Add xdp_drop_count example

This adds the xdp drop count example relicensed under ASL2, along with
some minor modifications to print pkt/s.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>

examples/networking/CMakeLists.txt

@@ -8,3 +8,4 @@ add_subdirectory(neighbor_sharing)
 add_subdirectory(vlan_learning)
 add_subdirectory(tunnel_monitor)
 add_subdirectory(http_filter)
+add_subdirectory(xdp)

examples/networking/xdp/CMakeLists.txt

+install(PROGRAMS xdp_drop_count.py DESTINATION share/bcc/examples/networking/xdp)

examples/networking/xdp/xdp_drop_count.py

+#!/usr/bin/env python
+#
+# xdp_drop_count.py Drop incoming packets on XDP layer and count for which
+#                   protocol type
+#
+# Copyright (c) 2016 PLUMgrid
+# Copyright (c) 2016 Jan Ruth
+# Licensed under the Apache License, Version 2.0 (the "License")
+
+from bcc import BPF
+import time
+import sys
+
+if (len(sys.argv) != 2):
+    print("Usage: {0} <ifdev>\n\ne.g.: {0} eth0".format(sys.argv[0]))
+    exit(1)
+
+device = sys.argv[1]
+
+# load BPF program
+b = BPF(text = """
+#define KBUILD_MODNAME "foo"
+#include <uapi/linux/bpf.h>
+#include <linux/in.h>
+#include <linux/if_ether.h>
+#include <linux/if_packet.h>
+#include <linux/if_vlan.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+
+
+BPF_TABLE("percpu_array", uint32_t, long, dropcnt, 256);
+
+static inline int parse_ipv4(void *data, u64 nh_off, void *data_end) {
+    struct iphdr *iph = data + nh_off;
+
+    if ((void*)&iph[1] > data_end)
+        return 0;
+    return iph->protocol;
+}
+
+static inline int parse_ipv6(void *data, u64 nh_off, void *data_end) {
+    struct ipv6hdr *ip6h = data + nh_off;
+
+    if ((void*)&ip6h[1] > data_end)
+        return 0;
+    return ip6h->nexthdr;
+}
+
+int xdp_prog1(struct xdp_md *ctx) {
+
+    void* data_end = (void*)(long)ctx->data_end;
+    void* data = (void*)(long)ctx->data;
+
+    struct ethhdr *eth = data;
+
+    // drop packets
+    int rc = XDP_DROP; // let pass XDP_PASS or redirect to tx via XDP_TX
+    long *value;
+    uint16_t h_proto;
+    uint64_t nh_off = 0;
+    uint32_t index;
+
+    nh_off = sizeof(*eth);
+
+    if (data + nh_off  > data_end)
+        return rc;
+
+    h_proto = eth->h_proto;
+
+    if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
+        struct vlan_hdr *vhdr;
+
+        vhdr = data + nh_off;
+        nh_off += sizeof(struct vlan_hdr);
+        if (data + nh_off > data_end)
+            return rc;
+            h_proto = vhdr->h_vlan_encapsulated_proto;
+    }
+    if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
+        struct vlan_hdr *vhdr;
+
+        vhdr = data + nh_off;
+        nh_off += sizeof(struct vlan_hdr);
+        if (data + nh_off > data_end)
+            return rc;
+            h_proto = vhdr->h_vlan_encapsulated_proto;
+    }
+
+    if (h_proto == htons(ETH_P_IP))
+        index = parse_ipv4(data, nh_off, data_end);
+    else if (h_proto == htons(ETH_P_IPV6))
+       index = parse_ipv6(data, nh_off, data_end);
+    else
+        index = 0;
+
+    value = dropcnt.lookup(&index);
+    if (value)
+        *value += 1;
+
+    return rc;
+}
+""", cflags=["-w"])
+
+xdp_func = b.load_func("xdp_prog1", BPF.XDP)
+b.attach_xdp(device, xdp_func)
+dropcnt = b.get_table("dropcnt")
+
+prev = [0] * 256
+print("Printing drops per IP protocol-number, hit CTRL+C to stop")
+while 1:
+    try:
+        for k in dropcnt.keys():
+            val = dropcnt.sum(k).value
+            i = k.value
+            if val:
+                delta = val - prev[i]
+                prev[i] = val
+                print("{}: {} pkt/s".format(i, delta))
+        time.sleep(1)
+    except KeyboardInterrupt:
+        print("Removing filter from device")
+        break;
+
+b.remove_xdp(device)