MLPPP on WRT54G/Tomato, progress report (with download)

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Guspaz
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MLPPP on WRT54G/Tomato, progress report (with download)

As some of you may know, DSL_Ricer and myself have been trying to get MLPPP (hereafter referred to as MP) working on the WRT54G series and Tomato firmware. Although, to be honest, it's 90% DSL_Ricer at this point. When I say "we", it often means "DSL_Ricer", as he's the one doing all the heavy lifting here ;)

There seems to be a fair amount of interest in getting MP working on Tomato, as it drastically reduces costs involved in setting it up. It should also reduce complexity to the point where anybody can do it.

Our initial attempts involved simply enabling MP on the built-in version of pppd included with Tomato. Tomato uses pppd for PPTP tunnels, but uses a separate app called "pppoecd" (seems to be written by Linksys) for doing PPPoE stuff.

Unfortunately, the version of pppd that ships with tomato is ancient, and doesn't support MP. Fine. Next step, recompile a modern version of pppd and try that out. It had support, but was having some odd failures where it failed to negotiate an IP when MP was enabled (all testing to date has been MP on a single DSL line).

We eventually realized that the kernel that Tomato shipped with was really old (2.4.20), and didn't have MP support enabled. Recompiling the kernel with MP support didn't he.

Around that point, Vinch lent us a second WRT54GL, which meant that DSL_Ricer actually had a local test box instead of having to mail me all the binaries and then try it on my WRT at night. He installed OpenWRT on it, as it gives an environment much more conducive to development.

OpenWRT uses the 2.6 kernel, but pppd still wasn't working with mlppp. He tried using the version of pppd from Debian (which has a MIPS port, keep in mind everything going on here is involving cross-compiling for MIPS :P), and boom! It worked.

That was a pretty big point; MLPPP support working on a WRT54GL router, although not the right distro, and the use of a 2.6 kernel meant that there was no support for wireless (a bit of a catch in a wireless router). Since the wireless drivers are binary ones by Broadcom, and nobody has the source, you just can't do wireless with the 2.6 kernel.

Next step was to try OpenWRT's build that used the 2.4 kernel series. It ships with the latest 2.4 kernel (2.4.35, I think). Wireless works, as this is the primary reason that OpenWRT maintains a 2.4 version. Lo and behold, it still worked, and wireless too. Which is nice, except now the big task is to figure out why it works on OpenWRT/2.4.35 and not Tomato/2.4.20.

The next attempts were to try to get Tomato loaded with the OpenWRT kernel. Unfortunately, it just didn't boot, and the only solution would have been to build a serial port for the WRT54GL. This involves equipment that we don't have (and soldering), so it was ruled out.

Last night, though, we had an idea: Maybe we could figure out what changed between 2.4.20 and 2.4.35 in the PPP code that might fix MP support.

DSL_Ricer backported the newer version of ppp_generic from OpenWRT's kernel into Tomato's ancient kernel. Apparently no major hangups, it patched in the diff almost without trouble, just a few changes to get it to compile.

And, to quote Steve Jobs, "boom". PPPd can use MLPPP under Tomato 0.19.

So, at this stage, what we have is a firmware image of a modified Tomato 0.19 that replaces the existing old pppd with the new pppd, and has the kernel patch applied.

What does this mean? It means that you can manually set up Tomato, by the command line, to use MLPPP. We've only tested with single DSL lines (as neither of us have two, so Vinch has been asked to do some testing), and haven't actually done much testing at all yet (we're going to poke at it some at my place tonight). But this was the big milestone we were shooting for.

What are our next steps? We'd like to integrate this into the Tomato GUI. The first step will be to write some sort of interface that will masquerade as pppoecd but will actually be calling pppd. This will enable you to use single-line multilink with Tomato exactly as if you were running the stock Tomato firmware. This has certain "benefits" over not running multilink on a single line.

The next step after that will be to get it working with two DSL lines. We can probably autodetect this scenario by checking for DSL modems on each interface and counting them. Ideally, we can then just automatically run two copies of pppd in a multilink config; I'm not aware of any possible pitfalls, though, so it may not be this simple. Obviously, we'll have to auto-retry on the second link until it hits the same ERX as the first.

So, we actually have a working build now (attached to this post). First, some disclaimers:

1) It has only been tested on the WRT54GL. It should work on the WRT54G (before v5), but WILL NOT work on any other router. It does NOT work on the WRT54GS. This just involves a recompile, but we won't bother until we've got a final solution done.

2) To quote DSL_Ricer, as this is so far poorly tested and rather experimental, "this version may suddenly start eating puppies". Or it might just brick your router. Your risk, here, we're not going to be held responsible for anything that goes wrong, you've been warned!

Now then, you should actually be able to get one or two DSL lines working with it. This is manual, so you're going to have to do it yourself via telnet/ssh, just like setting up stuff on a real Linux box. You may still be able to use the interface for port forwarding, not sure. Here's a sample pppd.conf file:

You'll probably have to change the interface from "br0" to something else. If your modem is plugged into the WAN port, that should be "vlan1". I believe br0 works with the modem plugged into any switch port (except WAN).

You'll also need to create a /etc/ppp/pap-secrets file with your username/password, format looks like this:

To execute this on a single DSL line (with multilink enabled, obviously), you would just call pppd like so:

All errors and warnings will be shoved in /var/log/messages, and you may want to remove "debug" from the config file after you get everything working.

To set up two DSL lines, you should just be able to make a second pppd.conf file (with a different name) that has the different interface that the second modem is on (so perhaps one "vlan1" and one "br0"), and execute a second copy of pppd. You'll need to retry the second link until you get it on the same ERX as the first one. Otherwise it just won't work.

Obviously, since neither of us have two DSL lines, we can't test this. We've got no idea if it'll work, although it should. If those of you who already have things working with two links can point out some stuff that we should know or take into account, please do!


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