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net/dns: ensure the Windows configurator does not touch the hosts file unless the configuration actually changed

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We build up maps of both the existing MagicDNS configuration in hosts
and the desired MagicDNS configuration, compare the two, and only
write out a new one if there are changes. The comparison doesn't need
to be perfect, as the occasional false-positive is fine, but this
should greatly reduce rewrites of the hosts file.

I also changed the hosts updating code to remove the CRLF/LF conversion
stuff, and use Fprintf instead of Frintln to let us write those inline.

Updates #14428

Signed-off-by: Aaron Klotz <aaron@tailscale.com>
This commit is contained in:
Aaron Klotz
2025-01-13 13:47:56 -07:00
parent 27477983e3
commit d818a58a77
2 changed files with 107 additions and 19 deletions
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52
net/dns/manager_windows_test.go
View File

@@ -15,6 +15,7 @@ import (
"golang.org/x/sys/windows"
"golang.org/x/sys/windows/registry"
"tailscale.com/types/logger"
"tailscale.com/util/dnsname"
"tailscale.com/util/winutil"
"tailscale.com/util/winutil/gp"
@@ -24,9 +25,56 @@ const testGPRuleID = "{7B1B6151-84E6-41A3-8967-62F7F7B45687}"
func TestHostFileNewLines(t *testing.T) {
in := []byte("#foo\r\n#bar\n#baz\n")
want := []byte("#foo\r\n#bar\r\n#baz\r\n")
want := []byte("#foo\r\n#bar\r\n#baz\r\n# TailscaleHostsSectionStart\r\n# This section contains MagicDNS entries for Tailscale.\r\n# Do not edit this section manually.\r\n\r\n192.168.1.1 aaron\r\n\r\n# TailscaleHostsSectionEnd\r\n")
got, err := setTailscaleHosts(in, nil)
he := []*HostEntry{
&HostEntry{
Addr: netip.MustParseAddr("192.168.1.1"),
Hosts: []string{"aaron"},
},
}
got, err := setTailscaleHosts(logger.Discard, in, he)
if err != nil {
t.Fatal(err)
}
if !bytes.Equal(got, want) {
t.Errorf("got %q, want %q\n", got, want)
}
}
func TestHostFileUnchanged(t *testing.T) {
in := []byte("#foo\r\n#bar\r\n#baz\r\n# TailscaleHostsSectionStart\r\n# This section contains MagicDNS entries for Tailscale.\r\n# Do not edit this section manually.\r\n\r\n192.168.1.1 aaron\r\n\r\n# TailscaleHostsSectionEnd\r\n")
he := []*HostEntry{
&HostEntry{
Addr: netip.MustParseAddr("192.168.1.1"),
Hosts: []string{"aaron"},
},
}
got, err := setTailscaleHosts(logger.Discard, in, he)
if err != nil {
t.Fatal(err)
}
if got != nil {
t.Errorf("got %q, want nil\n", got)
}
}
func TestHostFileChanged(t *testing.T) {
in := []byte("#foo\r\n#bar\r\n#baz\r\n# TailscaleHostsSectionStart\r\n# This section contains MagicDNS entries for Tailscale.\r\n# Do not edit this section manually.\r\n\r\n192.168.1.1 aaron1\r\n\r\n# TailscaleHostsSectionEnd\r\n")
want := []byte("#foo\r\n#bar\r\n#baz\r\n# TailscaleHostsSectionStart\r\n# This section contains MagicDNS entries for Tailscale.\r\n# Do not edit this section manually.\r\n\r\n192.168.1.1 aaron1\r\n192.168.1.2 aaron2\r\n\r\n# TailscaleHostsSectionEnd\r\n")
he := []*HostEntry{
&HostEntry{
Addr: netip.MustParseAddr("192.168.1.1"),
Hosts: []string{"aaron1"},
},
&HostEntry{
Addr: netip.MustParseAddr("192.168.1.2"),
Hosts: []string{"aaron2"},
},
}
got, err := setTailscaleHosts(logger.Discard, in, he)
if err != nil {
t.Fatal(err)
}