1 /** 2 * @file 3 * 4 * IPv6 address scopes, zones, and scoping policy. 5 * 6 * This header provides the means to implement support for IPv6 address scopes, 7 * as per RFC 4007. An address scope can be either global or more constrained. 8 * In lwIP, we say that an address "has a scope" or "is scoped" when its scope 9 * is constrained, in which case the address is meaningful only in a specific 10 * "zone." For unicast addresses, only link-local addresses have a scope; in 11 * that case, the scope is the link. For multicast addresses, there are various 12 * scopes defined by RFC 4007 and others. For any constrained scope, a system 13 * must establish a (potentially one-to-many) mapping between zones and local 14 * interfaces. For example, a link-local address is valid on only one link (its 15 * zone). That link may be attached to one or more local interfaces. The 16 * decisions on which scopes are constrained and the mapping between zones and 17 * interfaces is together what we refer to as the "scoping policy" - more on 18 * this in a bit. 19 * 20 * In lwIP, each IPv6 address has an associated zone index. This zone index may 21 * be set to "no zone" (IP6_NO_ZONE, 0) or an actual zone. We say that an 22 * address "has a zone" or "is zoned" when its zone index is *not* set to "no 23 * zone." In lwIP, in principle, each address should be "properly zoned," which 24 * means that if the address has a zone if and only if has a scope. As such, it 25 * is a rule that an unscoped (e.g., global) address must never have a zone. 26 * Even though one could argue that there is always one zone even for global 27 * scopes, this rule exists for implementation simplicity. Violation of the 28 * rule will trigger assertions or otherwise result in undesired behavior. 29 * 30 * Backward compatibility prevents us from requiring that applications always 31 * provide properly zoned addresses. We do enforce the rule that the in the 32 * lwIP link layer (everything below netif->output_ip6() and in particular ND6) 33 * *all* addresses are properly zoned. Thus, on the output paths down the 34 * stack, various places deal with the case of addresses that lack a zone. 35 * Some of them are best-effort for efficiency (e.g. the PCB bind and connect 36 * API calls' attempts to add missing zones); ultimately the IPv6 output 37 * handler (@ref ip6_output_if_src) will set a zone if necessary. 38 * 39 * Aside from dealing with scoped addresses lacking a zone, a proper IPv6 40 * implementation must also ensure that a packet with a scoped source and/or 41 * destination address does not leave its zone. This is currently implemented 42 * in the input and forward functions. However, for output, these checks are 43 * deliberately omitted in order to keep the implementation lightweight. The 44 * routing algorithm in @ref ip6_route will take decisions such that it will 45 * not cause zone violations unless the application sets bad addresses, though. 46 * 47 * In terms of scoping policy, lwIP implements the default policy from RFC 4007 48 * using macros in this file. This policy considers link-local unicast 49 * addresses and (only) interface-local and link-local multicast addresses as 50 * having a scope. For all these addresses, the zone is equal to the interface. 51 * As shown below in this file, it is possible to implement a custom policy. 52 */ 53 54 /* 55 * Copyright (c) 2017 The MINIX 3 Project. 56 * All rights reserved. 57 * 58 * Redistribution and use in source and binary forms, with or without modification, 59 * are permitted provided that the following conditions are met: 60 * 61 * 1. Redistributions of source code must retain the above copyright notice, 62 * this list of conditions and the following disclaimer. 63 * 2. Redistributions in binary form must reproduce the above copyright notice, 64 * this list of conditions and the following disclaimer in the documentation 65 * and/or other materials provided with the distribution. 66 * 3. The name of the author may not be used to endorse or promote products 67 * derived from this software without specific prior written permission. 68 * 69 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 70 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 71 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT 72 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 73 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT 74 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 75 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 76 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 77 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 78 * OF SUCH DAMAGE. 79 * 80 * This file is part of the lwIP TCP/IP stack. 81 * 82 * Author: David van Moolenbroek <david@minix3.org> 83 * 84 */ 85 #ifndef LWIP_HDR_IP6_ZONE_H 86 #define LWIP_HDR_IP6_ZONE_H 87 88 #if LWIP_IPV6 /* don't build if not configured for use in lwipopts.h */ 89 90 /** Identifier for "no zone". */ 91 #define IP6_NO_ZONE 0 92 93 #if LWIP_IPV6_SCOPES 94 95 /** Zone initializer for static IPv6 address initialization, including comma. */ 96 #define IPADDR6_ZONE_INIT , IP6_NO_ZONE 97 98 /** Return the zone index of the given IPv6 address; possibly "no zone". */ 99 #define ip6_addr_zone(ip6addr) ((ip6addr)->zone) 100 101 /** Does the given IPv6 address have a zone set? (0/1) */ 102 #define ip6_addr_has_zone(ip6addr) (ip6_addr_zone(ip6addr) != IP6_NO_ZONE) 103 104 /** Set the zone field of an IPv6 address to a particular value. */ 105 #define ip6_addr_set_zone(ip6addr, zone_idx) ((ip6addr)->zone = (zone_idx)) 106 107 /** Clear the zone field of an IPv6 address, setting it to "no zone". */ 108 #define ip6_addr_clear_zone(ip6addr) ((ip6addr)->zone = IP6_NO_ZONE) 109 110 /** Copy the zone field from the second IPv6 address to the first one. */ 111 #define ip6_addr_copy_zone(ip6addr1, ip6addr2) ((ip6addr1).zone = (ip6addr2).zone) 112 113 /** Is the zone field of the given IPv6 address equal to the given zone index? (0/1) */ 114 #define ip6_addr_equals_zone(ip6addr, zone_idx) ((ip6addr)->zone == (zone_idx)) 115 116 /** Are the zone fields of the given IPv6 addresses equal? (0/1) 117 * This macro must only be used on IPv6 addresses of the same scope. */ 118 #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) ((ip6addr1)->zone == (ip6addr2)->zone) 119 120 /** Symbolic constants for the 'type' parameters in some of the macros below. 121 * These exist for efficiency only, allowing the macros to avoid certain tests 122 * when the address is known not to be of a certain type. Dead code elimination 123 * will do the rest. IP6_MULTICAST is supported but currently not optimized. */ 124 #define IP6_UNKNOWN 0 125 #define IP6_UNICAST 1 126 #define IP6_MULTICAST 2 127 128 /** IPV6_CUSTOM_SCOPES: together, the following three macro definitions, 129 * @ref ip6_addr_has_scope, @ref ip6_addr_assign_zone, and 130 * @ref ip6_addr_test_zone, completely define the lwIP scoping policy. 131 * The definitions below implement the default policy from RFC 4007 Sec. 6. 132 * Should an implementation desire to implement a different policy, it can 133 * define IPV6_CUSTOM_SCOPES to 1 and supply its own definitions for the three 134 * macros instead. 135 */ 136 #ifndef IPV6_CUSTOM_SCOPES 137 #define IPV6_CUSTOM_SCOPES 0 138 #endif /* !IPV6_CUSTOM_SCOPES */ 139 140 #if !IPV6_CUSTOM_SCOPES 141 142 /** 143 * Determine whether an IPv6 address has a constrained scope, and as such is 144 * meaningful only if accompanied by a zone index to identify the scope's zone. 145 * The given address type may be used to eliminate at compile time certain 146 * checks that will evaluate to false at run time anyway. 147 * 148 * This default implementation follows the default model of RFC 4007, where 149 * only interface-local and link-local scopes are defined. 150 * 151 * Even though the unicast loopback address does have an implied link-local 152 * scope, in this implementation it does not have an explicitly assigned zone 153 * index. As such it should not be tested for in this macro. 154 * 155 * @param ip6addr the IPv6 address (const); only its address part is examined. 156 * @param type address type; one of IP6_UNICAST, IP6_MULTICAST, IP6_UNKNOWN. 157 * @return 1 if the address has a constrained scope, 0 if it does not. 158 */ 159 #define ip6_addr_has_scope(ip6addr, type) \ 160 (ip6_addr_islinklocal(ip6addr) || (((type) != IP6_UNICAST) && \ 161 (ip6_addr_ismulticast_iflocal(ip6addr) || \ 162 ip6_addr_ismulticast_linklocal(ip6addr)))) 163 164 /** 165 * Assign a zone index to an IPv6 address, based on a network interface. If the 166 * given address has a scope, the assigned zone index is that scope's zone of 167 * the given netif; otherwise, the assigned zone index is "no zone". 168 * 169 * This default implementation follows the default model of RFC 4007, where 170 * only interface-local and link-local scopes are defined, and the zone index 171 * of both of those scopes always equals the index of the network interface. 172 * As such, this default implementation need not distinguish between different 173 * constrained scopes when assigning the zone. 174 * 175 * @param ip6addr the IPv6 address; its address part is examined, and its zone 176 * index is assigned. 177 * @param type address type; one of IP6_UNICAST, IP6_MULTICAST, IP6_UNKNOWN. 178 * @param netif the network interface (const). 179 */ 180 #define ip6_addr_assign_zone(ip6addr, type, netif) \ 181 (ip6_addr_set_zone((ip6addr), \ 182 ip6_addr_has_scope((ip6addr), (type)) ? netif->ifindex : 0)) 183 184 /** 185 * Test whether an IPv6 address is "zone-compatible" with a network interface. 186 * That is, test whether the network interface is part of the zone associated 187 * with the address. For efficiency, this macro is only ever called if the 188 * given address is either scoped or zoned, and thus, it need not test this. 189 * If an address is scoped but not zoned, or zoned and not scoped, it is 190 * considered not zone-compatible with any netif. 191 * 192 * This default implementation follows the default model of RFC 4007, where 193 * only interface-local and link-local scopes are defined, and the zone index 194 * of both of those scopes always equals the index of the network interface. 195 * As such, there is always only one matching netif for a specific zone index, 196 * but all call sites of this macro currently support multiple matching netifs 197 * as well (at no additional expense in the common case). 198 * 199 * @param ip6addr the IPv6 address (const). 200 * @param netif the network interface (const). 201 * @return 1 if the address is scope-compatible with the netif, 0 if not. 202 */ 203 #define ip6_addr_test_zone(ip6addr, netif) \ 204 (ip6_addr_equals_zone((ip6addr), netif->ifindex)) 205 206 #endif /* !IPV6_CUSTOM_SCOPES */ 207 208 /** Does the given IPv6 address have a scope, and as such should also have a 209 * zone to be meaningful, but does not actually have a zone? (0/1) */ 210 #define ip6_addr_lacks_zone(ip6addr, type) \ 211 (!ip6_addr_has_zone(ip6addr) && ip6_addr_has_scope((ip6addr), (type))) 212 213 /** 214 * Try to select a zone for a scoped address that does not yet have a zone. 215 * Called from PCB bind and connect routines, for two reasons: 1) to save on 216 * this (relatively expensive) selection for every individual packet route 217 * operation and 2) to allow the application to obtain the selected zone from 218 * the PCB as is customary for e.g. getsockname/getpeername BSD socket calls. 219 * 220 * Ideally, callers would always supply a properly zoned address, in which case 221 * this function would not be needed. It exists both for compatibility with the 222 * BSD socket API (which accepts zoneless destination addresses) and for 223 * backward compatibility with pre-scoping lwIP code. 224 * 225 * It may be impossible to select a zone, e.g. if there are no netifs. In that 226 * case, the address's zone field will be left as is. 227 * 228 * @param dest the IPv6 address for which to select and set a zone. 229 * @param src source IPv6 address (const); may be equal to dest. 230 */ 231 #if LWIP_SO_DONTROUTE 232 #define ip6_addr_select_zone(dest, src) do { struct netif *selected_netif; \ 233 selected_netif = ip6_route((src), (dest), RT_SCOPE_UNIVERSAL); \ 234 if (selected_netif != NULL) { \ 235 ip6_addr_assign_zone((dest), IP6_UNKNOWN, selected_netif); \ 236 } } while (0) 237 #else 238 #define ip6_addr_select_zone(dest, src) do { struct netif *selected_netif; \ 239 selected_netif = ip6_route((src), (dest)); \ 240 if (selected_netif != NULL) { \ 241 ip6_addr_assign_zone((dest), IP6_UNKNOWN, selected_netif); \ 242 } } while (0) 243 #endif 244 #else /* LWIP_IPV6_SCOPES */ 245 246 #define IPADDR6_ZONE_INIT 247 #define ip6_addr_zone(ip6addr) (IP6_NO_ZONE) 248 #define ip6_addr_has_zone(ip6addr) (0) 249 #define ip6_addr_set_zone(ip6addr, zone_idx) 250 #define ip6_addr_clear_zone(ip6addr) 251 #define ip6_addr_copy_zone(ip6addr1, ip6addr2) 252 #define ip6_addr_equals_zone(ip6addr, zone_idx) (1) 253 #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) (1) 254 #define IPV6_CUSTOM_SCOPES 0 255 #define ip6_addr_has_scope(ip6addr, type) (0) 256 #define ip6_addr_assign_zone(ip6addr, type, netif) 257 #define ip6_addr_test_zone(ip6addr, netif) (1) 258 #define ip6_addr_lacks_zone(ip6addr, type) (0) 259 #define ip6_addr_select_zone(ip6addr, src) 260 261 #endif /* LWIP_IPV6_SCOPES */ 262 263 #if LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG 264 265 /** Verify that the given IPv6 address is properly zoned. */ 266 #define IP6_ADDR_ZONECHECK(ip6addr) LWIP_ASSERT("IPv6 zone check failed", \ 267 ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) == ip6_addr_has_zone(ip6addr)) 268 269 /** Verify that the given IPv6 address is properly zoned for the given netif. */ 270 #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif) LWIP_ASSERT("IPv6 netif zone check failed", \ 271 ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) ? \ 272 (ip6_addr_has_zone(ip6addr) && \ 273 (((netif) == NULL) || ip6_addr_test_zone((ip6addr), (netif)))) : \ 274 !ip6_addr_has_zone(ip6addr)) 275 276 #else /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */ 277 278 #define IP6_ADDR_ZONECHECK(ip6addr) 279 #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif) 280 281 #endif /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */ 282 283 #endif /* LWIP_IPV6 */ 284 285 #endif /* LWIP_HDR_IP6_ADDR_H */ 286