From 6816bcf104d69f9e306b3fca6dd8d0210c8bd172 Mon Sep 17 00:00:00 2001
From: Andrew Cornford <andrewcornford@groupmsl.co.uk>
Date: Tue, 7 Jul 2026 11:46:30 +0100
Subject: [PATCH] Allow application to set DHCP hostname (option 12) of varying
 size without modifying library code

---
 Internet/DHCP/dhcp.c | 10 +++++++++-
 Internet/DHCP/dhcp.h | 14 +++++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/Internet/DHCP/dhcp.c b/Internet/DHCP/dhcp.c
index 3925ca8..fcfb1e9 100644
--- a/Internet/DHCP/dhcp.c
+++ b/Internet/DHCP/dhcp.c
@@ -213,7 +213,7 @@ uint32_t DHCP_XID;      // Any number
 
 RIP_MSG* pDHCPMSG;      // Buffer pointer for DHCP processing
 
-uint8_t HOST_NAME[] = DCHP_HOST_NAME;
+uint8_t HOST_NAME[DHCP_HOST_NAME_MAX_LEN + 1] = DHCP_HOST_NAME;
 
 uint8_t DHCP_CHADDR[6]; // DHCP Client MAC address.
 
@@ -331,6 +331,14 @@ void reg_dhcp_cbfunc(void(*ip_assign)(void), void(*ip_update)(void), void(*ip_co
     }
 }
 
+void DHCP_set_hostname(const char* hostname) {
+    uint8_t i;
+    for (i = 0; i < DHCP_HOST_NAME_MAX_LEN && hostname[i] != 0; i++) {
+        HOST_NAME[i] = (uint8_t)hostname[i];
+    }
+    HOST_NAME[i] = 0;
+}
+
 /* make the common DHCP message */
 void makeDHCPMSG(void) {
     uint8_t  bk_mac[6];
diff --git a/Internet/DHCP/dhcp.h b/Internet/DHCP/dhcp.h
index 7d13a32..d83d79d 100644
--- a/Internet/DHCP/dhcp.h
+++ b/Internet/DHCP/dhcp.h
@@ -73,7 +73,10 @@ extern "C" {
 
 #define MAGIC_COOKIE             0x63825363  ///< You should not modify it number.
 
-#define DCHP_HOST_NAME           "WIZnet\0"
+#define DHCP_HOST_NAME           "WIZnet\0"
+
+/* Maximum length (excluding null terminator) of a hostname set via @ref DHCP_set_hostname */
+#define DHCP_HOST_NAME_MAX_LEN   32
 
 /*
     @brief return value of @ref DHCP_run()
@@ -108,6 +111,15 @@ void DHCP_time_handler(void);
 */
 void reg_dhcp_cbfunc(void(*ip_assign)(void), void(*ip_update)(void), void(*ip_conflict)(void));
 
+/*
+    @brief Set the hostname (DHCP option 12) sent with DISCOVER/REQUEST messages
+    @param hostname - null-terminated hostname string. Truncated to @ref DHCP_HOST_NAME_MAX_LEN
+                      characters if longer. May be called at any time before/while DHCP is running;
+                      takes effect on the next message sent.
+    @note If never called, defaults to @ref DHCP_HOST_NAME
+*/
+void DHCP_set_hostname(const char* hostname);
+
 /*
     @brief DHCP client in the main loop
     @return    The value is as the follow \n