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-rw-r--r--samples/bpf/lwt_len_hist.bpf.c62
1 files changed, 62 insertions, 0 deletions
diff --git a/samples/bpf/lwt_len_hist.bpf.c b/samples/bpf/lwt_len_hist.bpf.c
new file mode 100644
index 0000000000..dbab80e813
--- /dev/null
+++ b/samples/bpf/lwt_len_hist.bpf.c
@@ -0,0 +1,62 @@
+/* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+struct {
+ __uint(type, BPF_MAP_TYPE_PERCPU_HASH);
+ __type(key, u64);
+ __type(value, u64);
+ __uint(pinning, LIBBPF_PIN_BY_NAME);
+ __uint(max_entries, 1024);
+} lwt_len_hist_map SEC(".maps");
+
+static unsigned int log2(unsigned int v)
+{
+ unsigned int r;
+ unsigned int shift;
+
+ r = (v > 0xFFFF) << 4; v >>= r;
+ shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
+ shift = (v > 0xF) << 2; v >>= shift; r |= shift;
+ shift = (v > 0x3) << 1; v >>= shift; r |= shift;
+ r |= (v >> 1);
+ return r;
+}
+
+static unsigned int log2l(unsigned long v)
+{
+ unsigned int hi = v >> 32;
+ if (hi)
+ return log2(hi) + 32;
+ else
+ return log2(v);
+}
+
+SEC("len_hist")
+int do_len_hist(struct __sk_buff *skb)
+{
+ __u64 *value, key, init_val = 1;
+
+ key = log2l(skb->len);
+
+ value = bpf_map_lookup_elem(&lwt_len_hist_map, &key);
+ if (value)
+ __sync_fetch_and_add(value, 1);
+ else
+ bpf_map_update_elem(&lwt_len_hist_map, &key, &init_val, BPF_ANY);
+
+ return BPF_OK;
+}
+
+char _license[] SEC("license") = "GPL";