net: add set hostname function

This commit adds a function to set the hostname on runtime.

Signed-off-by: Gerhard Jörges <joerges@metratec.com>

include/zephyr/net/hostname.h

@@ -22,10 +22,16 @@ extern "C" {
  * @{
  */
 
+#if defined(CONFIG_NET_HOSTNAME_MAX_LEN)
 #define NET_HOSTNAME_MAX_LEN                                                                       \
+	MAX(CONFIG_NET_HOSTNAME_MAX_LEN,                                                           \
 	    (sizeof(CONFIG_NET_HOSTNAME) - 1 +                                                     \
-	 (IS_ENABLED(CONFIG_NET_HOSTNAME_UNIQUE) ?	\
+	     (IS_ENABLED(CONFIG_NET_HOSTNAME_UNIQUE) ? sizeof("0011223344556677") - 1 : 0)))
-	  sizeof("0011223344556677") - 1 : 0))
+#else
+#define NET_HOSTNAME_MAX_LEN                                                                       \
+	(sizeof(CONFIG_NET_HOSTNAME) - 1 +                                                         \
+	 (IS_ENABLED(CONFIG_NET_HOSTNAME_UNIQUE) ? sizeof("0011223344556677") - 1 : 0))
+#endif
 
 #if defined(CONFIG_NET_HOSTNAME_ENABLE)
 #define NET_HOSTNAME_SIZE NET_HOSTNAME_MAX_LEN + 1
@@ -49,6 +55,23 @@ static inline const char *net_hostname_get(void)
 }
 #endif /* CONFIG_NET_HOSTNAME_ENABLE */
 
+/**
+ * @brief Set the device hostname
+ *
+ * @param host new hostname as char array.
+ * @param len Length of the hostname array.
+ *
+ * @return 0 if ok, <0 on error
+ */
+#if defined(CONFIG_NET_HOSTNAME_DYNAMIC)
+int net_hostname_set(char *host, size_t len);
+#else
+static inline int net_hostname_set(char *host, size_t len)
+{
+	return -ENOTSUP;
+}
+#endif
+
 /**
  * @brief Initialize and set the device hostname.
  *

subsys/net/Kconfig.hostname

@@ -17,10 +17,25 @@ config NET_HOSTNAME
 	help
 	  The string should be a valid hostname.
 
+config NET_HOSTNAME_DYNAMIC
+	bool "Allow the hostname to be set by the application"
+	depends on !NET_HOSTNAME_UNIQUE_UPDATE
+	help
+	  This will enable the net_hostname_set() function. NET_HOSTNAME
+	  will be used as default hostname.
+
+config NET_HOSTNAME_MAX_LEN
+	int "The maximum allowed hostname length"
+	depends on NET_HOSTNAME_DYNAMIC
+	range 1 63
+	default 63
+	help
+	  This will set the number of bytes allocateed for the hostname.
+
 config NET_HOSTNAME_UNIQUE
 	bool "Make hostname unique"
 	help
-	  This will append link address to hostname to create a unique
+	  This will append link address to NET_HOSTNAME to create a unique
 	  hostname. For example, zephyr00005e005357 could be the hostname
 	  if this setting is enabled.
 

subsys/net/hostname.c

@@ -37,6 +37,23 @@ const char *net_hostname_get(void)
 	return hostname;
 }
 
+#if defined(CONFIG_NET_HOSTNAME_DYNAMIC)
+int net_hostname_set(char *host, size_t len)
+{
+	if (len > NET_HOSTNAME_MAX_LEN) {
+		return -ENOMEM;
+	}
+
+	memcpy(hostname, host, len);
+	hostname[len] = 0;
+
+	NET_DBG("New hostname %s", hostname);
+	trigger_net_event();
+
+	return 0;
+}
+#endif
+
 #if defined(CONFIG_NET_HOSTNAME_UNIQUE)
 int net_hostname_set_postfix(const uint8_t *hostname_postfix,
 			     int postfix_len)
@@ -62,8 +79,8 @@ int net_hostname_set_postfix(const uint8_t *hostname_postfix,
 	}
 
 	for (i = 0; i < postfix_len; i++, pos += 2) {
-		snprintk(&hostname[sizeof(CONFIG_NET_HOSTNAME) - 1 + pos],
+		snprintk(&hostname[sizeof(CONFIG_NET_HOSTNAME) - 1 + pos], 2 + 1, "%02x",
-			 2 + 1, "%02x", hostname_postfix[i]);
+			 hostname_postfix[i]);
 	}
 
 	NET_DBG("New hostname %s", hostname);