47 lines
1.3 KiB
Go
47 lines
1.3 KiB
Go
package resolver
|
|
|
|
import (
|
|
"context"
|
|
"fmt"
|
|
"net"
|
|
"strings"
|
|
"time"
|
|
)
|
|
|
|
// UDPQuery sends a raw DNS query to addr over UDP and returns the raw response bytes.
|
|
//
|
|
// addr may be "ip" or "ip:port" — ":53" is appended if no port is specified.
|
|
// timeout sets the per-query deadline for the read/write operations.
|
|
// ctx allows early cancellation; if the context already has a deadline that
|
|
// is sooner than timeout, the context deadline takes precedence.
|
|
func UDPQuery(ctx context.Context, addr string, query []byte, timeout time.Duration) ([]byte, error) {
|
|
if !strings.Contains(addr, ":") {
|
|
addr = addr + ":53"
|
|
}
|
|
|
|
dialer := net.Dialer{Timeout: timeout}
|
|
conn, err := dialer.DialContext(ctx, "udp", addr)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("connecting to %s: %w", addr, err)
|
|
}
|
|
defer conn.Close()
|
|
|
|
// Determine the effective deadline: use ctx deadline if sooner than timeout.
|
|
deadline := time.Now().Add(timeout)
|
|
if ctxDeadline, ok := ctx.Deadline(); ok && ctxDeadline.Before(deadline) {
|
|
deadline = ctxDeadline
|
|
}
|
|
conn.SetDeadline(deadline) //nolint:errcheck
|
|
|
|
if _, err := conn.Write(query); err != nil {
|
|
return nil, fmt.Errorf("sending query to %s: %w", addr, err)
|
|
}
|
|
|
|
buf := make([]byte, udpBufSize)
|
|
n, err := conn.Read(buf)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("reading response from %s: %w", addr, err)
|
|
}
|
|
return buf[:n], nil
|
|
}
|