scsi: target: Add virtual remote target

Create virtual remote target module.

This can be used to see a whole ACL/LUN/TPG configuration from all nodes in
storage cluster. For example, it permits setting up remote ports in ALUA
port groups. To report all ports in a cluster in REPORT TARGET PORT GROUP
command.

Suggested-by: Konstantin Shelekhin <[e-mail]>
Signed-off-by: Dmitry Bogdanov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Mike Christie <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/target/Kconfig

···
 source "drivers/target/tcm_fc/Kconfig"
 source "drivers/target/iscsi/Kconfig"
 source "drivers/target/sbp/Kconfig"
+source "drivers/target/tcm_remote/Kconfig"
 
 endif

drivers/target/Makefile

···
 obj-$(CONFIG_TCM_FC)		+= tcm_fc/
 obj-$(CONFIG_ISCSI_TARGET)	+= iscsi/
 obj-$(CONFIG_SBP_TARGET)	+= sbp/
+obj-$(CONFIG_REMOTE_TARGET)	+= tcm_remote/

drivers/target/tcm_remote/Kconfig

···
+# SPDX-License-Identifier: GPL-2.0-only
+config REMOTE_TARGET
+	tristate "TCM Virtual Remote target"
+	depends on SCSI
+	help
+	  Say Y here to enable the TCM Virtual Remote fabric
+	  That fabric is a dummy fabric to tell TCM about configuration
+	  of TPG/ACL/LUN on peer nodes in a cluster.

drivers/target/tcm_remote/Makefile

···
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_REMOTE_TARGET)	+= tcm_remote.o

drivers/target/tcm_remote/tcm_remote.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/configfs.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_tcq.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_cmnd.h>
+
+#include <target/target_core_base.h>
+#include <target/target_core_fabric.h>
+
+#include "tcm_remote.h"
+
+static inline struct tcm_remote_tpg *remote_tpg(struct se_portal_group *se_tpg)
+{
+	return container_of(se_tpg, struct tcm_remote_tpg, remote_se_tpg);
+}
+
+static char *tcm_remote_get_endpoint_wwn(struct se_portal_group *se_tpg)
+{
+	/*
+	 * Return the passed NAA identifier for the Target Port
+	 */
+	return &remote_tpg(se_tpg)->remote_hba->remote_wwn_address[0];
+}
+
+static u16 tcm_remote_get_tag(struct se_portal_group *se_tpg)
+{
+	/*
+	 * This Tag is used when forming SCSI Name identifier in EVPD=1 0x83
+	 * to represent the SCSI Target Port.
+	 */
+	return remote_tpg(se_tpg)->remote_tpgt;
+}
+
+static int tcm_remote_dummy_cmd_fn(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static void tcm_remote_dummy_cmd_void_fn(struct se_cmd *se_cmd)
+{
+
+}
+
+static char *tcm_remote_dump_proto_id(struct tcm_remote_hba *remote_hba)
+{
+	switch (remote_hba->remote_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return "SAS";
+	case SCSI_PROTOCOL_SRP:
+		return "SRP";
+	case SCSI_PROTOCOL_FCP:
+		return "FCP";
+	case SCSI_PROTOCOL_ISCSI:
+		return "iSCSI";
+	default:
+		break;
+	}
+
+	return "Unknown";
+}
+
+static int tcm_remote_port_link(
+	struct se_portal_group *se_tpg,
+	struct se_lun *lun)
+{
+	pr_debug("TCM_Remote_ConfigFS: Port Link LUN %lld Successful\n",
+		 lun->unpacked_lun);
+	return 0;
+}
+
+static void tcm_remote_port_unlink(
+	struct se_portal_group *se_tpg,
+	struct se_lun *lun)
+{
+	pr_debug("TCM_Remote_ConfigFS: Port Unlink LUN %lld Successful\n",
+		 lun->unpacked_lun);
+}
+
+static struct se_portal_group *tcm_remote_make_tpg(
+	struct se_wwn *wwn,
+	const char *name)
+{
+	struct tcm_remote_hba *remote_hba = container_of(wwn,
+			struct tcm_remote_hba, remote_hba_wwn);
+	struct tcm_remote_tpg *remote_tpg;
+	unsigned long tpgt;
+	int ret;
+
+	if (strstr(name, "tpgt_") != name) {
+		pr_err("Unable to locate \"tpgt_#\" directory group\n");
+		return ERR_PTR(-EINVAL);
+	}
+	if (kstrtoul(name + 5, 10, &tpgt))
+		return ERR_PTR(-EINVAL);
+
+	if (tpgt >= TL_TPGS_PER_HBA) {
+		pr_err("Passed tpgt: %lu exceeds TL_TPGS_PER_HBA: %u\n",
+		       tpgt, TL_TPGS_PER_HBA);
+		return ERR_PTR(-EINVAL);
+	}
+	remote_tpg = &remote_hba->remote_hba_tpgs[tpgt];
+	remote_tpg->remote_hba = remote_hba;
+	remote_tpg->remote_tpgt = tpgt;
+	/*
+	 * Register the remote_tpg as a emulated TCM Target Endpoint
+	 */
+	ret = core_tpg_register(wwn, &remote_tpg->remote_se_tpg,
+				remote_hba->remote_proto_id);
+	if (ret < 0)
+		return ERR_PTR(-ENOMEM);
+
+	pr_debug("TCM_Remote_ConfigFS: Allocated Emulated %s Target Port %s,t,0x%04lx\n",
+		 tcm_remote_dump_proto_id(remote_hba),
+		 config_item_name(&wwn->wwn_group.cg_item), tpgt);
+	return &remote_tpg->remote_se_tpg;
+}
+
+static void tcm_remote_drop_tpg(struct se_portal_group *se_tpg)
+{
+	struct se_wwn *wwn = se_tpg->se_tpg_wwn;
+	struct tcm_remote_tpg *remote_tpg = container_of(se_tpg,
+				struct tcm_remote_tpg, remote_se_tpg);
+	struct tcm_remote_hba *remote_hba;
+	unsigned short tpgt;
+
+	remote_hba = remote_tpg->remote_hba;
+	tpgt = remote_tpg->remote_tpgt;
+
+	/*
+	 * Deregister the remote_tpg as a emulated TCM Target Endpoint
+	 */
+	core_tpg_deregister(se_tpg);
+
+	remote_tpg->remote_hba = NULL;
+	remote_tpg->remote_tpgt = 0;
+
+	pr_debug("TCM_Remote_ConfigFS: Deallocated Emulated %s Target Port %s,t,0x%04x\n",
+		 tcm_remote_dump_proto_id(remote_hba),
+		 config_item_name(&wwn->wwn_group.cg_item), tpgt);
+}
+
+static struct se_wwn *tcm_remote_make_wwn(
+	struct target_fabric_configfs *tf,
+	struct config_group *group,
+	const char *name)
+{
+	struct tcm_remote_hba *remote_hba;
+	char *ptr;
+	int ret, off = 0;
+
+	remote_hba = kzalloc(sizeof(*remote_hba), GFP_KERNEL);
+	if (!remote_hba)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 * Determine the emulated Protocol Identifier and Target Port Name
+	 * based on the incoming configfs directory name.
+	 */
+	ptr = strstr(name, "naa.");
+	if (ptr) {
+		remote_hba->remote_proto_id = SCSI_PROTOCOL_SAS;
+		goto check_len;
+	}
+	ptr = strstr(name, "fc.");
+	if (ptr) {
+		remote_hba->remote_proto_id = SCSI_PROTOCOL_FCP;
+		off = 3; /* Skip over "fc." */
+		goto check_len;
+	}
+	ptr = strstr(name, "0x");
+	if (ptr) {
+		remote_hba->remote_proto_id = SCSI_PROTOCOL_SRP;
+		off = 2; /* Skip over "0x" */
+		goto check_len;
+	}
+	ptr = strstr(name, "iqn.");
+	if (!ptr) {
+		pr_err("Unable to locate prefix for emulated Target Port: %s\n",
+		       name);
+		ret = -EINVAL;
+		goto out;
+	}
+	remote_hba->remote_proto_id = SCSI_PROTOCOL_ISCSI;
+
+check_len:
+	if (strlen(name) >= TL_WWN_ADDR_LEN) {
+		pr_err("Emulated NAA %s Address: %s, exceeds max: %d\n",
+		       name, tcm_remote_dump_proto_id(remote_hba), TL_WWN_ADDR_LEN);
+		ret = -EINVAL;
+		goto out;
+	}
+	snprintf(&remote_hba->remote_wwn_address[0], TL_WWN_ADDR_LEN, "%s", &name[off]);
+
+	pr_debug("TCM_Remote_ConfigFS: Allocated emulated Target %s Address: %s\n",
+		 tcm_remote_dump_proto_id(remote_hba), name);
+	return &remote_hba->remote_hba_wwn;
+out:
+	kfree(remote_hba);
+	return ERR_PTR(ret);
+}
+
+static void tcm_remote_drop_wwn(struct se_wwn *wwn)
+{
+	struct tcm_remote_hba *remote_hba = container_of(wwn,
+				struct tcm_remote_hba, remote_hba_wwn);
+
+	pr_debug("TCM_Remote_ConfigFS: Deallocating emulated Target %s Address: %s\n",
+		 tcm_remote_dump_proto_id(remote_hba),
+		 remote_hba->remote_wwn_address);
+	kfree(remote_hba);
+}
+
+static ssize_t tcm_remote_wwn_version_show(struct config_item *item, char *page)
+{
+	return sprintf(page, "TCM Remote Fabric module %s\n", TCM_REMOTE_VERSION);
+}
+
+CONFIGFS_ATTR_RO(tcm_remote_wwn_, version);
+
+static struct configfs_attribute *tcm_remote_wwn_attrs[] = {
+	&tcm_remote_wwn_attr_version,
+	NULL,
+};
+
+static const struct target_core_fabric_ops remote_ops = {
+	.module				= THIS_MODULE,
+	.fabric_name			= "remote",
+	.tpg_get_wwn			= tcm_remote_get_endpoint_wwn,
+	.tpg_get_tag			= tcm_remote_get_tag,
+	.check_stop_free		= tcm_remote_dummy_cmd_fn,
+	.release_cmd			= tcm_remote_dummy_cmd_void_fn,
+	.write_pending			= tcm_remote_dummy_cmd_fn,
+	.queue_data_in			= tcm_remote_dummy_cmd_fn,
+	.queue_status			= tcm_remote_dummy_cmd_fn,
+	.queue_tm_rsp			= tcm_remote_dummy_cmd_void_fn,
+	.aborted_task			= tcm_remote_dummy_cmd_void_fn,
+	.fabric_make_wwn		= tcm_remote_make_wwn,
+	.fabric_drop_wwn		= tcm_remote_drop_wwn,
+	.fabric_make_tpg		= tcm_remote_make_tpg,
+	.fabric_drop_tpg		= tcm_remote_drop_tpg,
+	.fabric_post_link		= tcm_remote_port_link,
+	.fabric_pre_unlink		= tcm_remote_port_unlink,
+	.tfc_wwn_attrs			= tcm_remote_wwn_attrs,
+};
+
+static int __init tcm_remote_fabric_init(void)
+{
+	return target_register_template(&remote_ops);
+}
+
+static void __exit tcm_remote_fabric_exit(void)
+{
+	target_unregister_template(&remote_ops);
+}
+
+MODULE_DESCRIPTION("TCM virtual remote target");
+MODULE_AUTHOR("Dmitry Bogdanov <[e-mail]>");
+MODULE_LICENSE("GPL");
+module_init(tcm_remote_fabric_init);
+module_exit(tcm_remote_fabric_exit);

drivers/target/tcm_remote/tcm_remote.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/types.h>
+#include <linux/device.h>
+
+#define TCM_REMOTE_VERSION		"v0.1"
+#define TL_WWN_ADDR_LEN			256
+#define TL_TPGS_PER_HBA			32
+
+struct tcm_remote_tpg {
+	unsigned short remote_tpgt;
+	struct se_portal_group remote_se_tpg;
+	struct tcm_remote_hba *remote_hba;
+};
+
+struct tcm_remote_hba {
+	u8 remote_proto_id;
+	unsigned char remote_wwn_address[TL_WWN_ADDR_LEN];
+	struct tcm_remote_tpg remote_hba_tpgs[TL_TPGS_PER_HBA];
+	struct se_wwn remote_hba_wwn;
+};