海运的博客

先在配置文件内禁用ipv6 dhcp服务：

/etc/config/dhcp 
config dhcp 'lan'
        option interface 'lan'
        option start '150'
        option limit '100'
        option leasetime '12h'
        option ra 'disabled'
        option dhcpv6 'disabled'

config odhcpd 'odhcpd'
        option maindhcp '0'
        option leasefile '/tmp/hosts/odhcpd'
        option leasetrigger '/usr/sbin/odhcpd-update'
        option loglevel '4'

关闭odhcpd:

/etc/init.d/odhcpd stop
/etc/init.d/odhcpd disable

修改dnsmasq配置文件开启ra服务：

/etc/dnsmasq.conf 
enable-ra
dhcp-range=::,constructor:br-lan,ra-only
#其它slaac ra-stateless等参考man文档

只想通过ipv4查询dns，下面patch让dnsmasq无状态分配ip时候不包含RDNSS，这样客户端只配置ipv4 dns而不配置ipv6 dns。

diff -urN dnsmasq-2.86/src/radv.c dnsmasq-2.86-bak/src/radv.c
--- dnsmasq-2.86/src/radv.c     2021-09-09 04:21:22.000000000 +0800
+++ dnsmasq-2.86-bak/src/radv.c 2022-01-23 11:57:01.818963642 +0800
@@ -507,7 +507,7 @@
        }
     }
 
-  if (daemon->port == NAMESERVER_PORT && !done_dns && parm.link_pref_time != 0)
+  if ( 0 && daemon->port == NAMESERVER_PORT && !done_dns && parm.link_pref_time != 0)
     {
       /* default == us, as long as we are supplying DNS service. */
       put_opt6_char(ICMP6_OPT_RDNSS);

odhcpd新版本参数dns_service也可实现此需求。
再次开启ipv6 dns服务，如果有配置dhcp6 dns服务器，dnsmasq会将其设置为RDNSS:

dhcp-option=option6:dns-server,[xxxx:xxxx:xxxx:xxxx::1]

路由上跑dnsmasq通过将客户端ip添加为edns ip转发到其它dns服务器时可以根据客户端ip做相应操作，dnmasq只有在设置add-subnet为固定ip段时才缓存，add-subnet=32时动态添加客户端ip为edns ip时不缓存，做了下修改可以缓存。

--- dnsmasq-2.86/src/edns0.c    2021-09-09 04:21:22.000000000 +0800
+++ dnsmasq-2.86-bak/src/edns0.c        2022-01-23 18:54:04.801336879 +0800
@@ -375,6 +375,7 @@
   if (cacheablep)
     *cacheablep = cacheable;
   
+  *cacheablep = 1;
   return len + 4;
 }
  
diff -urN dnsmasq-2.86/src/forward.c dnsmasq-2.86-bak/src/forward.c
--- dnsmasq-2.86/src/forward.c  2021-09-09 04:21:22.000000000 +0800
+++ dnsmasq-2.86-bak/src/forward.c      2022-01-23 18:58:25.020648204 +0800
@@ -596,7 +596,7 @@
       /* Get extended RCODE. */
       rcode |= sizep[2] << 4;
 
-      if (check_subnet && !check_source(header, plen, pheader, query_source))
+      if ( 0 && check_subnet && !check_source(header, plen, pheader, query_source))
        {
          my_syslog(LOG_WARNING, _("discarding DNS reply: subnet option mismatch"));
          return 0;

操作系统下都有hosts文件可自定单个域名指向IP，要将特定域名下所有子域名都指向特定IP就需要转发DNS服务器来解决了，Dnsmasq就是比较轻量级的一个，很多第三方路由固件都自带Dnsmasq。
Dnsmasq域名泛解析配置：

address=/.www.haiyun.me/8.8.8.8
address=/.google.com/203.208.46.200
#这样所有www.haiyun.me子域名都解析到8.8.8.8

Dnsmasq禁止域名被劫持：

bogus-nxdomain=8.8.8.8
#8.8.8.8为劫持IP地址