Understanding systemd-resolved, Split DNS, and VPN Configuration

So, systemd-resolved is enabled by default in Fedora 33. Most users won’t notice the difference, but if you use VPNs — or depend on DNSSEC, more on that at the bottom of this post — then systemd-resolved might be big deal for you. When testing Fedora 33, we found one bug report where a user discovered that systemd-resolved broke his VPN configuration. After this bug was fixed, and nobody reported any further issues, I was pretty confident that migration to systemd-resolved would go smoothly. Then Fedora 33 was released, and I noticed a significant number of users on Ask Fedora and Reddit asking for help with broken VPNs, problems that Fedora 33 beta testers had failed to detect. This was especially surprising to me because Ubuntu has enabled systemd-resolved by default since Ubuntu 16.10, so we were four full years behind Ubuntu here, which should have been plenty of time for any problems to be ironed out. So what went wrong?

First, let’s talk about how things worked before systemd-resolved, so we can see what was wrong and why we needed change. We’ll see how split DNS with systemd-resolved is different than traditional DNS. Finally, we’ll learn how custom VPN software must configure systemd-resolved to avoid problems that result in broken DNS.

I want to note that, although I wrote the Fedora change proposal and have done some evangelism on behalf of systemd-resolved, I’m not a systemd developer and haven’t contributed any code to systemd-resolved.

Traditional DNS with nss-dns

Let’s first see how things worked before systemd-resolved. There are two important configuration files to discuss. The first is /etc/nsswitch.conf, which controls which NSS modules are invoked by glibc when performing name resolution. Note these are glibc Name Service Switch modules, which are totally unrelated to Firefox’s NSS, Network Security Services, which unfortunately uses the same acronym. Also note that, in Fedora (and also Red Hat Enterprise Linux), /etc/nsswitch.conf is managed by authselect and must not be edited directly. If you want to change it, you need to edit /etc/authselect/user-nsswitch.conf instead, then run sudo authselect apply-changes.

Anyway, in Fedora 32, the hosts line in /etc/nsswitch.conf looked like this:

hosts: files mdns4_minimal [NOTFOUND=return] dns myhostname

That means: first invoke nss-files, which looks at /etc/hosts to see if the hostname is hardcoded there. If it’s not, then invoke nss-mdns4_minimal, which uses avahi to implement mDNS resolution. [NOTFOUND=return] means it’s OK for avahi to not be installed; in that case, it just gets ignored. (Edit: this was wrong. Mantas mentioned in the comment below that this is to allow returning early for queries to .local domains, which should never go to the remaining nss modules.) Then most DNS resolution is performed by nss-dns. And finally, we have nss-myhostname, which is just there to guarantee that your own local hostname is always resolvable. Anyway, nss-dns is the key part here. nss-dns is what reads /etc/resolv.conf.

Next, let’s look at /etc/resolv.conf. This file contains a list of up to three DNS servers to use. The servers are attempted in order. If the first server in the list is broken, then the second server will be used. If the second server is broken, the third server will be used. If the third server is also broken, then everything fails, because no matter how many servers you list here, all except the first three are ignored. In Fedora 32, /etc/resolv.conf was, by default, a plain file managed by NetworkManager. It might look like this:

# Generated by NetworkManager
nameserver 192.168.122.1

That’s a pretty common example. It means that all DNS requests should be sent to my router. My router must have configured this via DHCP, causing NetworkManager to dutifully add it to /etc/resolv.conf.

Traditional DNS Problems

Traditional DNS is all well and good for a simple case like we had above, but turns out it’s really broken once you start adding VPNs to the mix. Let’s consider two types of VPNs: a privacy VPN that is always enabled and which is the default route for all web traffic, and a corporate VPN that only receives traffic for internal company resources. (To switch between these two different types of VPN configuration, use the checkbox “Use this connection only for resources on its network” at the bottom of the IPv4 and IPv6 tabs of your VPN’s configuration in System Settings.)

Now, what happens if we connect to both VPNs? The VPN that you connect to first gets listed first in /etc/resolv.conf, followed by the VPN that you connect to second, followed by your local DNS server. Assuming the DNS servers are all working properly, that means:

  • If you connect to your privacy VPN first and your corporate VPN second, all DNS requests will be sent to your privacy VPN, and you won’t be able to visit internal corporate websites. (This scenario is exactly why I become interested in systemd-resolved. After joining Red Hat, I discovered that I couldn’t access various redhat.com websites if I connected to my VPNs in the wrong order.)
  • If you connect to your corporate VPN first and your privacy VPN second, then all your DNS goes to your corporate VPN, and none to your privacy VPN. As that defeats the point of using the privacy VPN, we can be confident it’s not what users expect to happen.
  • If you ever connect the VPNs in the opposite order — say, if your connection to one temporarily drops, and you need to reconnect — then you’ll get the opposite behavior. If you don’t notice this pattern behind the failures, it can make problems difficult to reproduce.

You don’t need two VPNs for this to be a problem, of course. Let’s say you have no privacy VPN, only a corporate VPN.  Well, your employer may fire you if it notices DNS requests it doesn’t like. If you’re making 30 requests per hour to facebook.com, youtube.com, or more salacious websites, that sure looks like you’re not doing very much work. It’s really never in the employee’s best interests to send more DNS than necessary to an employer.

If you use only a privacy VPN, the failure case is arguably even more severe. Let’s say your privacy VPN’s DNS server temporarily goes offline. Then, because /etc/resolv.conf is a list, glibc will fall back to using your normal DNS, probably either your ISP’s DNS server, or your router that forwards everything to your ISP. And now your DNS query has gone to your ISP. If you’re making the wrong sort of DNS requests in the wrong sort of countries — say, if you’re visiting websites opposed to your government — this could get you imprisoned or executed.

Finally, either type of VPN will break resolution of local domains, e.g. fritz.box, because only your router can resolve that properly, but you’re sending your DNS query to your VPN’s DNS server. So local resources will be broken for as long as you’re connected to a VPN.

All things considered, the status quo prior to systemd-resolved was pretty terrible. The need for something better should be clear. Now let’s look at how systemd-resolved fixes this.

Modern DNS with nss-resolve

First, let’s look at /etc/nsswitch.conf, which looks a bit different in Fedora 33:

hosts: files mdns4_minimal [NOTFOUND=return] resolve [!UNAVAIL=return] myhostname dns

nss-myhostname and nss-dns have switched places, but that’s just a minor change that ensures your local hostname is always local even if your DNS server thinks otherwise. The important change here is the addition of resolve [!UNAVAIL=return]. nss-resolve uses systemd-resolved to resolve hostnames, via either its varlink API (with systemd 247) or its D-Bus API (with older versions of systemd). If systemd-resolved is running, glibc will stop there, and refuse to continue on to nss-myhostname or nss-dns even if nss-resolve doesn’t return a result, since both nss-myhostname and nss-dns are obsoleted by nss-resolve. But if systemd-resolved is not running, then it continues on (and, if resolving something other than the local hostname, will up using nss-dns and reading /etc/resolv.conf, as before).

Importantly, when nss-resolve is used, glibc does not read /etc/resolv.conf when performing name resolution, so any configuration that you put there is totally ignored. That means any script or program that writes to /etc/resolv.conf is probably broken. /etc/resolv.conf still exists, though: it’s managed by systemd-resolved to maintain compatibility with programs that manually read /etc/resolv.confand do their own name resolution, bypassing glibc. Although systemd-resolved supports several different modes for managing /etc/resolv.conf, the default mode, and the mode used in both Fedora and Ubuntu, is for /etc/resolv.conf to be a symlink to /run/systemd/resolve/stub-resolv.conf, which now looks like this:

# This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "resolvectl status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs should typically not access this file directly, but only
# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
# different way, replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.

nameserver 127.0.0.53
options edns0 trust-ad
search redhat.com lan

The redhat.com search domain is coming from my corporate VPN, but the rest of this /etc/resolv.conf should look like yours. Notably, 127.0.0.53 is systemd-resolved’s local stub responder. This allows programs that manually read /etc/resolv.conf to continue to work without changes: they will just wind up talking to systemd-resolved on 127.0.0.53 rather than directly connecting to your real DNS server, as before.

A Word about Ubuntu

Although Ubuntu has used systemd-resolved for four years now, it has not switched from nss-dns to nss-resolve, contrary to upstream recommendations. This means that on Ubuntu, glibc still reads /etc/resolv.conf, finds 127.0.0.53 listed there, and then makes an IP connection to systemd-resolved rather than talking to it via varlink or D-Bus, as occurs on Fedora. The practical effect is that, on Ubuntu, you can still manually edit /etc/resolv.conf and applications will respond to those changes, unlike Fedora. Of course, that would be a disaster, since it would cause all of your DNS configuration in systemd-resolved to be completely ignored. But it’s still possible on Ubuntu. On Fedora, that won’t work at all.

If you’re using custom VPN software that doesn’t work with systemd-resolved, chances are it probably tries to write to /etc/resolv.conf.

Split DNS with systemd-resolved

OK, so now we’ve looked at how /etc/nsswitch.conf and /etc/resolve.conf have changed, but we haven’t actually explained how split DNS is configured. Instead of sending all your DNS requests to the first server listed in /etc/resolv.conf, systemd-resolved is able to split your DNS on the basis of DNS routing domains.

IP Routing Domains, DNS Routing Domains, and DNS Search Domains: Oh My!

systemd-resolved works with DNS routing domains and DNS search domains. A DNS routing domain determines only which DNS server your DNS query goes to.  It doesn’t determine where IP traffic goes to: that would be an IP routing domain. Normally, when people talk about “routing domains,” they probably mean IP routing domains, not DNS routing domains, so be careful not to confuse these two concepts. For the rest of this article, I will use “routing domain” or “DNS domain” to mean DNS routing domain.

A DNS search domain is also different. When you query a name that is only a single label — a domain without any dots — a search domain gets appended to your query. For example, because I’m currently connected to my Red Hat VPN, I have a search domain configured for redhat.com. This means that if I make a query to a domain that is only a single label, redhat.com will be appended to the query. For example, I can query bugzilla and this will be treated as a query for bugzilla.redhat.com. This probably won’t work in your web browser, because web browsers like to convert single-label domains into web searches, but it does work at the DNS level.qt

In systemd-resolved, each DNS routing domain may or may not be used as a search domain. By default, systemd-resolved will add search domains for every configured routing domain that is not prefixed by a tilde. For example, ~example.com is a routing domain only, while example.com is both a routing domain and a search domain. There is also a global routing domain,  ~.

Example Split DNS Configurations

Let’s look at a complex example with three network interfaces:

$ resolvectl
Global
Protocols: LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub

Link 2 (enp4s0)
Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6 
Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 192.168.1.1 
DNS Servers: 192.168.1.1 
DNS Domain: lan

Link 5 (tun0)
Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6 
Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 10.8.0.1 
DNS Servers: 10.8.0.1 
DNS Domain: ~.

Link 9 (tun1)
Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6 
Protocols: -DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 10.9.0.1 
DNS Servers: 10.9.0.1 10.9.0.2
DNS Domain: example.com

To simplify this example, I’ve removed several uninteresting network interfaces from the output above: my unused second Ethernet interface, my unused Wi-Fi interface wlp5s0, and two virtual network interfaces that I presume are used by libvirt. This means we only have three interfaces to consider: normal Ethernet enp4s0, the privacy VPN tun0, and the corporate VPN tun1. I’m currently running NetworkManager 1.26.4, so I have also fudged the output a bit to make it look like it would if I were using NetworkManager 1.26.6 — I’ll discuss the difference below — so that this example will be good for the future. Let’s look at a few points of note:

  • enp4s0 is configured with +DefaultRoute and no routing domains.
  • tun0 is configured with +DefaultRoute and a global routing domain, ~.
  • tun1 is configured with -DefaultRoute and a routing domain for example.com. (It also has a search domain for example.com, because it doesn’t start with a tilde.)

systemd-resolved first decides which network interface is most appropriate for your DNS query based on the domain name you are querying, then sends your query to the DNS server associated with that interface. In this case, queries for example.com, foo.example.com, etc. will be sent to 10.9.0.1, since that is the DNS server configured for tun1, which is associated with the domain example.com. All other requests go to 10.8.0.1, since tun0 has the global domain ~. Nothing ever goes to 192.168.1.1, because a privacy VPN is enabled, and that would be a privacy disaster. Very simple, right?

If you do not use a privacy VPN, you will not have any ~. domain configured. In this case, your query will go to all interfaces that have +DefaultRoute. For example, if tun0 were removed from the above configuration, then queries not for example.com would be sent to 192.168.1.1, my router, which is good because tun1 is my corporate VPN and should only receive DNS queries corresponding to its own DNS domains.

Enter NetworkManager

How does systemd-resolved come up with the above configuration? It doesn’t. Everything I wrote in the previous section assumes that you are using NetworkManager, because systemd-resolved doesn’t actually make any decisions about where to send your DNS. That is all the responsibility of higher-level network management software, typically NetworkManager. If you use custom VPN software — anything that’s not a NetworkManager VPN plugin — then that software is also responsible for configuring systemd-resolved and playing nice with NetworkManager.

NetworkManager normally does a very good job of configuring systemd-resolved to work as you would expect, so most users should not need to make any changes. But if your DNS isn’t working as you expect, and you run resolvectl and find that systemd-resolved’s configuration is not what you want, do not report a bug against systemd-resolved! Report a bug against NetworkManager instead (if you’re confident there is a real bug).

If you don’t use NetworkManager, you can still make systemd-resolved do what you want, but you’re on your own. It will not configure itself for you.

NetworkManager 1.26.6

If you’re reading this in December 2020, you’re probably using NetworkManager 1.26.4 or earlier. Things are slightly different here, because NetworkManager recently landed a major behavior change. Previously, NetworkManager would always configure a ~. domain for exactly one network interface. This means that the value of systemd-resolved’s DefaultRoute settings was always ignored, since ~. takes precedence. Accordingly, NetworkManager did not bother to configure DefaultRoute at all. I told you that I fudged the output of the example above a little. In actuality, NetworkManager 1.26.4 has configured +DefaultRoute on my tun1 corporate VPN. That doesn’t make sense, because it should only receive DNS for example.com, but it previously did not matter, because there was previously always a ~. domain on some interface. If you’re not using any VPNs, then your Ethernet or Wi-Fi interface would receive the ~. domain. But since 1.26.6, NetworkManager now only ever configures a ~. domain when you are using a privacy VPN, so the DefaultRoute setting now matters.

Prior to NetworkManager 1.26.6, you could rely on resolvectl domain alone to see where your DNS goes, because there was always a ~. domain. Since NetworkManager 1.26.6 no longer always creates a ~. domain, that no longer works. You’ll need to use look at the full output of resolvectl instead, since that will show you the DefaultRoute settings, which are now important.

My Corporate VPN is Missing a Routing Domain, What Should I Do?

Say your corporate VPN is example.com. You want all requests for example.com to be resolved by the VPN, and they are, because NetworkManager creates an appropriate routing domain for it. But you also want requests for some other domain, say example.org, to be resolved by the VPN as well. What do you do?

Most VPN protocols allow the VPN to tell NetworkManager which domains should be resolved by the VPN. Others allow specifying this in the connection profile that you import into NetworkManager. Sadly, not all VPNs actually do this properly, since it doesn’t matter for traditional non-split DNS. Worse, there is no graphical configuration in GNOME System Settings to fix this. There really should be. But for now, you’ll have to use nmcli to set the ipv4.dns-search and ipv6.dns-search properties of your VPN connection profile. Confusingly, even though that setting says “search,” it also creates a routing domain. Hopefully you never have to mess with this. If you do this, consider contacting your IT department to ask them to fix your VPN configuration to properly declare its DNS routing domains, so you don’t have to fix it manually. (This actually sometimes works!) You might have to do this more than once, if you discover additional domains that need to be resolved by the corporate VPN.

Custom VPN Software

By “custom VPN software,” I mean any VPN that is not a NetworkManager plugin. That includes proprietary VPN applications offered by VPN services, and also packaged software like openvpn or wg-quick, when invoked by something other than NetworkManager.

If your custom VPN software is broken, you could report a bug against your VPN software to ask for support for systemd-resolved, but it’s really best to ditch your custom software and configure your VPN using NetworkManager instead, if possible. There are really only two good reasons to use custom VPN software: if NetworkManager doesn’t have a plugin appropriate for your corporate VPN, or if you need to use Wireguard and your desktop doesn’t support Wireguard yet. (NetworkManager itself supports Wireguard, but GNOME does not yet, because Wireguard is special and not treated the same as other VPNs. Help welcome.)

If you use NetworkManager to configure your VPN, as desktop developers intend for you to do, then NetworkManager will take care of configuring systemd-resolved appropriately. Fedora ships with several NetworkManager VPN plugins installed by default, so the vast majority of VPN users should be able to configure your VPN directly in System Settings. This also allows you to control your VPN using your desktop environment’s VPN integration, rather than using the command line or a custom proprietary application.

OpenVPN users will want to look into using the unofficial update-systemd-resolved script. However, NetworkManager has good support for OpenVPN, and this is totally unnecessary if you configure your VPN with NetworkManager. So it’s probably better to use NetworkManager instead.

Now, what if you maintain custom VPN software and want it to work properly with systemd-resolved, or what if you can’t use NetworkManager for whatever reason? First, stop trying to write to /etc/resolv.conf, at least if it’s managed by systemd-resolved. You’ll instead want to use the systemd-resolved D-Bus API to configure an appropriate routing domain for your VPN interface. Read this documentation. You could also shell out to resolvectl, but it’s probably better to use the D-Bus API unless your VPN is managed by a shell script. Privacy VPNs (or corporate VPNs that wish to eschew split DNS and hijack all the user’s DNS) can also use the resolvconf compatibility script, but note this will only work properly with NetworkManager 1.26.6 and newer, because the best you can do with it is add a global routing domain to a network interface, but that’s not going to work as expected if another network interface already has a global routing domain. Did I mention that you might want to use the D-Bus API instead? With the D-Bus API, you can remove the global routing domain from any other network interfaces, to ensure only your VPN’s interface gets a global routing domain.

Split DNS Without systemd-resolved

Quick tangent: systemd-resolved is not the only software available that implements split DNS. Previously, the most popular solution for this was to use dnsmasq. This has always been available in Fedora, but you had to go out of your way to install and configure it, so almost nobody did. Other custom solutions were possible too — I know one developer who runs unbound locally — but systemd-resolved and dnsmasq are the only options supported by NetworkManager.

One significant difference between systemd-resolved and dnsmasq is that systemd-resolved, as a system daemon, allows for multiple sources of configuration. In contrast, NetworkManager runs dnsmasq as a subprocess, so only NetworkManager itself is allowed to configure dnsmasq. For most users, this distinction will not matter, but it’s important for custom VPN software.

Servers and DNSSEC

You might have noticed that the rest of this blog post focused pretty much exclusively on desktop use cases. Your server is probably not using a VPN. It’s probably not using mDNS. It’s probably not expected to be able to resolve local hostnames. Conclusion: most servers don’t need split DNS! Servers do benefit from systemd-resolved’s systemwide DNS cache, so running systemd-resolved on servers is still a good idea. But it’s not nearly as important for servers as it is for desktops.

There are some disadvantages for servers as well. First, systemd-resolved is not intended to be used on DNS servers. If you’re running a DNS server, you’ll need to disable systemd-resolved before setting up BIND or Unbound instead. That is one extra step to get your DNS server working relative to before, so enabling systemd-resolved by default is an inconvenience here, but that’s hardly difficult to do, so not a big deal.

However, systemd-resolved currently has several bugs in how it handles DNSSEC, and this is potentially a big deal if you depend on that. If you’re a desktop user, you’ll probably never notice, because DNSSEC on desktops is a total failure. Due to widespread and unfixable compatibility issues, it’s very unlikely that we would be able to enable DNSSEC validation by default in the next 10-15 years. If you have a desktop computer that never leaves your home and a good ISP, or a server sitting in a data center, then you can probably safely turn it on manually in /etc/systemd/resolved.conf, but this is highly inadvisable for laptops. So DNSSEC is currently useful for securing DNS between DNS servers, but not for securing DNS between you devices and your DNS server.  (For that, we plan to use DNS over TLS instead.) And we’ve already established that DNS servers should not use systemd-resolved. So what’s the problem?

Well, it turns out DNS servers are not the only server software that expects DNSSEC to work properly. In particular, broken DNSSEC can result in broken mail servers. Other stuff might break too. If you’re running a server that needs functional DNSSEC, you’re going to need to disable systemd-resolved for now. These problems with DNSSEC resulted in some extremely vocal opposition to the Fedora 33 systemd-resolved change proposal, which unfortunately we didn’t properly appreciate until too late in the Fedora 33 development cycle. The good news is that these problems are being treated as bugs to be fixed. In particular, I am keeping an eye on this bug and this bug. Development is currently very active, so I’m hopeful that systemd-resolved’s DNSSEC support will look much better in time for Fedora 34.

Tell Me More!

Wow, you made it to the end of a long blog post, and you still want to know more? Next step is to read my colleague Zbigniew’s Fedora Magazine article, which describes some of the concepts I’ve already mentioned in greater deatil. (However, when reading that article, be aware of the NetworkManager 1.26.6 changes I mentioned above. The article predates NetworkManager 1.26.6, so you will see in the examples that a ~. global routing domain is assigned to non-VPN interfaces. That will no longer happen.)

Conclusion

Split DNS is designed to just work, like the rest of the modern Linux desktop, and it should for everyone not using custom VPN software. If you do run into trouble with custom VPN software, the bottom line is to try using a NetworkManager VPN plugin instead, if possible. In the short term, you will also need to disable systemd-resolved if you depend on DNSSEC, but hopefully that won’t be necessary for much longer. Everyone else should hopefully never notice that systemd-resolved is there.

Happy resolving!

Patching Vendored Rust Dependencies

Recently I had a difficult time trying to patch a CVE in librsvg. The issue itself was simple to patch because Federico kindly backported the series of commits required to fix it to the branch we are using downstream. Problem was, one of the vendored deps in the old librsvg tarball did not build with our modern rustc, because the code contained a borrow error that was not caught by older versions of rustc. After finding the appropriate upstream fix, I tried naively patching the vendored dep, but that failed because cargo tries very hard to prevent you from patching its dependencies, and complains if the dependency does not match its checksum in Cargo.lock. I tried modifying the checksum in Cargo.lock, but then it complains that you modified the Cargo.lock. It seems cargo is designed to make patching dependencies as difficult as possible, and that not much thought was put into how cargo would be used from rpmbuild with no network access.

Anyway, it seems the kosher way to patch Rust dependencies is to add a [patch] section to librsvg’s Cargo.toml, but I could not figure out how to make that work. Eventually, I got some help: you can edit the .cargo-checksum.json of the vendored dependency and change “files” to an empty array, like so:

diff --git a/vendor/cssparser/.cargo-checksum.json b/vendor/cssparser/.cargo-checksum.json
index 246bb70..713372d 100644
--- a/vendor/cssparser/.cargo-checksum.json
+++ b/vendor/cssparser/.cargo-checksum.json
@@ -1 +1 @@
-{"files":{".cargo-ok":"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",".travis.yml":"f1fb4b65964c81bc1240544267ea334f554ca38ae7a74d57066f4d47d2b5d568","Cargo.toml":"7807f16d417eb1a6ede56cd4ba2da6c5c63e4530289b3f0848f4b154e18eba02","LICENSE":"fab3dd6bdab226f1c08630b1dd917e11fcb4ec5e1e020e2c16f83a0a13863e85","README.md":"c5781e673335f37ed3d7acb119f8ed33efdf6eb75a7094b7da2abe0c3230adb8","build.rs":"b29fc57747f79914d1c2fb541e2bb15a003028bb62751dcb901081ccc174b119","build/match_byte.rs":"2c84b8ca5884347d2007f49aecbd85b4c7582085526e2704399817249996e19b","docs/.nojekyll":"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855","docs/404.html":"025861f76f8d1f6d67c20ab624c6e418f4f824385e2dd8ad8732c4ea563c6a2e","docs/index.html":"025861f76f8d1f6d67c20ab624c6e418f4f824385e2dd8ad8732c4ea563c6a2e","src/color.rs":"c60f1b0ab7a2a6213e434604ee33f78e7ef74347f325d86d0b9192d8225ae1cc","src/cow_rc_str.rs":"541216f8ef74ee3cc5cbbc1347e5f32ed66588c401851c9a7d68b867aede1de0","src/from_bytes.rs":"331fe63af2123ae3675b61928a69461b5ac77799fff3ce9978c55cf2c558f4ff","src/lib.rs":"46c377e0c9a75780d5cb0bcf4dfb960f0fb2a996a13e7349bb111b9082252233","src/macros.rs":"adb9773c157890381556ea83d7942dcc676f99eea71abbb6afeffee1e3f28960","src/nth.rs":"5c70fb542d1376cddab69922eeb4c05e4fcf8f413f27563a2af50f72a47c8f8c","src/parser.rs":"9ed4aec998221eb2d2ba99db2f9f82a02399fb0c3b8500627f68f5aab872adde","src/rules_and_declarations.rs":"be2c4f3f3bb673d866575b6cb6084f1879dff07356d583ca9a3595f63b7f916f","src/serializer.rs":"4ccfc9b4fe994aab3803662bbf31cc25052a6a39531073a867b14b224afe42dd","src/size_of_tests.rs":"e5f63c8c18721cc3ff7a5407e84f9889ffa10e66da96e8510a696c3e00ad72d5","src/tests.rs":"80b02c80ab0fd580dad9206615c918e0db7dff63dfed0feeedb66f317d24b24b","src/tokenizer.rs":"429b2cba419cf8b923fbcc32d3bd34c0b39284ebfcb9fc29b8eb8643d8d5f312","src/unicode_range.rs":"c1c4ed2493e09d248c526ce1ef8575a5f8258da3962b64ffc814ef3bdf9780d0"},"package":"8a807ac3ab7a217829c2a3b65732b926b2befe6a35f33b4bf8b503692430f223"}
\ No newline at end of file
+{"files":{},"package":"8a807ac3ab7a217829c2a3b65732b926b2befe6a35f33b4bf8b503692430f223"}

Then cargo will stop complaining and you can patch the dependency. Success!

Enable Git Commit Message Syntax Highlighting in Vim on Fedora

Were you looking forward to reading an exciting blog post about substantive technical issues affecting GNOME or the Linux desktop community? Sorry, not today.

When setting up new machines, I’m often frustrated by lack of syntax highlighting for git commit messages in vim. On my main workstation, vim uses comforting yellow letters for the first line of my commit message to let me know I’m good on line length, or red background to let me know my first line is too long, and after the first line it automatically inserts a new line break whenever I’ve typed past 72 characters. It’s pretty nice. I can never remember how I get it working in the end, and I spent too long today trying to figure it out yet again. Eventually I realized there was another difference besides the missing syntax highlighting: I couldn’t see the current line or column number, and I couldn’t see the mode indicator either. Now you might be able to guess my mistake: git was not using /usr/bin/vim at all! Because Fedora doesn’t have a default $EDITOR, git defaults to using /usr/bin/vi, which is basically sad trap vim. Solution:

$ git config --global core.editor vim

You also have to install the vim-enhanced package to get /usr/bin/vim, but that’s a lot harder to forget to do.

You’re welcome, Internet!

Let’s Learn Spelling!

Were you looking forward to reading an exciting blog post about substantive technical issues affecting GNOME or the Linux desktop community? Sorry, not today.

GNOME

It used to be an acronym, so it’s all uppercase. Write “GNOME,” never “Gnome.” Please stop writing “Gnome.”

Would it help if you imagine an adorable little garden gnome dying each time you get it wrong?

If you’re lazy and hate capital letters, or for technical contexts like package or project names, then all-lowercase “gnome” might be appropriate, but “Gnome” certainly never is.

Red Hat

This one’s not that hard. Why are some people writing “RedHat” without any space? It doesn’t make sense. Red Hat. Easy!

SUSE and openSUSE

S.u.S.E. and SuSE are both older spellings for the company currently called SUSE. Apparently at some point in the past they realized that the lowercase u was stupid and causes readers’ eyes to bleed.  Can we please let it die?

Similarly, openSUSE is spelled “openSUSE,” not “OpenSUSE.” Do not capitalize the o, even if it’s the first word in a sentence. Do not write “openSuSE” or “OpenSuSE” (which people somehow manage to do even when they’re not trolling) or anything at all other than “openSUSE.” I know this is probably too much to ask, but once you get the hang of it, it’s not so hard.

elementary OS

I don’t often see this one messed up. If you can write elementary OS, you can probably write openSUSE properly too! They’re basically the same structure, right? All lowercase, then all caps. I have faith in you, dear reader! Don’t let me down!

GTK and WebKitGTK

We removed the + from the end of both of these, because it was awful. You’re welcome!

Again, all lowercase is probably OK in technical contexts. “gtk-webkit” is not. WebKitGTK.

Mesa Update Breaks WebKitGTK+ in Fedora 29

If you’re using Fedora and discovered that WebKitGTK+ is displaying blank pages, the cause is a bad mesa update, mesa-18.2.3-1.fc29. This in turn was caused by a GCC bug that resulted in miscompilation of mesa.

To avoid this bug, downgrade to mesa-18.2.2-1.fc29:

$ sudo dnf downgrade mesa*

You can also update to mesa-18.2.4-2.fc29, but this build has not yet reached updates-testing, let alone stable, so downgrading is easier for now. Another workaround is to run your application with accelerated compositing mode disabled, to avoid OpenGL usage:

$ WEBKIT_DISABLE_COMPOSITING_MODE=1 epiphany

On the bright side of things, from all the bug reports I’ve received over the past two days I’ve discovered that lots of people use Epiphany and notice when it’s broken. That’s nice!

Huge thanks to Dave Airlie for quickly preparing the fixed mesa update, and to Jakub Jelenik for handling the same for GCC.

On Python Shebangs

So, how do you write a shebang for a Python program? Let’s first set aside the python2/python3 issue and focus on whether to use env. Which of the following is correct?

#!/usr/bin/env python
#!/usr/bin/python

The first option seems to work in all environments, but it is banned in popular distros like Fedora (and I believe also Debian, but I can’t find a reference for this). Using env in shebangs is dangerous because it can result in system packages using non-system versions of python. python is used in so many places throughout modern systems, it’s not hard to see how using #!/usr/bin/env in an important package could badly bork users’ operating systems if they install a custom version of python in /usr/local. Don’t do this.

The second option is broken too, because it doesn’t work in BSD environments. E.g. in FreeBSD, python is installed in /usr/local/bin. So FreeBSD contributors have been upstreaming patches to convert #!/usr/bin/python shebangs to #!/usr/bin/env python. Meanwhile, Fedora has begun automatically rewriting #!/usr/bin/env python to #!/usr/bin/python, but with a warning that this is temporary and that use of #!/usr/bin/env python will eventually become a fatal error causing package builds to fail.

So obviously there’s no way to write a shebang that will work for both major Linux distros and major BSDs. #!/usr/bin/env python seems to work today, but it’s subtly very dangerous. Lovely. I don’t even know what to recommend to upstream projects.

Next problem: python2 versus python3. By now, we should all be well-aware of PEP 394. PEP 394 says you should never write a shebang like this:

#!/usr/bin/env python
#!/usr/bin/python

unless your python script is compatible with both python2 and python3, because you don’t know what version you’re getting. Your python script is almost certainly not compatible with both python2 and python3 (and if you think it is, it’s probably somehow broken, because I doubt you regularly test it with both). Instead, you should write the shebang like this:

#!/usr/bin/env python2
#!/usr/bin/python2
#!/usr/bin/env python3
#!/usr/bin/python3

This works as long as you only care about Linux and BSDs. It doesn’t work on macOS, which provides /usr/bin/python and /usr/bin/python2.7, but still no /usr/bin/python2 symlink, even though it’s now been six years since PEP 394. It’s hard to understate how frustrating this is.

So let’s say you are WebKit, and need to write a python script that will be truly cross-platform. How do you do it? WebKit’s scripts are only needed (a) during the build process or (b) by developers, so we get a pass on the first problem: using /usr/bin/env should be OK, because the scripts should never be installed as part of the OS. Using #!/usr/bin/env python — which is actually what we currently do — is unacceptable, because our scripts are python2 and that’s broken on Arch, and some of our developers use that. Using #!/usr/bin/env python2 would be dead on arrival, because that doesn’t work on macOS. Seems like the option that works for everyone is #!/usr/bin/env python2.7. Then we just have to hope that the Python community sticks to its promise to never release a python2.8 (which seems likely).

…yay?

Endgame for WebKit Woes

In my original blog post On WebKit Security Updates, I identified three separate problems affecting WebKit users on Linux:

  • Distributions were not providing updates for WebKitGTK+. This was the main focus of that post.
  • Distributions were shipping a insecure compatibility package for old, unmaintained WebKitGTK+ 2.4 (“WebKit1”).
  • Distributions were shipping QtWebKit, which was also unmaintained and insecure.

Let’s review these problems one at a time.

Distributions Are Updating WebKitGTK+

Nowadays, most major community distributions are providing regular WebKitGTK+ updates, so this is no longer a problem for the vast majority of Linux users. If you’re using a supported version of Ubuntu (except Ubuntu 14.04), Fedora, or most other mainstream distributions, then you are good to go.

My main concern here is still Debian, but there are reasons to be optimistic. It’s too soon to say what Debian’s policy will be going forward, but I am encouraged that it broke freeze just before the Stretch release to update from WebKitGTK+ 2.14 to 2.16.3. Debian is slow and conservative and so has not yet updated to 2.16.6, which is sad because 2.16.3 is affected by a bug that causes crashes on a huge number of websites, but my understanding is it is likely to be updated in the near future. I’m not sure if Debian will update to 2.18 or not. We’ll have to wait and see.

openSUSE is another holdout. The latest stable version of openSUSE Leap, 42.3, is currently shipping WebKitGTK+ 2.12.5. That is disappointing.

Most other major distributions seem to be current.

Distributions Are Removing WebKitGTK+ 2.4

WebKitGTK+ 2.4 (often informally referred to as “WebKit1”) was the next problem. Tons of desktop applications depended on this old, insecure version of WebKitGTK+, and due to large API changes, upgrading applications was not going to be easy. But this transition is going much smoother and much faster than I expected. Several distributions, including Debian, Fedora, and Arch, have recently removed their compatibility packages. There will be no WebKitGTK+ 2.4 in Debian 10 (Buster) or Fedora 27 (scheduled for release this October). Most noteworthy applications have either ported to modern WebKitGTK+, or have configure flags to disable use of WebKitGTK+. In some cases, such as GnuCash in Fedora, WebKitGTK+ 2.4 is being bundled as part of the application build process. But more often, applications that have not yet ported simply no longer work or have been removed from these distributions.

Soon, users will no longer need to worry that a huge amount of WebKitGTK+ applications are not receiving security updates. That leaves one more problem….

QtWebKit is Back

Upstream QtWebKit has not been receiving security updates for the past four years or thereabouts, since it was abandoned by the Qt project. That is still the status quo for most distributions, but Arch and Fedora have recently switched to Konstantin Tokarev’s fork of QtWebKit, which is based on WebKitGTK+ 2.12. (Thank you Konstantin!) If you are using any supported version of Fedora, you should already have been switched to this fork. I am hopeful that the fork will be rebased on WebKitGTK+ 2.16 or 2.18 in the near future, to bring it current on security updates, but in the meantime, being a year and a half behind is an awful lot better than being four years behind. Now that Arch and Fedora have led the way, other distributions should find little trouble in making the switch to Konstantin’s QtWebKit. It would be a disservice to users to continue shipping the upstream version.

So That’s Cool

Things are better. Some distributions, notably Arch and Fedora, have resolved all of the above problems (or will in the very near future). Yay!

More On Private Internet Access

A few quick follow-up thoughts from my original review. First, problems I haven’t solved yet:

  • I forgot an important problem in my first blog: email. Evolution is borderline unusable with PIA. My personal GMail account usually works reliably, but my Google Apps school GMail account (which you’d think would function the same) and my Igalia email both time out with the error “Source doesn’t support prompt for credentials”. That’s Evolution’s generic error that it throws up whenever the mail server is taking too long to respond. So what’s going on here? I can check my email via webmail as a workaround in the meantime, but this is really terrible.
  • Still no solution for the first attempt to connect always failing. That’s really annoying! I was expecting some insight (or at least guesses) as to what might be going wrong here, but nobody has suggested anything about this yet. Update: The problem is that I had selected “Make available to other users” but “Store the password only for this user”, which results in the first attempt to connect always failing, because it’s performed by the gdm user. The fix is to store the password for all users.

Some solutions and answers to problems from my original post:

  • Jonh Wendell suggested using TCP instead of UDP to connect to PIA. I’ve been trying this and so far have not noticed a single instance of connection loss. So I think my biggest problem has been solved. Yay!
  • Dan LaManna posted a link to vpnfailsafe. I’m probably not going to use this since it’s a long shell script that I don’t understand, and since my connection drop problems seem to be solved now that I’ve switched to TCP, but it looks like it’d probably be a good solution to its problem. Real shame this is not built in to NetworkManager already.
  • Christel Dahlskjaer has confirmed that freenode requires NickServ/SASL authentication to use via PIA. This isn’t acceptable for me, since Empathy can’t handle it well, so I’m probably just going to stop using freenode for the most part. The only room I was ever really active in was #webkitgtk+, but in practice our use of that room is basically redundant with #epiphany on GIMPNet (where you’ll still find me, and which would be a better location for a WebKitGTK+ channel anyway), so I don’t think I’ll miss it. I’ve been looking to reduce the number of IRC rooms I join for a long time anyway. The only thing I really need freenode for is Fedora Workstation meetings, which I can attend via a web gateway. (Update: I realized that I am going to miss #webkit as well. Hmm, this could be a problem….)

So my biggest issue now is that I can’t use my email. That’s pretty surprising, as I wouldn’t think using a VPN would make any difference for that. I don’t actually care about my Google Apps account, but I need to be able to read my Igalia mail in Evolution. (Note: My actual IP seems to leak in my email headers, but I don’t care. My name is on my emails anyway. I just care that it works.)

On Private Internet Access

I’m soon going to be moving to Charter Communications territory, but I don’t trust Charter and don’t want it to keep records of all the websites that I visit.  The natural solution is to use a VPN, and the natural first choice is Private Internet Access, since it’s a huge financial supporter of GNOME, and I haven’t heard anybody complain about problems with using it. This will be a short review of my experience.

The service is not free. That’s actually good: it means I’m the customer, not the product. Cost is $40 per year if you pay a year in advance, but you should probably start with the $7/month plan until you’re sure you’re happy with the service and will be keeping it long-term. Anyway, this is a pretty reasonable price that I’m happy to pay.

The website is fairly good. It makes it easy to buy or discontinue service, so there are no pricing surprises, and there’s a pretty good library of support documentation. Unfortunately some of the claims on the website seem to be — arguably — borderline deceptive. A VPN service provides excellent anonymity against your ISP, but relying on a VPN would be a pretty bad idea if your adversary is the government (it can perform a traffic correlation attack) or advertising companies (they know your screen resolution, the performance characteristics of your graphics card, and until recently the rate your battery drains…). But my adversary is going to be Charter Communications, so a VPN is the perfect solution for me. If you need real anonymity, you absolutely must use the Tor Browser Bundle, but that’s going to make your life harder, and I don’t want my life to be harder, so I’ll stick with a VPN.

Private Internet Access provides an Ubuntu app, but I’m going to ignore that because (a) I use Fedora, not Ubuntu, and (b) why on Earth would you want a separate desktop app for your VPN when OpenVPN integration is already built-in on Ubuntu and all modern Linux desktops? Unfortunately the documentation provided by Private Internet Access is not really sufficient — they have a script to set it up automatically, but it’s really designed for Ubuntu and doesn’t work on Fedora — so configuration was slightly challenging.  I wound up following instructions on some third-party website, which I have long since forgotten. There are many third-party resources for how to configure PIA on Linux, which you might think is good but actually indicates a problem with the official documentation in my opinion. So there is some room for improvement here. PIA should ditch the pointless desktop app and improve its documentation for configuring OpenVPN via NetworkManager. (Update: After publishing this post, I discovered this article. Seems the installation script now supports for Fedora/RHEL and Arch Linux. So my claim that it only works on Ubuntu is outdated.) But anyway, once you get it configured properly with NetworkManager, it works: no need to install anything (besides the OpenVPN certificate, of course).

Well, it mostly works. Now, I have two main requirements to ensure that Charter can’t keep records of the websites I’m visiting:

  • NetworkManager must autoconnect to the VPN, so I don’t have to do it manually.
  • NetworkManager must reconnect to the VPN service if connection drops, and must never send any data if the VPN is off.

The first requirement was hard to solve, and I still don’t have it working perfectly. There is no GUI configuration option for this in gnome-control-center, but I eventually found it in nm-connection-editor: you have to edit your normal non-VPN connection, which has a preference to select a VPN to connect to automatically. So we should improve that in gnome-control-center. Unfortunately, it doesn’t work at all the first time your computer connects to the internet after it’s booted. Each time I boot my computer, I’m greeted with a Connection Failed notification on the login screen. This is probably a NetworkManager bug. Anyway, after logging in, I just have to manually connect once, then it works.

As for the next requirement, I’ve given up. My PIA connection is routinely lost about once every 30-45 minutes, usually when watching YouTube or otherwise using a lot of data. This is most likely a problem with PIA’s service, but I don’t know that: it could just as well be my current ISP cutting the connection, or maybe even some client-side NetworkManager bug. Anyway, I could live with brief connection interruptions, but when this happens, I lose connection entirely for about a minute — too long — and then the VPN times out and NetworkManager switches back to sending all the data outside the VPN. That’s totally unacceptable. To be clear, sending data outside the VPN is surely a NetworkManager problem, not a PIA problem, but it needs to be fixed for me to be comfortable using PIA. I see some discussion about that on this third-party GitHub issue, but the “solution” there is to stop using NetworkManager, which I’m not going to do. This is probably one of the reasons why PIA provides a desktop app — I think the PIA app doesn’t suffer from this issue? — but like I said, I’m not going to use a third-party OpenVPN app instead of the undoubtedly-nicer support that’s built in to GNOME.

Another problem is that I can’t connect to Freenode when I’m using the VPN. GIMPNet works fine, so it’s not a problem with IRC in general: Freenode is specifically blocking Private Internet Access users. This seems very strange, since Freenode has a bunch of prominent advertising for PIA all over its website. I could understand blocking PIA if there are too many users abusing it, but not if you’re going to simultaneously advertise it.

I also cannot access Igalia’s SIP service when using PIA. I need that too, but that’s probably something we have to fix on our end.

So I’m not sure what to do now. We have two NetworkManager bugs and a problem with Freenode. Eventually I’ll drop Empathy in favor of Matrix or some other IRC client where registering with NickServ is not a terrible mistake (presumably they’re only blocking unregistered users?), so the Freenode issue seems less-important. I think I’d be willing to just stop visiting Freenode if required to use PIA, anyway. But those NetworkManager issues are blockers to me. With those unfixed, I’m not sure if I’m going to renew my PIA subscription or not. I would definitely renew if someone were to fix those two issues. The ideal solution would be for PIA to adopt NetworkManager’s OpenVPN plugin and ensure it gets cared for, but if not, maybe someone else will fix it?

Update: See part two for how to solve some of these problems.

On “Insights On Companies/Developers Behind Wayland”

I recently read a peer-reviewed academic paper from a couple years ago that analyzed the contributions of different companies to WebKit. The authors didn’t bother to account for individuals using non-corporate email addresses, since that’s hard work, and did not realize that most Google developers contribute to the project using @chromium.org email addresses, resulting in Google’s contributions being massively undercounted. There were other serious mistakes in the paper too, but this is the one that came to mind when reading The FOSS Post’s article Insights On Companies/Developers Behind Wayland.

The FOSS Post didn’t bother to account for where some big developers work, incorrectly trusting that all employees use corporate emails when contributing to open source projects. It contains some interesting claims, like “Clearly, Samsung and the individual ‘Bryce Harrington’ are almost doing the same work [on Wayland build tools]” and “75% of the code [in libinput] is written by Peter Hutterer. Followed by 10% for a group of individuals and 5% by Red Hat.” I have only very passing familiarity with the Wayland project, but I do know that Bryce works for Samsung, and that Peter works for Red Hat. Suggesting that Red Hat contributed only 5% of the code to libinput, when the real number looks more like 80%, does not speak well of the quality of The FOSS Post’s insights. Also notably, Kristian Høgsberg’s massive contributions to the  project were not classed as contributions from Intel, where he was working at the time.

You don’t have to be an expert on the community to take the time to account for people not using corporate emails before publishing an analysis. This is why it’s important to understand the community you are analyzing at least somewhat before publishing such “insights.”

Update: The FOSS Post’s article was completely updated with new charts to address this issue.

Update #2: Jonas reports in the comments below that the charts are still completely wrong.