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，要么是链路本地地址，要么是任意地址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，第一个02表示scope是链路本地，第二个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：必须是链路本地地址
目的IPv6地址：rs包的源地址或者所有节点多播地址，FF02::1（第二个02是所有节点）
跳数限制：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).
当前跳数限制：直接填0，未定义。
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，若为1，则表示由DHCPv6完成地址配置。此处设置为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。此处设置为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.
路由器生存时间，暂时设置为0，会导致不出现在默认路由器列表上，会有什么影响吗？待确认。
原文地址：https://www.cnblogs.com/yanhc/p/8971399.html