A simple, go-based DNS resolver/caching server
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package main
import (
"net"
"time"
"github.com/hoisie/redis"
)
type Hosts struct {
providers []HostProvider
refreshInterval time.Duration
}
type HostProvider interface {
Get(domain string) ([]string, bool)
Refresh()
}
func NewHosts(hs HostsSettings, rs RedisSettings) Hosts {
providers := []HostProvider{
NewFileProvider(hs.HostsFile),
}
if hs.RedisEnable {
logger.Info("Redis is enabled: %s", rs.Addr())
rc := &redis.Client{Addr: rs.Addr(), Db: rs.DB, Password: rs.Password}
providers = append(providers, NewRedisProvider(rc, hs.RedisKey))
}
h := Hosts{providers, time.Second * time.Duration(hs.RefreshInterval)}
if h.refreshInterval > 0 {
h.refresh()
}
return h
}
func (h *Hosts) refresh() {
ticker := time.NewTicker(h.refreshInterval)
go func() {
for {
// Force a refresh every refreshInterval
for _, provider := range h.providers {
provider.Refresh()
}
<-ticker.C
}
}()
}
/*
Match local /etc/hosts file first, remote redis records second
*/
func (h *Hosts) Get(domain string, family int) ([]net.IP, bool) {
var sips []string
var ok bool
var ip net.IP
var ips []net.IP
for _, provider := range h.providers {
sips, ok = provider.Get(domain)
if ok {
break
}
}
if sips == nil {
return nil, false
}
for _, sip := range sips {
switch family {
case _IP4Query:
ip = net.ParseIP(sip).To4()
case _IP6Query:
ip = net.ParseIP(sip).To16()
default:
continue
}
if ip != nil {
ips = append(ips, ip)
}
}
return ips, ips != nil
}