dhcp function is a slow path and has quite a bit of complexity that is not appropriate for datapath. Normal dhcp is handled by user space dhclient. So I think it would be better to do the same in your case. As an orthogonal discussion it would be useful indeed to have push()/pop() like logic in bpf maps, so it can be used as a queue/stack.
On Fri, Jan 20, 2017 at 6:04 AM, Mauricio Vasquez via iovisor-dev <iovisor-dev@lists.iovisor.org> wrote: > Hello, > > We are having some issues for handling the address pool of a DHCP server > implemented with eBPF. > > We tried to implement it using a map containing all the available addresses, > this map is filled at the beginning and then addresses are taken (and also > released), however we cannot find a way to get an arbitrary element from a > map in eBPF. (something like a pop() function) > > By suggestion of Brenden Blanco, we had a look at the LRU [1] map, we > expected to find some function like "get_oldest_element()" but we cannot > find anything similar. > > We decided to implement it in a different way, the pool is handled by a map > of type array where all the addresses are saved, each of them has a flag > that indicates whether it is available or not. Then, in order to get an > available address it is necessary to perform a loop through the map (values > are saved using integer keys) until an available entry is found. > > With this approach a lot of instructions are wasted just to perform the > lookup of an available address, this limits the size of the pool. Hence, we > think having a kind of "pop()" function is necessary to handle "maps" of > free elements. > > > 1. Would it make sense to have a map of kind "set" that only implements the > push() and pop() methods? > > 2. Does it make sense to have a get_oldest_element() in the LRU map? > > > Thanks in advance, > > Mauricio V. > > [1] > https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=29ba732acbeece1e34c68483d1ec1f3720fa1bb3 > > _______________________________________________ > iovisor-dev mailing list > iovisor-dev@lists.iovisor.org > https://lists.iovisor.org/mailman/listinfo/iovisor-dev _______________________________________________ iovisor-dev mailing list iovisor-dev@lists.iovisor.org https://lists.iovisor.org/mailman/listinfo/iovisor-dev
