On 2019-08-30 18:37, Július Milan wrote:
Hi all Regarding 4K frame size constraint of AF_XDP, what does AF_XDP when receives frame bigger than 4K? Drops it or cut it or split it between more frames? Thinking about what to do with them on TX side.
AF_XDP stands on XDP's shoulders, and currently XDP does not support frames larger than a page (4k). This will most likely change for AF_XDP.
If you are interested in mentioned AF_XDP driver for vpp, here you can find it: https://gerrit.fd.io/r/c/vpp/+/21606 It is still work in progress, I submitted it for review just yesterday and rebased it on recently found code in review of Damjan.
Very cool! Will check it out! Cheers, Björn
To run it, you need to have compatible XDP program loaded on interface you want to attach to. This separation is here because we want user to be able to create custom XDP programs independently. We also consider automatic loading of some default XDP program (that just redirects) if none is loaded in time of interface creation, but that is of minor priority for us yet. For loading you can use attached loader (it will be added for review soon as well). It just loads the program and pins its maps. As XDP program, we use yet xdpsock_kern.c from kernel v5.0.0 sources (attached). XDP program compatibility requirements (from vpp point of view) are: having xskmap called "xsks_map" and pinned at /sys/fs/bpf/<ifname>/ I added support for multiple queues into my patch for vpp, as we discussed (1 NIC, n sockets on different queues), but I didn't test it yet. Other things should work fine. Tested on kernel 5.0.0. JúliusMany thanks guys, very appretiated. Going to take a look at OVS implementation, but I would like to ensure something before.I took the _user part and split it into two: "loader" - Executed once to setup environment and once to cleanup, loads _kern.o, attaches it to interface and pin maps under /sys/fs/bpf. and "worker" - Executed as many as required. Every instance loads maps from /sys/fs/bpf, create one AF_XDP sock, update xsks record and start listen/process packets from AF_XDP (in test scenario we are using l2fwd because of write-back). I had to add missing cleanups there( close(fd), munmap()). This should be vpp in final solution. So far so good. I'm unable to start more than one worker due to previously mentioned error. First instance works properly, every other fails on bind (lineno may not match due to local changes): xdpsock_user.c:xsk_configure:595: Assertion failed: bind(sfd, (struct sockaddr *)&sxdp, sizeof(sxdp)) == 0: errno: 16/"Device or resource busy"I don't think you can have multiple threads binding one XSK, see xsk_bind() in kernel source. For AF_XDP in OVS, we create multiple XSKs, non-shared umem and each has its thread.In OVS, can you bind two sockets with non-shared umem to the same interface? Our goal is to have 2 or more processes (VPPs) listening on the same interface via XDP socket, while XDP program decides where to redirect the packets at the moment. Best Regards Julius
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