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b896c4f9 AS |
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 <linux/skbuff.h> | |
8 | #include <linux/netdevice.h> | |
9 | #include <uapi/linux/bpf.h> | |
10 | #include <linux/version.h> | |
11 | #include "bpf_helpers.h" | |
12 | ||
13 | #define _(P) ({typeof(P) val = 0; bpf_probe_read(&val, sizeof(val), &P); val;}) | |
14 | ||
15 | /* kprobe is NOT a stable ABI | |
16 | * kernel functions can be removed, renamed or completely change semantics. | |
17 | * Number of arguments and their positions can change, etc. | |
18 | * In such case this bpf+kprobe example will no longer be meaningful | |
19 | */ | |
20 | SEC("kprobe/__netif_receive_skb_core") | |
21 | int bpf_prog1(struct pt_regs *ctx) | |
22 | { | |
23 | /* attaches to kprobe netif_receive_skb, | |
24 | * looks for packets on loobpack device and prints them | |
25 | */ | |
02413cab | 26 | char devname[IFNAMSIZ]; |
b896c4f9 AS |
27 | struct net_device *dev; |
28 | struct sk_buff *skb; | |
29 | int len; | |
30 | ||
31 | /* non-portable! works for the given kernel only */ | |
d912557b | 32 | skb = (struct sk_buff *) PT_REGS_PARM1(ctx); |
b896c4f9 | 33 | dev = _(skb->dev); |
b896c4f9 AS |
34 | len = _(skb->len); |
35 | ||
36 | bpf_probe_read(devname, sizeof(devname), dev->name); | |
37 | ||
38 | if (devname[0] == 'l' && devname[1] == 'o') { | |
39 | char fmt[] = "skb %p len %d\n"; | |
40 | /* using bpf_trace_printk() for DEBUG ONLY */ | |
41 | bpf_trace_printk(fmt, sizeof(fmt), skb, len); | |
42 | } | |
43 | ||
44 | return 0; | |
45 | } | |
46 | ||
47 | char _license[] SEC("license") = "GPL"; | |
48 | u32 _version SEC("version") = LINUX_VERSION_CODE; |