[PATCH v3] nvme: expose TLS mode

[Daniel Wagner <wagi@kernel.org>]

It is not possible to determine the active TLS mode from the
presence or absence of sysfs attributes like tls_key,
tls_configured_key, or dhchap_secret.

With the introduction of the concat mode and optional DH-CHAP
authentication, different configurations can result in identical
sysfs state. This makes user space detection unreliable.

Expose the TLS mode explicitly to allow user space to
unambiguously identify the active configuration and avoid
fragile heuristics in nvme-cli.

Signed-off-by: Daniel Wagner <wagi@kernel.org>
---
Fixed visibilty condition, the previous version used opts->tls_key but it should
opts->tls.

Original cover letter (with fixed example):

I am extending the test suite for nvme-cli to cover the use case of
nvme connect --tls/--concat.

Currently, nvme-cli uses heuristics to determine whether --tls was used
to initiate the connection. With the introduction of --concat, these
heuristics are no longer reliable.

By exposing the TLS mode explicitly, nvme config can now generate a
configuration based on the currently active connection.

$ nvme connect --transport tcp --traddr 192.168.30.30 --trsvcid 4420  \
  		--hostnqn nqn.2014-08.org.nvmexpress:uuid:befdec4c-2234-11b2-a85c-ca77c773af36  \
		--nqn nqn.io-1 --concat  \
		--dhchap-secret=DHHC-1:01:1+pb0VSbn3cBrOhwP5SHa6gwlbPikdZ0mmBKKXC74Sm0s0pb:   \
		--dump-config --output-format json
[
  {
    "hostnqn":"nqn.2014-08.org.nvmexpress:uuid:befdec4c-2234-11b2-a85c-ca77c773af36",
    "hostid":"befdec4c-2234-11b2-a85c-ca77c773af36",
    "dhchap_key":"DHHC-1:01:1+pb0VSbn3cBrOhwP5SHa6gwlbPikdZ0mmBKKXC74Sm0s0pb:",
    "subsystems":[
      {
        "nqn":"nqn.io-1",
        "ports":[
          {
            "transport":"tcp",
            "traddr":"192.168.30.30",
            "trsvcid":"4420",
            "dhchap_key":"DHHC-1:01:1+pb0VSbn3cBrOhwP5SHa6gwlbPikdZ0mmBKKXC74Sm0s0pb:",
            "concat":true
          }
        ]
      }
    ]
  }
]

$ nvme config --scan --dump --output-format json /dev/nvme1
[
  {
    "hostnqn":"nqn.2014-08.org.nvmexpress:uuid:befdec4c-2234-11b2-a85c-ca77c773af36",
    "hostid":"befdec4c-2234-11b2-a85c-ca77c773af36",
    "dhchap_key":"DHHC-1:01:1+pb0VSbn3cBrOhwP5SHa6gwlbPikdZ0mmBKKXC74Sm0s0pb:",
    "subsystems":[
      {
        "nqn":"nqn.io-1",
        "ports":[
          {
            "transport":"tcp",
            "traddr":"192.168.30.30",
            "trsvcid":"4420",
            "dhchap_key":"DHHC-1:01:1+pb0VSbn3cBrOhwP5SHa6gwlbPikdZ0mmBKKXC74Sm0s0pb:",
            "concat":true
          }
        ]
      }
    ]
  }
]

$ cat /sys/class/nvme-fabrics/ctl/nvme1/tls_mode
concat
---
Changes in v3:
- Fixed visibilty conditions to opts->tls instead of opts->tls_key
- Link to v2: https://patch.msgid.link/20260408-expose-tls-mode-v2-1-17a25aa414dc@kernel.org

Changes in v2:
- fixed the example output
- tls_mode only visible when either tls or concat is enabled. avoids 'none'
- Link to v1: https://patch.msgid.link/20260401-expose-tls-mode-v1-1-433a83d1d23f@kernel.org
---
 drivers/nvme/host/sysfs.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c
index 16c6fea4b2db..df25c8fef063 100644
--- a/drivers/nvme/host/sysfs.c
+++ b/drivers/nvme/host/sysfs.c
@@ -841,10 +841,26 @@ static ssize_t tls_keyring_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(tls_keyring);
 
+static ssize_t tls_mode_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
+	const char *mode;
+
+	if (ctrl->opts->tls)
+		mode = "tls";
+	else
+		mode = "concat";
+
+	return sysfs_emit(buf, "%s\n", mode);
+}
+static DEVICE_ATTR_RO(tls_mode);
+
 static struct attribute *nvme_tls_attrs[] = {
 	&dev_attr_tls_key.attr,
 	&dev_attr_tls_configured_key.attr,
 	&dev_attr_tls_keyring.attr,
+	&dev_attr_tls_mode.attr,
 	NULL,
 };
 
@@ -866,6 +882,9 @@ static umode_t nvme_tls_attrs_are_visible(struct kobject *kobj,
 	if (a == &dev_attr_tls_keyring.attr &&
 	    !ctrl->opts->keyring)
 		return 0;
+	if (a == &dev_attr_tls_mode.attr &&
+	    !ctrl->opts->tls && !ctrl->opts->concat)
+		return 0;
 
 	return a->mode;
 }

---
base-commit: 7aaa8047eafd0bd628065b15757d9b48c5f9c07d
change-id: 20260401-expose-tls-mode-10fdb5d459d4

Best regards,
--  
Daniel Wagner <wagi@kernel.org>