TUN-3456: New protocol option auto to automatically select between http2 and h2mux

edgediscovery/protocol.go

@@ -0,0 +1,45 @@
+package edgediscovery
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+	"strings"
+)
+
+const (
+	protocolRecord = "protocol.argotunnel.com"
+)
+
+var (
+	errNoProtocolRecord = fmt.Errorf("No TXT record found for %s to determine connection protocol", protocolRecord)
+)
+
+func HTTP2Percentage() (int32, error) {
+	records, err := net.LookupTXT(protocolRecord)
+	if err != nil {
+		return 0, err
+	}
+	if len(records) == 0 {
+		return 0, errNoProtocolRecord
+	}
+	return parseHTTP2Precentage(records[0])
+}
+
+// The record looks like http2=percentage
+func parseHTTP2Precentage(record string) (int32, error) {
+	const key = "http2"
+	slices := strings.Split(record, "=")
+	if len(slices) != 2 {
+		return 0, fmt.Errorf("Malformed TXT record %s, expect http2=percentage", record)
+	}
+	if slices[0] != key {
+		return 0, fmt.Errorf("Incorrect key %s, expect %s", slices[0], key)
+	}
+	percentage, err := strconv.ParseInt(slices[1], 10, 32)
+	if err != nil {
+		return 0, err
+	}
+	return int32(percentage), nil
+
+}