Use a systemd app-specific machine ID for hostnqn

If /etc/nvme/hostnqn is not present, the fabric commands will ask
systemd for an app-specific machine ID as a fallback.  This should
improve functionality if /etc/nvme/hostnqn is not present and should
allow packagers to avoid creating /etc/nvme/hostnqn.

Heavily based on an earlier patch from Tomasz Torcz.

Signed-off-by: Tomasz Torcz <[email protected]>
Signed-off-by: Andy Lutomirski <[email protected]>

Author: amluto

Documentation/nvme-show-hostnqn.txt

@@ -0,0 +1,29 @@
+nvme-show-hostnqn(1)
+===================
+
+NAME
+----
+nvme-show-hostnqn - Generate a host NVMe Qualified Name
+
+SYNOPSIS
+--------
+[verse]
+'nvme show-hostnqn'
+
+DESCRIPTION
+-----------
+Show the host NQN configured for the system.  If /etc/nvme/hostnqn is
+not present and systemd application-specific machine IDs are available,
+this will show the systemd-generated host NQN for the system.
+
+OPTIONS
+-------
+No options needed
+
+EXAMPLES
+--------
+nvme show-hostnqn
+
+NVME
+----
+Part of the nvme-user suite

Makefile

@@ -2,6 +2,7 @@ CFLAGS ?= -O2 -g -Wall -Werror
 override CFLAGS += -std=gnu99 -I.
 override CPPFLAGS += -D_GNU_SOURCE -D__CHECK_ENDIAN__
 LIBUUID = $(shell $(LD) -o /dev/null -luuid >/dev/null 2>&1; echo $$?)
+HAVE_SYSTEMD = $(shell pkg-config --exists systemd  --atleast-version=232; echo $$?)
 NVME = nvme
 INSTALL ?= install
 DESTDIR =
@@ -22,6 +23,11 @@ endif
 
 INC=-Iutil
 
+ifeq ($(HAVE_SYSTEMD),0)
+	override LDFLAGS += -lsystemd
+	override CFLAGS += -DHAVE_SYSTEMD
+endif
+
 RPMBUILD = rpmbuild
 TAR = tar
 RM = rm -f

fabrics.c

@@ -43,6 +43,11 @@
 
 #include "common.h"
 
+#ifdef HAVE_SYSTEMD
+#include <systemd/sd-id128.h>
+#define NVME_HOSTNQN_ID SD_ID128_MAKE(c7,f4,61,81,12,be,49,32,8c,83,10,6f,9d,dd,d8,6b)
+#endif
+
 #define NVMF_HOSTID_SIZE	36
 
 static struct config {
@@ -563,11 +568,11 @@ static void save_discovery_log(struct nvmf_disc_rsp_page_hdr *log, int numrec)
 	close(fd);
 }
 
-static int nvmf_hostnqn_file(void)
+static char *hostnqn_read_file(void)
 {
 	FILE *f;
 	char hostnqn[NVMF_NQN_SIZE];
-	int ret = false;
+	char *ret = NULL;
 
 	f = fopen(PATH_NVMF_HOSTNQN, "r");
 	if (f == NULL)
@@ -576,16 +581,54 @@ static int nvmf_hostnqn_file(void)
 	if (fgets(hostnqn, sizeof(hostnqn), f) == NULL)
 		goto out;
 
-	cfg.hostnqn = strndup(hostnqn, strcspn(hostnqn, "\n"));
-	if (!cfg.hostnqn)
-		goto out;
+	ret = strndup(hostnqn, strcspn(hostnqn, "\n"));
 
-	ret = true;
 out:
 	fclose(f);
 	return ret;
 }
 
+static char *hostnqn_generate_systemd(void)
+{
+#ifdef HAVE_SYSTEMD
+	sd_id128_t id;
+	char *ret;
+
+	if (sd_id128_get_machine_app_specific(NVME_HOSTNQN_ID, &id) < 0)
+		return NULL;
+
+	if (asprintf(&ret, "nqn.2014-08.org.nvmexpress:uuid:" SD_ID128_FORMAT_STR "\n", SD_ID128_FORMAT_VAL(id)) == -1)
+		ret = NULL;
+
+	return ret;
+#else
+	return NULL;
+#endif
+}
+
+/* returns an allocated string or NULL */
+char *hostnqn_read(void)
+{
+	char *ret;
+
+	ret = hostnqn_read_file();
+	if (ret)
+		return ret;
+
+	ret = hostnqn_generate_systemd();
+	if (ret)
+		return ret;
+
+	return NULL;
+}
+
+static int nvmf_hostnqn_file(void)
+{
+	cfg.hostnqn = hostnqn_read();
+
+	return cfg.hostnqn != NULL;
+}
+
 static int nvmf_hostid_file(void)
 {
 	FILE *f;

fabrics.h

@@ -3,6 +3,8 @@
 
 #define NVMF_DEF_DISC_TMO	30
 
+extern char *hostnqn_read(void);
+
 extern int discover(const char *desc, int argc, char **argv, bool connect);
 extern int connect(const char *desc, int argc, char **argv);
 extern int disconnect(const char *desc, int argc, char **argv);

nvme-builtin.h

@@ -70,6 +70,7 @@ COMMAND_LIST(
 	ENTRY("disconnect", "Disconnect from NVMeoF subsystem", disconnect_cmd)
 	ENTRY("disconnect-all", "Disconnect from all connected NVMeoF subsystems", disconnect_all_cmd)
 	ENTRY("gen-hostnqn", "Generate NVMeoF host NQN", gen_hostnqn_cmd)
+	ENTRY("show-hostnqn", "Show NVMeoF host NQN", show_hostnqn_cmd)
 	ENTRY("dir-receive", "Submit a Directive Receive command, return results", dir_receive)
 	ENTRY("dir-send", "Submit a Directive Send command, return results", dir_send)
 	ENTRY("virt-mgmt", "Manage Flexible Resources between Primary and Secondary Controller ", virtual_mgmt)

nvme.c

@@ -5026,6 +5026,21 @@ static int gen_hostnqn_cmd(int argc, char **argv, struct command *command, struc
 }
 #endif
 
+static int show_hostnqn_cmd(int argc, char **argv, struct command *command, struct plugin *plugin)
+{
+	char *hostnqn;
+
+	hostnqn = hostnqn_read();
+	if (hostnqn) {
+		fputs(hostnqn, stdout);
+		free(hostnqn);
+		return 0;
+	} else {
+		fprintf(stderr, "hostnqn is not available -- use nvme gen-hostnqn\n");
+		return -ENOENT;
+	}
+}
+
 static int discover_cmd(int argc, char **argv, struct command *command, struct plugin *plugin)
 {
 	const char *desc = "Send Get Log Page request to Discovery Controller.";