Mbed OS Reference | ip6_zone.h Source File

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 /**
  * @file
  *
  * IPv6 address scopes, zones, and scoping policy.
  *
  * This header provides the means to implement support for IPv6 address scopes,
  * as per RFC 4007. An address scope can be either global or more constrained.
  * In lwIP, we say that an address "has a scope" or "is scoped" when its scope
  * is constrained, in which case the address is meaningful only in a specific
  * "zone." For unicast addresses, only link-local addresses have a scope; in
  * that case, the scope is the link. For multicast addresses, there are various
  * scopes defined by RFC 4007 and others. For any constrained scope, a system
  * must establish a (potentially one-to-many) mapping between zones and local
  * interfaces. For example, a link-local address is valid on only one link (its
  * zone). That link may be attached to one or more local interfaces. The
  * decisions on which scopes are constrained and the mapping between zones and
  * interfaces is together what we refer to as the "scoping policy" - more on
  * this in a bit.
  *
  * In lwIP, each IPv6 address has an associated zone index. This zone index may
  * be set to "no zone" (IP6_NO_ZONE, 0) or an actual zone. We say that an
  * address "has a zone" or "is zoned" when its zone index is *not* set to "no
  * zone." In lwIP, in principle, each address should be "properly zoned," which
  * means that if the address has a zone if and only if has a scope. As such, it
  * is a rule that an unscoped (e.g., global) address must never have a zone.
  * Even though one could argue that there is always one zone even for global
  * scopes, this rule exists for implementation simplicity. Violation of the
  * rule will trigger assertions or otherwise result in undesired behavior.
  *
  * Backward compatibility prevents us from requiring that applications always
  * provide properly zoned addresses. We do enforce the rule that the in the
  * lwIP link layer (everything below netif->output_ip6() and in particular ND6)
  * *all* addresses are properly zoned. Thus, on the output paths down the
  * stack, various places deal with the case of addresses that lack a zone.
  * Some of them are best-effort for efficiency (e.g. the PCB bind and connect
  * API calls' attempts to add missing zones); ultimately the IPv6 output
  * handler (@ref ip6_output_if_src) will set a zone if necessary.
  *
  * Aside from dealing with scoped addresses lacking a zone, a proper IPv6
  * implementation must also ensure that a packet with a scoped source and/or
  * destination address does not leave its zone. This is currently implemented
  * in the input and forward functions. However, for output, these checks are
  * deliberately omitted in order to keep the implementation lightweight. The
  * routing algorithm in @ref ip6_route will take decisions such that it will
  * not cause zone violations unless the application sets bad addresses, though.
  *
  * In terms of scoping policy, lwIP implements the default policy from RFC 4007
  * using macros in this file. This policy considers link-local unicast
  * addresses and (only) interface-local and link-local multicast addresses as
  * having a scope. For all these addresses, the zone is equal to the interface.
  * As shown below in this file, it is possible to implement a custom policy.
  */
 
 /*
  * Copyright (c) 2017 The MINIX 3 Project.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *
  * 1. Redistributions of source code must retain the above copyright notice,
  *    this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright notice,
  *    this list of conditions and the following disclaimer in the documentation
  *    and/or other materials provided with the distribution.
  * 3. The name of the author may not be used to endorse or promote products
  *    derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
  * OF SUCH DAMAGE.
  *
  * This file is part of the lwIP TCP/IP stack.
  *
  * Author: David van Moolenbroek <david@minix3.org>
  *
  */
 #ifndef LWIP_HDR_IP6_ZONE_H
 #define LWIP_HDR_IP6_ZONE_H
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /**
  * @defgroup ip6_zones IPv6 Zones
  * @ingroup ip6
  * @{
  */
 
 #if LWIP_IPV6  /* don't build if not configured for use in lwipopts.h */
 
 /** Identifier for "no zone". */
 #define IP6_NO_ZONE 0
 
 #if LWIP_IPV6_SCOPES
 
 /** Zone initializer for static IPv6 address initialization, including comma. */
 #define IPADDR6_ZONE_INIT , IP6_NO_ZONE
 
 /** Return the zone index of the given IPv6 address; possibly "no zone". */
 #define ip6_addr_zone(ip6addr) ((ip6addr)->zone)
 
 /** Does the given IPv6 address have a zone set? (0/1) */
 #define ip6_addr_has_zone(ip6addr) (ip6_addr_zone(ip6addr) != IP6_NO_ZONE)
 
 /** Set the zone field of an IPv6 address to a particular value. */
 #define ip6_addr_set_zone(ip6addr, zone_idx) ((ip6addr)->zone = (zone_idx))
 
 /** Clear the zone field of an IPv6 address, setting it to "no zone". */
 #define ip6_addr_clear_zone(ip6addr) ((ip6addr)->zone = IP6_NO_ZONE)
 
 /** Copy the zone field from the second IPv6 address to the first one. */
 #define ip6_addr_copy_zone(ip6addr1, ip6addr2) ((ip6addr1).zone = (ip6addr2).zone)
 
 /** Is the zone field of the given IPv6 address equal to the given zone index? (0/1) */
 #define ip6_addr_equals_zone(ip6addr, zone_idx) ((ip6addr)->zone == (zone_idx))
 
 /** Are the zone fields of the given IPv6 addresses equal? (0/1)
  * This macro must only be used on IPv6 addresses of the same scope. */
 #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) ((ip6addr1)->zone == (ip6addr2)->zone)
 
 /** Symbolic constants for the 'type' parameters in some of the macros.
  * These exist for efficiency only, allowing the macros to avoid certain tests
  * when the address is known not to be of a certain type. Dead code elimination
  * will do the rest. IP6_MULTICAST is supported but currently not optimized.
  * @see ip6_addr_has_scope, ip6_addr_assign_zone, ip6_addr_lacks_zone.
  */
 enum lwip_ipv6_scope_type
 {
   /** Unknown */
   IP6_UNKNOWN   = 0,
   /** Unicast */
   IP6_UNICAST   = 1,
   /** Multicast */
   IP6_MULTICAST = 2
 };
 
 /** IPV6_CUSTOM_SCOPES: together, the following three macro definitions,
  * @ref ip6_addr_has_scope, @ref ip6_addr_assign_zone, and
  * @ref ip6_addr_test_zone, completely define the lwIP scoping policy.
  * The definitions below implement the default policy from RFC 4007 Sec. 6.
  * Should an implementation desire to implement a different policy, it can
  * define IPV6_CUSTOM_SCOPES to 1 and supply its own definitions for the three
  * macros instead.
  */
 #ifndef IPV6_CUSTOM_SCOPES
 #define IPV6_CUSTOM_SCOPES 0
 #endif /* !IPV6_CUSTOM_SCOPES */
 
 #if !IPV6_CUSTOM_SCOPES
 
 /**
  * Determine whether an IPv6 address has a constrained scope, and as such is
  * meaningful only if accompanied by a zone index to identify the scope's zone.
  * The given address type may be used to eliminate at compile time certain
  * checks that will evaluate to false at run time anyway.
  *
  * This default implementation follows the default model of RFC 4007, where
  * only interface-local and link-local scopes are defined.
  *
  * Even though the unicast loopback address does have an implied link-local
  * scope, in this implementation it does not have an explicitly assigned zone
  * index. As such it should not be tested for in this macro.
  *
  * @param ip6addr the IPv6 address (const); only its address part is examined.
  * @param type address type; see @ref lwip_ipv6_scope_type.
  * @return 1 if the address has a constrained scope, 0 if it does not.
  */
 #define ip6_addr_has_scope(ip6addr, type) \
   (ip6_addr_islinklocal(ip6addr) || (((type) != IP6_UNICAST) && \
    (ip6_addr_ismulticast_iflocal(ip6addr) || \
     ip6_addr_ismulticast_linklocal(ip6addr))))
 
 /**
  * Assign a zone index to an IPv6 address, based on a network interface. If the
  * given address has a scope, the assigned zone index is that scope's zone of
  * the given netif; otherwise, the assigned zone index is "no zone".
  *
  * This default implementation follows the default model of RFC 4007, where
  * only interface-local and link-local scopes are defined, and the zone index
  * of both of those scopes always equals the index of the network interface.
  * As such, this default implementation need not distinguish between different
  * constrained scopes when assigning the zone.
  *
  * @param ip6addr the IPv6 address; its address part is examined, and its zone
  *                index is assigned.
  * @param type address type; see @ref lwip_ipv6_scope_type.
  * @param netif the network interface (const).
  */
 #define ip6_addr_assign_zone(ip6addr, type, netif) \
     (ip6_addr_set_zone((ip6addr), \
       ip6_addr_has_scope((ip6addr), (type)) ? netif_get_index(netif) : 0))
 
 /**
  * Test whether an IPv6 address is "zone-compatible" with a network interface.
  * That is, test whether the network interface is part of the zone associated
  * with the address. For efficiency, this macro is only ever called if the
  * given address is either scoped or zoned, and thus, it need not test this.
  * If an address is scoped but not zoned, or zoned and not scoped, it is
  * considered not zone-compatible with any netif.
  *
  * This default implementation follows the default model of RFC 4007, where
  * only interface-local and link-local scopes are defined, and the zone index
  * of both of those scopes always equals the index of the network interface.
  * As such, there is always only one matching netif for a specific zone index,
  * but all call sites of this macro currently support multiple matching netifs
  * as well (at no additional expense in the common case).
  *
  * @param ip6addr the IPv6 address (const).
  * @param netif the network interface (const).
  * @return 1 if the address is scope-compatible with the netif, 0 if not.
  */
 #define ip6_addr_test_zone(ip6addr, netif) \
     (ip6_addr_equals_zone((ip6addr), netif_get_index(netif)))
 
 #endif /* !IPV6_CUSTOM_SCOPES */
 
 /** Does the given IPv6 address have a scope, and as such should also have a
  * zone to be meaningful, but does not actually have a zone? (0/1) */
 #define ip6_addr_lacks_zone(ip6addr, type) \
     (!ip6_addr_has_zone(ip6addr) && ip6_addr_has_scope((ip6addr), (type)))
 
 /**
  * Try to select a zone for a scoped address that does not yet have a zone.
  * Called from PCB bind and connect routines, for two reasons: 1) to save on
  * this (relatively expensive) selection for every individual packet route
  * operation and 2) to allow the application to obtain the selected zone from
  * the PCB as is customary for e.g. getsockname/getpeername BSD socket calls.
  *
  * Ideally, callers would always supply a properly zoned address, in which case
  * this function would not be needed. It exists both for compatibility with the
  * BSD socket API (which accepts zoneless destination addresses) and for
  * backward compatibility with pre-scoping lwIP code.
  *
  * It may be impossible to select a zone, e.g. if there are no netifs.  In that
  * case, the address's zone field will be left as is.
  *
  * @param dest the IPv6 address for which to select and set a zone.
  * @param src source IPv6 address (const); may be equal to dest.
  */
 #define ip6_addr_select_zone(dest, src) do { struct netif *selected_netif; \
   selected_netif = ip6_route((src), (dest)); \
   if (selected_netif != NULL) { \
     ip6_addr_assign_zone((dest), IP6_UNKNOWN, selected_netif); \
   } } while (0)
 
 /**
  * @}
  */
 
 #else /* LWIP_IPV6_SCOPES */
 
 #define IPADDR6_ZONE_INIT
 #define ip6_addr_zone(ip6addr) (IP6_NO_ZONE)
 #define ip6_addr_has_zone(ip6addr) (0)
 #define ip6_addr_set_zone(ip6addr, zone_idx)
 #define ip6_addr_clear_zone(ip6addr)
 #define ip6_addr_copy_zone(ip6addr1, ip6addr2)
 #define ip6_addr_equals_zone(ip6addr, zone_idx) (1)
 #define ip6_addr_cmp_zone(ip6addr1, ip6addr2) (1)
 #define IPV6_CUSTOM_SCOPES 0
 #define ip6_addr_has_scope(ip6addr, type) (0)
 #define ip6_addr_assign_zone(ip6addr, type, netif)
 #define ip6_addr_test_zone(ip6addr, netif) (1)
 #define ip6_addr_lacks_zone(ip6addr, type) (0)
 #define ip6_addr_select_zone(ip6addr, src)
 
 #endif /* LWIP_IPV6_SCOPES */
 
 #if LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG
 
 /** Verify that the given IPv6 address is properly zoned. */
 #define IP6_ADDR_ZONECHECK(ip6addr) LWIP_ASSERT("IPv6 zone check failed", \
     ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) == ip6_addr_has_zone(ip6addr))
 
 /** Verify that the given IPv6 address is properly zoned for the given netif. */
 #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif) LWIP_ASSERT("IPv6 netif zone check failed", \
     ip6_addr_has_scope(ip6addr, IP6_UNKNOWN) ? \
     (ip6_addr_has_zone(ip6addr) && \
      (((netif) == NULL) || ip6_addr_test_zone((ip6addr), (netif)))) : \
     !ip6_addr_has_zone(ip6addr))
 
 #else /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */
 
 #define IP6_ADDR_ZONECHECK(ip6addr)
 #define IP6_ADDR_ZONECHECK_NETIF(ip6addr, netif)
 
 #endif /* LWIP_IPV6_SCOPES && LWIP_IPV6_SCOPES_DEBUG */
 
 #endif /* LWIP_IPV6 */
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif /* LWIP_HDR_IP6_ZONE_H */
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