net: hostname: Add a function to set the hostname postfix as is.

Fixes: #72363

The existing function to set the postfix is converting postfix
string to hexadecimal. Adding a new function to handle a use case
where the provided postfix should be used as is without any conversion.

Signed-off-by: Vineeta S Narkhede <VineetaSNarkhede@Eaton.com>

doc/connectivity/networking/api/net_hostname.rst

@@ -27,10 +27,12 @@ interface is used as a postfix. In Ethernet networks, the link local address
 refers to MAC address. For example, if the link local address is
 ``01:02:03:04:05:06``, then the unique hostname could be
 ``zephyr010203040506``. If you want to set the prefix yourself, then call
-``net_hostname_set_postfix()`` before the network interfaces are created.
+``net_hostname_set_postfix_str()`` before the network interfaces are created.
-For example for the Ethernet networks, the initialization priority is set by
+Alternatively, if you prefer a hexadecimal conversion for the prefix, then call
-:kconfig:option:`CONFIG_ETH_INIT_PRIORITY` so you would need to set the postfix before
+``net_hostname_set_postfix()``. For example for the Ethernet networks,
-that. The postfix can be set only once.
+the initialization priority is set by :kconfig:option:`CONFIG_ETH_INIT_PRIORITY`
+so you would need to set the postfix before that.
+The postfix can be set only once.
 
 API Reference
 *************

include/zephyr/net/hostname.h

@@ -94,11 +94,12 @@ static inline void net_hostname_init(void)
 /**
  * @brief Set the device hostname postfix
  *
- * @details Set the device hostname to some value. This is only used if
+ * @details Convert the hostname postfix to hexadecimal value and set the
+ * device hostname with the converted value. This is only used if
  * CONFIG_NET_HOSTNAME_UNIQUE is set.
  *
  * @param hostname_postfix Usually link address. The function will convert this
- * to a string.
+ * to a hexadecimal string.
  * @param postfix_len Length of the hostname_postfix array.
  *
  * @return 0 if ok, <0 if error
@@ -116,6 +117,33 @@ static inline int net_hostname_set_postfix(const uint8_t *hostname_postfix,
 }
 #endif /* CONFIG_NET_HOSTNAME_UNIQUE */
 
+/**
+ * @brief Set the postfix string for the network hostname.
+ *
+ * @details Set the hostname postfix string for the network hostname as is, without any conversion.
+ * This is only used if CONFIG_NET_HOSTNAME_UNIQUE is set. The function checks if the combined
+ * length of the default hostname (defined by CONFIG_NET_HOSTNAME) and the postfix does not exceed
+ * NET_HOSTNAME_MAX_LEN. If the postfix is too long, the function returns an
+ * error.
+ *
+ * @param hostname_postfix Pointer to the postfix string to be appended to the network hostname.
+ * @param postfix_len Length of the hostname_postfix array.
+ *
+ * @return 0 if ok, <0 if error
+ */
+#if defined(CONFIG_NET_HOSTNAME_UNIQUE)
+int net_hostname_set_postfix_str(const uint8_t *hostname_postfix,
+			     int postfix_len);
+#else
+static inline int net_hostname_set_postfix_str(const uint8_t *hostname_postfix,
+					   int postfix_len)
+{
+	ARG_UNUSED(hostname_postfix);
+	ARG_UNUSED(postfix_len);
+	return -EMSGSIZE;
+}
+#endif /* CONFIG_NET_HOSTNAME_UNIQUE */
+
 /**
  * @}
  */

subsys/net/hostname.c

@@ -90,6 +90,41 @@ int net_hostname_set_postfix(const uint8_t *hostname_postfix,
 
 	NET_DBG("New hostname %s", hostname);
 
+#if !defined(CONFIG_NET_HOSTNAME_UNIQUE_UPDATE)
+	postfix_set = true;
+#endif
+	trigger_net_event();
+
+	return 0;
+}
+
+int net_hostname_set_postfix_str(const uint8_t *hostname_postfix,
+			     int postfix_len)
+{
+#if !defined(CONFIG_NET_HOSTNAME_UNIQUE_UPDATE)
+	static bool postfix_set;
+#endif
+	int net_hostname_len = sizeof(CONFIG_NET_HOSTNAME) - 1;
+	int hostname_len_remain = (NET_HOSTNAME_MAX_LEN - net_hostname_len) + 1;
+
+#if !defined(CONFIG_NET_HOSTNAME_UNIQUE_UPDATE)
+	if (postfix_set) {
+		return -EALREADY;
+	}
+#endif
+
+	NET_ASSERT(postfix_len > 0);
+
+	if (hostname_len_remain < postfix_len) {
+		NET_DBG("Hostname postfix length %d is exceeding limit of %d", postfix_len,
+			hostname_len_remain);
+		return -EMSGSIZE;
+	}
+
+	snprintk(&hostname[net_hostname_len], hostname_len_remain, "%s", hostname_postfix);
+
+	NET_DBG("New Unique hostname: %s", hostname);
+
 #if !defined(CONFIG_NET_HOSTNAME_UNIQUE_UPDATE)
 	postfix_set = true;
 #endif