72 lines
2.2 KiB
Go
72 lines
2.2 KiB
Go
// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build android
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// +build android
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package netns
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import (
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"fmt"
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"sync"
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"syscall"
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"tailscale.com/types/logger"
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)
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var (
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androidProtectFuncMu sync.Mutex
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androidProtectFunc func(fd int) error
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)
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// SetAndroidProtectFunc register a func that Android provides that JNI calls into
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// https://developer.android.com/reference/android/net/VpnService#protect(int)
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// which is documented as:
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//
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// "Protect a socket from VPN connections. After protecting, data sent
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// through this socket will go directly to the underlying network, so
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// its traffic will not be forwarded through the VPN. This method is
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// useful if some connections need to be kept outside of VPN. For
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// example, a VPN tunnel should protect itself if its destination is
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// covered by VPN routes. Otherwise its outgoing packets will be sent
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// back to the VPN interface and cause an infinite loop. This method
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// will fail if the application is not prepared or is revoked."
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//
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// A nil func disables the use the hook.
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//
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// This indirection is necessary because this is the supported, stable
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// interface to use on Android, and doing the sockopts to set the
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// fwmark return errors on Android. The actual implementation of
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// VpnService.protect ends up doing an IPC to another process on
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// Android, asking for the fwmark to be set.
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func SetAndroidProtectFunc(f func(fd int) error) {
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androidProtectFuncMu.Lock()
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defer androidProtectFuncMu.Unlock()
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androidProtectFunc = f
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}
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func control(logger.Logf) func(network, address string, c syscall.RawConn) error {
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return controlC
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}
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// controlC marks c as necessary to dial in a separate network namespace.
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//
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// It's intentionally the same signature as net.Dialer.Control
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// and net.ListenConfig.Control.
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func controlC(network, address string, c syscall.RawConn) error {
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var sockErr error
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err := c.Control(func(fd uintptr) {
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androidProtectFuncMu.Lock()
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f := androidProtectFunc
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androidProtectFuncMu.Unlock()
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if f != nil {
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sockErr = f(int(fd))
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}
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})
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if err != nil {
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return fmt.Errorf("RawConn.Control on %T: %w", c, err)
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}
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return sockErr
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}
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