include: uapi: linux: add rpl sr header definition

This patch adds a uapi header for rpl struct definition. The segments
data can be accessed over rpl_segaddr or rpl_segdata macros. In case of
compri and compre is zero the segment data is not compressed and can be
accessed by rpl_segaddr. In the other case the compressed data can be
accessed by rpl_segdata and interpreted as byte array.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/rpl.h

@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
+/*
+ *  IPv6 RPL-SR implementation
+ *
+ *  Author:
+ *  (C) 2020 Alexander Aring <alex.aring@gmail.com>
+ */
+
+#ifndef _UAPI_LINUX_RPL_H
+#define _UAPI_LINUX_RPL_H
+
+#include <asm/byteorder.h>
+#include <linux/types.h>
+#include <linux/in6.h>
+
+/*
+ * RPL SR Header
+ */
+struct ipv6_rpl_sr_hdr {
+	__u8	nexthdr;
+	__u8	hdrlen;
+	__u8	type;
+	__u8	segments_left;
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+	__u32	cmpre:4,
+		cmpri:4,
+		reserved:4,
+		pad:4,
+		reserved1:16;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+	__u32	reserved:20,
+		pad:4,
+		cmpri:4,
+		cmpre:4;
+#else
+#error  "Please fix <asm/byteorder.h>"
+#endif
+
+	union {
+		struct in6_addr addr[0];
+		__u8 data[0];
+	} segments;
+} __attribute__((packed));
+
+#define rpl_segaddr	segments.addr
+#define rpl_segdata	segments.data
+
+#endif