BadVPN – Rev 1
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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
/**
* @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 */
#endif /* LWIP_HDR_IP6_ADDR_H */