all: fork tailscale Linux dns manager package

With modification to fit our use case.
2026-08-23 01:27:13 +02:00 · 2023-02-03 02:47:31 +07:00
parent b8772d7b4a
commit 851f9b9742
18 changed files with 2735 additions and 9 deletions
@@ -0,0 +1,199 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package dns
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"net/netip"
+	"os"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+	"tailscale.com/util/dnsname"
+)
+
+func TestDirectManager(t *testing.T) {
+	tmp := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(tmp, "etc"), 0700); err != nil {
+		t.Fatal(err)
+	}
+	testDirect(t, directFS{prefix: tmp})
+}
+
+type boundResolvConfFS struct {
+	directFS
+}
+
+func (fs boundResolvConfFS) Rename(old, new string) error {
+	if old == "/etc/resolv.conf" || new == "/etc/resolv.conf" {
+		return errors.New("cannot move to/from /etc/resolv.conf")
+	}
+	return fs.directFS.Rename(old, new)
+}
+
+func (fs boundResolvConfFS) Remove(name string) error {
+	if name == "/etc/resolv.conf" {
+		return errors.New("cannot remove /etc/resolv.conf")
+	}
+	return fs.directFS.Remove(name)
+}
+
+func TestDirectBrokenRename(t *testing.T) {
+	tmp := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(tmp, "etc"), 0700); err != nil {
+		t.Fatal(err)
+	}
+	testDirect(t, boundResolvConfFS{directFS{prefix: tmp}})
+}
+
+func testDirect(t *testing.T, fs wholeFileFS) {
+	const orig = "nameserver 9.9.9.9 # orig"
+	resolvPath := "/etc/resolv.conf"
+	backupPath := "/etc/resolv.pre-ctrld-backup.conf"
+
+	if err := fs.WriteFile(resolvPath, []byte(orig), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	readFile := func(t *testing.T, path string) string {
+		t.Helper()
+		b, err := fs.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return string(b)
+	}
+	assertBaseState := func(t *testing.T) {
+		if got := readFile(t, resolvPath); got != orig {
+			t.Fatalf("resolv.conf:\n%s, want:\n%s", got, orig)
+		}
+		if _, err := fs.Stat(backupPath); !os.IsNotExist(err) {
+			t.Fatalf("resolv.conf backup: want it to be gone but: %v", err)
+		}
+	}
+
+	m := directManager{logf: t.Logf, fs: fs}
+	if err := m.SetDNS(OSConfig{
+		Nameservers:   []netip.Addr{netip.MustParseAddr("8.8.8.8"), netip.MustParseAddr("8.8.4.4")},
+		SearchDomains: []dnsname.FQDN{"controld.com."},
+		MatchDomains:  []dnsname.FQDN{"ignored."},
+	}); err != nil {
+		t.Fatal(err)
+	}
+	want := `# resolv.conf(5) file generated by ctrld
+# DO NOT EDIT THIS FILE BY HAND -- CHANGES WILL BE OVERWRITTEN
+
+nameserver 8.8.8.8
+nameserver 8.8.4.4
+search controld.com
+`
+	if got := readFile(t, resolvPath); got != want {
+		t.Fatalf("resolv.conf:\n%s, want:\n%s", got, want)
+	}
+	if got := readFile(t, backupPath); got != orig {
+		t.Fatalf("resolv.conf backup:\n%s, want:\n%s", got, orig)
+	}
+
+	// Test that a nil OSConfig cleans up resolv.conf.
+	if err := m.SetDNS(OSConfig{}); err != nil {
+		t.Fatal(err)
+	}
+	assertBaseState(t)
+
+	// Test that Close cleans up resolv.conf.
+	if err := m.SetDNS(OSConfig{Nameservers: []netip.Addr{netip.MustParseAddr("8.8.8.8")}}); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Close(); err != nil {
+		t.Fatal(err)
+	}
+	assertBaseState(t)
+}
+
+type brokenRemoveFS struct {
+	directFS
+}
+
+func (b brokenRemoveFS) Rename(_, _ string) error {
+	return errors.New("nyaaah I'm a silly container!")
+}
+
+func (b brokenRemoveFS) Remove(name string) error {
+	if strings.Contains(name, "/etc/resolv.conf") {
+		return fmt.Errorf("Faking remove failure: %q", &fs.PathError{Err: syscall.EBUSY})
+	}
+	return b.directFS.Remove(name)
+}
+
+func TestDirectBrokenRemove(t *testing.T) {
+	tmp := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(tmp, "etc"), 0700); err != nil {
+		t.Fatal(err)
+	}
+	testDirect(t, brokenRemoveFS{directFS{prefix: tmp}})
+}
+
+func TestReadResolve(t *testing.T) {
+	c := qt.New(t)
+	tests := []struct {
+		in      string
+		want    OSConfig
+		wantErr bool
+	}{
+		{in: `nameserver 192.168.0.100`,
+			want: OSConfig{
+				Nameservers: []netip.Addr{
+					netip.MustParseAddr("192.168.0.100"),
+				},
+			},
+		},
+		{in: `nameserver 192.168.0.100 # comment`,
+			want: OSConfig{
+				Nameservers: []netip.Addr{
+					netip.MustParseAddr("192.168.0.100"),
+				},
+			},
+		},
+		{in: `nameserver 192.168.0.100#`,
+			want: OSConfig{
+				Nameservers: []netip.Addr{
+					netip.MustParseAddr("192.168.0.100"),
+				},
+			},
+		},
+		{in: `nameserver #192.168.0.100`, wantErr: true},
+		{in: `nameserver`, wantErr: true},
+		{in: `# nameserver 192.168.0.100`, want: OSConfig{}},
+		{in: `nameserver192.168.0.100`, wantErr: true},
+
+		{in: `search controld.com`,
+			want: OSConfig{
+				SearchDomains: []dnsname.FQDN{"controld.com."},
+			},
+		},
+		{in: `search controld.com # typo`,
+			want: OSConfig{
+				SearchDomains: []dnsname.FQDN{"controld.com."},
+			},
+		},
+		{in: `searchcontrold.com`, wantErr: true},
+		{in: `search`, wantErr: true},
+	}
+
+	for _, test := range tests {
+		cfg, err := readResolv(strings.NewReader(test.in))
+		if test.wantErr {
+			c.Assert(err, qt.IsNotNil)
+		} else {
+			c.Assert(err, qt.IsNil)
+		}
+		c.Assert(cfg, qt.DeepEquals, test.want)
+	}
+}