From 07b27b7d9d7fc4359d5b500aaf76e9f81886c798 Mon Sep 17 00:00:00 2001
From: pantonshire <tom@tomandtally.co.uk>
Date: Sun, 6 Sep 2026 10:24:28 +0100
Subject: [PATCH] ipv4 helper macro

---
 include/public/endian.h | 21 +++++++++++++++++++++
 include/public/net.h    | 20 ++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 include/public/endian.h

diff --git a/include/public/endian.h b/include/public/endian.h
new file mode 100644
index 0000000..4105a7a
--- /dev/null
+++ b/include/public/endian.h
@@ -0,0 +1,21 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#pragma once
+
+#if !defined(__BYTE_ORDER__)
+#error "__BYTE_ORDER__ not defined"
+#elif !defined(__ORDER_BIG_ENDIAN__)
+#error "__ORDER_BIG_ENDIAN__ not defined"
+#elif !defined(__ORDER_LITTLE_ENDIAN__)
+#error "__ORDER_LITTLE_ENDIAN__ not defined"
+#endif
+
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define TLSL_BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define TLSL_LITTLE_ENDIAN
+#else
+#error "__BYTE_ORDER__ invalid"
+#endif
diff --git a/include/public/net.h b/include/public/net.h
index 4ef21bc..d3d0632 100644
--- a/include/public/net.h
+++ b/include/public/net.h
@@ -7,6 +7,7 @@
 #include <stdint.h>
 
 #include "str.h"
+#include "endian.h"
 
 enum {
   TLSL_L3PROTO_IPV4,
@@ -29,5 +30,24 @@ struct tlsl_ip_addr {
   uint8_t l3proto;
 };
 
+#if defined(TLSL_BIG_ENDIAN)
+#define TLSL_IPV4_ADDR_U32(BYTE0, BYTE1, BYTE2, BYTE3) \
+  (((uint32_t)(BYTE0))                                 \
+    | ((uint32_t)(BYTE1) << 8)                         \
+    | ((uint32_t)(BYTE1) << 16)                        \
+    | ((uint32_t)(BYTE1) << 24))
+#elif defined(TLSL_LITTLE_ENDIAN)
+#define TLSL_IPV4_ADDR_U32(BYTE0, BYTE1, BYTE2, BYTE3) \
+  (((uint32_t)(BYTE0) << 24)                           \
+    | ((uint32_t)(BYTE1) << 16)                        \
+    | ((uint32_t)(BYTE2) << 8)                         \
+    | ((uint32_t)(BYTE3)))
+#else
+#error "Byte order not set"
+#endif
+
+#define TLSL_IPV4_ADDR(BYTE0, BYTE1, BYTE2, BYTE3) \
+  ((struct tlsl_ipv4_addr) { .addr = TLSL_IPV4_ADDR_U32(BYTE0, BYTE1, BYTE2, BYTE3) })
+
 int tlsl_ip_addr_parse(const char *s, struct tlsl_ip_addr *out);
 str_buf_t tlsl_ip_addr_fmt(const struct tlsl_ip_addr *a);