`hosts-file-enabled` cannot be set from config file

[linuxgemini]

Hello,

hosts-file-enabled uses cmd.decodableBool declared in internal/cmd/options.go:

dnsproxy/internal/cmd/options.go

Lines 26 to 43 in 25e110a

	// decodableBool is a boolean that can be unmarshaled from a flags.
	//
	// TODO(e.burkov): This is a workaround for go-flags, see
	// https://github.com/AdguardTeam/dnsproxy/issues/182.
	type decodableBool struct {
	value bool
	}
	// type check
	var _ goFlags.Unmarshaler = (*decodableBool)(nil)
	// UnmarshalFlag implements the [goFlags.Unmarshaler] interface for
	// *decodableBool.
	func (b *decodableBool) UnmarshalFlag(text string) (err error) {
	b.value, err = strconv.ParseBool(text)
	return err
	}

While the option works as intended as a launch flag --hosts-file-enabled=false, setting it inside a YAML config (hosts-file-enabled: false) will not work:

Aug 20 16:22:47 hostname dnsproxy[738715]: dnsproxy config path: /etc/dnsproxy/config.yaml
Aug 20 16:22:47 hostname dnsproxy[738715]: parsing config file /etc/dnsproxy/config.yaml: unmarshalling file: yaml: unmarshal errors:
Aug 20 16:22:47 hostname dnsproxy[738715]:   line 84: cannot unmarshal !!bool `false` into cmd.decodableBool

Setting it as a string (hosts-file-enabled: "false") also fails:

Aug 20 16:24:47 hostname dnsproxy[738747]: dnsproxy config path: /etc/dnsproxy/config.yaml
Aug 20 16:24:47 hostname dnsproxy[738747]: parsing config file /etc/dnsproxy/config.yaml: unmarshalling file: yaml: unmarshal errors:
Aug 20 16:24:47 hostname dnsproxy[738747]:   line 84: cannot unmarshal !!str `false` into cmd.decodableBool

I don't understand why exactly this occurs (I'm not really proficient in Go), one might omit the YAML flag (seen below) and use it as a command line argument:

dnsproxy/internal/cmd/options.go

Lines 233 to 235 in 25e110a

	// HostsFileEnabled controls whether hosts files are used for resolving or
	// not.
	HostsFileEnabled decodableBool `yaml:"hosts-file-enabled" long:"hosts-file-enabled" description:"If specified, use hosts files for resolving" default:"true"`

[EugeneOne1]

@linuxgemini, hello and thanks for the detailed report. We've just committed the fix (559d2ef) for this issue to the master branch. Could you please build the dnsproxy binary from that commit and check if it now successfully decodes the value?

[timkgh]

The default also should not be true. Let users opt-in rather than opt-out by default. If you run dnsproxy in a cloud VM that has all sorts of local things (e.g. private IPs for hosts that would otherwise resolve through public DNS to public IPs) in /etc/hosts, dnsproxy shouldn't really pick those up if you're using it just as a generic/public DNS proxy and it might be a surprising behavior.

[ameshkov]

Eventually, we have in mind making dnsproxy a drop-in replacement for dnsmasq and that's why we're trying to follow its behavior.

PS: Of course we're very far from it now, but nevertheless.

[cyformatician]

I agree with @timkgh, at least until users / package maintainers become familiar with this option ... I also think it's best to pull the .73.0 release and replace it with a working release that includes the fix as I had issues with my openwrt router and internet due to dnsproxy crashing (with/without the hosts option disabled in config) which brought me here..

Wed Aug 21 13:09:44 2024 daemon.info dnsproxy[21942]: 2024/08/21 09:09:44.078661 INFO dnsproxy starting version=v0.73.0 revision="" branch="" commit_time=""
Wed Aug 21 13:09:44 2024 daemon.info dnsproxy[21942]: 2024/08/21 09:09:44.078879 ERROR running dnsproxy err="configuring proxy: creating default handler: open etc/hosts: no such file or directory"
Wed Aug 21 13:09:44 2024 daemon.info dnsproxy[21942]: jail: jail (21943) exited with exit: 1

Wed Aug 21 13:09:49 2024 daemon.info dnsproxy[21956]: jail: exec-ing /usr/bin/dnsproxy
Wed Aug 21 13:09:49 2024 daemon.info dnsproxy[21956]: 2024/08/21 09:09:49.128674 INFO dnsproxy starting version=v0.73.0 revision="" branch="" commit_time=""
Wed Aug 21 13:09:49 2024 daemon.info dnsproxy[21956]: 2024/08/21 09:09:49.128875 ERROR running dnsproxy err="configuring proxy: creating default handler: open etc/hosts: no such file or directory"
Wed Aug 21 13:09:49 2024 daemon.info dnsproxy[21956]: jail: jail (21957) exited with exit: 1

Wed Aug 21 13:09:54 2024 daemon.info dnsproxy[21977]: jail: exec-ing /usr/bin/dnsproxy
Wed Aug 21 13:09:54 2024 daemon.info dnsproxy[21977]: 2024/08/21 09:09:54.178876 INFO dnsproxy starting version=v0.73.0 revision="" branch="" commit_time=""
Wed Aug 21 13:09:54 2024 daemon.info dnsproxy[21977]: 2024/08/21 09:09:54.179094 ERROR running dnsproxy err="configuring proxy: creating default handler: open etc/hosts: no such file or directory"
Wed Aug 21 13:09:54 2024 daemon.info dnsproxy[21977]: jail: jail (21978) exited with exit: 1

For impacted openwrt users - temporary fix would be to edit /etc/init.d/dnsproxy and add the following to load_config_list() section then restart dnsproxy:

append_param "--hosts-file-enabled" "false"

[linuxgemini]

@linuxgemini, hello and thanks for the detailed report. We've just committed the fix (559d2ef) for this issue to the master branch. Could you please build the dnsproxy binary from that commit and check if it now successfully decodes the value?

Hi @EugeneOne1, sorry for the late reply; build from current master works yes.

[EugeneOne1]

@linuxgemini, good to hear! We'll release the patch version later today. I'll close this issue for now.