AdGuardHome/internal/aghnet/net_linux.go

177 lines
4.2 KiB
Go

// +build linux
package aghnet
import (
"bufio"
"errors"
"fmt"
"io"
"io/ioutil"
"net"
"os"
"strings"
"github.com/AdguardTeam/AdGuardHome/internal/aghio"
"github.com/google/renameio/maybe"
)
// maxConfigFileSize is the maximum length of interfaces configuration file.
const maxConfigFileSize = 1024 * 1024
func ifaceHasStaticIP(ifaceName string) (has bool, err error) {
// TODO(a.garipov): Currently, this function returns the first
// definitive result. So if /etc/dhcpcd.conf has a static IP while
// /etc/network/interfaces doesn't, it will return true. Perhaps this
// is not the most desirable behavior.
for _, check := range []struct {
checker func(io.Reader, string) (bool, error)
filePath string
}{{
checker: dhcpcdStaticConfig,
filePath: "/etc/dhcpcd.conf",
}, {
checker: ifacesStaticConfig,
filePath: "/etc/network/interfaces",
}} {
var f *os.File
f, err = os.Open(check.filePath)
if err != nil {
// ErrNotExist can happen here if there is no such file.
// This is normal, as not every system uses those files.
if errors.Is(err, os.ErrNotExist) {
err = nil
continue
}
return false, err
}
defer f.Close()
var fileReadCloser io.ReadCloser
fileReadCloser, err = aghio.LimitReadCloser(f, maxConfigFileSize)
if err != nil {
return false, err
}
defer fileReadCloser.Close()
has, err = check.checker(fileReadCloser, ifaceName)
if err != nil {
return false, err
}
return has, nil
}
return false, ErrNoStaticIPInfo
}
// dhcpcdStaticConfig checks if interface is configured by /etc/dhcpcd.conf to
// have a static IP.
func dhcpcdStaticConfig(r io.Reader, ifaceName string) (has bool, err error) {
s := bufio.NewScanner(r)
var withinInterfaceCtx bool
for s.Scan() {
line := strings.TrimSpace(s.Text())
if withinInterfaceCtx && len(line) == 0 {
// An empty line resets our state.
withinInterfaceCtx = false
}
if len(line) == 0 || line[0] == '#' {
continue
}
fields := strings.Fields(line)
if withinInterfaceCtx {
if len(fields) >= 2 && fields[0] == "static" && strings.HasPrefix(fields[1], "ip_address=") {
return true, nil
}
if len(fields) > 0 && fields[0] == "interface" {
// Another interface found.
withinInterfaceCtx = false
}
continue
}
if len(fields) == 2 && fields[0] == "interface" && fields[1] == ifaceName {
// The interface found.
withinInterfaceCtx = true
}
}
return false, s.Err()
}
// ifacesStaticConfig checks if interface is configured by
// /etc/network/interfaces to have a static IP.
func ifacesStaticConfig(r io.Reader, ifaceName string) (has bool, err error) {
s := bufio.NewScanner(r)
for s.Scan() {
line := strings.TrimSpace(s.Text())
if len(line) == 0 || line[0] == '#' {
continue
}
fields := strings.Fields(line)
// Man page interfaces(5) declares that interface definition
// should consist of the key word "iface" followed by interface
// name, and method at fourth field.
if len(fields) >= 4 && fields[0] == "iface" && fields[1] == ifaceName && fields[3] == "static" {
return true, nil
}
}
return false, s.Err()
}
func ifaceSetStaticIP(ifaceName string) (err error) {
ipNet := GetSubnet(ifaceName)
if ipNet.IP == nil {
return errors.New("can't get IP address")
}
gatewayIP := GatewayIP(ifaceName)
add := updateStaticIPdhcpcdConf(ifaceName, ipNet.String(), gatewayIP, ipNet.IP)
body, err := ioutil.ReadFile("/etc/dhcpcd.conf")
if err != nil {
return err
}
body = append(body, []byte(add)...)
err = maybe.WriteFile("/etc/dhcpcd.conf", body, 0o644)
if err != nil {
return fmt.Errorf("writing conf: %w", err)
}
return nil
}
// updateStaticIPdhcpcdConf sets static IP address for the interface by writing
// into dhcpd.conf.
func updateStaticIPdhcpcdConf(ifaceName, ip string, gatewayIP, dnsIP net.IP) string {
var body []byte
add := fmt.Sprintf("\ninterface %s\nstatic ip_address=%s\n",
ifaceName, ip)
body = append(body, []byte(add)...)
if gatewayIP != nil {
add = fmt.Sprintf("static routers=%s\n",
gatewayIP)
body = append(body, []byte(add)...)
}
add = fmt.Sprintf("static domain_name_servers=%s\n\n",
dnsIP)
body = append(body, []byte(add)...)
return string(body)
}