dns.go

package config

import (
	"context"
	"fmt"
	"io/ioutil"
	"os"
	"text/template"

	"github.com/containerd/containerd"
	"github.com/crosbymichael/boss/systemd"
	"github.com/urfave/cli"
)

const hostsFile = `127.0.0.1       localhost.localdomain   localhost {{.ID}}
::1             localhost6.localdomain6 localhost6 aegis-03

# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts`

type DNS struct {
	ID string
}

func (s *DNS) Name() string {
	return "dns"
}

func (s *DNS) Run(ctx context.Context, client *containerd.Client, clix *cli.Context) error {
	if err := systemd.Command(ctx, "disable", "systemd-resolved"); err != nil {
		return err
	}
	if err := systemd.Command(ctx, "stop", "systemd-resolved"); err != nil {
		return err
	}
	if err := writeResolveConf("127.0.0.1"); err != nil {
		return err
	}
	tmpl, err := template.New("hosts").Parse(hostsFile)
	if err != nil {
		return err
	}
	t, err := ioutil.TempFile("", "boss-hosts")
	if err != nil {
		return err
	}
	if err := t.Chmod(0666); err != nil {
		return err
	}
	err = tmpl.Execute(t, s)
	t.Close()
	if err != nil {
		return err
	}
	return os.Rename(t.Name(), "/etc/hosts")
}

func (s *DNS) Remove(ctx context.Context, client *containerd.Client, clix *cli.Context) error {
	return writeResolveConf("8.8.8.8", "8.8.4.4")
}

func writeResolveConf(nameservers ...string) error {
	t, err := ioutil.TempFile("", "boss-resolvconf")
	if err != nil {
		return err
	}
	if err := t.Chmod(0666); err != nil {
		return err
	}
	for _, ns := range nameservers {
		if _, err := t.WriteString(fmt.Sprintf("nameserver %s\n", ns)); err != nil {
			t.Close()
			return err
		}
	}
	t.Close()
	if err != nil {
		return err
	}
	return os.Rename(t.Name(), "/etc/resolv.conf")
}