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package resolver
import (
"fmt"
"net"
"linum/internal/dns"
)
type Forwarder struct {
upstream string
}
func NewForwarder(upstream string) *Forwarder {
return &Forwarder{upstream: upstream}
}
func (f *Forwarder) Resolve(query *dns.Msg) (*dns.Msg, error) {
query.Header.SetRD(true)
wire, err := dns.Pack(query)
if err != nil {
return nil, fmt.Errorf("pack: %w", err)
}
conn, err := net.Dial("udp", f.upstream)
if err != nil {
return nil, fmt.Errorf("dial %s: %w", f.upstream, err)
}
defer conn.Close()
if _, err := conn.Write(wire); err != nil {
return nil, fmt.Errorf("write: %w", err)
}
buf := make([]byte, 4096)
n, err := conn.Read(buf)
if err != nil {
return nil, fmt.Errorf("read: %w", err)
}
resp, err := dns.Unpack(buf[:n])
if err != nil {
return nil, fmt.Errorf("unpack response: %w", err)
}
return resp, nil
}
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