Pull request: all: fix lint and naming issues vol. 2

Merge in DNS/adguard-home from 2276-fix-lint-2 to master

Updates #2276.

Squashed commit of the following:

commit 24760b9586bb31be134ef9518dbece485560b1a0
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Dec 7 14:39:50 2020 +0300

    all: fix lint and naming issues vol. 2

internal/dhcpd/netutil.go

@@ -0,0 +1,312 @@
+package dhcpd
+
+import (
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"os/exec"
+	"regexp"
+	"runtime"
+	"strings"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/util"
+
+	"github.com/AdguardTeam/golibs/file"
+
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// HasStaticIP check if the network interface has a static IP configured
+//
+// Supports: Raspbian.
+func HasStaticIP(ifaceName string) (bool, error) {
+	if runtime.GOOS == "linux" {
+		body, err := ioutil.ReadFile("/etc/dhcpcd.conf")
+		if err != nil {
+			return false, err
+		}
+
+		return hasStaticIPDhcpcdConf(string(body), ifaceName), nil
+	}
+
+	if runtime.GOOS == "darwin" {
+		return hasStaticIPDarwin(ifaceName)
+	}
+
+	return false, fmt.Errorf("cannot check if IP is static: not supported on %s", runtime.GOOS)
+}
+
+// SetStaticIP sets a static IP for the network interface.
+func SetStaticIP(ifaceName string) error {
+	if runtime.GOOS == "linux" {
+		return setStaticIPDhcpdConf(ifaceName)
+	}
+
+	if runtime.GOOS == "darwin" {
+		return setStaticIPDarwin(ifaceName)
+	}
+
+	return fmt.Errorf("cannot set static IP on %s", runtime.GOOS)
+}
+
+// for dhcpcd.conf
+func hasStaticIPDhcpcdConf(dhcpConf, ifaceName string) bool {
+	lines := strings.Split(dhcpConf, "\n")
+	nameLine := fmt.Sprintf("interface %s", ifaceName)
+	withinInterfaceCtx := false
+
+	for _, line := range lines {
+		line = strings.TrimSpace(line)
+
+		if withinInterfaceCtx && len(line) == 0 {
+			// an empty line resets our state
+			withinInterfaceCtx = false
+		}
+
+		if len(line) == 0 || line[0] == '#' {
+			continue
+		}
+		line = strings.TrimSpace(line)
+
+		if !withinInterfaceCtx {
+			if line == nameLine {
+				// we found our interface
+				withinInterfaceCtx = true
+			}
+		} else {
+			if strings.HasPrefix(line, "interface ") {
+				// we found another interface - reset our state
+				withinInterfaceCtx = false
+				continue
+			}
+			if strings.HasPrefix(line, "static ip_address=") {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// Get gateway IP address
+func getGatewayIP(ifaceName string) string {
+	cmd := exec.Command("ip", "route", "show", "dev", ifaceName)
+	log.Tracef("executing %s %v", cmd.Path, cmd.Args)
+	d, err := cmd.Output()
+	if err != nil || cmd.ProcessState.ExitCode() != 0 {
+		return ""
+	}
+
+	fields := strings.Fields(string(d))
+	if len(fields) < 3 || fields[0] != "default" {
+		return ""
+	}
+
+	ip := net.ParseIP(fields[2])
+	if ip == nil {
+		return ""
+	}
+
+	return fields[2]
+}
+
+// setStaticIPDhcpdConf - updates /etc/dhcpd.conf and sets the current IP address to be static
+func setStaticIPDhcpdConf(ifaceName string) error {
+	ip := util.GetSubnet(ifaceName)
+	if len(ip) == 0 {
+		return errors.New("can't get IP address")
+	}
+
+	ip4, _, err := net.ParseCIDR(ip)
+	if err != nil {
+		return err
+	}
+	gatewayIP := getGatewayIP(ifaceName)
+	add := updateStaticIPDhcpcdConf(ifaceName, ip, gatewayIP, ip4.String())
+
+	body, err := ioutil.ReadFile("/etc/dhcpcd.conf")
+	if err != nil {
+		return err
+	}
+
+	body = append(body, []byte(add)...)
+	err = file.SafeWrite("/etc/dhcpcd.conf", body)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// updates dhcpd.conf content -- sets static IP address there
+// for dhcpcd.conf
+func updateStaticIPDhcpcdConf(ifaceName, ip, gatewayIP, dnsIP string) string {
+	var body []byte
+
+	add := fmt.Sprintf("\ninterface %s\nstatic ip_address=%s\n",
+		ifaceName, ip)
+	body = append(body, []byte(add)...)
+
+	if len(gatewayIP) != 0 {
+		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)
+}
+
+// Check if network interface has a static IP configured
+// Supports: MacOS.
+func hasStaticIPDarwin(ifaceName string) (bool, error) {
+	portInfo, err := getCurrentHardwarePortInfo(ifaceName)
+	if err != nil {
+		return false, err
+	}
+
+	return portInfo.static, nil
+}
+
+// setStaticIPDarwin - uses networksetup util to set the current IP address to be static
+// Additionally it configures the current DNS servers as well
+func setStaticIPDarwin(ifaceName string) error {
+	portInfo, err := getCurrentHardwarePortInfo(ifaceName)
+	if err != nil {
+		return err
+	}
+
+	if portInfo.static {
+		return errors.New("IP address is already static")
+	}
+
+	dnsAddrs, err := getEtcResolvConfServers()
+	if err != nil {
+		return err
+	}
+
+	args := make([]string, 0)
+	args = append(args, "-setdnsservers", portInfo.name)
+	args = append(args, dnsAddrs...)
+
+	// Setting DNS servers is necessary when configuring a static IP
+	code, _, err := util.RunCommand("networksetup", args...)
+	if err != nil {
+		return err
+	}
+	if code != 0 {
+		return fmt.Errorf("failed to set DNS servers, code=%d", code)
+	}
+
+	// Actually configures hardware port to have static IP
+	code, _, err = util.RunCommand("networksetup", "-setmanual",
+		portInfo.name, portInfo.ip, portInfo.subnet, portInfo.gatewayIP)
+	if err != nil {
+		return err
+	}
+	if code != 0 {
+		return fmt.Errorf("failed to set DNS servers, code=%d", code)
+	}
+
+	return nil
+}
+
+// getCurrentHardwarePortInfo gets information the specified network interface
+func getCurrentHardwarePortInfo(ifaceName string) (hardwarePortInfo, error) {
+	// First of all we should find hardware port name
+	m := getNetworkSetupHardwareReports()
+	hardwarePort, ok := m[ifaceName]
+	if !ok {
+		return hardwarePortInfo{}, fmt.Errorf("could not find hardware port for %s", ifaceName)
+	}
+
+	return getHardwarePortInfo(hardwarePort)
+}
+
+// getNetworkSetupHardwareReports parses the output of the `networksetup -listallhardwareports` command
+// it returns a map where the key is the interface name, and the value is the "hardware port"
+// returns nil if it fails to parse the output
+func getNetworkSetupHardwareReports() map[string]string {
+	_, out, err := util.RunCommand("networksetup", "-listallhardwareports")
+	if err != nil {
+		return nil
+	}
+
+	re, err := regexp.Compile("Hardware Port: (.*?)\nDevice: (.*?)\n")
+	if err != nil {
+		return nil
+	}
+
+	m := make(map[string]string)
+
+	matches := re.FindAllStringSubmatch(out, -1)
+	for i := range matches {
+		port := matches[i][1]
+		device := matches[i][2]
+		m[device] = port
+	}
+
+	return m
+}
+
+// hardwarePortInfo - information obtained using MacOS networksetup
+// about the current state of the internet connection
+type hardwarePortInfo struct {
+	name      string
+	ip        string
+	subnet    string
+	gatewayIP string
+	static    bool
+}
+
+func getHardwarePortInfo(hardwarePort string) (hardwarePortInfo, error) {
+	h := hardwarePortInfo{}
+
+	_, out, err := util.RunCommand("networksetup", "-getinfo", hardwarePort)
+	if err != nil {
+		return h, err
+	}
+
+	re := regexp.MustCompile("IP address: (.*?)\nSubnet mask: (.*?)\nRouter: (.*?)\n")
+
+	match := re.FindStringSubmatch(out)
+	if len(match) == 0 {
+		return h, errors.New("could not find hardware port info")
+	}
+
+	h.name = hardwarePort
+	h.ip = match[1]
+	h.subnet = match[2]
+	h.gatewayIP = match[3]
+
+	if strings.Index(out, "Manual Configuration") == 0 {
+		h.static = true
+	}
+
+	return h, nil
+}
+
+// Gets a list of nameservers currently configured in the /etc/resolv.conf
+func getEtcResolvConfServers() ([]string, error) {
+	body, err := ioutil.ReadFile("/etc/resolv.conf")
+	if err != nil {
+		return nil, err
+	}
+
+	re := regexp.MustCompile("nameserver ([a-zA-Z0-9.:]+)")
+
+	matches := re.FindAllStringSubmatch(string(body), -1)
+	if len(matches) == 0 {
+		return nil, errors.New("found no DNS servers in /etc/resolv.conf")
+	}
+
+	addrs := make([]string, 0)
+	for i := range matches {
+		addrs = append(addrs, matches[i][1])
+	}
+
+	return addrs, nil
+}