From 217ece6c45a8a1e0c5910024bb1f02da84484a16 Mon Sep 17 00:00:00 2001

From: Paulo Alcantara <pc@cjr.nz>

Date: Thu, 4 Nov 2021 13:13:28 -0300

Subject: [PATCH] cifs: set a minimum of 120s for next dns resolution

Git-commit: 4ac0536f8874a903a72bddc57eb88db774261e3a

Patch-mainline: v5.16-rc1

References: stable-5.14.19

commit 4ac0536f8874a903a72bddc57eb88db774261e3a upstream.

With commit 506c1da44fee ("cifs: use the expiry output of dns_query to

schedule next resolution") and after triggering the first reconnect,

the next async dns resolution of tcp server's hostname would be

scheduled based on dns_resolver's key expiry default, which happens to

default to 5s on most systems that use key.dns_resolver for upcall.

As per key.dns_resolver.conf(5):

       default_ttl=<number>

              The  number  of  seconds  to  set  as the expiration on a cached

              record.  This will be overridden if the program manages  to  re-

              trieve  TTL  information along with the addresses (if, for exam-

              ple, it accesses the DNS directly).  The default is  5  seconds.

              The value must be in the range 1 to INT_MAX.

Make the next async dns resolution no shorter than 120s as we do not

want to be upcalling too often.

Cc: stable@vger.kernel.org

Fixes: 506c1da44fee ("cifs: use the expiry output of dns_query to schedule next resolution")

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>

Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>

Signed-off-by: Steve French <stfrench@microsoft.com>

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 fs/cifs/cifsglob.h | 3 ++-

 fs/cifs/connect.c  | 2 +-

 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h

index cf2141483b37..3faf966df183 100644

--- a/fs/cifs/cifsglob.h

+++ b/fs/cifs/cifsglob.h

@@ -75,7 +75,8 @@

 #define SMB_ECHO_INTERVAL_MAX 600

 #define SMB_ECHO_INTERVAL_DEFAULT 60

-/* dns resolution interval in seconds */

+/* dns resolution intervals in seconds */

+#define SMB_DNS_RESOLVE_INTERVAL_MIN     120

 #define SMB_DNS_RESOLVE_INTERVAL_DEFAULT 600

 /* maximum number of PDUs in one compound */

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c

index 4f4064db08bd..14c925565dbe 100644

--- a/fs/cifs/connect.c

+++ b/fs/cifs/connect.c

@@ -116,7 +116,7 @@ static int reconn_set_ipaddr_from_hostname(struct TCP_Server_Info *server)

 			 * To make sure we don't use the cached entry, retry 1s

 			 * after expiry.

 			 */

-			ttl = (expiry - now + 1);

+			ttl = max_t(unsigned long, expiry - now, SMB_DNS_RESOLVE_INTERVAL_MIN) + 1;

 	}

 	rc = !rc ? -1 : 0;

-- 

2.26.2