/* 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 * All Rights Reserved. * * SPDX-License-Identifier: GPL-2.0+ * * 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. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see . * */ #include #include #include #include #if defined(__FreeBSD__) #include /* FreeBSD 10.x needs this before ip6.h */ #include #endif #include #include #include #include #include /* 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 */ /* RFC3307 link-local scope multicast address */ const struct in6_addr osmo_icmpv6_all_router_mcast_addr = { .s6_addr = { 0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2 } }; /* RFC4291 link-local solicited-node multicast address, FF02:0:0:0:0:1:FF, 104 bits = 13 bytes */ const uint8_t osmo_icmpv6_solicited_node_mcast_addr_prefix[13] = { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0xFF }; /* Prepends the ipv6 header and returns checksum content */ uint16_t osmo_icmpv6_prepend_ip6hdr(struct msgb *msg, const struct in6_addr *saddr, const struct in6_addr *daddr) { uint32_t len; uint16_t skb_csum; struct ip6_hdr *i6h; /* checksum */ skb_csum = osmo_ip_checksum_csum_partial(msgb_data(msg), msgb_length(msg), 0); len = msgb_length(msg); skb_csum = osmo_ip_checksum_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 skb_csum; } /*! construct a RFC4861 compliant ICMPv6 router soliciation * \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 *osmo_icmpv6_construct_rs(const struct in6_addr *saddr) { struct msgb *msg = msgb_alloc_headroom(512, 128, "IPv6 RS"); struct osmo_icmpv6_rsol_hdr *rs; OSMO_ASSERT(msg); rs = (struct osmo_icmpv6_rsol_hdr *) msgb_put(msg, sizeof(*rs)); rs->hdr.type = 133; /* see RFC4861 4.1 */ rs->hdr.code = 0; /* see RFC4861 4.1 */ rs->hdr.csum = 0; /* updated below */ rs->reserved = 0; /* see RFC4861 4.1 */ rs->hdr.csum = osmo_icmpv6_prepend_ip6hdr(msg, saddr, &osmo_icmpv6_all_router_mcast_addr); return msg; } /*! 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 *osmo_icmpv6_construct_ra(const struct in6_addr *saddr, const struct in6_addr *daddr, const struct in6_addr *prefix, uint32_t mtu) { struct msgb *msg = msgb_alloc_headroom(512, 128, "IPv6 RA"); struct osmo_icmpv6_radv_hdr *ra; struct osmo_icmpv6_opt_prefix *ra_opt_pref; struct osmo_icmpv6_opt_mtu *ra_opt_mtu; OSMO_ASSERT(msg); ra = (struct osmo_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 osmo_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)); /* RFC4861 Section 4.6.4, MTU */ ra_opt_mtu = (struct osmo_icmpv6_opt_mtu *) msgb_put(msg, sizeof(*ra_opt_mtu)); ra_opt_mtu->hdr.type = 5; /* RFC4861 4.6.4 */ ra_opt_mtu->hdr.len = 1; /* RFC4861 4.6.4 */ ra_opt_mtu->reserved = 0; ra_opt_mtu->mtu = htonl(mtu); /* 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 */ ra->hdr.csum = osmo_icmpv6_prepend_ip6hdr(msg, saddr, daddr); return msg; } /* Validate an ICMPv6 router solicitation according to RFC4861 6.1.1 */ bool osmo_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; } /* Validate an ICMPv6 router advertisement according to RFC4861 6.1.2. Returns pointer packet header on success, NULL otherwise. */ struct osmo_icmpv6_radv_hdr *osmo_icmpv6_validate_router_adv(const uint8_t *pack, unsigned len) { const struct ip6_hdr *ip6h = (struct ip6_hdr *)pack; const struct osmo_icmpv6_hdr *ic6h = (struct osmo_icmpv6_hdr *) (pack + sizeof(*ip6h)); /* ICMP length (derived from IP length) is 16 or more octets */ if (len < sizeof(*ip6h) + 16) return NULL; if (ic6h->type != 134) /* router advertismenet type */ return NULL; /*Routers must use their link-local address */ if (!IN6_IS_ADDR_LINKLOCAL(&ip6h->ip6_src)) return NULL; /* Hop limit field must have 255 */ if (ip6h->ip6_ctlun.ip6_un1.ip6_un1_hlim != 255) return NULL; /* ICMP Code is 0 */ if (ic6h->code != 0) return NULL; /* ICMP length (derived from IP length) is 16 or more octets */ if (ip6h->ip6_ctlun.ip6_un1.ip6_un1_plen < 16) return NULL; /* FIXME: All included options have a length > 0 */ /* FIXME: If IP source is unspecified, no source link-layer addr option */ return (struct osmo_icmpv6_radv_hdr *)ic6h; }