Move icmpv6 and checksum files from ggsn/ dir to lib/

They will be required by sgsnemu to implement ICMPv6 Router
Soliciations.

Change-Id: Ie878604f0fc0169cc98a1e9eee64b14d76be2c45

1 files changed, 232 insertions, 0 deletions

diff --git a/lib/icmpv6.c b/lib/icmpv6.c
new file mode 100644
index 0000000..a6545fd
--- /dev/null
+++ b/lib/icmpv6.c
@@ -0,0 +1,232 @@
+/* Minimal ICMPv6 code for generating router advertisements as required by
+ * relevant 3GPP specs for a GGSN with IPv6 PDP contexts */
+
+/* (C) 2017 by Harald Welte <laforge@gnumonks.org>
+ *
+ * The contents of this file may be used under the terms of the GNU
+ * General Public License Version 2, provided that the above copyright
+ * notice and this permission notice is included in all copies or
+ * substantial portions of the software.
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <netinet/in.h>
+#if defined(__FreeBSD__)
+#include <sys/types.h>	/* FreeBSD 10.x needs this before ip6.h */
+#include <sys/endian.h>
+#endif
+#include <netinet/ip6.h>
+
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/utils.h>
+#include "checksum.h"
+
+#include "../gtp/gtp.h"
+#include "../gtp/pdp.h"
+#include "ippool.h"
+#include "syserr.h"
+#include "config.h"
+
+/* 29.061 11.2.1.3.4 IPv6 Router Configuration Variables in GGSN */
+#define GGSN_MaxRtrAdvInterval	21600		/* 6 hours */
+#define GGSN_MinRtrAdvInterval 16200		/* 4.5 hours */
+#define GGSN_AdvValidLifetime	0xffffffff	/* infinite */
+#define GGSN_AdvPreferredLifetime 0xffffffff	/* infinite */
+
+struct icmpv6_hdr {
+	uint8_t type;
+	uint8_t code;
+	uint16_t csum;
+} __attribute__ ((packed));
+
+/* RFC4861 Section 4.2 */
+struct icmpv6_radv_hdr {
+	struct icmpv6_hdr hdr;
+	uint8_t cur_ho_limit;
+#if BYTE_ORDER == LITTLE_ENDIAN
+	uint8_t res:6,
+		m:1,
+		o:1;
+#elif BYTE_ORDER == BIG_ENDIAN
+	uint8_t m:1,
+		o:1,
+		res:6;
+#else
+# error	"Please fix <bits/endian.h>"
+#endif
+	uint16_t router_lifetime;
+	uint32_t reachable_time;
+	uint32_t retrans_timer;
+	uint8_t options[0];
+} __attribute__ ((packed));
+
+/* RFC4861 Section 4.6 */
+struct icmpv6_opt_hdr {
+	uint8_t type;
+	/* length in units of 8 octets, including type+len! */
+	uint8_t len;
+	uint8_t data[0];
+} __attribute__ ((packed));
+
+/* RFC4861 Section 4.6.2 */
+struct icmpv6_opt_prefix {
+	struct icmpv6_opt_hdr hdr;
+	uint8_t prefix_len;
+#if BYTE_ORDER == LITTLE_ENDIAN
+	uint8_t res:6,
+		a:1,
+		l:1;
+#elif BYTE_ORDER == BIG_ENDIAN
+	uint8_t l:1,
+		a:1,
+		res:6;
+#else
+# error	"Please fix <bits/endian.h>"
+#endif
+	uint32_t valid_lifetime;
+	uint32_t preferred_lifetime;
+	uint32_t res2;
+	uint8_t prefix[16];
+} __attribute__ ((packed));
+
+
+/*! construct a 3GPP 29.061 compliant router advertisement for a given prefix
+ *  \param[in] saddr Source IPv6 address for router advertisement
+ *  \param[in] daddr Destination IPv6 address for router advertisement IPv6 header
+ *  \param[in] prefix The single prefix to be advertised (/64 implied!)
+ *  \returns callee-allocated message buffer containing router advertisement */
+struct msgb *icmpv6_construct_ra(const struct in6_addr *saddr,
+				 const struct in6_addr *daddr,
+				 const struct in6_addr *prefix)
+{
+	struct msgb *msg = msgb_alloc_headroom(512,128, "IPv6 RA");
+	struct icmpv6_radv_hdr *ra;
+	struct icmpv6_opt_prefix *ra_opt_pref;
+	struct ip6_hdr *i6h;
+	uint32_t len;
+	uint16_t skb_csum;
+
+	OSMO_ASSERT(msg);
+
+	ra = (struct icmpv6_radv_hdr *) msgb_put(msg, sizeof(*ra));
+	ra->hdr.type = 134;	/* see RFC4861 4.2 */
+	ra->hdr.code = 0;	/* see RFC4861 4.2 */
+	ra->hdr.csum = 0;	/* updated below */
+	ra->cur_ho_limit = 64;	/* seems reasonable? */
+	/* the GGSN shall leave the M-flag cleared in the Router
+	 * Advertisement messages */
+	ra->m = 0;
+	/* The GGSN may set the O-flag if there are additional
+	 * configuration parameters that need to be fetched by the MS */
+	ra->o = 0;		/* no DHCPv6 */
+	ra->res = 0;
+	/* RFC4861 Default: 3 * MaxRtrAdvInterval */
+	ra->router_lifetime = htons(3*GGSN_MaxRtrAdvInterval);
+	ra->reachable_time = 0;	/* Unspecified */
+
+	/* RFC4861 Section 4.6.2 */
+	ra_opt_pref = (struct icmpv6_opt_prefix *) msgb_put(msg, sizeof(*ra_opt_pref));
+	ra_opt_pref->hdr.type = 3;	/* RFC4861 4.6.2 */
+	ra_opt_pref->hdr.len = 4;	/* RFC4861 4.6.2 */
+	ra_opt_pref->prefix_len = 64;	/* only prefix length as per 3GPP */
+	/* The Prefix is contained in the Prefix Information Option of
+	 * the Router Advertisements and shall have the A-flag set
+	 * and the L-flag cleared */
+	ra_opt_pref->a = 1;
+	ra_opt_pref->l = 0;
+	ra_opt_pref->res = 0;
+	/*  The lifetime of the prefix shall be set to infinity */
+	ra_opt_pref->valid_lifetime = htonl(GGSN_AdvValidLifetime);
+	ra_opt_pref->preferred_lifetime = htonl(GGSN_AdvPreferredLifetime);
+	ra_opt_pref->res2 = 0;
+	memcpy(ra_opt_pref->prefix, prefix, sizeof(ra_opt_pref->prefix));
+
+	/* checksum */
+	skb_csum = csum_partial(msgb_data(msg), msgb_length(msg), 0);
+	len = msgb_length(msg);
+	ra->hdr.csum = csum_ipv6_magic(saddr, daddr, len, IPPROTO_ICMPV6, skb_csum);
+
+	/* Push IPv6 header in front of ICMPv6 packet */
+	i6h = (struct ip6_hdr *) msgb_push(msg, sizeof(*i6h));
+	/* 4 bits version, 8 bits TC, 20 bits flow-ID */
+	i6h->ip6_ctlun.ip6_un1.ip6_un1_flow = htonl(0x60000000);
+	i6h->ip6_ctlun.ip6_un1.ip6_un1_plen = htons(len);
+	i6h->ip6_ctlun.ip6_un1.ip6_un1_nxt = IPPROTO_ICMPV6;
+	i6h->ip6_ctlun.ip6_un1.ip6_un1_hlim = 255;
+	i6h->ip6_src = *saddr;
+	i6h->ip6_dst = *daddr;
+
+	return msg;
+}
+
+/* Walidate an ICMPv6 router solicitation according to RFC4861 6.1.1 */
+static bool icmpv6_validate_router_solicit(const uint8_t *pack, unsigned len)
+{
+	const struct ip6_hdr *ip6h = (struct ip6_hdr *)pack;
+	//const struct icmpv6_hdr *ic6h = (struct icmpv6_hdr *) (pack + sizeof(*ip6h));
+
+	/* Hop limit field must have 255 */
+	if (ip6h->ip6_ctlun.ip6_un1.ip6_un1_hlim != 255)
+		return false;
+	/* FIXME: ICMP checksum is valid */
+	/* ICMP length (derived from IP length) is 8 or more octets */
+	if (ip6h->ip6_ctlun.ip6_un1.ip6_un1_plen < 8)
+		return false;
+	/* FIXME: All included options have a length > 0 */
+	/* FIXME: If IP source is unspecified, no source link-layer addr option */
+	return true;
+}
+
+/* handle incoming packets to the all-routers multicast address */
+int handle_router_mcast(struct gsn_t *gsn, struct pdp_t *pdp,
+			const struct in6_addr *pdp_prefix,
+			const struct in6_addr *own_ll_addr,
+			const uint8_t *pack, unsigned len)
+{
+	const struct ip6_hdr *ip6h = (struct ip6_hdr *)pack;
+	const struct icmpv6_hdr *ic6h = (struct icmpv6_hdr *) (pack + sizeof(*ip6h));
+	struct msgb *msg;
+
+	if (len < sizeof(*ip6h)) {
+		LOGP(DICMP6, LOGL_NOTICE, "Packet too short: %u bytes\n", len);
+		return -1;
+	}
+
+	/* we only treat ICMPv6 here */
+	if (ip6h->ip6_ctlun.ip6_un1.ip6_un1_nxt != IPPROTO_ICMPV6) {
+		LOGP(DICMP6, LOGL_DEBUG, "Ignoring non-ICMP to all-routers mcast\n");
+		return 0;
+	}
+
+	if (len < sizeof(*ip6h) + sizeof(*ic6h)) {
+		LOGP(DICMP6, LOGL_NOTICE, "Short ICMPv6 packet: %s\n", osmo_hexdump(pack, len));
+		return -1;
+	}
+
+	switch (ic6h->type) {
+	case 133:	/* router solicitation */
+		if (ic6h->code != 0) {
+			LOGP(DICMP6, LOGL_NOTICE, "ICMPv6 type 133 but code %d\n", ic6h->code);
+			return -1;
+		}
+		if (!icmpv6_validate_router_solicit(pack, len)) {
+			LOGP(DICMP6, LOGL_NOTICE, "Invalid Router Solicitation: %s\n",
+				osmo_hexdump(pack, len));
+			return -1;
+		}
+		/* Send router advertisement from GGSN link-local
+		 * address to MS link-local address, including prefix
+		 * allocated to this PDP context */
+		msg = icmpv6_construct_ra(own_ll_addr, &ip6h->ip6_src, pdp_prefix);
+		/* Send the constructed RA to the MS */
+		gtp_data_req(gsn, pdp, msgb_data(msg), msgb_length(msg));
+		msgb_free(msg);
+		break;
+	default:
+		LOGP(DICMP6, LOGL_DEBUG, "Unknown ICMPv6 type %u\n", ic6h->type);
+		break;
+	}
+	return 0;
+}