/* 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 * * 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 #include #include #include #if defined(__FreeBSD__) #include /* FreeBSD 10.x needs this before ip6.h */ #include #endif #include #include #include #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 " #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 " #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; }