1 files changed, 47 insertions, 0 deletions
diff --git a/internal/resolver/forward.go b/internal/resolver/forward.go
new file mode 100644
index 0000000..68edc5d
--- /dev/null
+++ b/internal/resolver/forward.go
@@ -0,0 +1,47 @@
+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
+}