primeiro commit

internal/hedns/hedns.go

@@ -0,0 +1,61 @@
+// Package hedns implements the Hurricane Electric dynamic DNS update protocol.
+package hedns
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+const (
+	updateURL      = "https://dyn.dns.he.net/nic/update"
+	requestTimeout = 15 * time.Second
+)
+
+// Update pushes a single hostname -> ip mapping. HE picks the A or AAAA
+// record based on the family of ip.
+func Update(hostname, token string, ip net.IP) error {
+	client := http.Client{Timeout: requestTimeout}
+
+	form := url.Values{
+		"hostname": {hostname},
+		"password": {token},
+		"myip":     {ip.String()},
+	}
+
+	resp, err := client.PostForm(updateURL, form)
+	if err != nil {
+		return fmt.Errorf("updating %s: %w", hostname, err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 4096))
+	if err != nil {
+		return fmt.Errorf("updating %s: reading response: %w", hostname, err)
+	}
+
+	return interpretResponse(hostname, strings.TrimSpace(string(body)))
+}
+
+func interpretResponse(hostname, body string) error {
+	switch {
+	case strings.HasPrefix(body, "good"), strings.HasPrefix(body, "nochg"):
+		return nil
+	case body == "badauth":
+		return fmt.Errorf("updating %s: authentication failed (bad hostname/token)", hostname)
+	case body == "nohost":
+		return fmt.Errorf("updating %s: hostname not found on account", hostname)
+	case body == "notfqdn":
+		return fmt.Errorf("updating %s: hostname is not a valid fully-qualified domain name", hostname)
+	case body == "abuse":
+		return fmt.Errorf("updating %s: blocked for abuse", hostname)
+	case body == "":
+		return fmt.Errorf("updating %s: empty response from server", hostname)
+	default:
+		return fmt.Errorf("updating %s: unexpected response %q", hostname, body)
+	}
+}