MiniUPnP now fully in Debian


With this last upload of the MiniUPnP daemon 1.7-3, I’ve reached a first milestone: all of the MiniUPnP libraries, daemons and clients are finally in Debian, in a shape which I am not ashamed anymore.

What is UPnP for?

Back in the days (around Linux 2.0.3x), the only way to share a single Internet connection was to run a Linux box as your gateway. These days are far gone, and nearly every home connection is done through a mini home router, which also often provides a small switch and a WiFi access point. Every computer on the LAN gets its connectivity through the router thanks to NAT, and to be more accurate, masquerading. That works very well for outbound connections (browse the web, send a mail, etc.), but it is then a lot harder that something connects to a “server” located in the LAN. If you run a permanent server with a fixed LAN IP address, that’s fine, you just configure your router to do some port forwarding, so that any inbound connection will be forwarded to the computer of your choice in the LAN. But if one application needs to listen on the public IP address just for a while (for example, IRC using DCC connection), so that “something” can connect to it, it becomes a way more tricky. That’s when UPnP comes into play. UPnP stands for Universal Plug and Play. It’s a protocol so that any application on the LAN can open ports on the public IP address of the gateway. Note that an UPnP router is also often referenced as UPnP IGD (Internet Gateway Device).

Why using MiniUPnP, don’t we have already linux-igd?

Before my packaging work, the only UPnP server that was available in Debian was linux-igd, which has a dependency on libupnpX. That library is quite big for what it does (about 500KiB, on top of which you have to install the 200KiB daemon itself), while MiniUPnP is designed to be lightweight (only 158K, with dependencies on iptables, iproute, uuid-runtime and libc6 only). That seems ridiculous, but when you have only 8MiB of flash in your old router, saving few hundreds KiB is┬áreally important, and here, we’re saving more than 500 KiB, with a full implementation of the UPnP protocol, and the Microsoft NATPmP implemented as well (yes, Microsoft decided that one protocol wasn’t enough, and that they should implement their own … (sic!)).

Who is using MiniUPNP?

Probably, you already have the libminiupnpc installed in your SID/wheezy desktop, because the transmission bittorent client which is installed with Gnome by default, depends on it, and minissdpd might be in your desktop too, if you installed the Recommends: packages as well. Which is why these are scoring quite high already in popcon. Previously, transmission was embedding its own version of the MiniUPnP client library, so it’s nice to have it as a standalone shared library now.

Also, because of its very light weight, and the fact that UPnP is often needed for gaming (both XBOX 360 and PSP need, and can use, the MiniUPnP daemon that runs on your IGD), many ISP who ship a router to their customer, install MiniUPnP in it. For example, at least, the 2nd and 3rd largest Internet access provider in France (Free Telecom and SFR) are shipping MiniUPnPd in their “box” (one of them using OpenWRT on their router). So probably as well, you are also using MiniUPnP daemon without knowing it.

But isn’t UPnP unsafe?

To this question, I’d answer that connecting to Internet is unsafe. It isn’t less safe than connecting to Internet on a WiFi hotspot for example. So adding UPnP support on your gateway doesn’t make it less safe, especially since MiniUPnP has some features to help with security (like an ACL with IP and port lists, or a secure mode were the router will only open ports to the client requesting it). Also, we are running a distribution where dependencies are easy to check, so it’s easy for you to check if a client uses UPnP or not, and decide to trust it (or not). I personally have no issue trusting transmission, x-chat or warzone2010 (more exactly: I don’t trust that incoming connectivity will make it less safe for these applications, there are so many other things that could go wrong).

MiniUPnP consists of what?

MiniUPnP is a set of 4 source packages to handle all of your UPnP needs:

– The client library, libminiupnpc (and the corresponding -dev package), with its sidekick miniupnpc client program (you can use it to check the public IP of your gateway, or manually open ports).

– The UPnP IGD daemon, miniupnpd, which just reached Debian Experimental. The latest version, 1.7-3, also includes debconf configuration so that you can choose the NIC and IP address to bind on. If you installed previous version, I strongly recommend upgrading to fix previous problems.

– The libnatpmp client library (and the -dev package) for implementing the Microsoft protocol as a client (it also has a client package binary for your tests).

– The minissdpd daemon to keep memory of all UPnP devices that announced themselves, and speed-up using the UPnP protocol (used by the MiniUPnP client library).

A long process to have MiniUPnP in Debian

All these 4 pieces of the puzzle were not as easy as it seems to be packaged in Debian. Especially, the IGD daemon, MiniUPnPd, used to depend on some header files that were not packaged in Debian. This was a decision of the iptables maintainers, which even after a long discussion, refused to add the necessary headers because it wasn’t supposed to be a kernel API. While this might really be truth, the issue was that there was no public API available in the Linux kernel at all, and other distributions (Fedora, Gentoo, etc.) really did supply these needed files. As a consequence, during a very long time (years… literally), shamefully, it was impossible to build the MiniUPnP daemon in Debian, while it was no problem on other distributions. Note that I do not want to start a troll discussion here, I’m just stating facts, both parties have very strong and respectable arguments. Anyway, this needed API was finally embedded in MiniUPnPd itself thanks to a contributor to the project, and now it builds on both the Squeeze and the Wheezy (that is Linux 3.2) kernel without any issue.

Call for testing

Unfortunately, I don’t have a Linux box as my Internet gateway. So I did the tests that I could: I installed MiniUPnPd on one computer on my LAN, and checked that I could open ports from another computer. So it seems to work, but I had no way to really test it “live”, with some “real” clients. So if you have an Debian SID box as your Internet gateway, feedback would be highly appreciated.

What is remaining to do?

A transition from libminiupnpc5 to libminiupnpc8 has to happen. Of course, this is too late for Wheezy, so this will happen right after the release. There’s not so many reverse dependencies, so it should be ok, but I (yet) have zero experience with transitions. BTW, I had hard time to find out what this transition process was, and maybe some more effort for documenting it would help others (I’m thinking about adding some text in the Debian wiki for that). Also, I have called for help on debian-devel, because I’m currently the only one maintaining all these 4 source packages, and I’m trying to have all my packages checked by others, and team maintained. So if you want to give a hand, or just declare yourself as a backup if I’m busy, please raise your hand! Upstream is a friend of mine, and is very reactive to any requests (it very rarely took more than 48 hours to get a reply).

Enjoy MiniUPnP and report bugs!

Again, feedback would be appreciated. :)