1 /* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 */
7 #include "vmlinux.h"
8 #include "net_shared.h"
9 #include <linux/version.h>
10 #include <bpf/bpf_helpers.h>
11 #include <bpf/bpf_core_read.h>
12 #include <bpf/bpf_tracing.h>
13
14 /* kprobe is NOT a stable ABI
15 * kernel functions can be removed, renamed or completely change semantics.
16 * Number of arguments and their positions can change, etc.
17 * In such case this bpf+kprobe example will no longer be meaningful
18 */
19 SEC("kprobe.multi/__netif_receive_skb_core*")
20 int bpf_prog1(struct pt_regs *ctx)
21 {
22 /* attaches to kprobe __netif_receive_skb_core,
23 * looks for packets on loobpack device and prints them
24 * (wildcard is used for avoiding symbol mismatch due to optimization)
25 */
26 char devname[IFNAMSIZ];
27 struct net_device *dev;
28 struct sk_buff *skb;
29 int len;
30
31 bpf_core_read(&skb, sizeof(skb), (void *)PT_REGS_PARM1(ctx));
32 dev = BPF_CORE_READ(skb, dev);
33 len = BPF_CORE_READ(skb, len);
34
35 BPF_CORE_READ_STR_INTO(&devname, dev, name);
36
37 if (devname[0] == 'l' && devname[1] == 'o') {
38 char fmt[] = "skb %p len %d\n";
39 /* using bpf_trace_printk() for DEBUG ONLY */
40 bpf_trace_printk(fmt, sizeof(fmt), skb, len);
41 }
42
43 return 0;
44 }
45
46 char _license[] SEC("license") = "GPL";
47 u32 _version SEC("version") = LINUX_VERSION_CODE;
48
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