From d98b217dee02f436c1c3fe99e2c87b92a1019d9d Mon Sep 17 00:00:00 2001
From: David Teigland <teigland@redhat.com>
Date: Dec 12 2023 19:46:26 +0000
Subject: sanlock: use product_uuid for host name


When there is no host name specified on the command line
or in the config file, use the value from
/sys/devices/virtual/dmi/id/product_uuid instead of
generating a random UUID each time the daemon is started.
If no product_uuid exists, the random UUID will be generated
for the host name.

---

diff --git a/src/main.c b/src/main.c
index a9ceee5..4e7f3c0 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1473,37 +1473,64 @@ int get_rand(int a, int b)
 	return a + (int) (((float)(b - a + 1)) * rv / (RAND_MAX+1.0));
 }
 
+static void read_product_uuid(char *buf, size_t buf_size)
+{
+	FILE *fp;
+	size_t len;
+
+	if (!(fp = fopen("/sys/devices/virtual/dmi/id/product_uuid", "r")))
+		return;
+
+	if (!fgets(buf, buf_size, fp))
+		return;
+
+	if ((len = strlen(buf)) && buf[len - 1] == '\n')
+		buf[--len] = '\0';
+
+	fclose(fp);
+}
+
 static void setup_host_name(void)
 {
-	struct utsname name;
+	char product_uuid[SANLK_NAME_LEN+1] = { 0 };
 	char uuid[37];
+	struct utsname name;
 	uuid_t uu;
 	int ret;
 
-	memset(rand_state, 0, sizeof(rand_state));
-	initstate(time(NULL), rand_state, sizeof(rand_state));
-
-	/* use host name from command line */
+	/*
+	 * Get host name value from:
+	 * 1. command line
+	 * 2. config file
+	 * 3. /sys/devices/virtual/dmi/id/product_uuid
+	 * 4. generate random uuid that won't collide with another host
+	 */
 
 	if (com.our_host_name[0]) {
 		memcpy(our_host_name_global, com.our_host_name, SANLK_NAME_LEN);
 		return;
 	}
 
-	/* make up something that's likely to be different among hosts */
-
 	memset(&our_host_name_global, 0, sizeof(our_host_name_global));
+	memset(product_uuid, 0, sizeof(product_uuid));
 	memset(&name, 0, sizeof(name));
 	memset(&uuid, 0, sizeof(uuid));
 
+	read_product_uuid(product_uuid, sizeof(product_uuid));
 	uname(&name);
-	uuid_generate(uu);
-	uuid_unparse_lower(uu, uuid);
 
-	ret = snprintf(our_host_name_global, NAME_ID_SIZE, "%s.", uuid);
+	if (product_uuid[0]) {
+		ret = snprintf(our_host_name_global, SANLK_NAME_LEN, "%s.", product_uuid);
+	} else {
+		memset(rand_state, 0, sizeof(rand_state));
+		initstate(time(NULL), rand_state, sizeof(rand_state));
+		uuid_generate(uu);
+		uuid_unparse_lower(uu, uuid);
+		ret = snprintf(our_host_name_global, SANLK_NAME_LEN, "%s.", uuid);
+	}
 
-	if (ret < NAME_ID_SIZE)
-		memcpy(our_host_name_global+ret, name.nodename, NAME_ID_SIZE-ret);
+	if (ret < SANLK_NAME_LEN)
+		memcpy(our_host_name_global+ret, name.nodename, SANLK_NAME_LEN-ret);
 }
 
 static void setup_limits(void)
diff --git a/src/sanlock.8 b/src/sanlock.8
index 0776b8f..5295bf5 100644
--- a/src/sanlock.8
+++ b/src/sanlock.8
@@ -120,9 +120,9 @@ delta lease disk sector, reading it back after a delay, and verifying
 it is the same.
 
 .IP \[bu]
-If a unique host name is not specified, sanlock generates a uuid to use
-as the host's name.  The delta lease algorithm depends on hosts using
-unique names.
+If a unique host name is not specified, sanlock uses the product_uuid
+if one is available, otherwise generates a uuid to use as the host's
+name.  The delta lease algorithm depends on hosts using unique names.
 
 .IP \[bu]
 The application on each host should be configured with a unique host_id,