AdGuardHome/internal/aghnet/net_linux.go
Eugene Burkov 5e71f5df6a Pull request: 2846 cover aghnet vol.3
Merge in DNS/adguard-home from 2846-cover-aghnet-vol.3 to master

Updates #2846.

Squashed commit of the following:

commit cb22987c43c17bbc8d098e65639cc84e2284bc7b
Merge: cf995e9d f31ffcc5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 30 15:01:10 2022 +0300

    Merge branch 'master' into 2846-cover-aghnet-vol.3

commit cf995e9dce635f16e10406a61e2ab12f06407f1f
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 18:29:50 2022 +0300

    aghnet: imp tests

commit bc225fe8800633b29216840bc7d5b82d7c2d2bfb
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 18:03:06 2022 +0300

    aghnet: imp tests

commit a82eb6045495b94a2e81ced9a3ef5bfe65788e56
Merge: f8081249 0d562a7b
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 17:39:13 2022 +0300

    Merge branch 'master' into 2846-cover-aghnet-vol.3

commit f80812490c49f69655d409c6f015b069affa2f19
Merge: edccaa79 3603b1fc
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 17:29:20 2022 +0300

    Merge branch 'master' into 2846-cover-aghnet-vol.3

commit edccaa79fca061ffeea1985c293eed123b16a09c
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Mar 28 13:53:40 2022 +0300

    aghnet: imp tests

commit 7c5028c92f0a6680516bda67c73e794182c9b825
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Mar 25 18:01:28 2022 +0300

    aghnet: imp code & docs

commit 7897c6b13e9be340ae8a71947a8a0bab82c682eb
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Mar 25 17:11:46 2022 +0300

    aghnet: imp coverage

commit 1eef110af3bf721a0275c695bf27c31815abff04
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Mar 23 21:10:29 2022 +0300

    all: return byte slice
2022-03-30 15:11:57 +03:00

178 lines
4.6 KiB
Go

//go:build linux
// +build linux
package aghnet
import (
"bufio"
"fmt"
"io"
"net"
"os"
"strings"
"github.com/AdguardTeam/AdGuardHome/internal/aghos"
"github.com/AdguardTeam/golibs/errors"
"github.com/google/renameio/maybe"
"golang.org/x/sys/unix"
)
// dhcpcdStaticConfig checks if interface is configured by /etc/dhcpcd.conf to
// have a static IP.
func (n interfaceName) dhcpcdStaticConfig(r io.Reader) (subsources []string, cont bool, err error) {
s := bufio.NewScanner(r)
if !findIfaceLine(s, string(n)) {
return nil, true, s.Err()
}
for s.Scan() {
line := strings.TrimSpace(s.Text())
fields := strings.Fields(line)
if len(fields) >= 2 &&
fields[0] == "static" &&
strings.HasPrefix(fields[1], "ip_address=") {
return nil, false, s.Err()
}
if len(fields) > 0 && fields[0] == "interface" {
// Another interface found.
break
}
}
return nil, true, s.Err()
}
// ifacesStaticConfig checks if the interface is configured by any file of
// /etc/network/interfaces format to have a static IP.
func (n interfaceName) ifacesStaticConfig(r io.Reader) (sub []string, cont bool, err error) {
s := bufio.NewScanner(r)
for s.Scan() {
line := strings.TrimSpace(s.Text())
if len(line) == 0 || line[0] == '#' {
continue
}
// TODO(e.burkov): As man page interfaces(5) says, a line may be
// extended across multiple lines by making the last character a
// backslash. Provide extended lines support.
fields := strings.Fields(line)
fieldsNum := len(fields)
// 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 fieldsNum >= 4 &&
fields[0] == "iface" && fields[1] == string(n) && fields[3] == "static" {
return nil, false, nil
}
if fieldsNum >= 2 && fields[0] == "source" {
sub = append(sub, fields[1])
}
}
return sub, true, s.Err()
}
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 and /etc/network/interfaces has no
// static IP configuration, it will return true. Perhaps this is not the
// most desirable behavior.
iface := interfaceName(ifaceName)
for _, pair := range [...]struct {
aghos.FileWalker
filename string
}{{
FileWalker: iface.dhcpcdStaticConfig,
filename: "etc/dhcpcd.conf",
}, {
FileWalker: iface.ifacesStaticConfig,
filename: "etc/network/interfaces",
}} {
has, err = pair.Walk(rootDirFS, pair.filename)
if err != nil {
return false, err
} else if has {
return true, nil
}
}
return false, ErrNoStaticIPInfo
}
func canBindPrivilegedPorts() (can bool, err error) {
cnbs, err := unix.PrctlRetInt(unix.PR_CAP_AMBIENT, unix.PR_CAP_AMBIENT_IS_SET, unix.CAP_NET_BIND_SERVICE, 0, 0)
// Don't check the error because it's always nil on Linux.
adm, _ := aghos.HaveAdminRights()
return cnbs == 1 || adm, err
}
// findIfaceLine scans s until it finds the line that declares an interface with
// the given name. If findIfaceLine can't find the line, it returns false.
func findIfaceLine(s *bufio.Scanner, name string) (ok bool) {
for s.Scan() {
line := strings.TrimSpace(s.Text())
fields := strings.Fields(line)
if len(fields) == 2 && fields[0] == "interface" && fields[1] == name {
return true
}
}
return false
}
// ifaceSetStaticIP configures the system to retain its current IP on the
// interface through dhcpdc.conf.
func ifaceSetStaticIP(ifaceName string) (err error) {
ipNet := GetSubnet(ifaceName)
if ipNet.IP == nil {
return errors.Error("can't get IP address")
}
gatewayIP := GatewayIP(ifaceName)
add := dhcpcdConfIface(ifaceName, ipNet, gatewayIP, ipNet.IP)
const filename = "/etc/dhcpcd.conf"
body, err := os.ReadFile(filename)
if err != nil && !errors.Is(err, os.ErrNotExist) {
return err
}
body = append(body, []byte(add)...)
err = maybe.WriteFile(filename, body, 0o644)
if err != nil {
return fmt.Errorf("writing conf: %w", err)
}
return nil
}
// dhcpcdConfIface returns configuration lines for the dhcpdc.conf files that
// configure the interface to have a static IP.
func dhcpcdConfIface(ifaceName string, ipNet *net.IPNet, gatewayIP, dnsIP net.IP) (conf string) {
var body []byte
add := fmt.Sprintf(
"\n# %[1]s added by AdGuard Home.\ninterface %[1]s\nstatic ip_address=%s\n",
ifaceName,
ipNet)
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)
}