[PATCH v2] exportfs: modify can_test() to use LONG_MAX when appropriate

[Harshula Jayasuriya <harshula@redhat.com>]

This patch is the nfs-utils patch corresponding to the kernel patch
"sunrpc: prepare NFS for 2038": "The kernel sunrpc code needs to handle
seconds since epoch greater than 2147483647. This means functions that
parse time as an int need to handle it as time_t."

When appropriate exportfs should use LONG_MAX in can_test() instead of
INT_MAX.

kernel INT_MAX + exportfs INT_MAX: "Tue Jan 19 03:14:08 UTC 2038"
=================================================================

exportfs: /mnt/export does not support NFS export:
------------------------------------------------------------
 # cat /proc/net/rpc/auth.unix.ip/content
 #class IP domain
------------------------------------------------------------

+ mount fail:
------------------------------------------------------------
 # cat /proc/net/rpc/auth.unix.ip/content
 #class IP domain
 # expiry=2147483768 refcnt=2 flags=4
 # nfsd 192.168.1.6 -no-domain-
------------------------------------------------------------

kernel LONG_MAX + exportfs INT_MAX: "Tue Jan 19 03:14:08 UTC 2038"
==================================================================

"exportfs: /mnt/export does not support NFS export":
------------------------------------------------------------
 # cat /proc/net/rpc/auth.unix.ip/content
 #class IP domain
------------------------------------------------------------

+ mount success:
------------------------------------------------------------
 # cat /proc/net/rpc/auth.unix.ip/content
 #class IP domain
 # expiry=2147485448 refcnt=2 flags=1
 nfsd 192.168.1.6 *
------------------------------------------------------------

kernel LONG_MAX + exportfs LONG_MAX: "Tue Jan 19 03:14:08 UTC 2038"
===================================================================

exportfs:
------------------------------------------------------------
 # cat /proc/net/rpc/auth.unix.ip/content
 #class IP domain
 # expiry=9223372036854775807 refcnt=1 flags=1
 nfsd 0.0.0.0 -test-client-
------------------------------------------------------------

+ mount success:
------------------------------------------------------------
 # cat /proc/net/rpc/auth.unix.ip/content
 #class IP domain
 # expiry=2147485448 refcnt=2 flags=1
 nfsd 192.168.1.6 *
 # expiry=9223372036854775807 refcnt=1 flags=1
 nfsd 0.0.0.0 -test-client-
------------------------------------------------------------

Signed-off-by: Harshula Jayasuriya <harshula@redhat.com>
---
 utils/exportfs/exportfs.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/utils/exportfs/exportfs.c b/utils/exportfs/exportfs.c
index da5fe21..9f13858 100644
--- a/utils/exportfs/exportfs.c
+++ b/utils/exportfs/exportfs.c
@@ -27,6 +27,8 @@
 #include <netdb.h>
 #include <errno.h>
 #include <dirent.h>
+#include <limits.h>
+#include <time.h>
 
 #include "sockaddr.h"
 #include "misc.h"
@@ -406,17 +408,34 @@ unexportfs(char *arg, int verbose)
 
 static int can_test(void)
 {
+	char buf[1024];
 	int fd;
 	int n;
-	char *setup = "nfsd 0.0.0.0 2147483647 -test-client-\n";
+
 	fd = open("/proc/net/rpc/auth.unix.ip/channel", O_WRONLY);
-	if ( fd < 0) return 0;
-	n = write(fd, setup, strlen(setup));
+	if (fd < 0)
+		return 0;
+
+	/* We introduce tolerance of 1 day to ensure that we use a
+	 * LONG_MAX for the expiry timestamp before it is actually
+	 * needed. To use LONG_MAX, the kernel code must have commit
+	 * 2f74f972d4cc7d83408ea0c32d424edcb44887bf
+	 * (sunrpc: prepare NFS for 2038).
+	 */
+#define INT_TO_LONG_THRESHOLD_SECS (INT_MAX - (60 * 60 * 24))
+	if (time(NULL) > INT_TO_LONG_THRESHOLD_SECS)
+		sprintf(buf, "nfsd 0.0.0.0 %ld -test-client-\n", LONG_MAX);
+	else
+		sprintf(buf, "nfsd 0.0.0.0 %d -test-client-\n", INT_MAX);
+
+	n = write(fd, buf, strlen(buf));
 	close(fd);
 	if (n < 0)
 		return 0;
+
 	fd = open("/proc/net/rpc/nfsd.export/channel", O_WRONLY);
-	if ( fd < 0) return 0;
+	if (fd < 0)
+		return 0;
 	close(fd);
 	return 1;
 }
-- 
1.8.3.1