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/*
* This file is part of the go-nft project
*
* 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.
*
* Copyright 2021 Red Hat, Inc.
*
*/
package exec
import (
"bytes"
"fmt"
"io/ioutil"
"os"
"os/exec"
"strings"
nftconfig "github.com/networkplumbing/go-nft/nft/config"
)
const (
cmdBin = "nft"
cmdFile = "-f"
cmdJSON = "-j"
cmdList = "list"
cmdRuleset = "ruleset"
)
// ReadConfig loads the nftables configuration from the system and
// returns it as a nftables config structure.
// The system is expected to have the `nft` executable deployed and nftables enabled in the kernel.
func ReadConfig() (*nftconfig.Config, error) {
stdout, err := execCommand(cmdJSON, cmdList, cmdRuleset)
if err != nil {
return nil, err
}
config := nftconfig.New()
if err := config.FromJSON(stdout.Bytes()); err != nil {
return nil, fmt.Errorf("failed to list ruleset: %v", err)
}
return config, nil
}
// ApplyConfig applies the given nftables config on the system.
// The system is expected to have the `nft` executable deployed and nftables enabled in the kernel.
func ApplyConfig(c *nftconfig.Config) error {
data, err := c.ToJSON()
if err != nil {
return err
}
tmpFile, err := ioutil.TempFile(os.TempDir(), "spoofcheck-")
if err != nil {
return fmt.Errorf("failed to create temporary file: %v", err)
}
defer os.Remove(tmpFile.Name())
if _, err = tmpFile.Write(data); err != nil {
return fmt.Errorf("failed to write to temporary file: %v", err)
}
if err := tmpFile.Close(); err != nil {
return fmt.Errorf("failed to close temporary file: %v", err)
}
if _, err := execCommand(cmdJSON, cmdFile, tmpFile.Name()); err != nil {
return err
}
return nil
}
func execCommand(args ...string) (*bytes.Buffer, error) {
cmd := exec.Command(cmdBin, args...)
var stdout, stderr bytes.Buffer
cmd.Stderr = &stderr
cmd.Stdout = &stdout
if err := cmd.Run(); err != nil {
return nil, fmt.Errorf(
"failed to execute %s %s: %v stdout:'%s' stderr:'%s'",
cmd.Path, strings.Join(cmd.Args, " "), err, stdout.String(), stderr.String(),
)
}
return &stdout, nil
}
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