samples: bpf: Add BPF support for xdp_exception tracepoint

This would allow us to store stats for each XDP action, including their
per-CPU counts. Consolidating this here allows all redirect samples to
detect xdp_exception events.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210821002010.845777-7-memxor@gmail.com

diff --git a/samples/bpf/xdp_sample.bpf.c b/samples/bpf/xdp_sample.bpf.c
index e22f2a9..53ab5a9 100644 (file)
--- a/samples/bpf/xdp_sample.bpf.c
+++ b/samples/bpf/xdp_sample.bpf.c
@@ -8,6 +8,7 @@
 
 array_map rx_cnt SEC(".maps");
 array_map redir_err_cnt SEC(".maps");
+array_map exception_cnt SEC(".maps");
 
 const volatile int nr_cpus = 0;
 
@@ -110,3 +111,29 @@ int BPF_PROG(tp_xdp_redirect_map, const struct net_device *dev,
 {
        return xdp_redirect_collect_stat(dev->ifindex, err);
 }
+
+SEC("tp_btf/xdp_exception")
+int BPF_PROG(tp_xdp_exception, const struct net_device *dev,
+            const struct bpf_prog *xdp, u32 act)
+{
+       u32 cpu = bpf_get_smp_processor_id();
+       struct datarec *rec;
+       u32 key = act, idx;
+
+       if (!IN_SET(from_match, dev->ifindex))
+               return 0;
+       if (!IN_SET(to_match, dev->ifindex))
+               return 0;
+
+       if (key > XDP_REDIRECT)
+               key = XDP_REDIRECT + 1;
+
+       idx = key * nr_cpus + cpu;
+       rec = bpf_map_lookup_elem(&exception_cnt, &idx);
+       if (!rec)
+               return 0;
+       NO_TEAR_INC(rec->dropped);
+
+       return 0;
+}
+