/
server.go
132 lines (119 loc) · 3.58 KB
/
server.go
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package main
import (
"database/sql"
_ "github.com/go-sql-driver/mysql"
"github.com/miekg/dns"
"strings"
"time"
"fmt"
"github.com/elgs/gosqljson"
"strconv"
)
func main() {
server := &dns.Server{Addr: ":10015", Net: "udp", Handler: nil, Unsafe: true}
dns.HandleFunc(".", handlerToAnswer)
err := server.ListenAndServe()
if(err !=nil){
fmt.Println(err);
}
}
/*Function that strips undesired characters from string */
func stripchars(str, chr string) string {
return strings.Map(func(r rune) rune {
if strings.IndexRune(chr, r) < 0 {
return r
}
return -1
}, str)
}
/* Function that caches new information to DB */
func dbWriter(gotAns []dns.RR, db *sql.DB, question string) {
stmIns, err := db.Prepare("INSERT INTO dnsCache(`question`,`name`,`typeC`,`classC`,`dateCame`,`TTL`,`dateExpire`,`ip`) VALUES (?,?,?,?,?,?,?,?)")
if err != nil {
panic(err.Error())
}
for _, element := range gotAns {
toDb := element.String()
toDb = stripchars(toDb, ";")
toDbSplit := strings.Split(toDb, "\t")
timeLeft, _ := time.ParseDuration(toDbSplit[1]+"s");
_, err = stmIns.Exec(question,toDbSplit[0], toDbSplit[3], toDbSplit[2], time.Now().UTC(),toDbSplit[1], time.Now().UTC().Add(timeLeft),toDbSplit[4])
}
}
/* Delete dead TTL */
func deleteTable(db *sql.DB, id []string){
stm,err := db.Prepare("DELETE FROM dnsCache WHERE `id`=?");
if(err !=nil){
panic(err.Error());
}
defer stm.Close();
for _, element := range id{
_, err = stm.Exec(element);
if err !=nil{
panic(err.Error());
}
}
}
/* Function that gets needed tables */
func dbRespond(db *sql.DB, question string)(answerToHand []dns.RR){
var deleter []string
var handOver []string
const layout = "2006-01-02 15:04:05"
stm :="SELECT * FROM dnsCache WHERE question=?";
data, _ := gosqljson.QueryDbToMap(db, "none" , stm, question)
if(len(data) >0){
for i := 0; i<len(data); i++{
timer,_ :=time.Parse(layout, data[i]["dateExpire"])
if(time.Now().UTC().After(timer)){
deleter = append(deleter, data[i]["id"]);
}else{
temp := data[i]["name"]+" "+stripchars(strconv.Itoa(int(time.Now().UTC().Sub(timer).Seconds())),"-")+" "+data[i]["classC"]+" "+data[i]["typeC"]+" "+data[i]["ip"]
handOver = append(handOver, temp);
}
}
go deleteTable(db, deleter);
answerToHand = buildRR(handOver);
}else if(len(data) == 0){
answerToHand = nil
}
return
}
/* Function that creates RR records in array from DB (accessible only from dbRespond function) */
func buildRR(handOver []string)(answerHand []dns.RR){
for _, stringAns := range handOver{
temp, err:= dns.NewRR(stringAns)
if(err !=nil){
panic(err.Error());
}
answerHand = append(answerHand, temp);
}
return
}
func handlerToAnswer(w dns.ResponseWriter, r *dns.Msg) {
db, err := sql.Open("mysql", "inserter:qwerty@/dnsServerCache") //Handler for database
if err != nil {
panic(err.Error()) // Just for example purpose. You should use proper error handling instead of panic
}
answer := new(dns.Msg) //Set answer to client
answer.SetReply(r) //Set reply flag and start collecting data for reply
var answersAll []dns.RR
answersAll = dbRespond(db,r.Question[0].String())
if(len(answersAll) != 0){
for _, answers := range answersAll {
answer.Answer = append(answer.Answer, answers);
}
}else{
client := new(dns.Client)
var err1 error
config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
answer, _, err1 = client.Exchange(r, config.Servers[0]+":"+config.Port)
if err1 != nil {
panic(err1.Error());
}
if r.Rcode != dns.RcodeSuccess {
return
}
go dbWriter(answer.Answer,db,r.Question[0].String())
}
w.WriteMsg(answer)
}