mirror of
https://github.com/ProtonMail/proton-bridge.git
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72 lines
1.9 KiB
Go
72 lines
1.9 KiB
Go
// Copyright (c) 2023 Proton AG
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//
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// This file is part of Proton Mail Bridge.
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//
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// Proton Mail Bridge is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Proton Mail Bridge is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
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package ports
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import (
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"fmt"
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"net"
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"github.com/ProtonMail/proton-bridge/v3/internal/constants"
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"golang.org/x/exp/slices"
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)
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const (
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maxPortNumber = 65535
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)
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// IsPortFree checks if the port is free to use.
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func IsPortFree(port int) bool {
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if !(0 < port && port < maxPortNumber) {
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return false
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}
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// First, check localhost only.
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if isOccupied(fmt.Sprintf("%v:%d", constants.Host, port)) {
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return false
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}
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// Second, check also ports opened to public.
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return !isOccupied(fmt.Sprintf(":%d", port))
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}
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func isOccupied(port string) bool {
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// Try to create server at port.
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dummyServer, err := net.Listen("tcp", port)
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if err != nil {
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return true
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}
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_ = dummyServer.Close()
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return false
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}
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// FindFreePortFrom finds first empty port, starting with `startPort`, and excluding ports listed in exclude.
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func FindFreePortFrom(startPort int, exclude ...int) int {
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loopedOnce := false
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freePort := startPort
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for slices.Contains(exclude, freePort) || !IsPortFree(freePort) {
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freePort++
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if freePort >= maxPortNumber {
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freePort = 1
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if loopedOnce {
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freePort = startPort
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break
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}
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loopedOnce = true
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}
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}
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return freePort
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}
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