frp/pkg/util/system/system_android.go

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// Copyright 2024 The frp Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package system
import (
"context"
"net"
"os/exec"
"strings"
"time"
)
func EnableCompatibilityMode() {
fixTimezone()
fixDNSResolver()
}
// fixTimezone is used to try our best to fix timezone issue on some Android devices.
func fixTimezone() {
out, err := exec.Command("/system/bin/getprop", "persist.sys.timezone").Output()
if err != nil {
return
}
loc, err := time.LoadLocation(strings.TrimSpace(string(out)))
if err != nil {
return
}
time.Local = loc
}
// fixDNSResolver will first attempt to resolve google.com to check if the current DNS is available.
// If it is not available, it will default to using 8.8.8.8 as the DNS server.
// This is a workaround for the issue that golang can't get the default DNS servers on Android.
func fixDNSResolver() {
// First, we attempt to resolve a domain. If resolution is successful, no modifications are necessary.
// In real-world scenarios, users may have already configured /etc/resolv.conf, or compiled directly
// in the Android environment instead of using cross-platform compilation, so this issue does not arise.
if net.DefaultResolver != nil {
timeoutCtx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
_, err := net.DefaultResolver.LookupHost(timeoutCtx, "google.com")
if err == nil {
return
}
}
// If the resolution fails, use 8.8.8.8 as the DNS server.
// Note: If there are other methods to obtain the default DNS servers, the default DNS servers should be used preferentially.
net.DefaultResolver = &net.Resolver{
PreferGo: true,
Dial: func(ctx context.Context, network, addr string) (net.Conn, error) {
if addr == "127.0.0.1:53" || addr == "[::1]:53" {
addr = "8.8.8.8:53"
}
var d net.Dialer
return d.DialContext(ctx, network, addr)
},
}
}