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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,71 @@ | ||
| package main | ||
|
|
||
| import ( | ||
| "github.com/miekg/dns" | ||
| log "github.com/sirupsen/logrus" | ||
| "net" | ||
| ) | ||
|
|
||
| type DNSForwarder struct { | ||
| server *dns.Server | ||
| } | ||
|
|
||
| type DNSRewriteForwardHandler struct { | ||
| upstreamServer string | ||
| redirectTo string | ||
| } | ||
|
|
||
| func (D DNSRewriteForwardHandler) ServeDNS(w dns.ResponseWriter, r *dns.Msg) { | ||
| client := dns.Client{ | ||
| Net: "udp", | ||
| } | ||
| response, _, err := client.Exchange(r, D.upstreamServer+":53") | ||
| if err != nil { | ||
| log.Errorln("Error connecting to upstream: ", err) | ||
| return | ||
| } | ||
| for _, rr := range response.Answer { | ||
| switch rr.Header().Rrtype { | ||
| case dns.TypeA: | ||
| if t, ok := rr.(*dns.A); ok { | ||
| if t.A.Equal(net.IPv4(127, 0, 0, 1)) { | ||
| log.Debugln("Redirecting answer for ", t.Header().Name, "to ", D.redirectTo) | ||
| t.A = net.ParseIP(D.redirectTo) | ||
| } | ||
| } | ||
| } | ||
| } | ||
| err = w.WriteMsg(response) | ||
| if err != nil { | ||
| log.Errorln("Error writing response: ", err) | ||
| } | ||
| } | ||
|
|
||
| func NewDnsForwarder(upstreamServer string) (*DNSForwarder, error) { | ||
| forwarder := &DNSForwarder{ | ||
| server: &dns.Server{ | ||
| Net: "udp", | ||
| Handler: DNSRewriteForwardHandler{ | ||
| upstreamServer: upstreamServer, | ||
| redirectTo: upstreamServer, | ||
| }, | ||
| }, | ||
| } | ||
| return forwarder, nil | ||
| } | ||
|
|
||
| func (c *DNSForwarder) Start() { | ||
| go func() { | ||
| err := c.server.ListenAndServe() | ||
| if err != nil { | ||
| log.Errorln("Error starting DNS server: ", err) | ||
| } | ||
| }() | ||
| } | ||
|
|
||
| func (c *DNSForwarder) Shutdown() { | ||
| err := c.server.Shutdown() | ||
| if err != nil { | ||
| log.Errorln("Error shutting down DNS server: ", err) | ||
| } | ||
| } |
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