Internet Engineering Task Force (IETF) J. Jeong
Request for Comments: 6106 Brocade/ETRI
Obsoletes: 5006 S. Park
Category: Standards Track SAMSUNG Electronics
ISSN: 2070-1721 L. Beloeil
France Telecom R&D
S. Madanapalli
iRam Technologies
November 2010
Internet Engineering Task Force (IETF) J. Jeong
Request for Comments: 6106 Brocade/ETRI
Obsoletes: 5006 S. Park
Category: Standards Track SAMSUNG Electronics
ISSN: 2070-1721 L. Beloeil
France Telecom R&D
S. Madanapalli
iRam Technologies
November 2010
IPv6 Router Advertisement Options for DNS Configuration
用于DNS配置的IPv6路由器播发选项
Abstract
摘要
This document specifies IPv6 Router Advertisement options to allow IPv6 routers to advertise a list of DNS recursive server addresses and a DNS Search List to IPv6 hosts.
本文档指定IPv6路由器播发选项，以允许IPv6路由器向IPv6主机播发DNS递归服务器地址列表和DNS搜索列表。
Status of This Memo
关于下段备忘
This is an Internet Standards Track document.
这是一份互联网标准跟踪文件。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。有关互联网标准的更多信息，请参见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6106.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc6106.
Copyright Notice
版权公告
Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2010 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction ....................................................3
1.1. Applicability Statements ...................................3
1.2. Coexistence of RA Options and DHCP Options for DNS
Configuration ..............................................4
2. Requirements Language ...........................................4
3. Terminology .....................................................4
4. Overview ........................................................5
5. Neighbor Discovery Extension ....................................5
5.1. Recursive DNS Server Option ................................6
5.2. DNS Search List Option .....................................7
5.3. Procedure of DNS Configuration .............................8
5.3.1. Procedure in IPv6 Host ..............................8
5.3.2. Warnings for DNS Options Configuration .............10
6. Implementation Considerations ..................................10
6.1. DNS Repository Management .................................10
6.2. Synchronization between DNS Server List and
Resolver Repository .......................................11
6.3. Synchronization between DNS Search List and
Resolver Repository .......................................12
7. Security Considerations ........................................13
7.1. Security Threats ..........................................13
7.2. Recommendations ...........................................14
8. IANA Considerations ............................................15
9. Acknowledgements ...............................................15
10. References ....................................................16
10.1. Normative References .....................................16
10.2. Informative References ...................................16
Appendix A. Changes from RFC 5006 ................................18
1. Introduction ....................................................3
1.1. Applicability Statements ...................................3
1.2. Coexistence of RA Options and DHCP Options for DNS
Configuration ..............................................4
2. Requirements Language ...........................................4
3. Terminology .....................................................4
4. Overview ........................................................5
5. Neighbor Discovery Extension ....................................5
5.1. Recursive DNS Server Option ................................6
5.2. DNS Search List Option .....................................7
5.3. Procedure of DNS Configuration .............................8
5.3.1. Procedure in IPv6 Host ..............................8
5.3.2. Warnings for DNS Options Configuration .............10
6. Implementation Considerations ..................................10
6.1. DNS Repository Management .................................10
6.2. Synchronization between DNS Server List and
Resolver Repository .......................................11
6.3. Synchronization between DNS Search List and
Resolver Repository .......................................12
7. Security Considerations ........................................13
7.1. Security Threats ..........................................13
7.2. Recommendations ...........................................14
8. IANA Considerations ............................................15
9. Acknowledgements ...............................................15
10. References ....................................................16
10.1. Normative References .....................................16
10.2. Informative References ...................................16
Appendix A. Changes from RFC 5006 ................................18
The purpose of this document is to standardize an IPv6 Router Advertisement (RA) option for DNS Recursive Server Addresses used for the DNS name resolution in IPv6 hosts. This RA option was specified in an earlier Experimental specification [RFC5006]. This document is also to define a new RA option for Domain Name Search Lists for an enhanced DNS configuration. Thus, this document obsoletes [RFC5006], which only defines the RA option for DNS Recursive Server Addresses.
本文档旨在对IPv6主机中用于DNS名称解析的DNS递归服务器地址的IPv6路由器公告（RA）选项进行标准化。该RA选项在早期的实验规范[RFC5006]中规定。本文档还将为增强DNS配置的域名搜索列表定义一个新的RA选项。因此，本文档废弃了[RFC5006]，它只定义了DNS递归服务器地址的RA选项。
Neighbor Discovery (ND) for IP version 6 and IPv6 stateless address autoconfiguration provide ways to configure either fixed or mobile nodes with one or more IPv6 addresses, default routers, and some other parameters [RFC4861][RFC4862]. Most Internet services are identified by using a DNS name. The two RA options defined in this document provide the DNS information needed for an IPv6 host to reach Internet services.
IP版本6的邻居发现（ND）和IPv6无状态地址自动配置提供了使用一个或多个IPv6地址、默认路由器和一些其他参数配置固定或移动节点的方法[RFC4861][RFC4862]。大多数Internet服务都是通过使用DNS名称来标识的。本文档中定义的两个RA选项提供IPv6主机访问Internet服务所需的DNS信息。
It is infeasible to manually configure nomadic hosts each time they connect to a different network. While a one-time static configuration is possible, it is generally not desirable on general-purpose hosts such as laptops. For instance, locally defined name spaces would not be available to the host if it were to run its own name server software directly connected to the global DNS.
不可能在游牧主机每次连接到不同的网络时手动配置它们。虽然一次性静态配置是可能的，但在笔记本电脑等通用主机上通常不可取。例如，如果主机运行自己的直接连接到全局DNS的名称服务器软件，则本地定义的名称空间将不可用于主机。
The DNS information can also be provided through DHCP [RFC3315][RFC3736][RFC3646]. However, the access to DNS is a fundamental requirement for almost all hosts, so IPv6 stateless autoconfiguration cannot stand on its own as an alternative deployment model in any practical network without any support for DNS configuration.
DNS信息也可以通过DHCP[RFC3315][RFC3736][RFC3646]提供。然而，对DNS的访问是几乎所有主机的基本要求，因此IPv6无状态自动配置不能单独作为任何实际网络中的替代部署模型，而不支持DNS配置。
These issues are not pressing in dual-stack networks as long as a DNS server is available on the IPv4 side, but they become more critical with the deployment of IPv6-only networks. As a result, this document defines a mechanism based on IPv6 RA options to allow IPv6 hosts to perform the automatic DNS configuration.
只要IPv4端有DNS服务器可用，这些问题在双栈网络中并不紧迫，但随着仅IPv6网络的部署，这些问题变得更加关键。因此，本文档定义了一种基于IPv6 RA选项的机制，以允许IPv6主机执行自动DNS配置。
RA-based DNS configuration is a useful alternative in networks where an IPv6 host's address is autoconfigured through IPv6 stateless address autoconfiguration and where there is either no DHCPv6 infrastructure at all or some hosts do not have a DHCPv6 client. The intention is to enable the full configuration of basic networking information for hosts without requiring DHCPv6. However, when in
在通过IPv6无状态地址自动配置自动配置IPv6主机地址的网络中，以及在完全没有DHCPv6基础设施或某些主机没有DHCPv6客户端的网络中，基于RA的DNS配置是一种有用的替代方案。其目的是在不需要DHCPv6的情况下为主机启用基本网络信息的完整配置。然而，在
many networks some additional information needs to be distributed, those networks are likely to employ DHCPv6. In these networks, RA-based DNS configuration may not be needed.
许多网络需要分发一些附加信息，这些网络可能采用DHCPv6。在这些网络中，可能不需要基于RA的DNS配置。
RA-based DNS configuration allows an IPv6 host to acquire the DNS configuration (i.e., DNS recursive server addresses and DNS Search List) for the link(s) to which the host is connected. Furthermore, the host learns this DNS configuration from the same RA message that provides configuration information for the link, thereby avoiding also running DHCPv6.
基于RA的DNS配置允许IPv6主机获取主机所连接链路的DNS配置（即DNS递归服务器地址和DNS搜索列表）。此外，主机从为链路提供配置信息的相同RA消息中学习此DNS配置，从而避免也运行DHCPv6。
The advantages and disadvantages of the RA-based approach are discussed in [RFC4339] along with other approaches, such as the DHCP and well-known anycast address approaches.
[RFC4339]中讨论了基于RA的方法的优缺点以及其他方法，如DHCP和众所周知的选播地址方法。
Two protocols exist to configure the DNS information on a host, the Router Advertisement options described in this document and the DHCPv6 options described in [RFC3646]. They can be used together. The rules governing the decision to use stateful configuration mechanisms are specified in [RFC4861]. Hosts conforming to this specification MUST extract DNS information from Router Advertisement messages, unless static DNS configuration has been specified by the user. If there is DNS information available from multiple Router Advertisements and/or from DHCP, the host MUST maintain an ordered list of this information as specified in Section 5.3.1.
存在两种协议来配置主机上的DNS信息，本文档中描述的路由器播发选项和[RFC3646]中描述的DHCPv6选项。它们可以一起使用。[RFC4861]中规定了决定使用有状态配置机制的规则。符合此规范的主机必须从路由器广告消息中提取DNS信息，除非用户指定了静态DNS配置。如果有来自多个路由器广告和/或DHCP的DNS信息可用，主机必须按照第5.3.1节的规定维护该信息的有序列表。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中所述进行解释。
This document uses the terminology described in [RFC4861] and [RFC4862]. In addition, four new terms are defined below:
本文件使用[RFC4861]和[RFC4862]中描述的术语。此外，以下定义了四个新术语：
o Recursive DNS Server (RDNSS): Server that provides a recursive DNS resolution service for translating domain names into IP addresses as defined in [RFC1034] and [RFC1035].
o 递归DNS服务器（RDNS）：提供递归DNS解析服务的服务器，用于将域名转换为[RFC1034]和[RFC1035]中定义的IP地址。
o RDNSS Option: IPv6 RA option to deliver the RDNSS information to IPv6 hosts [RFC4861].
o RDNSS选项：用于将RDNSS信息传送到IPv6主机的IPv6 RA选项[RFC4861]。
o DNS Search List (DNSSL): The list of DNS suffix domain names used by IPv6 hosts when they perform DNS query searches for short, unqualified domain names.
o DNS搜索列表（DNSSL）：IPv6主机在执行DNS查询搜索短域名时使用的DNS后缀域名列表。
o DNSSL Option: IPv6 RA option to deliver the DNSSL information to IPv6 hosts.
o DNSSL选项：用于将DNSSL信息传递到IPv6主机的IPv6 RA选项。
o DNS Repository: Two data structures for managing DNS Configuration Information in the IPv6 protocol stack in addition to Neighbor Cache and Destination Cache for Neighbor Discovery [RFC4861]. The first data structure is the DNS Server List for RDNSS addresses and the second is the DNS Search List for DNS search domain names.
o DNS存储库：除邻居缓存和目标缓存外，用于管理IPv6协议栈中的DNS配置信息的两种数据结构，用于邻居发现[RFC4861]。第一个数据结构是用于RDNS地址的DNS服务器列表，第二个数据结构是用于DNS搜索域名的DNS搜索列表。
o Resolver Repository: Configuration repository with RDNSS addresses and a DNS Search List that a DNS resolver on the host uses for DNS name resolution; for example, the Unix resolver file (i.e., /etc/ resolv.conf) and Windows registry.
o 解析程序存储库：具有RDNS地址和DNS搜索列表的配置存储库，主机上的DNS解析程序用于DNS名称解析；例如，Unix解析器文件（即/etc/resolv.conf）和Windows注册表。
This document standardizes the ND option called the RDNSS option defined in [RFC5006] that contains the addresses of recursive DNS servers. This document also defines a new ND option called the DNSSL option for the Domain Search List. This is to maintain parity with the DHCPv6 options and to ensure that there is necessary functionality to determine the search domains.
本文档标准化了在[RFC5006]中定义的名为RDNSS选项的ND选项，该选项包含递归DNS服务器的地址。本文档还为域搜索列表定义了一个称为DNSSL选项的新ND选项。这是为了与DHCPv6选项保持一致，并确保有必要的功能来确定搜索域。
The existing ND message (i.e., Router Advertisement) is used to carry this information. An IPv6 host can configure the IPv6 addresses of one or more RDNSSes via RA messages. Through the RDNSS and DNSSL options, along with the prefix information option based on the ND protocol ([RFC4861] and [RFC4862]), an IPv6 host can perform the network configuration of its IPv6 address and the DNS information simultaneously without needing DHCPv6 for the DNS configuration. The RA options for RDNSS and DNSSL can be used on any network that supports the use of ND.
现有ND消息（即路由器广告）用于承载该信息。IPv6主机可以通过RA消息配置一个或多个RDNSE的IPv6地址。通过RDNS和DNSSL选项，以及基于ND协议的前缀信息选项（[RFC4861]和[RFC4862]），IPv6主机可以同时执行其IPv6地址和DNS信息的网络配置，而无需DHCPv6进行DNS配置。RDNS和DNSSL的RA选项可用于支持ND使用的任何网络。
This approach requires the manual configuration or other automatic mechanisms (e.g., DHCPv6 or vendor proprietary configuration mechanisms) to configure the DNS information in routers sending the advertisements. The automatic configuration of RDNSS addresses and a DNS Search List in routers is out of scope for this document.
这种方法需要手动配置或其他自动机制（例如，DHCPv6或供应商专有配置机制）来配置发送广告的路由器中的DNS信息。路由器中RDNS地址和DNS搜索列表的自动配置超出了本文档的范围。
The IPv6 DNS configuration mechanism in this document needs two new ND options in Neighbor Discovery: (i) the Recursive DNS Server (RDNSS) option and (ii) the DNS Search List (DNSSL) option.
本文档中的IPv6 DNS配置机制在邻居发现中需要两个新的ND选项：（i）递归DNS服务器（RDNS）选项和（ii）DNS搜索列表（DNSSL）选项。
The RDNSS option contains one or more IPv6 addresses of recursive DNS servers. All of the addresses share the same Lifetime value. If it is desirable to have different Lifetime values, multiple RDNSS options can be used. Figure 1 shows the format of the RDNSS option.
RDNSS选项包含递归DNS服务器的一个或多个IPv6地址。所有地址共享相同的生存期值。如果希望具有不同的生存期值，则可以使用多个RDNS选项。图1显示了RDNS选项的格式。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Addresses of IPv6 Recursive DNS Servers :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Addresses of IPv6 Recursive DNS Servers :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Recursive DNS Server (RDNSS) Option Format
图1：递归DNS服务器（RDNSS）选项格式
Fields: Type 8-bit identifier of the RDNSS option type as assigned by the IANA: 25
字段：输入IANA分配的RDNS选项类型的8位标识符：25
Length 8-bit unsigned integer. The length of the option (including the Type and Length fields) is in units of 8 octets. The minimum value is 3 if one IPv6 address is contained in the option. Every additional RDNSS address increases the length by 2. The Length field is used by the receiver to determine the number of IPv6 addresses in the option.
长度为8位无符号整数。选项的长度（包括类型和长度字段）以8个八位字节为单位。如果选项中包含一个IPv6地址，则最小值为3。每增加一个RDNS地址，长度就会增加2。接收器使用长度字段来确定选项中的IPv6地址数。
Lifetime 32-bit unsigned integer. The maximum time, in seconds (relative to the time the packet is sent), over which this RDNSS address MAY be used for name resolution. Hosts MAY send a Router Solicitation to ensure the RDNSS information is fresh before the interval expires. In order to provide fixed hosts with stable DNS service and allow mobile hosts to prefer local RDNSSes to remote RDNSSes, the value of Lifetime SHOULD be bounded as MaxRtrAdvInterval <= Lifetime <= 2*MaxRtrAdvInterval where MaxRtrAdvInterval is the Maximum RA Interval defined in [RFC4861]. A value of all one bits (0xffffffff) represents infinity. A value of zero means that the RDNSS address MUST no longer be used.
生存期32位无符号整数。此RDNS地址可用于名称解析的最长时间，以秒为单位（相对于发送数据包的时间）。主机可以发送路由器请求，以确保在间隔到期之前RDNS信息是新的。为了向固定主机提供稳定的DNS服务，并允许移动主机更喜欢本地RDNSE而不是远程RDNSE，生存期的值应限定为MaxRtrAdvInterval<=生存期<=2*MaxRtrAdvInterval，其中MaxRtrAdvInterval是[RFC4861]中定义的最大RA间隔。所有一位的值（0xFFFFFF）表示无穷大。值为零表示不能再使用RDNS地址。
Addresses of IPv6 Recursive DNS Servers One or more 128-bit IPv6 addresses of the recursive DNS servers. The number of addresses is determined by the Length field. That is, the number of addresses is equal to (Length - 1) / 2.
IPv6递归DNS服务器的地址递归DNS服务器的一个或多个128位IPv6地址。地址数由长度字段决定。也就是说，地址数等于（长度-1）/2。
The DNSSL option contains one or more domain names of DNS suffixes. All of the domain names share the same Lifetime value. If it is desirable to have different Lifetime values, multiple DNSSL options can be used. Figure 2 shows the format of the DNSSL option.
DNSSL选项包含一个或多个DNS后缀域名。所有域名共享相同的生存期值。如果希望具有不同的生存期值，则可以使用多个DNSSL选项。图2显示了DNSSL选项的格式。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Domain Names of DNS Search List :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Domain Names of DNS Search List :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: DNS Search List (DNSSL) Option Format
图2:DNS搜索列表（DNSSL）选项格式
Fields: Type 8-bit identifier of the DNSSL option type as assigned by the IANA: 31
字段：输入IANA分配的DNSSL选项类型的8位标识符：31
Length 8-bit unsigned integer. The length of the option (including the Type and Length fields) is in units of 8 octets. The minimum value is 2 if at least one domain name is contained in the option. The Length field is set to a multiple of 8 octets to accommodate all the domain names in the field of Domain Names of DNS Search List.
长度为8位无符号整数。选项的长度（包括类型和长度字段）以8个八位字节为单位。如果选项中至少包含一个域名，则最小值为2。长度字段设置为8个八位字节的倍数，以容纳DNS搜索列表域名字段中的所有域名。
Lifetime 32-bit unsigned integer. The maximum time, in seconds (relative to the time the packet is sent), over which this DNSSL domain name MAY be used for name resolution. The Lifetime value has the same semantics as with the RDNSS option. That is, Lifetime SHOULD be bounded as follows: MaxRtrAdvInterval <= Lifetime <= 2*MaxRtrAdvInterval.
生存期32位无符号整数。此DNSSL域名可用于名称解析的最长时间，以秒为单位（相对于发送数据包的时间）。生存期值的语义与RDNSS选项相同。也就是说，生命周期的界限应如下所示：maxrtradvnterval<=生命周期<=2*maxrtradvnterval。
A value of all one bits (0xffffffff) represents infinity. A value of zero means that the DNSSL domain name MUST no longer be used.
所有一位的值（0xFFFFFF）表示无穷大。值为零表示不能再使用DNSSL域名。
Domain Names of DNS Search List One or more domain names of DNS Search List that MUST be encoded using the technique described in Section 3.1 of [RFC1035]. By this technique, each domain name is represented as a sequence of labels ending in a zero octet, defined as domain name representation. For more than one domain name, the corresponding domain name representations are concatenated as they are. Note that for the simple decoding, the domain names MUST NOT be encoded in a compressed form, as described in Section 4.1.4 of [RFC1035]. Because the size of this field MUST be a multiple of 8 octets, for the minimum multiple including the domain name representations, the remaining octets other than the encoding parts of the domain name representations MUST be padded with zeros.
DNS搜索列表域名必须使用[RFC1035]第3.1节中所述的技术对DNS搜索列表中的一个或多个域名进行编码。通过这种技术，每个域名都表示为一系列以零八位元结尾的标签，定义为域名表示。对于多个域名，相应的域名表示按原样连接。注意，对于简单解码，不得以压缩形式对域名进行编码，如[RFC1035]第4.1.4节所述。由于此字段的大小必须是8个八位字节的倍数，对于包含域名表示的最小倍数，除域名表示的编码部分之外的其余八位字节必须用零填充。
Note: An RDNSS address or a DNSSL domain name MUST be used only as long as both the RA router Lifetime (advertised by a Router Advertisement message [RFC4861]) and the corresponding option Lifetime have not expired. The reason is that in the current network to which an IPv6 host is connected, the RDNSS may not be currently reachable, that the DNSSL domain name is not valid any more, or that these options do not provide service to the host's current address (e.g., due to network ingress filtering [RFC2827][RFC5358]).
注意：RDNS地址或DNSSL域名必须在RA路由器生存期（通过路由器公告消息[RFC4861]公告）和相应的选项生存期未过期的情况下使用。原因是，在IPv6主机连接的当前网络中，RDNS当前可能无法访问，DNSSL域名不再有效，或者这些选项不向主机的当前地址提供服务（例如，由于网络入口过滤[RFC2827][RFC5358]）。
The procedure of DNS configuration through the RDNSS and DNSSL options is the same as with any other ND option [RFC4861].
通过RDNS和DNSSL选项进行DNS配置的过程与任何其他ND选项相同[RFC4861]。
When an IPv6 host receives DNS options (i.e., RDNSS option and DNSSL option) through RA messages, it processes the options as follows:
当IPv6主机通过RA消息接收DNS选项（即RDNSS选项和DNSSL选项）时，它将按如下方式处理选项：
o The validity of DNS options is checked with the Length field; that is, the value of the Length field in the RDNSS option is greater than or equal to the minimum value (3), and the value of the Length field in the DNSSL option is greater than or equal to the minimum value (2).
o 使用长度字段检查DNS选项的有效性；即，RDNSS选项中长度字段的值大于或等于最小值（3），DNSSL选项中长度字段的值大于或等于最小值（2）。
o If the DNS options are valid, the host SHOULD copy the values of the options into the DNS Repository and the Resolver Repository in order. Otherwise, the host MUST discard the options. Refer to Section 6 for the detailed procedure.
o 如果DNS选项有效，主机应按顺序将选项的值复制到DNS存储库和解析程序存储库中。否则，主机必须放弃这些选项。有关详细程序，请参阅第6节。
When the IPv6 host has gathered a sufficient number (e.g., three) of RDNSS addresses (or DNS search domain names), it SHOULD maintain RDNSS addresses (or DNS search domain names) by the sufficient number such that the latest received RDNSS or DNSSL is more preferred to the old ones; that is, when the number of RDNSS addresses (or DNS search domain names) is already the sufficient number, the new one replaces the old one that will expire first in terms of Lifetime. As an exceptional case, if the received RDNSS addresses (or DNS search domain names) already exist in the IPv6 host, their Lifetime fields update their Expiration-time, that is, when the corresponding DNS information expires in the IPv6 host; note that when the Lifetime field has zero, the corresponding RDNSS (or DNS search domain name) is deleted from the IPv6 host. Except for this update, the IPv6 host SHOULD ignore other RDNSS addresses (or DNS search domain names) within an RDNSS (or a DNSSL) option and/or additional RDNSS (or DNSSL) options within an RA. Refer to Section 6 for the detailed procedure. Note that the sufficient number is a system parameter, so it can be determined by a local policy. Also, separate parameters can be specified for the sufficient number of RDNSS addresses and that of DNS search domain names, respectively. In this document, three is RECOMMENDED as a sufficient number considering both the robust DNS query and the reasonably time-bounded recognition of the unreachability of DNS servers.
当IPv6主机收集了足够数量（如三个）的RDNS地址（或DNS搜索域名）时，它应保持足够数量的RDNS地址（或DNS搜索域名），以便最新收到的RDNS或DNSSL比旧的更优先；也就是说，当rdns地址（或DNS搜索域名）的数量已经足够时，新地址将替换将在生存期内首先过期的旧地址。作为例外情况，如果接收到的RDNS地址（或DNS搜索域名）已存在于IPv6主机中，则其生存期字段将更新其过期时间，即当相应的DNS信息在IPv6主机中过期时；请注意，当生存期字段为零时，将从IPv6主机中删除相应的RDNS（或DNS搜索域名）。除此更新外，IPv6主机应忽略RDNS（或DNSSL）选项中的其他RDNS地址（或DNS搜索域名）和/或RA中的其他RDNS（或DNSSL）选项。有关详细程序，请参阅第6节。请注意，足够数量是一个系统参数，因此可以由本地策略确定。此外，可以分别为足够数量的RDNS地址和DNS搜索域名指定单独的参数。在本文中，考虑到稳健的DNS查询和对DNS服务器不可访问性的合理时间限制识别，建议将三个作为足够的数目。
In the case where the DNS options of RDNSS and DNSSL can be obtained from multiple sources, such as RA and DHCP, the IPv6 host SHOULD keep some DNS options from all sources. Unless explicitly specified for the discovery mechanism, the exact number of addresses and domain names to keep is a matter of local policy and implementation choice. However, the ability to store at least three RDNSS addresses (or DNSSL domain names) from at least two different sources is RECOMMENDED. The DNS options from Router Advertisements and DHCP SHOULD be stored into the DNS Repository and Resolver Repository so that information from DHCP appears there first and therefore takes precedence. Thus, the DNS information from DHCP takes precedence over that from RA for DNS queries. On the other hand, for DNS options announced by RA, if some RAs use the Secure Neighbor Discovery (SEND) protocol [RFC3971] for RA security, they MUST be preferred over those that do not use SEND. Refer to Section 7 for the detailed discussion on SEND for RA DNS options.
如果可以从多个源（如RA和DHCP）获取RDNS和DNSSL的DNS选项，IPv6主机应保留来自所有源的一些DNS选项。除非为发现机制明确指定，否则要保留的地址和域名的确切数量取决于本地策略和实现选择。但是，建议能够存储至少两个不同来源的至少三个RDNS地址（或DNSSL域名）。路由器播发和DHCP中的DNS选项应存储在DNS存储库和解析程序存储库中，以便DHCP中的信息首先出现在那里，因此优先。因此，对于DNS查询，来自DHCP的DNS信息优先于来自RA的DNS信息。另一方面，对于RA宣布的DNS选项，如果一些RA使用安全邻居发现（SEND）协议[RFC3971]来实现RA安全，则必须优先于不使用SEND的。有关发送RA DNS选项的详细讨论，请参阅第7节。
There are two warnings for DNS options configuration: (i) warning for multiple sources of DNS options and (ii) warning for multiple network interfaces. First, in the case of multiple sources for DNS options (e.g., RA and DHCP), an IPv6 host can configure its IP addresses from these sources. In this case, it is not possible to control how the host uses DNS information and what source addresses it uses to send DNS queries. As a result, configurations where different information is provided by different sources may lead to problems. Therefore, the network administrator needs to configure DNS options in multiple sources in order to prevent such problems from happening.
DNS选项配置有两个警告：（i）多个DNS选项源的警告和（ii）多个网络接口的警告。首先，对于DNS选项的多个源（例如RA和DHCP），IPv6主机可以从这些源配置其IP地址。在这种情况下，无法控制主机如何使用DNS信息以及它用于发送DNS查询的源地址。因此，由不同来源提供不同信息的配置可能会导致问题。因此，网络管理员需要在多个源中配置DNS选项，以防止发生此类问题。
Second, if different DNS information is provided on different network interfaces, this can lead to inconsistent behavior. The IETF is working on solving this problem for both DNS and other information obtained by multiple interfaces [MIF-PROBLEM][MIF-PRACTICE].
其次，如果在不同的网络接口上提供不同的DNS信息，这可能会导致不一致的行为。IETF正致力于解决DNS和通过多个接口获得的其他信息的这个问题[MIF-problem][MIF-PRACTICE]。
Note: This non-normative section gives some hints for implementing the processing of the RDNSS and DNSSL options in an IPv6 host.
注意：本非规范性部分给出了在IPv6主机中实现RDNS和DNSSL选项处理的一些提示。
For the configuration and management of DNS information, the advertised DNS configuration information can be stored and managed in both the DNS Repository and the Resolver Repository.
对于DNS信息的配置和管理，可以在DNS存储库和解析程序存储库中存储和管理公布的DNS配置信息。
In environments where the DNS information is stored in user space and ND runs in the kernel, it is necessary to synchronize the DNS information (i.e., RDNSS addresses and DNS search domain names) in kernel space and the Resolver Repository in user space. For the synchronization, an implementation where ND works in the kernel should provide a write operation for updating DNS information from the kernel to the Resolver Repository. One simple approach is to have a daemon (or a program that is called at defined intervals) that keeps monitoring the Lifetimes of RDNSS addresses and DNS search domain names all the time. Whenever there is an expired entry in the DNS Repository, the daemon can delete the corresponding entry from the Resolver Repository.
在DNS信息存储在用户空间且ND在内核中运行的环境中，需要同步内核空间中的DNS信息（即RDNS地址和DNS搜索域名）和用户空间中的解析程序存储库。对于同步，ND在内核中工作的实现应该提供一个写操作，用于将DNS信息从内核更新到解析器存储库。一种简单的方法是使用一个守护进程（或一个按定义的时间间隔调用的程序），该守护进程始终监视RDNS地址和DNS搜索域名的生命周期。每当DNS存储库中有过期的条目时，守护进程都可以从解析器存储库中删除相应的条目。
For DNS repository management, the kernel or user-space process (depending on where RAs are processed) should maintain two data structures: (i) DNS Server List that keeps the list of RDNSS addresses and (ii) DNS Search List that keeps the list of DNS search domain names. Each entry in these two lists consists of a pair of an RDNSS address (or DNSSL domain name) and Expiration-time as follows:
对于DNS存储库管理，内核或用户空间进程（取决于处理RAs的位置）应维护两个数据结构：（i）保留RDNS地址列表的DNS服务器列表和（ii）保留DNS搜索域名列表的DNS搜索列表。这两个列表中的每个条目由一对RDNSS地址（或DNSSL域名）和过期时间组成，如下所示：
o RDNSS address for DNS Server List: IPv6 address of the Recursive DNS Server, which is available for recursive DNS resolution service in the network advertising the RDNSS option.
o DNS服务器的RDNS地址列表：递归DNS服务器的IPv6地址，该地址可用于发布RDNS选项的网络中的递归DNS解析服务。
o DNSSL domain name for DNS Search List: DNS suffix domain names, which are used to perform DNS query searches for short, unqualified domain names in the network advertising the DNSSL option.
o DNS搜索列表的DNSSL域名：DNS后缀域名，用于在公布DNSSL选项的网络中对短的、不合格的域名执行DNS查询搜索。
o Expiration-time for DNS Server List or DNS Search List: The time when this entry becomes invalid. Expiration-time is set to the value of the Lifetime field of the RDNSS option or DNSSL option plus the current system time. Whenever a new RDNSS option with the same address (or DNSSL option with the same domain name) is received on the same interface as a previous RDNSS option (or DNSSL option), this field is updated to have a new Expiration-time. When Expiration-time becomes less than the current system time, this entry is regarded as expired.
o DNS服务器列表或DNS搜索列表的过期时间：此项无效的时间。过期时间设置为RDNSS选项或DNSSL选项的生存期字段值加上当前系统时间。每当在与以前的RDNS选项（或DNSSL选项）相同的接口上接收到具有相同地址的新RDNS选项（或具有相同域名的DNSSL选项）时，此字段将更新为具有新的过期时间。当过期时间小于当前系统时间时，此条目被视为过期。
When an IPv6 host receives the information of multiple RDNSS addresses within a network (e.g., campus network and company network) through an RA message with RDNSS option(s), it stores the RDNSS addresses (in order) into both the DNS Server List and the Resolver Repository. The processing of the RDNSS consists of (i) the processing of RDNSS option(s) included in an RA message and (ii) the handling of expired RDNSSes. The processing of RDNSS option(s) is as follows:
当IPv6主机通过带有RDNS选项的RA消息接收到网络（如校园网和公司网）内多个RDNS地址的信息时，它会将RDNS地址（按顺序）存储到DNS服务器列表和解析程序存储库中。RDNS的处理包括（i）处理RA消息中包含的RDNS选项和（ii）处理过期的RDNS。RDNS选项的处理如下所示：
Step (a): Receive and parse the RDNSS option(s). For the RDNSS addresses in each RDNSS option, perform Steps (b) through (d).
步骤（a）：接收并解析RDNSS选项。对于每个RDNS选项中的RDNS地址，执行步骤（b）至（d）。
Step (b): For each RDNSS address, check the following: If the RDNSS address already exists in the DNS Server List and the RDNSS option's Lifetime field is set to zero, delete the corresponding RDNSS entry from both the DNS Server List and the Resolver Repository in order to prevent the RDNSS address from being used any more for certain reasons in network management, e.g., the termination of the RDNSS or a renumbering situation. That is, the RDNSS can resign from its DNS service because the machine running the RDNSS is out of service intentionally or unintentionally. Also, under the renumbering situation, the RDNSS's IPv6 address will be changed, so the previous RDNSS address should not be used any more. The processing of this RDNSS address is finished here. Otherwise, go to Step (c).
步骤（b）：对于每个RDNS地址，检查以下内容：如果DNS服务器列表中已经存在RDNS地址，并且RDNS选项的生存期字段设置为零，从DNS服务器列表和解析程序存储库中删除相应的RDNS条目，以防止RDNS地址因网络管理中的某些原因而被再次使用，例如，RDNS终止或重新编号情况。也就是说，RDNS可以退出其DNS服务，因为运行RDNS的机器有意或无意地停止服务。此外，在重新编号的情况下，RDNS的IPv6地址将发生更改，因此不应再使用以前的RDNS地址。此RDNS地址的处理在此完成。否则，转至步骤（c）。
Step (c): For each RDNSS address, if it already exists in the DNS Server List, then just update the value of the Expiration-time field according to the procedure specified in the third bullet of Section 6.1. Otherwise, go to Step (d).
步骤（c）：对于每个RDNS地址，如果它已经存在于DNS服务器列表中，则只需根据第6.1节第三个项目符号中指定的程序更新过期时间字段的值。否则，转至步骤（d）。
Step (d): For each RDNSS address, if it does not exist in the DNS Server List, register the RDNSS address and Lifetime with the DNS Server List and then insert the RDNSS address in front of the Resolver Repository. In the case where the data structure for the DNS Server List is full of RDNSS entries (that is, has more RDNSSes than the sufficient number discussed in Section 5.3.1), delete from the DNS Server List the entry with the shortest Expiration-time (i.e., the entry that will expire first). The corresponding RDNSS address is also deleted from the Resolver Repository. For the ordering of RDNSS addresses in an RDNSS option, position the first RDNSS address in the RDNSS option as the first one in the Resolver Repository, the second RDNSS address in the option as the second one in the repository, and so on. This ordering allows the RDNSS addresses in the RDNSS option to be preferred according to their order in the RDNSS option for the DNS name resolution. The processing of these RDNSS addresses is finished here.
步骤（d）：对于每个RDNS地址，如果它不存在于DNS服务器列表中，则向DNS服务器列表注册RDNS地址和生存期，然后将RDNS地址插入解析程序存储库前面。如果DNS服务器列表的数据结构中满是RDNSS条目（即，RDNSS的数量超过第5.3.1节中讨论的足够数量），请从DNS服务器列表中删除过期时间最短的条目（即首先过期的条目）。相应的RDNS地址也将从冲突解决程序存储库中删除。对于RDNSS选项中RDNSS地址的排序，请将RDNSS选项中的第一个RDNSS地址定位为冲突解决程序存储库中的第一个，将选项中的第二个RDNSS地址定位为存储库中的第二个，依此类推。此顺序允许根据DNS名称解析的RDNSS选项中的RDNSS地址顺序，优先选择RDNSS选项中的RDNSS地址。这些RDNS地址的处理在此完成。
The handling of expired RDNSSes is as follows: Whenever an entry expires in the DNS Server List, the expired entry is deleted from the DNS Server List, and also the RDNSS address corresponding to the entry is deleted from the Resolver Repository.
过期的RDNSS的处理如下：每当DNS服务器列表中的条目过期时，过期的条目将从DNS服务器列表中删除，并且与该条目对应的RDNSS地址也将从解析程序存储库中删除。
When an IPv6 host receives the information of multiple DNSSL domain names within a network (e.g., campus network and company network) through an RA message with DNSSL option(s), it stores the DNSSL domain names (in order) into both the DNS Search List and the Resolver Repository. The processing of the DNSSL consists of (i) the processing of DNSSL option(s) included in an RA message and (ii) the handling of expired DNSSLs. The processing of DNSSL option(s) is as follows:
当IPv6主机通过带有DNSSL选项的RA消息接收到网络（例如校园网和公司网络）内多个DNSSL域名的信息时，它会将DNSSL域名（按顺序）存储到DNS搜索列表和解析程序存储库中。DNSSL的处理包括（i）处理RA消息中包含的DNSSL选项和（ii）处理过期的DNSSL。DNSSL选项的处理如下所示：
Step (a): Receive and parse the DNSSL option(s). For the DNSSL domain names in each DNSSL option, perform Steps (b) through (d).
步骤（a）：接收并解析DNSSL选项。对于每个DNSSL选项中的DNSSL域名，执行步骤（b）至（d）。
Step (b): For each DNSSL domain name, check the following: If the DNSSL domain name already exists in the DNS Search List and the DNSSL option's Lifetime field is set to zero, delete the corresponding DNSSL entry from both the DNS Search List and the Resolver Repository in order to prevent the DNSSL domain name from being used any more for certain reasons in network management,
步骤（b）：对于每个DNSSL域名，检查以下内容：如果DNS搜索列表中已经存在DNSSL域名，并且DNSSL选项的生存期字段设置为零，从DNS搜索列表和解析程序存储库中删除相应的DNSSL条目，以防止由于网络管理中的某些原因再次使用DNSSL域名，
e.g., the termination of the RDNSS or a renaming situation. That is, the RDNSS can resign from its DNS service because the machine running the RDNSS is out of service intentionally or unintentionally. Also, under the renaming situation, the DNSSL domain names will be changed, so the previous domain names should not be used any more. The processing of this DNSSL domain name is finished here. Otherwise, go to Step (c).
e、 例如，RDNS的终止或重命名情况。也就是说，RDNS可以退出其DNS服务，因为运行RDNS的机器有意或无意地停止服务。另外，在重命名情况下，DNSSL域名将被更改，因此不应再使用以前的域名。此DNSSL域名的处理在此完成。否则，转至步骤（c）。
Step (c): For each DNSSL domain name, if it already exists in the DNS Server List, then just update the value of the Expiration-time field according to the procedure specified in the third bullet of Section 6.1. Otherwise, go to Step (d).
步骤（c）：对于每个DNSSL域名，如果它已经存在于DNS服务器列表中，则只需根据第6.1节第三个项目符号中指定的程序更新过期时间字段的值。否则，转至步骤（d）。
Step (d): For each DNSSL domain name, if it does not exist in the DNS Search List, register the DNSSL domain name and Lifetime with the DNS Search List and then insert the DNSSL domain name in front of the Resolver Repository. In the case where the data structure for the DNS Search List is full of DNSSL domain name entries (that is, has more DNSSL domain names than the sufficient number discussed in Section 5.3.1), delete from the DNS Server List the entry with the shortest Expiration-time (i.e., the entry that will expire first). The corresponding DNSSL domain name is also deleted from the Resolver Repository. For the ordering of DNSSL domain names in a DNSSL option, position the first DNSSL domain name in the DNSSL option as the first one in the Resolver Repository, the second DNSSL domain name in the option as the second one in the repository, and so on. This ordering allows the DNSSL domain names in the DNSSL option to be preferred according to their order in the DNSSL option for the DNS domain name used by the DNS query. The processing of these DNSSL domain name is finished here.
步骤（d）：对于每个DNSSL域名，如果它不在DNS搜索列表中，请在DNS搜索列表中注册DNSSL域名和生存期，然后将DNSSL域名插入解析程序存储库前面。如果DNS搜索列表的数据结构中满是DNSSL域名条目（即，DNSSL域名的数量超过第5.3.1节中讨论的足够数量），请从DNS服务器列表中删除过期时间最短的条目（即首先过期的条目）。相应的DNSSL域名也将从冲突解决程序存储库中删除。对于DNSSL选项中DNSSL域名的排序，请将DNSSL选项中的第一个DNSSL域名定位为冲突解决程序存储库中的第一个，将选项中的第二个DNSSL域名定位为存储库中的第二个，依此类推。此排序允许根据DNS查询使用的DNS域名在DNSSL选项中的顺序，优先选择DNSSL选项中的DNSSL域名。这些DNSSL域名的处理在此完成。
The handling of expired DNSSLs is as follows: Whenever an entry expires in the DNS Search List, the expired entry is deleted from the DNS Search List, and also the DNSSL domain name corresponding to the entry is deleted from the Resolver Repository.
过期DNSSL的处理如下：每当DNS搜索列表中的条目过期时，将从DNS搜索列表中删除过期条目，并从解析程序存储库中删除该条目对应的DNSSL域名。
In this section, we analyze security threats related to DNS options and then suggest recommendations to cope with such security threats.
在本节中，我们将分析与DNS选项相关的安全威胁，然后提出应对此类安全威胁的建议。
For the RDNSS option, an attacker could send an RA with a fraudulent RDNSS address, misleading IPv6 hosts into contacting an unintended DNS server for DNS name resolution. Also, for the DNSSL option, an
对于RDNSS选项，攻击者可以发送带有欺诈性RDNSS地址的RA，从而误导IPv6主机联系意外的DNS服务器进行DNS名称解析。另外，对于DNSSL选项
attacker can let IPv6 hosts resolve a host name without a DNS suffix into an unintended host's IP address with a fraudulent DNS Search List.
攻击者可以让IPv6主机使用欺诈性DNS搜索列表将不带DNS后缀的主机名解析为非预期主机的IP地址。
These attacks are similar to Neighbor Discovery attacks that use Redirect or Neighbor Advertisement messages to redirect traffic to individual addresses of malicious parties. That is, as a rogue router, a malicious node on a LAN can promiscuously receive packets for any router's Media Access Control (MAC) address and send packets with the router's MAC address as the source MAC address in the Layer 2 (L2) header. As a result, L2 switches send packets addressed to the router to the malicious node. Also, this attack can send redirects that tell the hosts to send their traffic somewhere else. The malicious node can send unsolicited RA or Neighbor Advertisement (NA) replies, answer RS or Neighbor Solicitation (NS) requests, etc. Thus, the attacks related to RDNSS and DNSSL are similar to both Neighbor Discovery attacks and attacks against unauthenticated DHCP, as both can be used for both "wholesale" traffic redirection and more specific attacks.
这些攻击与邻居发现攻击类似，邻居发现攻击使用重定向或邻居广告消息将流量重定向到恶意方的各个地址。也就是说，作为流氓路由器，LAN上的恶意节点可以杂乱地接收任何路由器的媒体访问控制（MAC）地址的数据包，并在第2层（L2）报头中以路由器的MAC地址作为源MAC地址发送数据包。因此，L2交换机将发送到路由器的数据包发送到恶意节点。此外，此攻击还可以发送重定向，通知主机将其流量发送到其他地方。恶意节点可以发送未经请求的RA或邻居公告（NA）回复、应答RS或邻居请求（NS）请求等。因此，与RDNS和DNSSL相关的攻击类似于邻居发现攻击和针对未经验证的DHCP的攻击，因为这两种攻击都可用于“批发”流量重定向和更具体的攻击。
However, the security of these RA options for DNS configuration does not affect ND protocol security [RFC4861]. This is because learning DNS information via the RA options cannot be worse than learning bad router information via the RA options. Therefore, the vulnerability of ND is not worse and is a subset of the attacks that any node attached to a LAN can do independently of ND.
但是，DNS配置的这些RA选项的安全性不影响ND协议安全性[RFC4861]。这是因为通过RA选项学习DNS信息比通过RA选项学习坏路由器信息更糟糕。因此，ND的漏洞并不更严重，而是连接到LAN的任何节点都可以独立于ND进行的攻击的子集。
The Secure Neighbor Discovery (SEND) protocol [RFC3971] is used as a security mechanism for ND. It is RECOMMENDED that ND use SEND to allow all the ND options including the RDNSS and DNSSL options to be automatically included in the signatures. Through SEND, the transport for the RA options is integrity protected; that is, SEND can prevent the spoofing of these DNS options with signatures. Also, SEND enables an IPv6 host to verify that the sender of an RA is actually a router authorized to act as a router. However, since any valid SEND router can still insert RDNSS and DNSSL options, the current SEND cannot verify which one is or is not authorized to send the options. Thus, this verification of the authorized routers for ND options will be required. [CSI-SEND-CERT] specifies the usage of extended key for the certificate deployed in SEND. This document defines the roles of routers (i.e., routers acting as proxy and address owner) and explains the authorization of the roles. The mechanism in this document can be extended to verify which routers are authorized to insert RDNSS and DNSSL options.
安全邻居发现（SEND）协议[RFC3971]用作ND的安全机制。建议ND使用SEND允许所有ND选项（包括RDNS和DNSSL选项）自动包含在签名中。通过发送，RA选项的传输受到完整性保护；也就是说，SEND可以防止使用签名欺骗这些DNS选项。此外，SEND允许IPv6主机验证RA的发送方实际上是被授权充当路由器的路由器。但是，由于任何有效的发送路由器仍然可以插入RDNS和DNSSL选项，因此当前发送无法验证哪个路由器有权或没有权发送选项。因此，需要对ND选项的授权路由器进行验证。[CSI-SEND-CERT]指定在SEND中部署的证书的扩展密钥的用法。本文档定义了路由器的角色（即作为代理和地址所有者的路由器），并解释了角色的授权。本文档中的机制可以扩展以验证哪些路由器有权插入RDNS和DNSSL选项。
It is common for network devices such as switches to include mechanisms to block unauthorized ports from running a DHCPv6 server to provide protection from rogue DHCP servers. That means that an attacker on other ports cannot insert bogus DNS servers using DHCPv6. The corresponding technique for network devices is RECOMMENDED to block rogue Router Advertisement messages including the RDNSS and DNSSL options from unauthorized nodes.
网络设备（如交换机）通常包括阻止未经授权端口运行DHCPv6服务器的机制，以提供针对恶意DHCP服务器的保护。这意味着其他端口上的攻击者无法使用DHCPv6插入伪造的DNS服务器。建议使用网络设备的相应技术来阻止来自未经授权节点的恶意路由器广告消息，包括RDNS和DNSSL选项。
An attacker may provide a bogus DNS Search List option in order to cause the victim to send DNS queries to a specific DNS server when the victim queries non-FQDNs (fully qualified domain names). For this attack, the DNS resolver in IPv6 hosts can mitigate the vulnerability with the recommendations mentioned in [RFC1535], [RFC1536], and [RFC3646].
攻击者可能提供虚假DNS搜索列表选项，以便在受害者查询非FQDNs（完全限定域名）时，使受害者向特定DNS服务器发送DNS查询。对于此攻击，IPv6主机中的DNS解析器可以使用[RFC1535]、[RFC1536]和[RFC3646]中提到的建议来缓解此漏洞。
The RDNSS option defined in this document uses the IPv6 Neighbor Discovery Option type defined in RFC 5006 [RFC5006], which was assigned by the IANA as follows:
本文档中定义的RDNSS选项使用RFC 5006[RFC5006]中定义的IPv6邻居发现选项类型，IANA将其分配如下：
Option Name Type Recursive DNS Server Option 25
选项名称类型递归DNS服务器选项25
The IANA has assigned a new IPv6 Neighbor Discovery Option type for the DNSSL option defined in this document:
IANA已为本文档中定义的DNSSL选项分配了新的IPv6邻居发现选项类型：
Option Name Type DNS Search List Option 31
选项名称类型DNS搜索列表选项31
These options have been registered in the "Internet Control Message Protocol version 6 (ICMPv6) Parameters" registry (http://www.iana.org).
这些选项已在“Internet控制消息协议版本6（ICMPv6）参数”注册表中注册(http://www.iana.org).
This document has greatly benefited from inputs by Robert Hinden, Pekka Savola, Iljitsch van Beijnum, Brian Haberman, Tim Chown, Erik Nordmark, Dan Wing, Jari Arkko, Ben Campbell, Vincent Roca, and Tony Cheneau. The authors sincerely appreciate their contributions.
本文件从Robert Hinden、Pekka Savola、Iljitsch van Beijnum、Brian Haberman、Tim Chown、Erik Nordmark、Dan Wing、Jari Arkko、Ben Campbell、Vincent Roca和Tony Cheneau的投入中获益匪浅。作者衷心感谢他们的贡献。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007.
[RFC4861]Narten，T.，Nordmark，E.，Simpson，W.，和H.Soliman，“IP版本6（IPv6）的邻居发现”，RFC 48612007年9月。
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, September 2007.
[RFC4862]Thomson，S.，Narten，T.，和T.Jinmei，“IPv6无状态地址自动配置”，RFC 48622007年9月。
[RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987.
[RFC1035]Mockapetris，P.，“域名-实现和规范”，STD 13，RFC 1035，1987年11月。
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987.
[RFC1034]Mockapetris，P.，“域名-概念和设施”，STD 13，RFC 1034，1987年11月。
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3315]Droms，R.，Bound，J.，Volz，B.，Lemon，T.，Perkins，C.，和M.Carney，“IPv6的动态主机配置协议（DHCPv6）”，RFC3315，2003年7月。
[RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6", RFC 3736, April 2004.
[RFC3736]Droms，R.，“IPv6的无状态动态主机配置协议（DHCP）服务”，RFC 3736，2004年4月。
[RFC3646] Droms, R., "DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, December 2003.
[RFC3646]Droms，R.，“IPv6动态主机配置协议（DHCPv6）的DNS配置选项”，RFC 36462003年12月。
[RFC5006] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, "IPv6 Router Advertisement Option for DNS Configuration", RFC 5006, September 2007.
[RFC5006]Jeong，J.，Park，S.，Beloeil，L.，和S.Madanapalli，“DNS配置的IPv6路由器广告选项”，RFC 5006，2007年9月。
[RFC4339] Jeong, J., "IPv6 Host Configuration of DNS Server Information Approaches", RFC 4339, February 2006.
[RFC4339]Jeong，J.，“DNS服务器信息方法的IPv6主机配置”，RFC 4339，2006年2月。
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC3971]Arkko，J.，Kempf，J.，Zill，B.，和P.Nikander，“安全邻居发现（SEND）”，RFC 39712005年3月。
[RFC5358] Damas, J. and F. Neves, "Preventing Use of Recursive Nameservers in Reflector Attacks", BCP 140, RFC 5358, October 2008.
[RFC5358]Damas，J.和F.Neves，“防止在反射器攻击中使用递归名称服务器”，BCP 140，RFC 5358，2008年10月。
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, May 2000.
[RFC2827]Ferguson，P.和D.Senie，“网络入口过滤：击败利用IP源地址欺骗的拒绝服务攻击”，BCP 38，RFC 2827，2000年5月。
[RFC1535] Gavron, E., "A Security Problem and Proposed Correction With Widely Deployed DNS Software", RFC 1535, October 1993.
[RFC1535]Gavron，E.，“广泛部署DNS软件的安全问题和建议纠正”，RFC 1535，1993年10月。
[RFC1536] Kumar, A., Postel, J., Neuman, C., Danzig, P., and S. Miller, "Common DNS Implementation Errors and Suggested Fixes", RFC 1536, October 1993.
[RFC1536]Kumar，A.，Postel，J.，Neuman，C.，Danzig，P.，和S.Miller，“常见DNS实现错误和建议修复”，RFC 1536，1993年10月。
[MIF-PROBLEM] Blanchet, M. and P. Seite, "Multiple Interfaces Problem Statement", Work in Progress, August 2010.
[MIF-PROBLEM]Blanchet，M.和P.Seite，“多接口问题陈述”，正在进行的工作，2010年8月。
[MIF-PRACTICE] Wasserman, M. and P. Seite, "Current Practices for Multiple Interface Hosts", Work in Progress, August 2010.
[MIF-PRACTICE]Wasserman，M.和P.Seite，“多接口主机的当前实践”，正在进行的工作，2010年8月。
[CSI-SEND-CERT] Gagliano, R., Krishnan, S., and A. Kukec, "Certificate profile and certificate management for SEND", Work in Progress, October 2010.
[CSI-SEND-CERT]Gagliano，R.，Krishnan，S.，和A.Kukec，“SEND的证书配置文件和证书管理”，正在进行的工作，2010年10月。
The following changes were made from RFC 5006 "IPv6 Router Advertisement Option for DNS Configuration":
RFC 5006“DNS配置的IPv6路由器播发选项”进行了以下更改：
o Added the DNS Search List (DNSSL) option to support the advertisement of DNS suffixes used in the DNS search along with RDNSS option in RFC 5006.
o 添加了DNS搜索列表（DNSSL）选项，以支持在RFC 5006中公布DNS搜索中使用的DNS后缀以及RDNS选项。
o Clarified the coexistence of RA options and DHCP options for DNS configuration.
o 阐明了DNS配置的RA选项和DHCP选项的共存性。
o Modified the procedure in IPv6 host:
o 已修改IPv6主机中的过程：
* Clarified the procedure for DNS options in an IPv6 host.
* 阐明了IPv6主机中DNS选项的过程。
* Specified a sufficient number of RDNSS addresses or DNS search domain names as three.
* 将足够数量的RDNS地址或DNS搜索域名指定为三个。
* Specified a way to deal with DNS options from multiple sources, such as RA and DHCP.
* 指定了处理来自多个源（如RA和DHCP）的DNS选项的方法。
o Modified the implementation considerations for DNSSL option handling.
o 修改了DNSSL选项处理的实现注意事项。
o Modified the security considerations to consider more attack scenarios and the corresponding possible solutions.
o 修改了安全考虑，考虑更多的攻击场景和相应的可能的解决方案。
o Modified the IANA considerations to require another IPv6 Neighbor Discovery Option type for the DNSSL option.
o 修改了IANA注意事项，使DNSSL选项需要另一种IPv6邻居发现选项类型。
Authors' Addresses
作者地址
Jaehoon Paul Jeong Brocade Communications Systems/ETRI 6000 Nathan Ln N Plymouth, MN 55442 USA
美国明尼苏达州北普利茅斯市内森区杰洪保罗正博科通信系统/ETRI 6000
Phone: +1 763 268 7173
Fax: +1 763 268 6800
EMail: pjeong@brocade.com
URI: http://www.cs.umn.edu/~jjeong/
Phone: +1 763 268 7173
Fax: +1 763 268 6800
EMail: pjeong@brocade.com
URI: http://www.cs.umn.edu/~jjeong/
Soohong Daniel Park Digital Media & Communications R&D Center SAMSUNG Electronics 416 Maetan-3dong, Yeongtong-Gu Suwon, Gyeonggi-Do 443-742 Korea
韩国京畿道永通古水原三星电子416 Maetan-3dong，Soohong Daniel Park数字媒体与通信研发中心，邮编443-742
Phone: +82 31 279 8876
EMail: soohong.park@samsung.com
Phone: +82 31 279 8876
EMail: soohong.park@samsung.com
Luc Beloeil France Telecom R&D 42, rue des coutures BP 6243 14066 CAEN Cedex 4 France
Luc Beloeil法国电信研发部，法国邮政街42号BP 6243 14066卡恩塞德克斯4号
Phone: +33 2 40 44 97 40
EMail: luc.beloeil@orange-ftgroup.com
Phone: +33 2 40 44 97 40
EMail: luc.beloeil@orange-ftgroup.com
Syam Madanapalli iRam Technologies #H304, Shriram Samruddhi, Thubarahalli Bangalore - 560066 India
Syam Madanapalli iRam Technologies#H304，Shriram Samruddhi，Thubarahali Bangalore-560066印度
EMail: smadanapalli@gmail.com
EMail: smadanapalli@gmail.com