IPv6: Implement IPv6 prefix assignment via ICMPv6 router advertisement

The 3GPP specs are quite strange when it comes to how an IPv6 address
or rather prefix is assigned to an IPv6 PDP context.  The designated
method for allocating the IPv6 address via the PDP EUA (End User
Address) Information Element in the GTP signalling plane is *not*
used to allocate the address/prefix.  Instead, the EUA is used to
allocate an "interface identifier" to the MS, which it the uses
to derive its link-local source address to send a router solicitation.

The GGSN subsequently answers witha router advertisement, advertising
a single/64 prefix, whihcthe MS then uses to generate it's real IPv6
source address for subsequent communication.

Change-Id: Icddf7d30e01d76a4784bcef5787b36f52f703a9f

1 files changed, 211 insertions, 0 deletions

diff --git a/ggsn/checksum.c b/ggsn/checksum.c
new file mode 100644
index 0000000..4b23897
--- /dev/null
+++ b/ggsn/checksum.c
@@ -0,0 +1,211 @@
+/*
+ *
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		IP/TCP/UDP checksumming routines
+ *
+ * Authors:	Jorge Cwik, <jorge@laser.satlink.net>
+ *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
+ *		Tom May, <ftom@netcom.com>
+ *		Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>
+ *		Lots of code moved from tcp.c and ip.c; see those files
+ *		for more names.
+ *
+ * 03/02/96	Jes Sorensen, Andreas Schwab, Roman Hodek:
+ *		Fixed some nasty bugs, causing some horrible crashes.
+ *		A: At some points, the sum (%0) was used as
+ *		length-counter instead of the length counter
+ *		(%1). Thanks to Roman Hodek for pointing this out.
+ *		B: GCC seems to mess up if one uses too many
+ *		data-registers to hold input values and one tries to
+ *		specify d0 and d1 as scratch registers. Letting gcc
+ *		choose these registers itself solves the problem.
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ */
+
+/* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access
+ kills, so most of the assembly has to go. */
+
+#if defined(__FreeBSD__)
+#define _KERNEL	/* needed on FreeBSD 10.x for s6_addr32 */
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <sys/endian.h>
+#endif
+
+#include "checksum.h"
+#include <arpa/inet.h>
+
+static inline unsigned short from32to16(unsigned int x)
+{
+	/* add up 16-bit and 16-bit for 16+c bit */
+	x = (x & 0xffff) + (x >> 16);
+	/* add up carry.. */
+	x = (x & 0xffff) + (x >> 16);
+	return x;
+}
+
+static unsigned int do_csum(const unsigned char *buff, int len)
+{
+	int odd;
+	unsigned int result = 0;
+
+	if (len <= 0)
+		goto out;
+	odd = 1 & (unsigned long) buff;
+	if (odd) {
+#if BYTE_ORDER == LITTLE_ENDIAN
+		result += (*buff << 8);
+#else
+		result = *buff;
+#endif
+		len--;
+		buff++;
+	}
+	if (len >= 2) {
+		if (2 & (unsigned long) buff) {
+			result += *(unsigned short *) buff;
+			len -= 2;
+			buff += 2;
+		}
+		if (len >= 4) {
+			const unsigned char *end = buff + ((unsigned)len & ~3);
+			unsigned int carry = 0;
+			do {
+				unsigned int w = *(unsigned int *) buff;
+				buff += 4;
+				result += carry;
+				result += w;
+				carry = (w > result);
+			} while (buff < end);
+			result += carry;
+			result = (result & 0xffff) + (result >> 16);
+		}
+		if (len & 2) {
+			result += *(unsigned short *) buff;
+			buff += 2;
+		}
+	}
+	if (len & 1)
+#if BYTE_ORDER == LITTLE_ENDIAN
+		result += *buff;
+#else
+		result += (*buff << 8);
+#endif
+	result = from32to16(result);
+	if (odd)
+		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
+out:
+	return result;
+}
+
+/*
+ *	This is a version of ip_compute_csum() optimized for IP headers,
+ *	which always checksum on 4 octet boundaries.
+ */
+uint16_t ip_fast_csum(const void *iph, unsigned int ihl)
+{
+	return (uint16_t)~do_csum(iph, ihl*4);
+}
+
+/*
+ * computes the checksum of a memory block at buff, length len,
+ * and adds in "sum" (32-bit)
+ *
+ * returns a 32-bit number suitable for feeding into itself
+ * or csum_tcpudp_magic
+ *
+ * this function must be called with even lengths, except
+ * for the last fragment, which may be odd
+ *
+ * it's best to have buff aligned on a 32-bit boundary
+ */
+uint32_t csum_partial(const void *buff, int len, uint32_t wsum)
+{
+	unsigned int sum = (unsigned int)wsum;
+	unsigned int result = do_csum(buff, len);
+
+	/* add in old sum, and carry.. */
+	result += sum;
+	if (sum > result)
+		result += 1;
+	return (uint32_t)result;
+}
+
+/*
+ * this routine is used for miscellaneous IP-like checksums, mainly
+ * in icmp.c
+ */
+uint16_t ip_compute_csum(const void *buff, int len)
+{
+	return (uint16_t)~do_csum(buff, len);
+}
+
+uint16_t csum_ipv6_magic(const struct in6_addr *saddr,
+			const struct in6_addr *daddr,
+			uint32_t len, uint8_t proto, uint32_t csum)
+{
+	int carry;
+	uint32_t ulen;
+	uint32_t uproto;
+	uint32_t sum = (uint32_t)csum;
+
+	sum += (uint32_t)saddr->s6_addr32[0];
+	carry = (sum < (uint32_t)saddr->s6_addr32[0]);
+	sum += carry;
+
+	sum += (uint32_t)saddr->s6_addr32[1];
+	carry = (sum < (uint32_t)saddr->s6_addr32[1]);
+	sum += carry;
+
+	sum += (uint32_t)saddr->s6_addr32[2];
+	carry = (sum < (uint32_t)saddr->s6_addr32[2]);
+	sum += carry;
+
+	sum += (uint32_t)saddr->s6_addr32[3];
+	carry = (sum < (uint32_t)saddr->s6_addr32[3]);
+	sum += carry;
+
+	sum += (uint32_t)daddr->s6_addr32[0];
+	carry = (sum < (uint32_t)daddr->s6_addr32[0]);
+	sum += carry;
+
+	sum += (uint32_t)daddr->s6_addr32[1];
+	carry = (sum < (uint32_t)daddr->s6_addr32[1]);
+	sum += carry;
+
+	sum += (uint32_t)daddr->s6_addr32[2];
+	carry = (sum < (uint32_t)daddr->s6_addr32[2]);
+	sum += carry;
+
+	sum += (uint32_t)daddr->s6_addr32[3];
+	carry = (sum < (uint32_t)daddr->s6_addr32[3]);
+	sum += carry;
+
+	ulen = (uint32_t)htonl((uint32_t) len);
+	sum += ulen;
+	carry = (sum < ulen);
+	sum += carry;
+
+	uproto = (uint32_t)htonl(proto);
+	sum += uproto;
+	carry = (sum < uproto);
+	sum += carry;
+
+	return csum_fold((uint32_t)sum);
+}
+
+/* fold a partial checksum */
+uint16_t csum_fold(uint32_t csum)
+{
+	uint32_t sum = (uint32_t)csum;
+	sum = (sum & 0xffff) + (sum >> 16);
+	sum = (sum & 0xffff) + (sum >> 16);
+	return (uint16_t)~sum;
+}