12/06/2018 15:33, Wiles, Keith: > > > On Jun 12, 2018, at 7:58 AM, Thomas Monjalon <tho...@monjalon.net> wrote: > > > > 12/06/2018 14:36, Wiles, Keith: > >> > >>> On Jun 12, 2018, at 7:26 AM, Thomas Monjalon <tho...@monjalon.net> wrote: > >>> > >>> 11/06/2018 18:35, Wiles, Keith: > >>>> > >>>>> On Jun 11, 2018, at 11:06 AM, Ophir Munk <ophi...@mellanox.com> wrote: > >>>>> > >>>>> This commit explains how to manually compile the C source file > >>>>> tap_bpf_program.c into an ELF file using the clang compiler. > >>>>> The code in tap_bpf_program.c requires definitions found in iproute2 > >>>>> source code. This commit suggests cloning the iproute2 git tree and > >>>>> include its path in the clang command. It also adds inclusion of file > >>>>> bpf_api.h (required for eBPF definitions) which is located in iproute2 > >>>>> source tree. For more details refer to TAP documentation. > >>>>> This commit is related to commits [1] and [2]. > >>>> > >>>> Normally I would have suggested that eBPF be disable in the TAP driver > >>>> as it requires external code and programs, but that ship has sailed. > >>> > >>> The external programs are required only to generate new instructions, > >>> changing the behaviour of the BPF program. > >>> Currently, the instructions for RSS behaviour are provided. > >>> > >>>> I would like to see building the tap_bpf_program.o as a target in the > >>>> Makefile, this way the developer can just run the ‘make bpf_program’ > >>>> target and it would be simpler and less error prone. > > > > As explained in the documentation, for now there is a dependency on iproute2 > > for the compilation of this BPF program. > > So we cannot make it as simple as a "make command". > > Probably that we can rework it to change the dependency. > > I heard there are some good BPF libraries available now? > > Well the dependence of iproute2 is really no different then requiring say > libnuma, they just have to pull the code first to type the ‘make bpf_program’ > right?
The iproute2 dependency is different because it is not a library. The .h file is never packaged. So we need to download the sources and set -I to this directory. > If that is the case then a make target make sense to me. If iproute2 is not > found then an error, right? > >>> For this to happen, we need to improve the tools. > >> > >> In what way do we need to improve the tools and which tools are we talking > >> about. Building the .o file below appears to be a simple set of command > >> lines. I have a question in my original email about what tool. > > > > The .o file is only the an intermediate file. > > The next step (numbered as 5 in this patch) is to extract the section > > of BPF instructions to be uploaded in the kernel. > > This step must be done by a "tool". Ophir did it by hacking tc, > > but it is not upstreamed yet. > > There could be other ways (possibly easier) to achieve the same result. > > Please change the doc to reflect the tool is not upstreamed yet and the > developer needs to figure out how to extract the data from the binary. > > I used objdump -j l3_l4 -s tap_bpf_program.o and got a hex dump of the l3_l4 > section > > 0000 bf160000 00000000 61681000 00000000 <Ascii characters> > ... > > Someone schooled in the art of Python coding should be able to convert that > output to a ‘C’ data array. :-) > > > > >>> It is a work in progress. > > > > Contributions are welcome. > > > >>> This is a very first step to use Linux BPF with DPDK. > >>> If there are more interests, we should really streamline its usage > >>> for all parts of DPDK which runs on top of some kernel code. > >> > >> streamlining other parts of DPDK would be nice, but we are now talking > >> about the tap/eBPF patch. > > Regards, > Keith > >
