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 #ifdef __cplusplus 89 extern "C" { 90 #endif 91 92 /** 93 * @defgroup ip6_zones IPv6 Zones 94 * @ingroup ip6 95 * @{ 96 */ 97 98 #if LWIP_IPV6 /* don't build if not configured for use in lwipopts.h */ 99 100 /** Identifier for "no zone". */ 101 #define IP6_NO_ZONE 0 102 103 #if LWIP_IPV6_SCOPES 104 105 /** Zone initializer for static IPv6 address initialization, including comma. */ 106 #define IPADDR6_ZONE_INIT , IP6_NO_ZONE 107 108 /** Return the zone index of the given IPv6 address; possibly "no zone". */ 109 #define ip6_addr_zone(ip6addr) ((ip6addr)->zone) 110 111 /** Does the given IPv6 address have a zone set? (0/1) */ 112 #define ip6_addr_has_zone(ip6addr) (ip6_addr_zone(ip6addr) != IP6_NO_ZONE) 113 114 /** Set the zone field of an IPv6 address to a particular value. */ 115 #define ip6_addr_set_zone(ip6addr, zone_idx) ((ip6addr)->zone = (zone_idx)) 116 117 /** Clear the zone field of an IPv6 address, setting it to "no zone". */ 118 #define ip6_addr_clear_zone(ip6addr) ((ip6addr)->zone = IP6_NO_ZONE) 119 120 /** Copy the zone field from the second IPv6 address to the first one. */ 121 #define ip6_addr_copy_zone(ip6addr1, ip6addr2) ((ip6addr1).zone = (ip6addr2).zone) 122 123 /** Is the zone field of the given IPv6 address equal to the given zone index? (0/1) */ 124 #define ip6_addr_equals_zone(ip6addr, zone_idx) ((ip6addr)->zone == (zone_idx)) 125 126 /** Are the zone fields of the given IPv6 addresses equal? (0/1) 127 * This macro must only be used on IPv6 addresses of the same scope. */ 128 #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) ((ip6addr1)->zone == (ip6addr2)->zone) 129 130 /** Symbolic constants for the 'type' parameters in some of the macros. 131 * These exist for efficiency only, allowing the macros to avoid certain tests 132 * when the address is known not to be of a certain type. Dead code elimination 133 * will do the rest. IP6_MULTICAST is supported but currently not optimized. 134 * @see ip6_addr_has_scope, ip6_addr_assign_zone, ip6_addr_lacks_zone. 135 */ 136 enum lwip_ipv6_scope_type 137 { 138 /** Unknown */ 139 IP6_UNKNOWN = 0, 140 /** Unicast */ 141 IP6_UNICAST = 1, 142 /** Multicast */ 143 IP6_MULTICAST = 2 144 }; 145 146 /** IPV6_CUSTOM_SCOPES: together, the following three macro definitions, 147 * @ref ip6_addr_has_scope, @ref ip6_addr_assign_zone, and 148 * @ref ip6_addr_test_zone, completely define the lwIP scoping policy. 149 * The definitions below implement the default policy from RFC 4007 Sec. 6. 150 * Should an implementation desire to implement a different policy, it can 151 * define IPV6_CUSTOM_SCOPES to 1 and supply its own definitions for the three 152 * macros instead. 153 */ 154 #ifndef IPV6_CUSTOM_SCOPES 155 #define IPV6_CUSTOM_SCOPES 0 156 #endif /* !IPV6_CUSTOM_SCOPES */ 157 158 #if !IPV6_CUSTOM_SCOPES 159 160 /** 161 * Determine whether an IPv6 address has a constrained scope, and as such is 162 * meaningful only if accompanied by a zone index to identify the scope's zone. 163 * The given address type may be used to eliminate at compile time certain 164 * checks that will evaluate to false at run time anyway. 165 * 166 * This default implementation follows the default model of RFC 4007, where 167 * only interface-local and link-local scopes are defined. 168 * 169 * Even though the unicast loopback address does have an implied link-local 170 * scope, in this implementation it does not have an explicitly assigned zone 171 * index. As such it should not be tested for in this macro. 172 * 173 * @param ip6addr the IPv6 address (const); only its address part is examined. 174 * @param type address type; see @ref lwip_ipv6_scope_type. 175 * @return 1 if the address has a constrained scope, 0 if it does not. 176 */ 177 #define ip6_addr_has_scope(ip6addr, type) \ 178 (ip6_addr_islinklocal(ip6addr) || (((type) != IP6_UNICAST) && \ 179 (ip6_addr_ismulticast_iflocal(ip6addr) || \ 180 ip6_addr_ismulticast_linklocal(ip6addr)))) 181 182 /** 183 * Assign a zone index to an IPv6 address, based on a network interface. If the 184 * given address has a scope, the assigned zone index is that scope's zone of 185 * the given netif; otherwise, the assigned zone index is "no zone". 186 * 187 * This default implementation follows the default model of RFC 4007, where 188 * only interface-local and link-local scopes are defined, and the zone index 189 * of both of those scopes always equals the index of the network interface. 190 * As such, this default implementation need not distinguish between different 191 * constrained scopes when assigning the zone. 192 * 193 * @param ip6addr the IPv6 address; its address part is examined, and its zone 194 * index is assigned. 195 * @param type address type; see @ref lwip_ipv6_scope_type. 196 * @param netif the network interface (const). 197 */ 198 #define ip6_addr_assign_zone(ip6addr, type, netif) \ 199 (ip6_addr_set_zone((ip6addr), \ 200 ip6_addr_has_scope((ip6addr), (type)) ? netif_get_index(netif) : 0)) 201 202 /** 203 * Test whether an IPv6 address is "zone-compatible" with a network interface. 204 * That is, test whether the network interface is part of the zone associated 205 * with the address. For efficiency, this macro is only ever called if the 206 * given address is either scoped or zoned, and thus, it need not test this. 207 * If an address is scoped but not zoned, or zoned and not scoped, it is 208 * considered not zone-compatible with any netif. 209 * 210 * This default implementation follows the default model of RFC 4007, where 211 * only interface-local and link-local scopes are defined, and the zone index 212 * of both of those scopes always equals the index of the network interface. 213 * As such, there is always only one matching netif for a specific zone index, 214 * but all call sites of this macro currently support multiple matching netifs 215 * as well (at no additional expense in the common case). 216 * 217 * @param ip6addr the IPv6 address (const). 218 * @param netif the network interface (const). 219 * @return 1 if the address is scope-compatible with the netif, 0 if not. 220 */ 221 #define ip6_addr_test_zone(ip6addr, netif) \ 222 (ip6_addr_equals_zone((ip6addr), netif_get_index(netif))) 223 224 #endif /* !IPV6_CUSTOM_SCOPES */ 225 226 /** Does the given IPv6 address have a scope, and as such should also have a 227 * zone to be meaningful, but does not actually have a zone? (0/1) */ 228 #define ip6_addr_lacks_zone(ip6addr, type) \ 229 (!ip6_addr_has_zone(ip6addr) && ip6_addr_has_scope((ip6addr), (type))) 230 231 /** 232 * Try to select a zone for a scoped address that does not yet have a zone. 233 * Called from PCB bind and connect routines, for two reasons: 1) to save on 234 * this (relatively expensive) selection for every individual packet route 235 * operation and 2) to allow the application to obtain the selected zone from 236 * the PCB as is customary for e.g. getsockname/getpeername BSD socket calls. 237 * 238 * Ideally, callers would always supply a properly zoned address, in which case 239 * this function would not be needed. It exists both for compatibility with the 240 * BSD socket API (which accepts zoneless destination addresses) and for 241 * backward compatibility with pre-scoping lwIP code. 242 * 243 * It may be impossible to select a zone, e.g. if there are no netifs. In that 244 * case, the address's zone field will be left as is. 245 * 246 * @param dest the IPv6 address for which to select and set a zone. 247 * @param src source IPv6 address (const); may be equal to dest. 248 */ 249 #define ip6_addr_select_zone(dest, src) do { struct netif *selected_netif; \ 250 selected_netif = ip6_route((src), (dest)); \ 251 if (selected_netif != NULL) { \ 252 ip6_addr_assign_zone((dest), IP6_UNKNOWN, selected_netif); \ 253 } } while (0) 254 255 /** 256 * @} 257 */ 258 259 #else /* LWIP_IPV6_SCOPES */ 260 261 #define IPADDR6_ZONE_INIT 262 #define ip6_addr_zone(ip6addr) (IP6_NO_ZONE) 263 #define ip6_addr_has_zone(ip6addr) (0) 264 #define ip6_addr_set_zone(ip6addr, zone_idx) 265 #define ip6_addr_clear_zone(ip6addr) 266 #define ip6_addr_copy_zone(ip6addr1, ip6addr2) 267 #define ip6_addr_equals_zone(ip6addr, zone_idx) (1) 268 #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) (1) 269 #define IPV6_CUSTOM_SCOPES 0 270 #define ip6_addr_has_scope(ip6addr, type) (0) 271 #define ip6_addr_assign_zone(ip6addr, type, netif) 272 #define ip6_addr_test_zone(ip6addr, netif) (1) 273 #define ip6_addr_lacks_zone(ip6addr, type) (0) 274 #define ip6_addr_select_zone(ip6addr, src) 275 276 #endif /* LWIP_IPV6_SCOPES */ 277 278 #if LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG 279 280 /** Verify that the given IPv6 address is properly zoned. */ 281 #define IP6_ADDR_ZONECHECK(ip6addr) LWIP_ASSERT("IPv6 zone check failed", \ 282 ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) == ip6_addr_has_zone(ip6addr)) 283 284 /** Verify that the given IPv6 address is properly zoned for the given netif. */ 285 #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif) LWIP_ASSERT("IPv6 netif zone check failed", \ 286 ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) ? \ 287 (ip6_addr_has_zone(ip6addr) && \ 288 (((netif) == NULL) || ip6_addr_test_zone((ip6addr), (netif)))) : \ 289 !ip6_addr_has_zone(ip6addr)) 290 291 #else /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */ 292 293 #define IP6_ADDR_ZONECHECK(ip6addr) 294 #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif) 295 296 #endif /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */ 297 298 #endif /* LWIP_IPV6 */ 299 300 #ifdef __cplusplus 301 } 302 #endif 303 304 #endif /* LWIP_HDR_IP6_ZONE_H */ 305