Hacking day 1

Fri, 07 Oct 2005 02:00:00 CEST

The formal workshop is over but we have two more days of hacking planned. This first day we tried to divide ourselves up into small groups where each group works/discusses one area, like {nf,ct}netlink, nfhipac, tcpwindowtracking etc... I mostly experimented with the hashtrie but I also attended the nfhipac discussions and I have to say that nfhipac is going to kick butt when the proposed changes are made. These changes adds a generic userspace to kernelspace format based on nfnetlink that is going to be documented so you actually can have diffrent userspace applications to manage rules, and you can even have diffrent filtering backends in the kernel. We just don't want to paint ourselves into a corner, we like to think we've learned from previous mistakes. Another really nice result of this discussion is a new way to pass the data needed for matches between userspace and kernelspace. Currently that is performed by passing structs around, which has a lot of problems, one problem is the 64bit kernel and 32bit userspace issue which becomes a problem when you have things like pointers in the structs. Another problem is when you want to add more members to the struct, then the size of the struct definition in an old kernel and in the new userspace library doesn't match anymore, thus we've broken backwards compatibility which just isn't allowed. The new idea is to pass this data around with netlink TLVs and then you build your internal representation from these TLVs and then the other way around when you list the rules.

We had nothing planned for the evening so we went back to the hotel to leave all the hardware and then just go out somewhere to eat and drink some beer. 15 of us went out barhopping. Later in the evening we ended up at a fairly small street, I have to say I've never ever seen so many people in one place before. The reason for this was that there's 4 bars located within a total distance of 10 meters. We had a really good time there but when we finally decided to head back to the hotel we noticed that Pablo, who knew the way back to the hotel, was missing. We ended up walking for a while but we eventually found the hotel.