cifs: Set witness notification handler for messages from userspace daemon

+ Set a handler for the witness notification messages received from the
userspace daemon.

+ Handle the resource state change notification. When the resource
becomes unavailable or available set the tcp status to
CifsNeedReconnect for all channels.

Signed-off-by: Samuel Cabrero <[e-mail]>
Reviewed-by: Aurelien Aptel <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/cifs/cifs_swn.c

···
 	mutex_unlock(&cifs_swnreg_idr_mutex);
 }
 
+static int cifs_swn_resource_state_changed(struct cifs_swn_reg *swnreg, const char *name, int state)
+{
+	int i;
+
+	switch (state) {
+	case CIFS_SWN_RESOURCE_STATE_UNAVAILABLE:
+		cifs_dbg(FYI, "%s: resource name '%s' become unavailable\n", __func__, name);
+		for (i = 0; i < swnreg->tcon->ses->chan_count; i++) {
+			spin_lock(&GlobalMid_Lock);
+			if (swnreg->tcon->ses->chans[i].server->tcpStatus != CifsExiting)
+				swnreg->tcon->ses->chans[i].server->tcpStatus = CifsNeedReconnect;
+			spin_unlock(&GlobalMid_Lock);
+		}
+		break;
+	case CIFS_SWN_RESOURCE_STATE_AVAILABLE:
+		cifs_dbg(FYI, "%s: resource name '%s' become available\n", __func__, name);
+		for (i = 0; i < swnreg->tcon->ses->chan_count; i++) {
+			spin_lock(&GlobalMid_Lock);
+			if (swnreg->tcon->ses->chans[i].server->tcpStatus != CifsExiting)
+				swnreg->tcon->ses->chans[i].server->tcpStatus = CifsNeedReconnect;
+			spin_unlock(&GlobalMid_Lock);
+		}
+		break;
+	case CIFS_SWN_RESOURCE_STATE_UNKNOWN:
+		cifs_dbg(FYI, "%s: resource name '%s' changed to unknown state\n", __func__, name);
+		break;
+	}
+	return 0;
+}
+
+int cifs_swn_notify(struct sk_buff *skb, struct genl_info *info)
+{
+	struct cifs_swn_reg *swnreg;
+	char name[256];
+	int type;
+
+	if (info->attrs[CIFS_GENL_ATTR_SWN_REGISTRATION_ID]) {
+		int swnreg_id;
+
+		swnreg_id = nla_get_u32(info->attrs[CIFS_GENL_ATTR_SWN_REGISTRATION_ID]);
+		mutex_lock(&cifs_swnreg_idr_mutex);
+		swnreg = idr_find(&cifs_swnreg_idr, swnreg_id);
+		mutex_unlock(&cifs_swnreg_idr_mutex);
+		if (swnreg == NULL) {
+			cifs_dbg(FYI, "%s: registration id %d not found\n", __func__, swnreg_id);
+			return -EINVAL;
+		}
+	} else {
+		cifs_dbg(FYI, "%s: missing registration id attribute\n", __func__);
+		return -EINVAL;
+	}
+
+	if (info->attrs[CIFS_GENL_ATTR_SWN_NOTIFICATION_TYPE]) {
+		type = nla_get_u32(info->attrs[CIFS_GENL_ATTR_SWN_NOTIFICATION_TYPE]);
+	} else {
+		cifs_dbg(FYI, "%s: missing notification type attribute\n", __func__);
+		return -EINVAL;
+	}
+
+	switch (type) {
+	case CIFS_SWN_NOTIFICATION_RESOURCE_CHANGE: {
+		int state;
+
+		if (info->attrs[CIFS_GENL_ATTR_SWN_RESOURCE_NAME]) {
+			nla_strlcpy(name, info->attrs[CIFS_GENL_ATTR_SWN_RESOURCE_NAME],
+					sizeof(name));
+		} else {
+			cifs_dbg(FYI, "%s: missing resource name attribute\n", __func__);
+			return -EINVAL;
+		}
+		if (info->attrs[CIFS_GENL_ATTR_SWN_RESOURCE_STATE]) {
+			state = nla_get_u32(info->attrs[CIFS_GENL_ATTR_SWN_RESOURCE_STATE]);
+		} else {
+			cifs_dbg(FYI, "%s: missing resource state attribute\n", __func__);
+			return -EINVAL;
+		}
+		return cifs_swn_resource_state_changed(swnreg, name, state);
+	}
+	default:
+		cifs_dbg(FYI, "%s: unknown notification type %d\n", __func__, type);
+		break;
+	}
+
+	return 0;
+}
+
 int cifs_swn_register(struct cifs_tcon *tcon)
 {
 	struct cifs_swn_reg *swnreg;

fs/cifs/cifs_swn.h

···
 #define _CIFS_SWN_H
 
 struct cifs_tcon;
+struct sk_buff;
+struct genl_info;
 
 extern int cifs_swn_register(struct cifs_tcon *tcon);
 
 extern int cifs_swn_unregister(struct cifs_tcon *tcon);
+
+extern int cifs_swn_notify(struct sk_buff *skb, struct genl_info *info);
 
 #endif /* _CIFS_SWN_H */

fs/cifs/netlink.c

···
 #include "netlink.h"
 #include "cifsglob.h"
 #include "cifs_debug.h"
+#include "cifs_swn.h"
 
 static const struct nla_policy cifs_genl_policy[CIFS_GENL_ATTR_MAX + 1] = {
 	[CIFS_GENL_ATTR_SWN_REGISTRATION_ID]	= { .type = NLA_U32 },
···
 	[CIFS_GENL_ATTR_SWN_USER_NAME]		= { .type = NLA_STRING },
 	[CIFS_GENL_ATTR_SWN_PASSWORD]		= { .type = NLA_STRING },
 	[CIFS_GENL_ATTR_SWN_DOMAIN_NAME]	= { .type = NLA_STRING },
+	[CIFS_GENL_ATTR_SWN_NOTIFICATION_TYPE]	= { .type = NLA_U32 },
+	[CIFS_GENL_ATTR_SWN_RESOURCE_STATE]	= { .type = NLA_U32 },
+	[CIFS_GENL_ATTR_SWN_RESOURCE_NAME]	= { .type = NLA_STRING},
 };
 
 static struct genl_ops cifs_genl_ops[] = {
+	{
+		.cmd = CIFS_GENL_CMD_SWN_NOTIFY,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = cifs_swn_notify,
+	},
 };
 
 static const struct genl_multicast_group cifs_genl_mcgrps[] = {

include/uapi/linux/cifs/cifs_netlink.h

···
 	CIFS_GENL_ATTR_SWN_USER_NAME,
 	CIFS_GENL_ATTR_SWN_PASSWORD,
 	CIFS_GENL_ATTR_SWN_DOMAIN_NAME,
+	CIFS_GENL_ATTR_SWN_NOTIFICATION_TYPE,
+	CIFS_GENL_ATTR_SWN_RESOURCE_STATE,
+	CIFS_GENL_ATTR_SWN_RESOURCE_NAME,
 	__CIFS_GENL_ATTR_MAX,
 };
 #define CIFS_GENL_ATTR_MAX (__CIFS_GENL_ATTR_MAX - 1)
···
 	CIFS_GENL_CMD_UNSPEC,
 	CIFS_GENL_CMD_SWN_REGISTER,
 	CIFS_GENL_CMD_SWN_UNREGISTER,
+	CIFS_GENL_CMD_SWN_NOTIFY,
 	__CIFS_GENL_CMD_MAX
 };
 #define CIFS_GENL_CMD_MAX (__CIFS_GENL_CMD_MAX - 1)
+
+enum cifs_swn_notification_type {
+	CIFS_SWN_NOTIFICATION_RESOURCE_CHANGE = 0x01,
+	CIFS_SWN_NOTIFICATION_CLIENT_MOVE	 = 0x02,
+	CIFS_SWN_NOTIFICATION_SHARE_MOVE	 = 0x03,
+	CIFS_SWN_NOTIFICATION_IP_CHANGE	 = 0x04,
+};
+
+enum cifs_swn_resource_state {
+	CIFS_SWN_RESOURCE_STATE_UNKNOWN     = 0x00,
+	CIFS_SWN_RESOURCE_STATE_AVAILABLE   = 0x01,
+	CIFS_SWN_RESOURCE_STATE_UNAVAILABLE = 0xFF
+};
 
 #endif /* _UAPILINUX_CIFS_NETLINK_H */