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-rw-r--r--ggsn/icmpv6.c234
1 files changed, 234 insertions, 0 deletions
diff --git a/ggsn/icmpv6.c b/ggsn/icmpv6.c
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index 0000000..94c980b
--- /dev/null
+++ b/ggsn/icmpv6.c
@@ -0,0 +1,234 @@
+/* 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>
+#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 "../lib/ippool.h"
+#include "../lib/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!)i
+ * \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;
+}
+
+/* RFC3307 link-local scope multicast address */
+static const struct in6_addr my_local_addr = {
+ .s6_addr = { 0x01,0x02,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0xff }
+};
+
+/* handle incoming packets to the all-routers multicast address */
+int handle_router_mcast(struct gsn_t *gsn, struct pdp_t *pdp, const uint8_t *pack, unsigned len)
+{
+ struct ippoolm_t *member = pdp->peer;
+ const struct ip6_hdr *ip6h = (struct ip6_hdr *)pack;
+ const struct icmpv6_hdr *ic6h = (struct icmpv6_hdr *) (pack + sizeof(*ip6h));
+ struct msgb *msg;
+
+ OSMO_ASSERT(pdp);
+ OSMO_ASSERT(member);
+
+ 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;
+ }
+ /* FIXME: Send router advertisement from GGSN link-local
+ * address to MS link-local address, including prefix
+ * allocated to this PDP context */
+ msg = icmpv6_construct_ra(&my_local_addr, &ip6h->ip6_src, &member->addr.v6);
+ /* 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;
+}