1 files changed, 52 insertions, 3 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 01dc45178f66..f1a7e63ab58f 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -78,6 +78,8 @@ static int reconn_set_ipaddr_from_hostname(struct TCP_Server_Info *server)
 	int rc;
 	int len;
 	char *unc, *ipaddr = NULL;
+	time64_t expiry, now;
+	unsigned long ttl = SMB_DNS_RESOLVE_INTERVAL_DEFAULT;
 
 	if (!server->hostname)
 		return -EINVAL;
@@ -91,13 +93,13 @@ static int reconn_set_ipaddr_from_hostname(struct TCP_Server_Info *server)
 	}
 	scnprintf(unc, len, "\\\\%s", server->hostname);
 
-	rc = dns_resolve_server_name_to_ip(unc, &ipaddr);
+	rc = dns_resolve_server_name_to_ip(unc, &ipaddr, &expiry);
 	kfree(unc);
 
 	if (rc < 0) {
 		cifs_dbg(FYI, "%s: failed to resolve server part of %s to IP: %d\n",
 			 __func__, server->hostname, rc);
-		return rc;
+		goto requeue_resolve;
 	}
 
 	spin_lock(&cifs_tcp_ses_lock);
@@ -106,7 +108,45 @@ static int reconn_set_ipaddr_from_hostname(struct TCP_Server_Info *server)
 	spin_unlock(&cifs_tcp_ses_lock);
 	kfree(ipaddr);
 
-	return !rc ? -1 : 0;
+	/* rc == 1 means success here */
+	if (rc) {
+		now = ktime_get_real_seconds();
+		if (expiry && expiry > now)
+			/*
+			 * To make sure we don't use the cached entry, retry 1s
+			 * after expiry.
+			 */
+			ttl = (expiry - now + 1);
+	}
+	rc = !rc ? -1 : 0;
+
+requeue_resolve:
+	cifs_dbg(FYI, "%s: next dns resolution scheduled for %lu seconds in the future\n",
+		 __func__, ttl);
+	mod_delayed_work(cifsiod_wq, &server->resolve, (ttl * HZ));
+
+	return rc;
+}
+
+
+static void cifs_resolve_server(struct work_struct *work)
+{
+	int rc;
+	struct TCP_Server_Info *server = container_of(work,
+					struct TCP_Server_Info, resolve.work);
+
+	mutex_lock(&server->srv_mutex);
+
+	/*
+	 * Resolve the hostname again to make sure that IP address is up-to-date.
+	 */
+	rc = reconn_set_ipaddr_from_hostname(server);
+	if (rc) {
+		cifs_dbg(FYI, "%s: failed to resolve hostname: %d\n",
+				__func__, rc);
+	}
+
+	mutex_unlock(&server->srv_mutex);
 }
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
@@ -680,6 +720,7 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
 	spin_unlock(&cifs_tcp_ses_lock);
 
 	cancel_delayed_work_sync(&server->echo);
+	cancel_delayed_work_sync(&server->resolve);
 
 	spin_lock(&GlobalMid_Lock);
 	server->tcpStatus = CifsExiting;
@@ -1260,6 +1301,7 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 	spin_unlock(&cifs_tcp_ses_lock);
 
 	cancel_delayed_work_sync(&server->echo);
+	cancel_delayed_work_sync(&server->resolve);
 
 	if (from_reconnect)
 		/*
@@ -1342,6 +1384,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx)
 	INIT_LIST_HEAD(&tcp_ses->tcp_ses_list);
 	INIT_LIST_HEAD(&tcp_ses->smb_ses_list);
 	INIT_DELAYED_WORK(&tcp_ses->echo, cifs_echo_request);
+	INIT_DELAYED_WORK(&tcp_ses->resolve, cifs_resolve_server);
 	INIT_DELAYED_WORK(&tcp_ses->reconnect, smb2_reconnect_server);
 	mutex_init(&tcp_ses->reconnect_mutex);
 	memcpy(&tcp_ses->srcaddr, &ctx->srcaddr,
@@ -1427,6 +1470,12 @@ smbd_connected:
 	/* queue echo request delayed work */
 	queue_delayed_work(cifsiod_wq, &tcp_ses->echo, tcp_ses->echo_interval);
 
+	/* queue dns resolution delayed work */
+	cifs_dbg(FYI, "%s: next dns resolution scheduled for %d seconds in the future\n",
+		 __func__, SMB_DNS_RESOLVE_INTERVAL_DEFAULT);
+
+	queue_delayed_work(cifsiod_wq, &tcp_ses->resolve, (SMB_DNS_RESOLVE_INTERVAL_DEFAULT * HZ));
+
 	return tcp_ses;
 
 out_err_crypto_release: