* Re: Split DNS for macOS
2021-10-29 21:07 ` Stephen Larew
@ 2021-10-30 21:00 ` Dusan Zivadinovic
2021-11-03 9:15 ` Harald Dunkel
` (2 subsequent siblings)
3 siblings, 0 replies; 14+ messages in thread
From: Dusan Zivadinovic @ 2021-10-30 21:00 UTC (permalink / raw)
To: Stephen Larew; +Cc: wireguard
Hi list,
I would appreciate that, its a usefull feature.
Think of connecting to multiple remote VPN peers simultaneously,
and use different DNSes for certain domains in each VPN connection.
Just as an example, the iOS app DNSCloak also sports a split DNS function.
regards,
Dusan
> Am 29.10.2021 um 23:07 schrieb Stephen Larew <stephen@slarew.net>:
>
>> On Oct 29, 2021, at 10:03, Andrew Fried <afried@spamteq.com> wrote:
>>
>>> On Oct 29, 2021, at 08:33, Stephen Larew <stephen@slarew.net> wrote:
>>>
>>>> On Oct 28, 2021, at 02:58, Bruce Ferrell <bferrell@baywinds.org> wrote:
>>>>
>>>> On 10/28/21 12:16 AM, Stephen Larew wrote:
>>>>> For many months now, I have been running a patched WireGuard macOS app
>>>>> that enables a split DNS configuration. I would like to try to upstream
>>>>> my patches for split DNS.
>>>>>
>>>>> There has been some interest in this patch:
>>>>> - "Mac APP DNS Search Domain" thread from July and August 2021 [1]
>>>>> - A commenter on my GitHub fork of wireguard-apple.
>>>>>
>>>>> What is split DNS? It allows sending DNS queries to a specific server
>>>>> based on the domain name. Systemd-resolved calls it a routing domain.
>>>>> Apple's Network Extension framework calls it a match domain. Split DNS
>>>>> is especially useful for internal DNS servers.
>>>>>
>>>>> For example, if corp.example.com is a routing domain for the DNS server
>>>>> at 192.0.2.1 (only accessible over WireGuard), then
>>>>> server.corp.example.com is resolved using 192.0.2.1 while
>>>>> www.example.com is resolved using some other DNS resolver (depending on
>>>>> the other network settings in macOS).
>>>>>
>>>>> The proposed patch adds new syntax to the wg-quick DNS= line.
>>>>> Specifically, a tilde prefixed domain is treated as a routing domain.
>>>>> Multiple routing domains can be added.
>>>>>
>>>>> Limitations:
>>>>> - Needs modifications to iOS UI to work on iOS.
>>>>> - Only matching routing domains are sent to the DNS servers specified in
>>>>> the DNS= config line. No separate fallback catch-all DNS server can
>>>>> be set.
>>>>> - Routing/match domains are also included in the list of search domains.
>>>>> This could be changed with the matchDomainsNoSearch API, but lacking
>>>>> more UI or config file changes to expose this option to the user, I
>>>>> went with the default.
>>>>>
>>>>> [1] https://lore.kernel.org/wireguard/20210810074232.aah5ktq5yzysaaey@SvensMacBookAir-2.local/T/
>>>>> [2] https://github.com/slarew/wireguard-apple/commit/6ebc356d9e11ab91443e06de5e89f1af57fcdff8
>>>>
>>>> That seems to be a redefinition of the existing definition of split DNS.
>>>>
>>>> Most usually, split DNS is done at the DNS server and different zones are served to the resolver based on various criteria... Usually the origination IP of the query; If the query comes from a client on your LAN, or a particular subnet, the contents of a particular, private, zone are returned. If the query comes from, say the internet, a public zone is returned.
>>>>
>>>> YOUR description, is how DNS works in general... Except your patch also seems to either bypass the resolver libraries or wedge itself in front of them The system resolver libraries well tested and understood and they handle the following very nicely.
>>>>
>>>> There is the issue of what happens with large DNS responses. Any DNS response over 512 bytes UDP fails and is required to be retried as a TCP query, which can handle the large response. It's late and I'm too tired to look it up, but there IS an RFC for this.
>>>>
>>>> It's a little known issue, but I've seen it when working with other VPN products that ignored/didn't understand the behavior. The results weren't pretty and really embarrassing.
>>>>
>>>> Systemd has a bad habit of re-inventing the wheel... Badly. Eventually it get's sorted, but is that really progress? In the long haul, "move fast and break things" is a MAJOR pita for the vast majority of us. But some like it.
>>>>
>>>> For some real fun, look into DHCPCD. It faithfully implements a particular RFC. In some networking environments using VPNs, it breaks routing horribly.... But it meets the RFC. You'll find it in Raspbian by default, and most other Debian derived distros. I automatically rip it out and replace it with the also available ISC DHCP client. That one is fully compatible with Windows, OS X, iOS, and every android and smart device I could test it with. A DHCP server configured to be compatible with DHCPCD broke all of the previously named.
>>>>
>>>> I'm giving this opinion away for free, so it's worth what you paid for it.
>>>
>>> Regardless of naming or definitions, I think the ability for a *local device* to route DNS queries to different DNS servers based on domain matching criteria is certainly useful. It’s not always possible or desirable to control and configure an upstream DNS server. Hence, this patch enables the local device to do split DNS.
>>>
>>> To be clear, this patch does not bypass or wedge around anything. In fact, it configures the native macOS DNS settings in the appropriate manner to effect a split DNS configuration.
>>>
>>> As a result of controlling the native macOS DNS resolution logic, any feature, absent or present, in the macOS DNS resolver libraries should be unaffected. This includes the large DNS response and TCP behavior. I do not expect the small/large UDP/TCP DNS features to change behavior when using a split DNS configuration as proposed in this patch.
>>>
>>> -Stephen
>>
>> Hi Stephen,
>>
>> A better solution to your problem would be to deploy DNSDIST:
>> https://dnsdist.org/
>>
>> I for one would hope that esoteric requests that address a solution for less than 1% of the users would be rejected with the overall goal of preventing feature creep and bloat.
>>
>> Andrew
>
> DNSDIST may allow (I have not tried) one to create a split DNS scenario, but it is an extra piece of software that would need to be discovered, installed, configured, and maintained by a user or system administrator. I do not believe it would properly integrate with the macOS DNS resolution machinery. I do not believe it is a better solution to the problem.
>
> As I understand it, under some circumstances, the Tailscale macOS app also implements split DNS in roughly the same manner as done in my patch. Namely, the tailscale app appears to use the Network Extension APIs to directly integrate with the macOS DNS resolution machinery. Perhaps the relevant difference is that tailscale approaches configuration differently (not based on wg-quick) than the WireGuard macOS app.
>
> I do not have statistics or polling on who desires this split DNS feature. I have received private and public requests to upstream the feature. Tailscale also implements split DNS; presumable customers demand it. I suspect if the feature was available to users of the WireGuard app, then it would be used with precision to great effect. Users who do not need this split DNS feature do not lose any previous functionality in the macOS WireGuard app.
>
> Personally, my one hesitation with this patch is that, as currently implemented, a new syntax is added to the wg-quick config file (tilde prefixed route/match domains). My patch does not address compatibility issues nor does it add documentation to wg-quick for the new syntax.
>
> -Stephen
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: Split DNS for macOS
2021-10-29 21:07 ` Stephen Larew
2021-10-30 21:00 ` Dusan Zivadinovic
@ 2021-11-03 9:15 ` Harald Dunkel
2021-11-03 9:42 ` Matty Driessen
2021-11-03 11:54 ` Alex Burke
2021-11-06 4:54 ` David Anderson
3 siblings, 1 reply; 14+ messages in thread
From: Harald Dunkel @ 2021-11-03 9:15 UTC (permalink / raw)
To: wireguard
Hi folks,
I really like this patch. Currently DNS on MacOS is unable to resolve
both my local DNS names and the domain in the office in parallel, if
Wireguard is enabled. I have to use somehost.local to fall back to
zeroconf for my LAN as a workaround, which is pretty annoying.
My suggestion would be to set SupplementalMatchDomains instead(!) of
SearchDomains, using the current config file syntax without '~'. Since
SupplementalMatchDomainsNoSearch is disabled by default, setting
SupplementalMatchDomains is sufficient to configure both lists. See
https://developer.apple.com/business/documentation/Configuration-Profile-Reference.pdf
This has to be verified, of course.
Regards
Harri
On 2021-10-29 23:07:38, Stephen Larew wrote:
>> On Oct 29, 2021, at 10:03, Andrew Fried <afried@spamteq.com> wrote:
>>
>>> On Oct 29, 2021, at 08:33, Stephen Larew <stephen@slarew.net> wrote:
>>>
>>>> On Oct 28, 2021, at 02:58, Bruce Ferrell <bferrell@baywinds.org> wrote:
>>>>
>>>> On 10/28/21 12:16 AM, Stephen Larew wrote:
>>>>> For many months now, I have been running a patched WireGuard macOS app
>>>>> that enables a split DNS configuration. I would like to try to upstream
>>>>> my patches for split DNS.
>>>>>
>>>>> There has been some interest in this patch:
>>>>> - "Mac APP DNS Search Domain" thread from July and August 2021 [1]
>>>>> - A commenter on my GitHub fork of wireguard-apple.
>>>>>
>>>>> What is split DNS? It allows sending DNS queries to a specific server
>>>>> based on the domain name. Systemd-resolved calls it a routing domain.
>>>>> Apple's Network Extension framework calls it a match domain. Split DNS
>>>>> is especially useful for internal DNS servers.
>>>>>
>>>>> For example, if corp.example.com is a routing domain for the DNS server
>>>>> at 192.0.2.1 (only accessible over WireGuard), then
>>>>> server.corp.example.com is resolved using 192.0.2.1 while
>>>>> www.example.com is resolved using some other DNS resolver (depending on
>>>>> the other network settings in macOS).
>>>>>
>>>>> The proposed patch adds new syntax to the wg-quick DNS= line.
>>>>> Specifically, a tilde prefixed domain is treated as a routing domain.
>>>>> Multiple routing domains can be added.
>>>>>
>>>>> Limitations:
>>>>> - Needs modifications to iOS UI to work on iOS.
>>>>> - Only matching routing domains are sent to the DNS servers specified in
>>>>> the DNS= config line. No separate fallback catch-all DNS server can
>>>>> be set.
>>>>> - Routing/match domains are also included in the list of search domains.
>>>>> This could be changed with the matchDomainsNoSearch API, but lacking
>>>>> more UI or config file changes to expose this option to the user, I
>>>>> went with the default.
>>>>>
>>>>> [1] https://lore.kernel.org/wireguard/20210810074232.aah5ktq5yzysaaey@SvensMacBookAir-2.local/T/
>>>>> [2] https://github.com/slarew/wireguard-apple/commit/6ebc356d9e11ab91443e06de5e89f1af57fcdff8
>>>>
>>>> That seems to be a redefinition of the existing definition of split DNS.
>>>>
>>>> Most usually, split DNS is done at the DNS server and different zones are served to the resolver based on various criteria... Usually the origination IP of the query; If the query comes from a client on your LAN, or a particular subnet, the contents of a particular, private, zone are returned. If the query comes from, say the internet, a public zone is returned.
>>>>
>>>> YOUR description, is how DNS works in general... Except your patch also seems to either bypass the resolver libraries or wedge itself in front of them The system resolver libraries well tested and understood and they handle the following very nicely.
>>>>
>>>> There is the issue of what happens with large DNS responses. Any DNS response over 512 bytes UDP fails and is required to be retried as a TCP query, which can handle the large response. It's late and I'm too tired to look it up, but there IS an RFC for this.
>>>>
>>>> It's a little known issue, but I've seen it when working with other VPN products that ignored/didn't understand the behavior. The results weren't pretty and really embarrassing.
>>>>
>>>> Systemd has a bad habit of re-inventing the wheel... Badly. Eventually it get's sorted, but is that really progress? In the long haul, "move fast and break things" is a MAJOR pita for the vast majority of us. But some like it.
>>>>
>>>> For some real fun, look into DHCPCD. It faithfully implements a particular RFC. In some networking environments using VPNs, it breaks routing horribly.... But it meets the RFC. You'll find it in Raspbian by default, and most other Debian derived distros. I automatically rip it out and replace it with the also available ISC DHCP client. That one is fully compatible with Windows, OS X, iOS, and every android and smart device I could test it with. A DHCP server configured to be compatible with DHCPCD broke all of the previously named.
>>>>
>>>> I'm giving this opinion away for free, so it's worth what you paid for it.
>>>
>>> Regardless of naming or definitions, I think the ability for a *local device* to route DNS queries to different DNS servers based on domain matching criteria is certainly useful. It’s not always possible or desirable to control and configure an upstream DNS server. Hence, this patch enables the local device to do split DNS.
>>>
>>> To be clear, this patch does not bypass or wedge around anything. In fact, it configures the native macOS DNS settings in the appropriate manner to effect a split DNS configuration.
>>>
>>> As a result of controlling the native macOS DNS resolution logic, any feature, absent or present, in the macOS DNS resolver libraries should be unaffected. This includes the large DNS response and TCP behavior. I do not expect the small/large UDP/TCP DNS features to change behavior when using a split DNS configuration as proposed in this patch.
>>>
>>> -Stephen
>>
>> Hi Stephen,
>>
>> A better solution to your problem would be to deploy DNSDIST:
>> https://dnsdist.org/
>>
>> I for one would hope that esoteric requests that address a solution for less than 1% of the users would be rejected with the overall goal of preventing feature creep and bloat.
>>
>> Andrew
>
> DNSDIST may allow (I have not tried) one to create a split DNS scenario, but it is an extra piece of software that would need to be discovered, installed, configured, and maintained by a user or system administrator. I do not believe it would properly integrate with the macOS DNS resolution machinery. I do not believe it is a better solution to the problem.
>
> As I understand it, under some circumstances, the Tailscale macOS app also implements split DNS in roughly the same manner as done in my patch. Namely, the tailscale app appears to use the Network Extension APIs to directly integrate with the macOS DNS resolution machinery. Perhaps the relevant difference is that tailscale approaches configuration differently (not based on wg-quick) than the WireGuard macOS app.
>
> I do not have statistics or polling on who desires this split DNS feature. I have received private and public requests to upstream the feature. Tailscale also implements split DNS; presumable customers demand it. I suspect if the feature was available to users of the WireGuard app, then it would be used with precision to great effect. Users who do not need this split DNS feature do not lose any previous functionality in the macOS WireGuard app.
>
> Personally, my one hesitation with this patch is that, as currently implemented, a new syntax is added to the wg-quick config file (tilde prefixed route/match domains). My patch does not address compatibility issues nor does it add documentation to wg-quick for the new syntax.
>
> -Stephen
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Split DNS for macOS
2021-11-03 9:15 ` Harald Dunkel
@ 2021-11-03 9:42 ` Matty Driessen
0 siblings, 0 replies; 14+ messages in thread
From: Matty Driessen @ 2021-11-03 9:42 UTC (permalink / raw)
To: wireguard
Hello,
I just want to chime in here and say that I think the current
implementation of search domains is simply not working the way it
should on the MacOS client.
My use case is pretty common, an internal DNS server that has entries
for internal servers. I defined a search domain in the WireGuard
configuration; DNS = 10.13.13.1 mydomain.internal. The search domain
is for convenience, so I can just use the servername instead of
servername.mydomain.internal. Now this works fine when I route all the
traffic through the VPN (AllowedIPs = 0.0.0.0/0) but the search domain
is completely ignored when I only route the traffic I need to
(AllowedIPs = 10.13.13.0/24 192.168.0.0/24).
I don't think this is a configuration error on my side. The DNS
responds fine when using servername.mydomain.internal. This problem is
even mentioned in the "WireGuard macOS & iOS TODO List"
9. matchDomains=[“”] doesn’t do what the documentation says.
Specifically, DNS servers are not used if allowed IPs isn’t 0.0.0.0/0.
The description isn't 100% accurate (or outdated), the DNS server is
used but the search domain isn't being set on the primary resolver.
Some have solved this issue by adding the search domains to the list
of matchDomains; dnsSettings.matchDomains = [""] +
dnsSettings.searchDomains. But that way the DNS server specified in
WireGuard is still the primary resolver for all DNS queries.
Here is a link on how OpenVPN handles this and I think it's how it
should work when not using AllowedIPs 0.0.0.0/0.
https://openvpn.net/faq/how-does-ios-interpret-pushed-dns-servers-and-search-domains/
On a split-tunnel, where redirect-gateway is not pushed by the server,
and at least one pushed DNS server is present:
- route all DNS requests through pushed DNS server(s) if no added
search domains.
- route DNS requests for added search domains only, if at least one
added search domain.
Regards,
Matty
On Wed, Nov 3, 2021 at 10:20 AM Harald Dunkel <harald.dunkel@aixigo.com> wrote:
>
> Hi folks,
>
> I really like this patch. Currently DNS on MacOS is unable to resolve
> both my local DNS names and the domain in the office in parallel, if
> Wireguard is enabled. I have to use somehost.local to fall back to
> zeroconf for my LAN as a workaround, which is pretty annoying.
>
> My suggestion would be to set SupplementalMatchDomains instead(!) of
> SearchDomains, using the current config file syntax without '~'. Since
> SupplementalMatchDomainsNoSearch is disabled by default, setting
> SupplementalMatchDomains is sufficient to configure both lists. See
>
> https://developer.apple.com/business/documentation/Configuration-Profile-Reference.pdf
>
> This has to be verified, of course.
>
>
> Regards
> Harri
>
>
>
> On 2021-10-29 23:07:38, Stephen Larew wrote:
> >> On Oct 29, 2021, at 10:03, Andrew Fried <afried@spamteq.com> wrote:
> >>
> >>> On Oct 29, 2021, at 08:33, Stephen Larew <stephen@slarew.net> wrote:
> >>>
> >>>> On Oct 28, 2021, at 02:58, Bruce Ferrell <bferrell@baywinds.org> wrote:
> >>>>
> >>>> On 10/28/21 12:16 AM, Stephen Larew wrote:
> >>>>> For many months now, I have been running a patched WireGuard macOS app
> >>>>> that enables a split DNS configuration. I would like to try to upstream
> >>>>> my patches for split DNS.
> >>>>>
> >>>>> There has been some interest in this patch:
> >>>>> - "Mac APP DNS Search Domain" thread from July and August 2021 [1]
> >>>>> - A commenter on my GitHub fork of wireguard-apple.
> >>>>>
> >>>>> What is split DNS? It allows sending DNS queries to a specific server
> >>>>> based on the domain name. Systemd-resolved calls it a routing domain.
> >>>>> Apple's Network Extension framework calls it a match domain. Split DNS
> >>>>> is especially useful for internal DNS servers.
> >>>>>
> >>>>> For example, if corp.example.com is a routing domain for the DNS server
> >>>>> at 192.0.2.1 (only accessible over WireGuard), then
> >>>>> server.corp.example.com is resolved using 192.0.2.1 while
> >>>>> www.example.com is resolved using some other DNS resolver (depending on
> >>>>> the other network settings in macOS).
> >>>>>
> >>>>> The proposed patch adds new syntax to the wg-quick DNS= line.
> >>>>> Specifically, a tilde prefixed domain is treated as a routing domain.
> >>>>> Multiple routing domains can be added.
> >>>>>
> >>>>> Limitations:
> >>>>> - Needs modifications to iOS UI to work on iOS.
> >>>>> - Only matching routing domains are sent to the DNS servers specified in
> >>>>> the DNS= config line. No separate fallback catch-all DNS server can
> >>>>> be set.
> >>>>> - Routing/match domains are also included in the list of search domains.
> >>>>> This could be changed with the matchDomainsNoSearch API, but lacking
> >>>>> more UI or config file changes to expose this option to the user, I
> >>>>> went with the default.
> >>>>>
> >>>>> [1] https://lore.kernel.org/wireguard/20210810074232.aah5ktq5yzysaaey@SvensMacBookAir-2.local/T/
> >>>>> [2] https://github.com/slarew/wireguard-apple/commit/6ebc356d9e11ab91443e06de5e89f1af57fcdff8
> >>>>
> >>>> That seems to be a redefinition of the existing definition of split DNS.
> >>>>
> >>>> Most usually, split DNS is done at the DNS server and different zones are served to the resolver based on various criteria... Usually the origination IP of the query; If the query comes from a client on your LAN, or a particular subnet, the contents of a particular, private, zone are returned. If the query comes from, say the internet, a public zone is returned.
> >>>>
> >>>> YOUR description, is how DNS works in general... Except your patch also seems to either bypass the resolver libraries or wedge itself in front of them The system resolver libraries well tested and understood and they handle the following very nicely.
> >>>>
> >>>> There is the issue of what happens with large DNS responses. Any DNS response over 512 bytes UDP fails and is required to be retried as a TCP query, which can handle the large response. It's late and I'm too tired to look it up, but there IS an RFC for this.
> >>>>
> >>>> It's a little known issue, but I've seen it when working with other VPN products that ignored/didn't understand the behavior. The results weren't pretty and really embarrassing.
> >>>>
> >>>> Systemd has a bad habit of re-inventing the wheel... Badly. Eventually it get's sorted, but is that really progress? In the long haul, "move fast and break things" is a MAJOR pita for the vast majority of us. But some like it.
> >>>>
> >>>> For some real fun, look into DHCPCD. It faithfully implements a particular RFC. In some networking environments using VPNs, it breaks routing horribly.... But it meets the RFC. You'll find it in Raspbian by default, and most other Debian derived distros. I automatically rip it out and replace it with the also available ISC DHCP client. That one is fully compatible with Windows, OS X, iOS, and every android and smart device I could test it with. A DHCP server configured to be compatible with DHCPCD broke all of the previously named.
> >>>>
> >>>> I'm giving this opinion away for free, so it's worth what you paid for it.
> >>>
> >>> Regardless of naming or definitions, I think the ability for a *local device* to route DNS queries to different DNS servers based on domain matching criteria is certainly useful. It’s not always possible or desirable to control and configure an upstream DNS server. Hence, this patch enables the local device to do split DNS.
> >>>
> >>> To be clear, this patch does not bypass or wedge around anything. In fact, it configures the native macOS DNS settings in the appropriate manner to effect a split DNS configuration.
> >>>
> >>> As a result of controlling the native macOS DNS resolution logic, any feature, absent or present, in the macOS DNS resolver libraries should be unaffected. This includes the large DNS response and TCP behavior. I do not expect the small/large UDP/TCP DNS features to change behavior when using a split DNS configuration as proposed in this patch.
> >>>
> >>> -Stephen
> >>
> >> Hi Stephen,
> >>
> >> A better solution to your problem would be to deploy DNSDIST:
> >> https://dnsdist.org/
> >>
> >> I for one would hope that esoteric requests that address a solution for less than 1% of the users would be rejected with the overall goal of preventing feature creep and bloat.
> >>
> >> Andrew
> >
> > DNSDIST may allow (I have not tried) one to create a split DNS scenario, but it is an extra piece of software that would need to be discovered, installed, configured, and maintained by a user or system administrator. I do not believe it would properly integrate with the macOS DNS resolution machinery. I do not believe it is a better solution to the problem.
> >
> > As I understand it, under some circumstances, the Tailscale macOS app also implements split DNS in roughly the same manner as done in my patch. Namely, the tailscale app appears to use the Network Extension APIs to directly integrate with the macOS DNS resolution machinery. Perhaps the relevant difference is that tailscale approaches configuration differently (not based on wg-quick) than the WireGuard macOS app.
> >
> > I do not have statistics or polling on who desires this split DNS feature. I have received private and public requests to upstream the feature. Tailscale also implements split DNS; presumable customers demand it. I suspect if the feature was available to users of the WireGuard app, then it would be used with precision to great effect. Users who do not need this split DNS feature do not lose any previous functionality in the macOS WireGuard app.
> >
> > Personally, my one hesitation with this patch is that, as currently implemented, a new syntax is added to the wg-quick config file (tilde prefixed route/match domains). My patch does not address compatibility issues nor does it add documentation to wg-quick for the new syntax.
> >
> > -Stephen
> >
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Split DNS for macOS
2021-10-29 21:07 ` Stephen Larew
2021-10-30 21:00 ` Dusan Zivadinovic
2021-11-03 9:15 ` Harald Dunkel
@ 2021-11-03 11:54 ` Alex Burke
2021-11-06 4:54 ` David Anderson
3 siblings, 0 replies; 14+ messages in thread
From: Alex Burke @ 2021-11-03 11:54 UTC (permalink / raw)
To: wireguard
The functionality in [mac,i,iPad]OS that enables zone-based split DNS is quite powerful, and Stephen's contribution would fit my use case as well.
I use a specific DNS resolver of my choice, but having Wireguard able to automagically resolve "host.corp.internal"-style FQDNs when the relevant Wireguard connection is up would be a huge win, not only for me but for corporations with split-horizon DNS which want to implement Wireguard without having to route irrelevant traffic into that tunnel.
> On 29 October 2021 at 22:07, Stephen Larew <stephen@slarew.net> wrote:
>
>
>>
>>> On Oct 29, 2021, at 10:03, Andrew Fried <afried@spamteq.com> wrote:
>>>
>>>> On Oct 29, 2021, at 08:33, Stephen Larew <stephen@slarew.net> wrote:
>>>
>>>> On Oct 28, 2021, at 02:58, Bruce Ferrell <bferrell@baywinds.org> wrote:
>>>>
>>>> On 10/28/21 12:16 AM, Stephen Larew wrote:
>>>>> For many months now, I have been running a patched WireGuard macOS app
>>>>> that enables a split DNS configuration. I would like to try to upstream
>>>>> my patches for split DNS.
>>>>>
>>>>> There has been some interest in this patch:
>>>>> - "Mac APP DNS Search Domain" thread from July and August 2021 [1]
>>>>> - A commenter on my GitHub fork of wireguard-apple.
>>>>>
>>>>> What is split DNS? It allows sending DNS queries to a specific server
>>>>> based on the domain name. Systemd-resolved calls it a routing domain.
>>>>> Apple's Network Extension framework calls it a match domain. Split DNS
>>>>> is especially useful for internal DNS servers.
>>>>>
>>>>> For example, if corp.example.com is a routing domain for the DNS server
>>>>> at 192.0.2.1 (only accessible over WireGuard), then
>>>>> server.corp.example.com is resolved using 192.0.2.1 while
>>>>> www.example.com is resolved using some other DNS resolver (depending on
>>>>> the other network settings in macOS).
>>>>>
>>>>> The proposed patch adds new syntax to the wg-quick DNS= line.
>>>>> Specifically, a tilde prefixed domain is treated as a routing domain.
>>>>> Multiple routing domains can be added.
>>>>>
>>>>> Limitations:
>>>>> - Needs modifications to iOS UI to work on iOS.
>>>>> - Only matching routing domains are sent to the DNS servers specified in
>>>>> the DNS= config line. No separate fallback catch-all DNS server can
>>>>> be set.
>>>>> - Routing/match domains are also included in the list of search domains.
>>>>> This could be changed with the matchDomainsNoSearch API, but lacking
>>>>> more UI or config file changes to expose this option to the user, I
>>>>> went with the default.
>>>>>
>>>>> [1] https://lore.kernel.org/wireguard/20210810074232.aah5ktq5yzysaaey@SvensMacBookAir-2.local/T/
>>>>> [2] https://github.com/slarew/wireguard-apple/commit/6ebc356d9e11ab91443e06de5e89f1af57fcdff8
>>>>
>>>> That seems to be a redefinition of the existing definition of split DNS.
>>>>
>>>> Most usually, split DNS is done at the DNS server and different zones are served to the resolver based on various criteria... Usually the origination IP of the query; If the query comes from a client on your LAN, or a particular subnet, the contents of a particular, private, zone are returned. If the query comes from, say the internet, a public zone is returned.
>>>>
>>>> YOUR description, is how DNS works in general... Except your patch also seems to either bypass the resolver libraries or wedge itself in front of them The system resolver libraries well tested and understood and they handle the following very nicely.
>>>>
>>>> There is the issue of what happens with large DNS responses. Any DNS response over 512 bytes UDP fails and is required to be retried as a TCP query, which can handle the large response. It's late and I'm too tired to look it up, but there IS an RFC for this.
>>>>
>>>> It's a little known issue, but I've seen it when working with other VPN products that ignored/didn't understand the behavior. The results weren't pretty and really embarrassing.
>>>>
>>>> Systemd has a bad habit of re-inventing the wheel... Badly. Eventually it get's sorted, but is that really progress? In the long haul, "move fast and break things" is a MAJOR pita for the vast majority of us. But some like it.
>>>>
>>>> For some real fun, look into DHCPCD. It faithfully implements a particular RFC. In some networking environments using VPNs, it breaks routing horribly.... But it meets the RFC. You'll find it in Raspbian by default, and most other Debian derived distros. I automatically rip it out and replace it with the also available ISC DHCP client. That one is fully compatible with Windows, OS X, iOS, and every android and smart device I could test it with. A DHCP server configured to be compatible with DHCPCD broke all of the previously named.
>>>>
>>>> I'm giving this opinion away for free, so it's worth what you paid for it.
>>>
>>> Regardless of naming or definitions, I think the ability for a *local device* to route DNS queries to different DNS servers based on domain matching criteria is certainly useful. It’s not always possible or desirable to control and configure an upstream DNS server. Hence, this patch enables the local device to do split DNS.
>>>
>>> To be clear, this patch does not bypass or wedge around anything. In fact, it configures the native macOS DNS settings in the appropriate manner to effect a split DNS configuration.
>>>
>>> As a result of controlling the native macOS DNS resolution logic, any feature, absent or present, in the macOS DNS resolver libraries should be unaffected. This includes the large DNS response and TCP behavior. I do not expect the small/large UDP/TCP DNS features to change behavior when using a split DNS configuration as proposed in this patch.
>>>
>>> -Stephen
>>
>> Hi Stephen,
>>
>> A better solution to your problem would be to deploy DNSDIST:
>> https://dnsdist.org/
>>
>> I for one would hope that esoteric requests that address a solution for less than 1% of the users would be rejected with the overall goal of preventing feature creep and bloat.
>>
>> Andrew
>
> DNSDIST may allow (I have not tried) one to create a split DNS scenario, but it is an extra piece of software that would need to be discovered, installed, configured, and maintained by a user or system administrator. I do not believe it would properly integrate with the macOS DNS resolution machinery. I do not believe it is a better solution to the problem.
>
> As I understand it, under some circumstances, the Tailscale macOS app also implements split DNS in roughly the same manner as done in my patch. Namely, the tailscale app appears to use the Network Extension APIs to directly integrate with the macOS DNS resolution machinery. Perhaps the relevant difference is that tailscale approaches configuration differently (not based on wg-quick) than the WireGuard macOS app.
>
> I do not have statistics or polling on who desires this split DNS feature. I have received private and public requests to upstream the feature. Tailscale also implements split DNS; presumable customers demand it. I suspect if the feature was available to users of the WireGuard app, then it would be used with precision to great effect. Users who do not need this split DNS feature do not lose any previous functionality in the macOS WireGuard app.
>
> Personally, my one hesitation with this patch is that, as currently implemented, a new syntax is added to the wg-quick config file (tilde prefixed route/match domains). My patch does not address compatibility issues nor does it add documentation to wg-quick for the new syntax.
>
> -Stephen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Split DNS for macOS
2021-10-29 21:07 ` Stephen Larew
` (2 preceding siblings ...)
2021-11-03 11:54 ` Alex Burke
@ 2021-11-06 4:54 ` David Anderson
2021-11-06 9:47 ` Matty Driessen
3 siblings, 1 reply; 14+ messages in thread
From: David Anderson @ 2021-11-06 4:54 UTC (permalink / raw)
To: wireguard
On Fri, Oct 29, 2021, at 14:07, Stephen Larew wrote:
> As I understand it, under some circumstances, the Tailscale macOS app also implements split DNS in roughly the same manner as done in my patch. Namely, the tailscale app appears to use the Network Extension APIs to directly integrate with the macOS DNS resolution machinery. Perhaps the relevant difference is that tailscale approaches configuration differently (not based on wg-quick) than the WireGuard macOS app.
Hi, Tailscale person here.
Yes, the Tailscale macOS app supports configuring either split DNS. It's situationally popular for things like "direct anything under amazonaws.com to the AWS VPC internal resolver on the other side of my tunnel", which makes your AWS VMs and such magically resolve correctly without shoveling all your unrelated requests through AWS.
The semantics of NEDNSSettings I've worked out so far:
* `searchDomains` sets interface-scoped search domains only, which appear to not be used at all for single-label DNS query expansion. IOW, it seems to do mostly nothing - or at least, I've not discovered anything it affects.
* `matchDomains` specifies what DNS suffixes should be sent to your resolvers (specified in `servers`). Specifying a list of suffixes here implements split-DNS. Specifying "" (the empty suffix, which matches all names) captures all queries.
* `matchDomains` _also_ installs any non-empty string you specify in the global search path.
* `matchDomainsNoSearch` lets you make `matchDomains` be just match domains, without modifying the global search path. You don't get more granularity than that, either all `matchDomains` are search paths, or none.
* If you want to fully capture all DNS traffic but also set some global search domains, you can list both the empty string and non-empty strings in `matchDomains`, and you'll get that behavior.
* You only get a single set of resolver IPs. This means you can have many DNS suffixes with `matchDomains`, but all of them will go to the pool of `servers` you provided. You can't route foo.com to 1.2.3.4 and bar.com to 2.3.4.5 without having another intermediate proxy to break things out further.
* Apple's DNS management service only installs the "default" resolver into the legacy /etc/resolv.conf, so a bunch of commandline tools inherited from BSD will be completely unaware of split DNS configurations, because they don't use whatever the "correct" resolution API is (I presume mach port something something).
* Apple doesn't have a public API for reading back the OS DNS settings, because they don't want other applications poorly reimplementing the OS's algorithm for selecting among contributed configuration. There is presumably an undocumented API that scutil et al. can use to read things out, but I've not dug into that at all.
Regarding upstreaming: OS-level DNS capabilities vary wildly across linux, apple and windows, and across versions of same (e.g. Windows 8+ can do split DNS, Windows 7 cannot - but WSL/WSL2 can't on any version to date). I can ramble at length about each OS if desired, but the bottom line is "send all DNS to these servers" is the only configuration that can be implemented reliably on all of them.
So, the question would be: do you want upstream WireGuard applications to have consistent behavior on all platforms? If so, you have to either forego split DNS, or do a lot of work to polyfill missing features on each platform (Tailscale's attempt at this is https://github.com/tailscale/tailscale/tree/main/net/dns). Or expose the uneven feature surface to the user, and delegate the pain of non-portability to them.
- Dave
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: Split DNS for macOS
2021-11-06 4:54 ` David Anderson
@ 2021-11-06 9:47 ` Matty Driessen
0 siblings, 0 replies; 14+ messages in thread
From: Matty Driessen @ 2021-11-06 9:47 UTC (permalink / raw)
To: wireguard
Hello Dave,
Thank you for this explanation and the challenges that come with split-DNS.
The biggest gripe I have with the current implementation in WireGuard
is that the search domain is not set as a global search domain when
using a split-tunnel. As you said the reason for this is "If you want
to fully capture all DNS traffic but also set some global search
domains, you can list both the empty string and non-empty strings in
`matchDomains`, and you'll get that behavior.".
When I use the same configuration file with the wg-quick utility the
search domain from the configuration file is set as a global search
domain. I think this is the case for all OS'es and should at least be
the case when using the WireGuard UI tool as well?
Regards,
Matty
On Sat, Nov 6, 2021 at 5:59 AM David Anderson <dave@natulte.net> wrote:
>
> On Fri, Oct 29, 2021, at 14:07, Stephen Larew wrote:
> > As I understand it, under some circumstances, the Tailscale macOS app also implements split DNS in roughly the same manner as done in my patch. Namely, the tailscale app appears to use the Network Extension APIs to directly integrate with the macOS DNS resolution machinery. Perhaps the relevant difference is that tailscale approaches configuration differently (not based on wg-quick) than the WireGuard macOS app.
>
> Hi, Tailscale person here.
>
> Yes, the Tailscale macOS app supports configuring either split DNS. It's situationally popular for things like "direct anything under amazonaws.com to the AWS VPC internal resolver on the other side of my tunnel", which makes your AWS VMs and such magically resolve correctly without shoveling all your unrelated requests through AWS.
>
> The semantics of NEDNSSettings I've worked out so far:
> * `searchDomains` sets interface-scoped search domains only, which appear to not be used at all for single-label DNS query expansion. IOW, it seems to do mostly nothing - or at least, I've not discovered anything it affects.
> * `matchDomains` specifies what DNS suffixes should be sent to your resolvers (specified in `servers`). Specifying a list of suffixes here implements split-DNS. Specifying "" (the empty suffix, which matches all names) captures all queries.
> * `matchDomains` _also_ installs any non-empty string you specify in the global search path.
> * `matchDomainsNoSearch` lets you make `matchDomains` be just match domains, without modifying the global search path. You don't get more granularity than that, either all `matchDomains` are search paths, or none.
> * If you want to fully capture all DNS traffic but also set some global search domains, you can list both the empty string and non-empty strings in `matchDomains`, and you'll get that behavior.
> * You only get a single set of resolver IPs. This means you can have many DNS suffixes with `matchDomains`, but all of them will go to the pool of `servers` you provided. You can't route foo.com to 1.2.3.4 and bar.com to 2.3.4.5 without having another intermediate proxy to break things out further.
> * Apple's DNS management service only installs the "default" resolver into the legacy /etc/resolv.conf, so a bunch of commandline tools inherited from BSD will be completely unaware of split DNS configurations, because they don't use whatever the "correct" resolution API is (I presume mach port something something).
> * Apple doesn't have a public API for reading back the OS DNS settings, because they don't want other applications poorly reimplementing the OS's algorithm for selecting among contributed configuration. There is presumably an undocumented API that scutil et al. can use to read things out, but I've not dug into that at all.
>
> Regarding upstreaming: OS-level DNS capabilities vary wildly across linux, apple and windows, and across versions of same (e.g. Windows 8+ can do split DNS, Windows 7 cannot - but WSL/WSL2 can't on any version to date). I can ramble at length about each OS if desired, but the bottom line is "send all DNS to these servers" is the only configuration that can be implemented reliably on all of them.
>
> So, the question would be: do you want upstream WireGuard applications to have consistent behavior on all platforms? If so, you have to either forego split DNS, or do a lot of work to polyfill missing features on each platform (Tailscale's attempt at this is https://github.com/tailscale/tailscale/tree/main/net/dns). Or expose the uneven feature surface to the user, and delegate the pain of non-portability to them.
>
> - Dave
^ permalink raw reply [flat|nested] 14+ messages in thread