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