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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;

unbound做mosdns前置的时候会重新查询域名返回的dns cname记录，这样mosdns做dns域名分流的时候还要额外添加cname域名规则，写了一个mosdns插件删除cname信息直接返回a记录避免二次查询。

//dispatcher/plugin/executable/dcname/dcname.go
package dcname

import (
  "context"
  "github.com/IrineSistiana/mosdns/v3/dispatcher/handler"
  "github.com/IrineSistiana/mosdns/v3/dispatcher/pkg/dnsutils"
  "github.com/miekg/dns"
)

const (
  PluginType = "dcname"
)

func init() {
  handler.RegInitFunc(PluginType, Init, func() interface{} { return new(Args) })
}

var _ handler.ExecutablePlugin = (*dcname)(nil)

type Args struct {
}

type dcname struct {
  *handler.BP
  args *Args
}

func Init(bp *handler.BP, args interface{}) (p handler.Plugin, err error) {
  return newDcname(bp, args.(*Args)), nil
}

func newDcname(bp *handler.BP, args *Args) handler.Plugin {
  return &dcname{
    BP:   bp,
    args: args,
  }
}

func (t *dcname) Exec(ctx context.Context, qCtx *handler.Context, next handler.ExecutableChainNode) error {
  if r := qCtx.R(); r != nil {
    q := qCtx.Q()
    if (len(q.Question) == 1 && len(r.Answer) >= 1) {
      qname := q.Question[0].Name
      qtype := q.Question[0].Qtype
      rname := r.Answer[0].Header().Name
      rtype := r.Answer[0].Header().Rrtype
      if ((qtype == dns.TypeA || qtype == dns.TypeAAAA) && qname == rname && rtype == dns.TypeCNAME) {
        var Answer2 []dns.RR
        for i := range r.Answer {
          var rr2 dns.RR
          switch rr := r.Answer[i].(type) {
          case *dns.A:
            rr2 = &dns.A{
              Hdr: dns.RR_Header{
                Name:   qname,
                Rrtype: dns.TypeA,
                Class:  dns.ClassINET,
                Ttl:    r.Answer[i].Header().Ttl,
              },
              A: rr.A,
            }
          case *dns.AAAA:
            rr2 = &dns.AAAA{
              Hdr: dns.RR_Header{
                Name:   qname,
                Rrtype: dns.TypeAAAA,
                Class:  dns.ClassINET,
                Ttl:    r.Answer[i].Header().Ttl,
              },
              AAAA: rr.AAAA,
            }
          default:
            continue
          }
          Answer2 = append(Answer2, rr2)
        }
        r.Answer = Answer2
      }
    }
  }
  return handler.ExecChainNode(ctx, qCtx, next)
}

开启插件：

dispatcher/plugin/enabled_plugin.go 
_ "github.com/IrineSistiana/mosdns/v3/dispatcher/plugin/executable/dcname"

qCtx.Q()和qCtx.R()分别获取查询和返回的信息，*dns.Msg定义在：
https://github.com/miekg/dns/blob/master/msg.go#L109
查询信息Question []Question定义在：
https://github.com/miekg/dns/blob/master/types.go#L228
返回信息Answer RR[]定义在：
https://github.com/miekg/dns/blob/master/dns.go#L31
Answer Header：
https://github.com/miekg/dns/blob/master/dns.go#L67
DNS TYPE:
https://github.com/miekg/dns/blob/master/types.go#L25