* Generate an RPC client handle connected to the mountd servi=

Quoted 6 lines

utils/showmount/showmount.c

Quoted 6 lines

=C2=A0* at @hostname, or die trying.
=C2=A0*
=C2=A0* Supports both AF_INET and AF_INET6 server addresses. =C2=A0*/

utils/showmount/showmount.c +1 -1

-static CLIENT *nfs_get_mount_client(const char *hostname)
+static CLIENT *nfs_get_mount_client(const char *hostname, int vers=

Quoted 6 lines

RPC version numbers are rpcvers_t, not int. =C2=A0At the very least, clnt_create(3t) takes an unsigned version number argument.

Quoted 2 lines

{
=C2=A0 =C2=A0 rpcprog_t program =3D nfs_getrpcbyname(MOUNTPROG, nfs=

Quoted 3 lines

Quoted 3 lines

=C2=A0 =C2=A0 CLIENT *client;

- =C2=A0 =C2=A0client =3D clnt_create(hostname, program, MOUNTVERS,=

Quoted 1 line

Quoted 1 line

+ =C2=A0 =C2=A0client =3D clnt_create(hostname, program, vers, "tcp=

Quoted 4 lines

Quoted 4 lines

=C2=A0 =C2=A0 if (client)
=C2=A0 =C2=A0 =C2=A0 =C2=A0 return client;

- =C2=A0 =C2=A0client =3D clnt_create(hostname, program, MOUNTVERS,=

Quoted 1 line

Quoted 1 line

+ =C2=A0 =C2=A0client =3D clnt_create(hostname, program, vers, "udp=

Quoted 12 lines

utils/showmount/showmount.c int main(int argc, char **argv) · line 132

Quoted 9 lines

=C2=A0 =C2=A0 if (client)
=C2=A0 =C2=A0 =C2=A0 =C2=A0 return client;

utils/showmount/showmount.c +1 -1

@@ -122,7 +129,7 @@ int main(int argc, char **argv)
 =C2=A0 =C2=A0 mountlist list;
 =C2=A0 =C2=A0 int i;
 =C2=A0 =C2=A0 int n;
- =C2=A0 =C2=A0int maxlen;
+ =C2=A0 =C2=A0int maxlen, vers=3D0;

Array indices are unsigned integers.

Quoted 1 line

Calling this "vers" suggests it's actually a version number, and not=

Quoted 1 line

index into the version array; that's confusing.

and an index call 'j' or 'i' is descriptive?? vers is clear enough im=

Quoted 4 lines

Quoted 4 lines

utils/showmount/showmount.c +0 -0

 =C2=A0 =C2=A0 char **dumpv;
 

Quoted 8 lines

utils/showmount/showmount.c int main(int argc, char **argv) · line 196

Quoted 8 lines

utils/showmount/showmount.c +2 -1

 =C2=A0 =C2=A0 program_name =3D argv[0];

@@ -185,7 +192,8 @@ int main(int argc, char **argv)
 =C2=A0 =C2=A0 =C2=A0 =C2=A0 break;
 =C2=A0 =C2=A0 }
 
- =C2=A0 =C2=A0mclient =3D nfs_get_mount_client(hostname);
+again:
+ =C2=A0 =C2=A0mclient =3D nfs_get_mount_client(hostname, mount_ver=

Quoted 5 lines

Quoted 5 lines

utils/showmount/showmount.c +0 -0

 =C2=A0 =C2=A0 mclient->cl_auth =3D authunix_create_default();
 =C2=A0 =C2=A0 total_timeout.tv_sec =3D TOTAL_TIMEOUT;
 =C2=A0 =C2=A0 total_timeout.tv_usec =3D 0;

@@ -197,6 +205,10 @@ int main(int argc, char **argv)

=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 (xdrproc_t) xdr_void, NUL=

Quoted 1 line

Quoted 1 line

=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 (xdrproc_t) xdr_exports, =

Quoted 2 lines

Quoted 2 lines

=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 total_timeout);
+ =C2=A0 =C2=A0 =C2=A0 =C2=A0if (clnt_stat =3D=3D RPC_PROGVERSMISMA=

Quoted 1 line

Quoted 1 line

+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0if (++vers < =C2=A0max_v=

Quoted 1 line

Quoted 1 line

+ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0goto again=

Quoted 4 lines

Quoted 1 line

+ =C2=A0 =C2=A0 =C2=A0 =C2=A0}

clnt_create(3t) should tell you if the requested version number is working; libtirpc's version does a NULLPROC call, for example. =C2=A0=

Quoted 2 lines

be simpler to move this check into nfs_get_mount_client(), then you wouldn't need the retry loop here.

clnt_create() does not fail.. the clnt_call() does..

Quoted 2 lines

But nfs_get_mount_client() already doesn't care why the clnt_create(=

Quoted 1 line

call fails, it just retries the creation with different parameters i=

Quoted 1 line

didn't succeed. =C2=A0Do we really care enough to retry _only_ if th=

Quoted 1 line

specific RPC version isn't available? =C2=A0We use the same procedur=

Quoted 2 lines

with the same arguments and the same results for all three protocol versions, yes?

Let not make a mountain out of mole hill... the goal of this patch is=

more...

Revised patch incorporating the code review comments...

steved.

commit a96b79f57f49ce5b4d05b6b9da79bdec03b13764

Author: Steve Dickson <[email protected]>
Date:   Tue Jan 5 15:39:00 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 <[email protected]>

utils/showmount/showmount.c +16 -7

index 418e8b9..74cf116 100644
@@ -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 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];

@@ -185,7 +193,8 @@ int main(int argc, char **argv)
 		break;
 	}
 
-	mclient = nfs_get_mount_client(hostname);
+again:
+	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;

utils/showmount/showmount.c +4 -1

 		if (clnt_stat != RPC_SUCCESS) {
 			clnt_perror(mclient, "rpc mount export");
 			clnt_destroy(mclient);

@@ -232,6 +245,10 @@ 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_tblsz)
+			goto again;
+	}
 	if (clnt_stat != RPC_SUCCESS) {
 		clnt_perror(mclient, "rpc mount dump");
 		clnt_destroy(mclient);
 
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Quoted 90 lines · Steve Dickson

Revised patch incorporating the code review comments...

steved.

commit a96b79f57f49ce5b4d05b6b9da79bdec03b13764

Author: Steve Dickson <[email protected]>
Date:   Tue Jan 5 15:39:00 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 <[email protected]>

utils/showmount/showmount.c +19 -7

index 418e8b9..74cf116 100644
@@ -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 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];

@@ -185,7 +193,8 @@ int main(int argc, char **argv)
        break;
    }
 
-    mclient = nfs_get_mount_client(hostname);
+again:
+    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;

@@ -197,6 +206,10 @@ 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_tblsz)
+                goto again;

utils/showmount/showmount.c int main(int argc, char **argv) · line 212

Quoted 1 line

utils/showmount/showmount.c +1 -0

+        }

If you're going to do this, you should destroy the clnt before retrying. Better yet you can use CLNT_CONTROL() to change the RPC version of the clnt on the fly... that way you don't have to destroy the clnt and create a new one, which has to try creating both "tcp" and "udp" in some cases, making for a long timeout each time if the server doesn't support "tcp".

My preference however, is to do the simple thing, and use clnt_create_vers(3t) in nfs_get_mount_client(). AFAICT you wouldn't need any of this extra logic or the new table.

Quoted 96 lines · Chuck Lever

Quoted 93 lines · Steve Dickson

Revised patch incorporating the code review comments...

steved.

commit a96b79f57f49ce5b4d05b6b9da79bdec03b13764

Author: Steve Dickson <[email protected]>
Date:   Tue Jan 5 15:39:00 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 <[email protected]>

utils/showmount/showmount.c +19 -7

index 418e8b9..74cf116 100644
@@ -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 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];

@@ -185,7 +193,8 @@ int main(int argc, char **argv)
       break;
   }
 
-    mclient = nfs_get_mount_client(hostname);
+again:
+    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;

@@ -197,6 +206,10 @@ 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_tblsz)
+                goto again;

Quoted 8 lines

utils/showmount/showmount.c int main(int argc, char **argv) · line 212

Quoted 1 line

utils/showmount/showmount.c +1 -0

+        }

If you're going to do this, you should destroy the clnt before retrying. Better yet you can use CLNT_CONTROL() to change the RPC version of the clnt on the fly... that way you don't have to destroy the clnt and create a new one, which has to try creating both "tcp" and "udp" in some cases, making for a long timeout each time if the server doesn't support "tcp".

This is a very short lived command and 99.9% of the time this code will not executed... so I guess I was not too worried about opening a couple extra fd in the every unlikely case a server does not support v3...