[PATCH 04/11] nvmet-tcp: register target mptcp transport

[Geliang Tang]

From: Geliang Tang <tanggeliang at kylinos.cn>

This patch adds a new nvme target transport type NVMF_TRTYPE_MPTCP for
MPTCP. And defines a new nvmet_fabrics_ops named nvmet_mptcp_ops, which
is almost the same as nvmet_tcp_ops except .type. It is registered in
nvmet_tcp_init() and unregistered in nvmet_tcp_exit().

A MODULE_ALIAS for "nvmet-transport-4" is also added.

Note: NVMF_TRTYPE_MPTCP is temporarily assigned 4, a value currently
reserved in the NVMe over Fabrics specification. During "NVMe over
MPTCP" discussion at the LSF/MM/BPF 2026 conference, it was concluded
that MPTCP should be treated as a new transport type, rather than a
TCP variant. A request will be submitted to the NVMe working group to
officially allocate this value for MPTCP.

Cc: Hannes Reinecke <hare at suse.de>
Cc: John Meneghini <jmeneghi at redhat.com>
Cc: Randy Jennings <randyj at purestorage.com>
Cc: Nilay Shroff <nilay at linux.ibm.com>
Co-developed-by: zhenwei pi <zhenwei.pi at linux.dev>
Signed-off-by: zhenwei pi <zhenwei.pi at linux.dev>
Co-developed-by: Hui Zhu <zhuhui at kylinos.cn>
Signed-off-by: Hui Zhu <zhuhui at kylinos.cn>
Co-developed-by: Gang Yan <yangang at kylinos.cn>
Signed-off-by: Gang Yan <yangang at kylinos.cn>
Signed-off-by: Geliang Tang <tanggeliang at kylinos.cn>
---
 drivers/nvme/target/configfs.c |  1 +
 drivers/nvme/target/tcp.c      | 29 +++++++++++++++++++++++++++++
 include/linux/nvme.h           |  1 +
 3 files changed, 31 insertions(+)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index b88f897f06e2..51fc0f4d0c32 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -37,6 +37,7 @@ static struct nvmet_type_name_map nvmet_transport[] = {
 	{ NVMF_TRTYPE_RDMA,	"rdma" },
 	{ NVMF_TRTYPE_FC,	"fc" },
 	{ NVMF_TRTYPE_TCP,	"tcp" },
+	{ NVMF_TRTYPE_MPTCP,	"mptcp" },
 	{ NVMF_TRTYPE_PCI,	"pci" },
 	{ NVMF_TRTYPE_LOOP,	"loop" },
 };
diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 83fe001fc619..e2f3de364c2b 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -2299,6 +2299,23 @@ static const struct nvmet_fabrics_ops nvmet_tcp_ops = {
 	.host_traddr		= nvmet_tcp_host_port_addr,
 };
 
+#ifdef CONFIG_MPTCP
+static bool nvmet_mptcp_registered;
+
+static const struct nvmet_fabrics_ops nvmet_mptcp_ops = {
+	.owner			= THIS_MODULE,
+	.type			= NVMF_TRTYPE_MPTCP,
+	.msdbd			= 1,
+	.add_port		= nvmet_tcp_add_port,
+	.remove_port		= nvmet_tcp_remove_port,
+	.queue_response		= nvmet_tcp_queue_response,
+	.delete_ctrl		= nvmet_tcp_delete_ctrl,
+	.install_queue		= nvmet_tcp_install_queue,
+	.disc_traddr		= nvmet_tcp_disc_port_addr,
+	.host_traddr		= nvmet_tcp_host_port_addr,
+};
+#endif
+
 static int __init nvmet_tcp_init(void)
 {
 	int ret;
@@ -2312,6 +2329,11 @@ static int __init nvmet_tcp_init(void)
 	if (ret)
 		goto err;
 
+#ifdef CONFIG_MPTCP
+	if (!nvmet_register_transport(&nvmet_mptcp_ops))
+		nvmet_mptcp_registered = true;
+#endif
+
 	return 0;
 err:
 	destroy_workqueue(nvmet_tcp_wq);
@@ -2322,6 +2344,10 @@ static void __exit nvmet_tcp_exit(void)
 {
 	struct nvmet_tcp_queue *queue;
 
+#ifdef CONFIG_MPTCP
+	if (nvmet_mptcp_registered)
+		nvmet_unregister_transport(&nvmet_mptcp_ops);
+#endif
 	nvmet_unregister_transport(&nvmet_tcp_ops);
 
 	flush_workqueue(nvmet_wq);
@@ -2341,3 +2367,6 @@ module_exit(nvmet_tcp_exit);
 MODULE_DESCRIPTION("NVMe target TCP transport driver");
 MODULE_LICENSE("GPL v2");
 MODULE_ALIAS("nvmet-transport-3"); /* 3 == NVMF_TRTYPE_TCP */
+#ifdef CONFIG_MPTCP
+MODULE_ALIAS("nvmet-transport-4"); /* 4 == NVMF_TRTYPE_MPTCP */
+#endif
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index 041f30931a90..0eada1e0c652 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -68,6 +68,7 @@ enum {
 	NVMF_TRTYPE_RDMA	= 1,	/* RDMA */
 	NVMF_TRTYPE_FC		= 2,	/* Fibre Channel */
 	NVMF_TRTYPE_TCP		= 3,	/* TCP/IP */
+	NVMF_TRTYPE_MPTCP	= 4,	/* Multipath TCP */
 	NVMF_TRTYPE_LOOP	= 254,	/* Reserved for host usage */
 	NVMF_TRTYPE_MAX,
 };
-- 
2.53.0