cifs: periodically query network interfaces from server

Currently, we only query the server for network interfaces
information at the time of mount, and never afterwards.
This can be a problem, especially for services like Azure,
where the IP address of the channel endpoints can change
over time.

With this change, we schedule a 600s polling of this info
from the server for each tree connect.

An alternative for periodic polling was to do this only at
the time of reconnect. But this could delay the reconnect
time slightly. Also, there are some challenges w.r.t how
we have cifs_reconnect implemented today.
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsglob.h

@@ -80,6 +80,9 @@
 #define SMB_DNS_RESOLVE_INTERVAL_MIN     120
 #define SMB_DNS_RESOLVE_INTERVAL_DEFAULT 600
 
+/* smb multichannel query server interfaces interval in seconds */
+#define SMB_INTERFACE_POLL_INTERVAL	600
+
 /* maximum number of PDUs in one compound */
 #define MAX_COMPOUND 5
 
@@ -1255,6 +1258,7 @@ struct cifs_tcon {
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	struct list_head ulist; /* cache update list */
 #endif
+	struct delayed_work	query_interfaces; /* query interfaces workqueue job */
 };
 
 /*

fs/cifs/cifsproto.h

@@ -641,6 +641,8 @@ cifs_chan_is_iface_active(struct cifs_ses *ses,
 			  struct TCP_Server_Info *server);
 int
 cifs_chan_update_iface(struct cifs_ses *ses, struct TCP_Server_Info *server);
+int
+SMB3_request_interfaces(const unsigned int xid, struct cifs_tcon *tcon);
 
 void extract_unc_hostname(const char *unc, const char **h, size_t *len);
 int copy_path_name(char *dst, const char *src);

fs/cifs/connect.c

@@ -145,6 +145,25 @@ static int reconn_set_ipaddr_from_hostname(struct TCP_Server_Info *server)
 	return rc;
 }
 
+static void smb2_query_server_interfaces(struct work_struct *work)
+{
+	int rc;
+	struct cifs_tcon *tcon = container_of(work,
+					struct cifs_tcon,
+					query_interfaces.work);
+
+	/*
+	 * query server network interfaces, in case they change
+	 */
+	rc = SMB3_request_interfaces(0, tcon);
+	if (rc) {
+		cifs_dbg(FYI, "%s: failed to query server interfaces: %d\n",
+				__func__, rc);
+	}
+
+	queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
+			   (SMB_INTERFACE_POLL_INTERVAL * HZ));
+}
 
 static void cifs_resolve_server(struct work_struct *work)
 {
@@ -2276,6 +2295,9 @@ cifs_put_tcon(struct cifs_tcon *tcon)
 	list_del_init(&tcon->tcon_list);
 	spin_unlock(&cifs_tcp_ses_lock);
 
+	/* cancel polling of interfaces */
+	cancel_delayed_work_sync(&tcon->query_interfaces);
+
 	if (tcon->use_witness) {
 		int rc;
 
@@ -2513,6 +2535,12 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb3_fs_context *ctx)
 	tcon->local_lease = ctx->local_lease;
 	INIT_LIST_HEAD(&tcon->pending_opens);
 
+	/* schedule query interfaces poll */
+	INIT_DELAYED_WORK(&tcon->query_interfaces,
+			  smb2_query_server_interfaces);
+	queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
+			   (SMB_INTERFACE_POLL_INTERVAL * HZ));
+
 	spin_lock(&cifs_tcp_ses_lock);
 	list_add(&tcon->tcon_list, &ses->tcon_list);
 	spin_unlock(&cifs_tcp_ses_lock);

fs/cifs/smb2ops.c

@@ -671,7 +671,7 @@ parse_server_interfaces(struct network_interface_info_ioctl_rsp *buf,
 	return rc;
 }
 
-static int
+int
 SMB3_request_interfaces(const unsigned int xid, struct cifs_tcon *tcon)
 {
 	int rc;