Re: [PATCH bpf-next v7 3/3] selftests/bpf: Add selftest for XDP_REDIRECT in bpf_prog_run()
flat view
From: Alexei Starovoitov <hidden>
Date: 2022-01-08 19:32:52
Also in:
bpf
On Fri, Jan 7, 2022 at 1:54 PM Toke Høiland-Jørgensen [off-list ref] wrote:
+ +#define NUM_PKTS 1000000
It takes 7 seconds on my kvm with kasan and lockdep and will take much longer in BPF CI. So it needs to be lower otherwise CI will struggle.
quoted hunk ↗ jump to hunk
+ /* The XDP program we run with bpf_prog_run() will cycle through all + * three xmit (PASS/TX/REDIRECT) return codes starting from above, and + * ending up with PASS, so we should end up with two packets on the dst + * iface and NUM_PKTS-2 in the TC hook. We match the packets on the UDP + * payload. + */
could you keep cycling through all return codes? That should make the test stronger.
quoted hunk ↗ jump to hunk
+ + /* We enable forwarding in the test namespace because that will cause + * the packets that go through the kernel stack (with XDP_PASS) to be + * forwarded back out the same interface (because of the packet dst + * combined with the interface addresses). When this happens, the + * regular forwarding path will end up going through the same + * veth_xdp_xmit() call as the XDP_REDIRECT code, which can cause a + * deadlock if it happens on the same CPU. There's a local_bh_disable() + * in the test_run code to prevent this, but an earlier version of the + * code didn't have this, so we keep the test behaviour to make sure the + * bug doesn't resurface. + */ + SYS("sysctl -qw net.ipv6.conf.all.forwarding=1");
Does it mean that without forwarding=1 the kernel will dead lock ?!