ipv6_ext: add fragmentation extension definitions

sys/include/net/ipv6/ext.h

@@ -22,6 +22,7 @@
 
 #include <stdint.h>
 
+#include "net/ipv6/ext/frag.h"
 #include "net/ipv6/ext/rh.h"
 
 #ifdef __cplusplus

sys/include/net/ipv6/ext/frag.h

@@ -0,0 +1,119 @@
+/*
+ * Copyright (C) 2019 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    net_ipv6_ext_frag   IPv6 fragmentation extension
+ * @ingroup     net_ipv6_ext
+ * @brief       Definitions for IPv6 fragmentation extension
+ * @see         [RFC 8200, section 4.5](https://tools.ietf.org/html/rfc8200#section-4.5)
+ * @{
+ *
+ * @file
+ * @brief   Fragmentation extension definitions
+ *
+ * @author  Martine Lenders <m.lenders@fu-berlin.de>
+ */
+#ifndef NET_IPV6_EXT_FRAG_H
+#define NET_IPV6_EXT_FRAG_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "byteorder.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define IPV6_EXT_FRAG_OFFSET_MASK   (0xFFF8)    /**< Mask for the offset */
+#define IPV6_EXT_FRAG_M             (0x0001)    /**< M flag */
+
+/**
+ * @brief   Fragment header definition
+ */
+typedef struct __attribute__((packed)) {
+    uint8_t nh;                     /**< next header */
+    uint8_t resv;                   /**< reserved */
+    /**
+     * @brief   11-bit fragment offset and flags
+     *
+     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+     * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+     * |      Fragment Offset    |Res|M|
+     * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+     */
+    network_uint16_t offset_flags;
+    network_uint32_t id;            /**< identification */
+} ipv6_ext_frag_t;
+
+/**
+ * @brief   Get offset of fragment in bytes
+ *
+ * @param[in] frag  A fragment header
+ *
+ * @return  Offset of fragment in bytes.
+ */
+static inline unsigned ipv6_ext_frag_get_offset(const ipv6_ext_frag_t *frag)
+{
+    /* The offset is left-shifted by 3 bytes in the header * (equivalent to
+     * multiplication with 8), and the offset is in units 8 bytes
+     * so no shifting or multiplying necessary to get offset in bytes */
+    return (byteorder_ntohs(frag->offset_flags) & IPV6_EXT_FRAG_OFFSET_MASK);
+}
+
+/**
+ * @brief   Checks if more fragments are coming after the given fragment
+ *
+ * @param[in] frag  A fragment header
+ *
+ * @return  true, when more fragments are coming after the given fragment.
+ * @return  false, when the given fragment is the last.
+ */
+static inline bool ipv6_ext_frag_more(const ipv6_ext_frag_t *frag)
+{
+    return (byteorder_ntohs(frag->offset_flags) & IPV6_EXT_FRAG_M);
+}
+
+/**
+ * @brief   Sets the offset field of a fragment header
+ *
+ * @note    Must be called before @ref ipv6_ext_frag_set_more()
+ *
+ * @param[in,out] frag  A fragment header
+ * @param[in] offset    The offset of the fragment in bytes.
+ *                      Is assumed to be a multiple of 8.
+ *                      Is assumed to be lesser or equal to 65528.
+ */
+static inline void ipv6_ext_frag_set_offset(ipv6_ext_frag_t *frag,
+                                            unsigned offset)
+{
+    /* The offset is left-shifted by 3 bytes in the header * (equivalent to
+     * multiplication with 8), and the offset is a multiple of 8 bytes
+     * so no shifting or division necessary to set offset in units of 8 bytes */
+    frag->offset_flags = byteorder_htons(offset & IPV6_EXT_FRAG_OFFSET_MASK);
+}
+
+/**
+ * @brief   Sets the M flag of a fragment header
+ *
+ * @note    Must be called after @ref ipv6_ext_frag_set_offset()
+ *
+ * @param[in,out] frag      A fragment header
+ */
+static inline void ipv6_ext_frag_set_more(ipv6_ext_frag_t *frag)
+{
+    frag->offset_flags.u8[1] |= IPV6_EXT_FRAG_M;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* NET_IPV6_EXT_FRAG_H */
+/** @} */