[457] | 1 | /**
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| 2 | * @file
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| 3 | *
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| 4 | * IPv6 address scopes, zones, and scoping policy.
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| 5 | *
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| 6 | * This header provides the means to implement support for IPv6 address scopes,
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| 7 | * as per RFC 4007. An address scope can be either global or more constrained.
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| 8 | * In lwIP, we say that an address "has a scope" or "is scoped" when its scope
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| 9 | * is constrained, in which case the address is meaningful only in a specific
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| 10 | * "zone." For unicast addresses, only link-local addresses have a scope; in
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| 11 | * that case, the scope is the link. For multicast addresses, there are various
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| 12 | * scopes defined by RFC 4007 and others. For any constrained scope, a system
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| 13 | * must establish a (potentially one-to-many) mapping between zones and local
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| 14 | * interfaces. For example, a link-local address is valid on only one link (its
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| 15 | * zone). That link may be attached to one or more local interfaces. The
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| 16 | * decisions on which scopes are constrained and the mapping between zones and
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| 17 | * interfaces is together what we refer to as the "scoping policy" - more on
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| 18 | * this in a bit.
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| 19 | *
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| 20 | * In lwIP, each IPv6 address has an associated zone index. This zone index may
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| 21 | * be set to "no zone" (IP6_NO_ZONE, 0) or an actual zone. We say that an
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| 22 | * address "has a zone" or "is zoned" when its zone index is *not* set to "no
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| 23 | * zone." In lwIP, in principle, each address should be "properly zoned," which
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| 24 | * means that if the address has a zone if and only if has a scope. As such, it
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| 25 | * is a rule that an unscoped (e.g., global) address must never have a zone.
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| 26 | * Even though one could argue that there is always one zone even for global
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| 27 | * scopes, this rule exists for implementation simplicity. Violation of the
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| 28 | * rule will trigger assertions or otherwise result in undesired behavior.
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| 29 | *
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| 30 | * Backward compatibility prevents us from requiring that applications always
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| 31 | * provide properly zoned addresses. We do enforce the rule that the in the
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| 32 | * lwIP link layer (everything below netif->output_ip6() and in particular ND6)
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| 33 | * *all* addresses are properly zoned. Thus, on the output paths down the
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| 34 | * stack, various places deal with the case of addresses that lack a zone.
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| 35 | * Some of them are best-effort for efficiency (e.g. the PCB bind and connect
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| 36 | * API calls' attempts to add missing zones); ultimately the IPv6 output
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| 37 | * handler (@ref ip6_output_if_src) will set a zone if necessary.
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| 38 | *
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| 39 | * Aside from dealing with scoped addresses lacking a zone, a proper IPv6
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| 40 | * implementation must also ensure that a packet with a scoped source and/or
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| 41 | * destination address does not leave its zone. This is currently implemented
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| 42 | * in the input and forward functions. However, for output, these checks are
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| 43 | * deliberately omitted in order to keep the implementation lightweight. The
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| 44 | * routing algorithm in @ref ip6_route will take decisions such that it will
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| 45 | * not cause zone violations unless the application sets bad addresses, though.
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| 46 | *
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| 47 | * In terms of scoping policy, lwIP implements the default policy from RFC 4007
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| 48 | * using macros in this file. This policy considers link-local unicast
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| 49 | * addresses and (only) interface-local and link-local multicast addresses as
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| 50 | * having a scope. For all these addresses, the zone is equal to the interface.
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| 51 | * As shown below in this file, it is possible to implement a custom policy.
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| 52 | */
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| 53 |
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| 54 | /*
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| 55 | * Copyright (c) 2017 The MINIX 3 Project.
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| 56 | * All rights reserved.
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| 57 | *
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| 58 | * Redistribution and use in source and binary forms, with or without modification,
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| 59 | * are permitted provided that the following conditions are met:
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| 60 | *
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| 61 | * 1. Redistributions of source code must retain the above copyright notice,
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| 62 | * this list of conditions and the following disclaimer.
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| 63 | * 2. Redistributions in binary form must reproduce the above copyright notice,
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| 64 | * this list of conditions and the following disclaimer in the documentation
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| 65 | * and/or other materials provided with the distribution.
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| 66 | * 3. The name of the author may not be used to endorse or promote products
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| 67 | * derived from this software without specific prior written permission.
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| 68 | *
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| 69 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
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| 70 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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| 71 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
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| 72 | * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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| 73 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
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| 74 | * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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| 75 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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| 76 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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| 77 | * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
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| 78 | * OF SUCH DAMAGE.
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| 79 | *
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| 80 | * This file is part of the lwIP TCP/IP stack.
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| 81 | *
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| 82 | * Author: David van Moolenbroek <david@minix3.org>
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| 83 | *
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| 84 | */
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| 85 | #ifndef LWIP_HDR_IP6_ZONE_H
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| 86 | #define LWIP_HDR_IP6_ZONE_H
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| 87 |
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| 88 | #ifdef __cplusplus
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| 89 | extern "C" {
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| 90 | #endif
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| 91 |
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| 92 | /**
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| 93 | * @defgroup ip6_zones IPv6 Zones
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| 94 | * @ingroup ip6
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| 95 | * @{
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| 96 | */
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| 97 |
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| 98 | #if LWIP_IPV6 /* don't build if not configured for use in lwipopts.h */
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| 99 |
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| 100 | /** Identifier for "no zone". */
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| 101 | #define IP6_NO_ZONE 0
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| 102 |
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| 103 | #if LWIP_IPV6_SCOPES
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| 104 |
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| 105 | /** Zone initializer for static IPv6 address initialization, including comma. */
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| 106 | #define IPADDR6_ZONE_INIT , IP6_NO_ZONE
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| 107 |
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| 108 | /** Return the zone index of the given IPv6 address; possibly "no zone". */
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| 109 | #define ip6_addr_zone(ip6addr) ((ip6addr)->zone)
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| 110 |
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| 111 | /** Does the given IPv6 address have a zone set? (0/1) */
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| 112 | #define ip6_addr_has_zone(ip6addr) (ip6_addr_zone(ip6addr) != IP6_NO_ZONE)
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| 113 |
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| 114 | /** Set the zone field of an IPv6 address to a particular value. */
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| 115 | #define ip6_addr_set_zone(ip6addr, zone_idx) ((ip6addr)->zone = (zone_idx))
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| 116 |
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| 117 | /** Clear the zone field of an IPv6 address, setting it to "no zone". */
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| 118 | #define ip6_addr_clear_zone(ip6addr) ((ip6addr)->zone = IP6_NO_ZONE)
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| 119 |
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| 120 | /** Copy the zone field from the second IPv6 address to the first one. */
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| 121 | #define ip6_addr_copy_zone(ip6addr1, ip6addr2) ((ip6addr1).zone = (ip6addr2).zone)
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| 122 |
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| 123 | /** Is the zone field of the given IPv6 address equal to the given zone index? (0/1) */
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| 124 | #define ip6_addr_equals_zone(ip6addr, zone_idx) ((ip6addr)->zone == (zone_idx))
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| 125 |
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| 126 | /** Are the zone fields of the given IPv6 addresses equal? (0/1)
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| 127 | * This macro must only be used on IPv6 addresses of the same scope. */
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| 128 | #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) ((ip6addr1)->zone == (ip6addr2)->zone)
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| 129 |
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| 130 | /** Symbolic constants for the 'type' parameters in some of the macros.
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| 131 | * These exist for efficiency only, allowing the macros to avoid certain tests
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| 132 | * when the address is known not to be of a certain type. Dead code elimination
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| 133 | * will do the rest. IP6_MULTICAST is supported but currently not optimized.
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| 134 | * @see ip6_addr_has_scope, ip6_addr_assign_zone, ip6_addr_lacks_zone.
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| 135 | */
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| 136 | enum lwip_ipv6_scope_type
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| 137 | {
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| 138 | /** Unknown */
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| 139 | IP6_UNKNOWN = 0,
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| 140 | /** Unicast */
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| 141 | IP6_UNICAST = 1,
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| 142 | /** Multicast */
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| 143 | IP6_MULTICAST = 2
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| 144 | };
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| 145 |
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| 146 | /** IPV6_CUSTOM_SCOPES: together, the following three macro definitions,
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| 147 | * @ref ip6_addr_has_scope, @ref ip6_addr_assign_zone, and
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| 148 | * @ref ip6_addr_test_zone, completely define the lwIP scoping policy.
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| 149 | * The definitions below implement the default policy from RFC 4007 Sec. 6.
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| 150 | * Should an implementation desire to implement a different policy, it can
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| 151 | * define IPV6_CUSTOM_SCOPES to 1 and supply its own definitions for the three
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| 152 | * macros instead.
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| 153 | */
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| 154 | #ifndef IPV6_CUSTOM_SCOPES
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| 155 | #define IPV6_CUSTOM_SCOPES 0
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| 156 | #endif /* !IPV6_CUSTOM_SCOPES */
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| 157 |
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| 158 | #if !IPV6_CUSTOM_SCOPES
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| 159 |
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| 160 | /**
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| 161 | * Determine whether an IPv6 address has a constrained scope, and as such is
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| 162 | * meaningful only if accompanied by a zone index to identify the scope's zone.
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| 163 | * The given address type may be used to eliminate at compile time certain
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| 164 | * checks that will evaluate to false at run time anyway.
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| 165 | *
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| 166 | * This default implementation follows the default model of RFC 4007, where
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| 167 | * only interface-local and link-local scopes are defined.
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| 168 | *
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| 169 | * Even though the unicast loopback address does have an implied link-local
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| 170 | * scope, in this implementation it does not have an explicitly assigned zone
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| 171 | * index. As such it should not be tested for in this macro.
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| 172 | *
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| 173 | * @param ip6addr the IPv6 address (const); only its address part is examined.
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| 174 | * @param type address type; see @ref lwip_ipv6_scope_type.
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| 175 | * @return 1 if the address has a constrained scope, 0 if it does not.
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| 176 | */
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| 177 | #define ip6_addr_has_scope(ip6addr, type) \
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| 178 | (ip6_addr_islinklocal(ip6addr) || (((type) != IP6_UNICAST) && \
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| 179 | (ip6_addr_ismulticast_iflocal(ip6addr) || \
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| 180 | ip6_addr_ismulticast_linklocal(ip6addr))))
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| 181 |
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| 182 | /**
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| 183 | * Assign a zone index to an IPv6 address, based on a network interface. If the
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| 184 | * given address has a scope, the assigned zone index is that scope's zone of
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| 185 | * the given netif; otherwise, the assigned zone index is "no zone".
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| 186 | *
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| 187 | * This default implementation follows the default model of RFC 4007, where
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| 188 | * only interface-local and link-local scopes are defined, and the zone index
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| 189 | * of both of those scopes always equals the index of the network interface.
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| 190 | * As such, this default implementation need not distinguish between different
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| 191 | * constrained scopes when assigning the zone.
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| 192 | *
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| 193 | * @param ip6addr the IPv6 address; its address part is examined, and its zone
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| 194 | * index is assigned.
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| 195 | * @param type address type; see @ref lwip_ipv6_scope_type.
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| 196 | * @param netif the network interface (const).
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| 197 | */
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| 198 | #define ip6_addr_assign_zone(ip6addr, type, netif) \
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| 199 | (ip6_addr_set_zone((ip6addr), \
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| 200 | ip6_addr_has_scope((ip6addr), (type)) ? netif_get_index(netif) : 0))
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| 201 |
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| 202 | /**
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| 203 | * Test whether an IPv6 address is "zone-compatible" with a network interface.
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| 204 | * That is, test whether the network interface is part of the zone associated
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| 205 | * with the address. For efficiency, this macro is only ever called if the
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| 206 | * given address is either scoped or zoned, and thus, it need not test this.
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| 207 | * If an address is scoped but not zoned, or zoned and not scoped, it is
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| 208 | * considered not zone-compatible with any netif.
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| 209 | *
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| 210 | * This default implementation follows the default model of RFC 4007, where
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| 211 | * only interface-local and link-local scopes are defined, and the zone index
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| 212 | * of both of those scopes always equals the index of the network interface.
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| 213 | * As such, there is always only one matching netif for a specific zone index,
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| 214 | * but all call sites of this macro currently support multiple matching netifs
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| 215 | * as well (at no additional expense in the common case).
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| 216 | *
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| 217 | * @param ip6addr the IPv6 address (const).
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| 218 | * @param netif the network interface (const).
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| 219 | * @return 1 if the address is scope-compatible with the netif, 0 if not.
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| 220 | */
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| 221 | #define ip6_addr_test_zone(ip6addr, netif) \
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| 222 | (ip6_addr_equals_zone((ip6addr), netif_get_index(netif)))
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| 223 |
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| 224 | #endif /* !IPV6_CUSTOM_SCOPES */
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| 225 |
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| 226 | /** Does the given IPv6 address have a scope, and as such should also have a
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| 227 | * zone to be meaningful, but does not actually have a zone? (0/1) */
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| 228 | #define ip6_addr_lacks_zone(ip6addr, type) \
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| 229 | (!ip6_addr_has_zone(ip6addr) && ip6_addr_has_scope((ip6addr), (type)))
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| 230 |
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| 231 | /**
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| 232 | * Try to select a zone for a scoped address that does not yet have a zone.
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| 233 | * Called from PCB bind and connect routines, for two reasons: 1) to save on
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| 234 | * this (relatively expensive) selection for every individual packet route
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| 235 | * operation and 2) to allow the application to obtain the selected zone from
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| 236 | * the PCB as is customary for e.g. getsockname/getpeername BSD socket calls.
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| 237 | *
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| 238 | * Ideally, callers would always supply a properly zoned address, in which case
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| 239 | * this function would not be needed. It exists both for compatibility with the
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| 240 | * BSD socket API (which accepts zoneless destination addresses) and for
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| 241 | * backward compatibility with pre-scoping lwIP code.
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| 242 | *
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| 243 | * It may be impossible to select a zone, e.g. if there are no netifs. In that
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| 244 | * case, the address's zone field will be left as is.
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| 245 | *
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| 246 | * @param dest the IPv6 address for which to select and set a zone.
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| 247 | * @param src source IPv6 address (const); may be equal to dest.
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| 248 | */
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| 249 | #define ip6_addr_select_zone(dest, src) do { struct netif *selected_netif; \
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| 250 | selected_netif = ip6_route((src), (dest)); \
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| 251 | if (selected_netif != NULL) { \
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| 252 | ip6_addr_assign_zone((dest), IP6_UNKNOWN, selected_netif); \
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| 253 | } } while (0)
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| 254 |
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| 255 | /**
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| 256 | * @}
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| 257 | */
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| 258 |
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| 259 | #else /* LWIP_IPV6_SCOPES */
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| 260 |
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| 261 | #define IPADDR6_ZONE_INIT
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| 262 | #define ip6_addr_zone(ip6addr) (IP6_NO_ZONE)
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| 263 | #define ip6_addr_has_zone(ip6addr) (0)
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| 264 | #define ip6_addr_set_zone(ip6addr, zone_idx)
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| 265 | #define ip6_addr_clear_zone(ip6addr)
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| 266 | #define ip6_addr_copy_zone(ip6addr1, ip6addr2)
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| 267 | #define ip6_addr_equals_zone(ip6addr, zone_idx) (1)
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| 268 | #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) (1)
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| 269 | #define IPV6_CUSTOM_SCOPES 0
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| 270 | #define ip6_addr_has_scope(ip6addr, type) (0)
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| 271 | #define ip6_addr_assign_zone(ip6addr, type, netif)
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| 272 | #define ip6_addr_test_zone(ip6addr, netif) (1)
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| 273 | #define ip6_addr_lacks_zone(ip6addr, type) (0)
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| 274 | #define ip6_addr_select_zone(ip6addr, src)
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| 275 |
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| 276 | #endif /* LWIP_IPV6_SCOPES */
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| 277 |
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| 278 | #if LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG
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| 279 |
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| 280 | /** Verify that the given IPv6 address is properly zoned. */
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| 281 | #define IP6_ADDR_ZONECHECK(ip6addr) LWIP_ASSERT("IPv6 zone check failed", \
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| 282 | ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) == ip6_addr_has_zone(ip6addr))
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| 283 |
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| 284 | /** Verify that the given IPv6 address is properly zoned for the given netif. */
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| 285 | #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif) LWIP_ASSERT("IPv6 netif zone check failed", \
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| 286 | ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) ? \
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| 287 | (ip6_addr_has_zone(ip6addr) && \
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| 288 | (((netif) == NULL) || ip6_addr_test_zone((ip6addr), (netif)))) : \
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| 289 | !ip6_addr_has_zone(ip6addr))
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| 290 |
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| 291 | #else /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */
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| 292 |
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| 293 | #define IP6_ADDR_ZONECHECK(ip6addr)
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| 294 | #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif)
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| 295 |
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| 296 | #endif /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */
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| 297 |
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| 298 | #endif /* LWIP_IPV6 */
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| 299 |
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| 300 | #ifdef __cplusplus
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| 301 | }
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| 302 | #endif
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| 303 |
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| 304 | #endif /* LWIP_HDR_IP6_ZONE_H */
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