dingdayu/dnsx

package dns

import (
    "strconv"
    "strings"

    "github.com/miekg/dns"

    "github.com/xyser/dnsx/model/dao"
)

// TypeSRV is a specification of servers in the Domain Name System by hostname and port number.
// With an SRV record, it is possible to make a server discoverable and designate high priority
// and high availability servers using a single domain without having to know the exact address
// of the servers.
func TypeSRV(msg *dns.Msg) error {
    domain := msg.Question[0].Name
    rrs, err := dao.GetRecordByNameAndType(domain, msg.Question[0].Qtype)
    if err != nil {
        return err
    }
    for _, rr := range rrs {
        // 优先级 权重 端口 目标地址 1 1 80 www.baidu.com
        vs := strings.Split(rr.Value, " ")
        var priority, weight, port uint64
        if len(vs) == 4 {
            priority, _ = strconv.ParseUint(vs[0], 16, 16)
            weight, _ = strconv.ParseUint(vs[1], 16, 16)
            port, _ = strconv.ParseUint(vs[2], 16, 16)
        } else if len(vs) == 3 {
            priority = uint64(rr.Priority)
            weight, _ = strconv.ParseUint(vs[0], 16, 16)
            port, _ = strconv.ParseUint(vs[1], 16, 16)
        }
        msg.Answer = append(msg.Answer, &dns.SRV{
            Hdr:      dns.RR_Header{Name: msg.Question[0].Name, Rrtype: msg.Question[0].Qtype, Class: dns.ClassINET, Ttl: rr.TTL},
            Priority: uint16(priority), // 优先级
            Weight:   uint16(weight),   // 权重
            Port:     uint16(port),     // 端口
            Target:   vs[len(vs)-1],    // 对应目标地址,可以是域名或IP
        })
    }
    return nil
}