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utils.go
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utils.go
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/*
* Copyright (c) 2017, Psiphon Inc.
* All rights reserved.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package tun
import (
"errors"
"fmt"
"net"
"os/exec"
"strconv"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common"
)
var unsupportedError = errors.New("operation unsupported on this platform")
// runNetworkConfigCommand execs a network config command, such as "ifconfig"
// or "iptables". On platforms that support capabilities, the network config
// capabilities of the current process is made available to the command
// subprocess. Alternatively, "sudo" will be used when useSudo is true.
func runNetworkConfigCommand(
logger common.Logger,
useSudo bool,
commandName string, commandArgs ...string) error {
// configureSubprocessCapabilities will set inheritable
// capabilities on platforms which support that (Linux).
// Specifically, CAP_NET_ADMIN will be transferred from
// this process to the child command.
err := configureNetworkConfigSubprocessCapabilities()
if err != nil {
return common.ContextError(err)
}
// TODO: use CommandContext to interrupt on server shutdown?
// (the commands currently being issued shouldn't block...)
if useSudo {
commandArgs = append([]string{commandName}, commandArgs...)
commandName = "sudo"
}
cmd := exec.Command(commandName, commandArgs...)
output, err := cmd.CombinedOutput()
logger.WithContextFields(common.LogFields{
"command": commandName,
"args": commandArgs,
"output": string(output),
"error": err,
}).Debug("exec")
if err != nil {
err := fmt.Errorf(
"command %s %+v failed with %s", commandName, commandArgs, string(output))
return common.ContextError(err)
}
return nil
}
func splitIPMask(IPAddressCIDR string) (string, string, error) {
IP, IPNet, err := net.ParseCIDR(IPAddressCIDR)
if err != nil {
return "", "", common.ContextError(err)
}
var netmask string
IPv4Mask := net.IP(IPNet.Mask).To4()
if IPv4Mask != nil {
netmask = fmt.Sprintf(
"%d.%d.%d.%d", IPv4Mask[0], IPv4Mask[1], IPv4Mask[2], IPv4Mask[3])
} else {
netmask = IPNet.Mask.String()
}
return IP.String(), netmask, nil
}
func splitIPPrefixLen(IPAddressCIDR string) (string, string, error) {
IP, IPNet, err := net.ParseCIDR(IPAddressCIDR)
if err != nil {
return "", "", common.ContextError(err)
}
prefixLen, _ := IPNet.Mask.Size()
return IP.String(), strconv.Itoa(prefixLen), nil
}
func getMTU(configMTU int) int {
if configMTU <= 0 {
return DEFAULT_MTU
} else if configMTU > 65536 {
return 65536
}
return configMTU
}