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 /** 89 * @defgroup ip6_zones IPv6 Zones 90 * @ingroup ip6 91 * @{ 92 */ 93 94 #if LWIP_IPV6 /* don't build if not configured for use in lwipopts.h */ 95 96 /** Identifier for "no zone". */ 97 #define IP6_NO_ZONE 0 98 99 #if LWIP_IPV6_SCOPES 100 101 /** Zone initializer for static IPv6 address initialization, including comma. */ 102 #define IPADDR6_ZONE_INIT , IP6_NO_ZONE 103 104 /** Return the zone index of the given IPv6 address; possibly "no zone". */ 105 #define ip6_addr_zone(ip6addr) ((ip6addr)->zone) 106 107 /** Does the given IPv6 address have a zone set? (0/1) */ 108 #define ip6_addr_has_zone(ip6addr) (ip6_addr_zone(ip6addr) != IP6_NO_ZONE) 109 110 /** Set the zone field of an IPv6 address to a particular value. */ 111 #define ip6_addr_set_zone(ip6addr, zone_idx) ((ip6addr)->zone = (zone_idx)) 112 113 /** Clear the zone field of an IPv6 address, setting it to "no zone". */ 114 #define ip6_addr_clear_zone(ip6addr) ((ip6addr)->zone = IP6_NO_ZONE) 115 116 /** Copy the zone field from the second IPv6 address to the first one. */ 117 #define ip6_addr_copy_zone(ip6addr1, ip6addr2) ((ip6addr1).zone = (ip6addr2).zone) 118 119 /** Is the zone field of the given IPv6 address equal to the given zone index? (0/1) */ 120 #define ip6_addr_equals_zone(ip6addr, zone_idx) ((ip6addr)->zone == (zone_idx)) 121 122 /** Are the zone fields of the given IPv6 addresses equal? (0/1) 123 * This macro must only be used on IPv6 addresses of the same scope. */ 124 #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) ((ip6addr1)->zone == (ip6addr2)->zone) 125 126 /** Symbolic constants for the 'type' parameters in some of the macros. 127 * These exist for efficiency only, allowing the macros to avoid certain tests 128 * when the address is known not to be of a certain type. Dead code elimination 129 * will do the rest. IP6_MULTICAST is supported but currently not optimized. 130 * @see ip6_addr_has_scope, ip6_addr_assign_zone, ip6_addr_lacks_zone. 131 */ 132 enum lwip_ipv6_scope_type 133 { 134 /** Unknown */ 135 IP6_UNKNOWN = 0, 136 /** Unicast */ 137 IP6_UNICAST = 1, 138 /** Multicast */ 139 IP6_MULTICAST = 2 140 }; 141 142 /** IPV6_CUSTOM_SCOPES: together, the following three macro definitions, 143 * @ref ip6_addr_has_scope, @ref ip6_addr_assign_zone, and 144 * @ref ip6_addr_test_zone, completely define the lwIP scoping policy. 145 * The definitions below implement the default policy from RFC 4007 Sec. 6. 146 * Should an implementation desire to implement a different policy, it can 147 * define IPV6_CUSTOM_SCOPES to 1 and supply its own definitions for the three 148 * macros instead. 149 */ 150 #ifndef IPV6_CUSTOM_SCOPES 151 #define IPV6_CUSTOM_SCOPES 0 152 #endif /* !IPV6_CUSTOM_SCOPES */ 153 154 #if !IPV6_CUSTOM_SCOPES 155 156 /** 157 * Determine whether an IPv6 address has a constrained scope, and as such is 158 * meaningful only if accompanied by a zone index to identify the scope's zone. 159 * The given address type may be used to eliminate at compile time certain 160 * checks that will evaluate to false at run time anyway. 161 * 162 * This default implementation follows the default model of RFC 4007, where 163 * only interface-local and link-local scopes are defined. 164 * 165 * Even though the unicast loopback address does have an implied link-local 166 * scope, in this implementation it does not have an explicitly assigned zone 167 * index. As such it should not be tested for in this macro. 168 * 169 * @param ip6addr the IPv6 address (const); only its address part is examined. 170 * @param type address type; see @ref lwip_ipv6_scope_type. 171 * @return 1 if the address has a constrained scope, 0 if it does not. 172 */ 173 #define ip6_addr_has_scope(ip6addr, type) \ 174 (ip6_addr_islinklocal(ip6addr) || (((type) != IP6_UNICAST) && \ 175 (ip6_addr_ismulticast_iflocal(ip6addr) || \ 176 ip6_addr_ismulticast_linklocal(ip6addr)))) 177 178 /** 179 * Assign a zone index to an IPv6 address, based on a network interface. If the 180 * given address has a scope, the assigned zone index is that scope's zone of 181 * the given netif; otherwise, the assigned zone index is "no zone". 182 * 183 * This default implementation follows the default model of RFC 4007, where 184 * only interface-local and link-local scopes are defined, and the zone index 185 * of both of those scopes always equals the index of the network interface. 186 * As such, this default implementation need not distinguish between different 187 * constrained scopes when assigning the zone. 188 * 189 * @param ip6addr the IPv6 address; its address part is examined, and its zone 190 * index is assigned. 191 * @param type address type; see @ref lwip_ipv6_scope_type. 192 * @param netif the network interface (const). 193 */ 194 #define ip6_addr_assign_zone(ip6addr, type, netif) \ 195 (ip6_addr_set_zone((ip6addr), \ 196 ip6_addr_has_scope((ip6addr), (type)) ? netif_get_index(netif) : 0)) 197 198 /** 199 * Test whether an IPv6 address is "zone-compatible" with a network interface. 200 * That is, test whether the network interface is part of the zone associated 201 * with the address. For efficiency, this macro is only ever called if the 202 * given address is either scoped or zoned, and thus, it need not test this. 203 * If an address is scoped but not zoned, or zoned and not scoped, it is 204 * considered not zone-compatible with any netif. 205 * 206 * This default implementation follows the default model of RFC 4007, where 207 * only interface-local and link-local scopes are defined, and the zone index 208 * of both of those scopes always equals the index of the network interface. 209 * As such, there is always only one matching netif for a specific zone index, 210 * but all call sites of this macro currently support multiple matching netifs 211 * as well (at no additional expense in the common case). 212 * 213 * @param ip6addr the IPv6 address (const). 214 * @param netif the network interface (const). 215 * @return 1 if the address is scope-compatible with the netif, 0 if not. 216 */ 217 #define ip6_addr_test_zone(ip6addr, netif) \ 218 (ip6_addr_equals_zone((ip6addr), netif_get_index(netif))) 219 220 #endif /* !IPV6_CUSTOM_SCOPES */ 221 222 /** Does the given IPv6 address have a scope, and as such should also have a 223 * zone to be meaningful, but does not actually have a zone? (0/1) */ 224 #define ip6_addr_lacks_zone(ip6addr, type) \ 225 (!ip6_addr_has_zone(ip6addr) && ip6_addr_has_scope((ip6addr), (type))) 226 227 /** 228 * Try to select a zone for a scoped address that does not yet have a zone. 229 * Called from PCB bind and connect routines, for two reasons: 1) to save on 230 * this (relatively expensive) selection for every individual packet route 231 * operation and 2) to allow the application to obtain the selected zone from 232 * the PCB as is customary for e.g. getsockname/getpeername BSD socket calls. 233 * 234 * Ideally, callers would always supply a properly zoned address, in which case 235 * this function would not be needed. It exists both for compatibility with the 236 * BSD socket API (which accepts zoneless destination addresses) and for 237 * backward compatibility with pre-scoping lwIP code. 238 * 239 * It may be impossible to select a zone, e.g. if there are no netifs. In that 240 * case, the address's zone field will be left as is. 241 * 242 * @param dest the IPv6 address for which to select and set a zone. 243 * @param src source IPv6 address (const); may be equal to dest. 244 */ 245 #define ip6_addr_select_zone(dest, src) do { struct netif *selected_netif; \ 246 selected_netif = ip6_route((src), (dest)); \ 247 if (selected_netif != NULL) { \ 248 ip6_addr_assign_zone((dest), IP6_UNKNOWN, selected_netif); \ 249 } } while (0) 250 251 /** 252 * @} 253 */ 254 255 #else /* LWIP_IPV6_SCOPES */ 256 257 #define IPADDR6_ZONE_INIT 258 #define ip6_addr_zone(ip6addr) (IP6_NO_ZONE) 259 #define ip6_addr_has_zone(ip6addr) (0) 260 #define ip6_addr_set_zone(ip6addr, zone_idx) 261 #define ip6_addr_clear_zone(ip6addr) 262 #define ip6_addr_copy_zone(ip6addr1, ip6addr2) 263 #define ip6_addr_equals_zone(ip6addr, zone_idx) (1) 264 #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) (1) 265 #define IPV6_CUSTOM_SCOPES 0 266 #define ip6_addr_has_scope(ip6addr, type) (0) 267 #define ip6_addr_assign_zone(ip6addr, type, netif) 268 #define ip6_addr_test_zone(ip6addr, netif) (1) 269 #define ip6_addr_lacks_zone(ip6addr, type) (0) 270 #define ip6_addr_select_zone(ip6addr, src) 271 272 #endif /* LWIP_IPV6_SCOPES */ 273 274 #if LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG 275 276 /** Verify that the given IPv6 address is properly zoned. */ 277 #define IP6_ADDR_ZONECHECK(ip6addr) LWIP_ASSERT("IPv6 zone check failed", \ 278 ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) == ip6_addr_has_zone(ip6addr)) 279 280 /** Verify that the given IPv6 address is properly zoned for the given netif. */ 281 #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif) LWIP_ASSERT("IPv6 netif zone check failed", \ 282 ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) ? \ 283 (ip6_addr_has_zone(ip6addr) && \ 284 (((netif) == NULL) || ip6_addr_test_zone((ip6addr), (netif)))) : \ 285 !ip6_addr_has_zone(ip6addr)) 286 287 #else /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */ 288 289 #define IP6_ADDR_ZONECHECK(ip6addr) 290 #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif) 291 292 #endif /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */ 293 294 #endif /* LWIP_IPV6 */ 295 296 #endif /* LWIP_HDR_IP6_ADDR_H */ 297