net: add a default host netdev backed by raw Linux syscalls

lookup.go

@@ -17,3 +17,42 @@ import (
 func LookupPort(network, service string) (port int, err error) {
 	return 0, errors.New("net:LookupPort not implemented")
 }
+
+// DNSError represents a DNS lookup error.
+//
+// TINYGO: Trimmed copy of the standard library's net.DNSError so that name
+// resolution errors keep a familiar, type-assertable shape.
+type DNSError struct {
+	UnwrapErr   error  // error returned by the [DNSError.Unwrap] method, might be nil
+	Err         string // description of the error
+	Name        string // name looked for
+	Server      string // server used
+	IsTimeout   bool   // if true, timed out; not all timeouts set this
+	IsTemporary bool   // if true, error is temporary; not all errors set this
+
+	// IsNotFound is set to true when the requested name does not
+	// contain any records of the requested type (data not found),
+	// or the name itself was not found (NXDOMAIN).
+	IsNotFound bool
+}
+
+// Unwrap returns e.UnwrapErr.
+func (e *DNSError) Unwrap() error { return e.UnwrapErr }
+
+func (e *DNSError) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	s := "lookup " + e.Name
+	if e.Server != "" {
+		s += " on " + e.Server
+	}
+	s += ": " + e.Err
+	return s
+}
+
+// Timeout reports whether the DNS lookup is known to have timed out.
+func (e *DNSError) Timeout() bool { return e.IsTimeout }
+
+// Temporary reports whether the DNS error is known to be temporary.
+func (e *DNSError) Temporary() bool { return e.IsTimeout || e.IsTemporary }