Router Solicitation Message

Source Address An IP address assigned to the sending interface, or the unspecified address if no address is assigned to the sending interface.

Destination Address Typically the all-routers multicast address.

源IPv6地址：在lwip中，要麽是鏈路本地地址，要麽是任意地址IP6_ADDR_ANY6，也就是全零地址。

目的IPv6地址：所有路由器多播地址，FF02::2（多播地址FF::/8，第一個02表示scope是鏈路本地，第二個02是所有路由器）

Router Advertisement Message

      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      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Cur Hop Limit |M|O|  Reserved |       Router Lifetime         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Reachable Time                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Retrans Timer                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Options ...
     +-+-+-+-+-+-+-+-+-+-+-+-

Source Address MUST be the link-local address assigned to the interface from which this message is sent.

Destination Address Typically the Source Address of an invoking Router Solicitation or the all-nodes multicast address.

Hop Limit 255

源IPv6地址：必須是鏈路本地地址

目的IPv6地址：rs包的源地址或者所有節點多播地址，FF02::1（第二個02是所有節點）

跳數限制：255

Cur Hop Limit 8-bit unsigned integer. The default value that should be placed in the Hop Count field of the IP header for outgoing IP packets. A value of zero means unspecified (by this router).

當前跳數限制：直接填0，未定義。

M 1-bit "Managed address configuration" flag. When set, it indicates that addresses are available via Dynamic Host Configuration Protocol [DHCPv6]. If the M flag is set, the O flag is redundant and can be ignored because DHCPv6 will return all available configuration information.

M，管理的地址配置，若為1，則表示由DHCPv6完成地址配置。此處設置為0，不由DHCPv6配置。

O 1-bit "Other configuration" flag. When set, it indicates that other configuration information is available via DHCPv6. Examples of such information are DNS-related information or information on other servers within the network.

O，其它配置，比如DNS。此處設置為0。

Router Lifetime 16-bit unsigned integer. The lifetime associated with the default router in units of seconds. The field can contain values up to 65535 and receivers should handle any value, while the sending rules in Section 6 limit the lifetime to 9000 seconds. A Lifetime of 0 indicates that the router is not a default router and SHOULD NOT appear on the default router list. The Router Lifetime applies only to the router‘s usefulness as a default router; it does not apply to information contained in other message fields or options. Options that need time limits for their information include their own lifetime fields.

路由器生存時間，暫時設置為0，會導致不出現在默認路由器列表上，會有什麽影響嗎？待確認。

RFC筆記—Neighbor Discovery for IP version 6 (IPv6)