| Alexei Starovoitov | b896c4f | 2015-03-25 12:49:23 -0700 | [diff] [blame] | 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 | */ |
| 26 | char devname[IFNAMSIZ] = {}; |
| 27 | struct net_device *dev; |
| 28 | struct sk_buff *skb; |
| 29 | int len; |
| 30 | |
| 31 | /* non-portable! works for the given kernel only */ |
| 32 | skb = (struct sk_buff *) ctx->di; |
| 33 | |
| 34 | dev = _(skb->dev); |
| 35 | |
| 36 | len = _(skb->len); |
| 37 | |
| 38 | bpf_probe_read(devname, sizeof(devname), dev->name); |
| 39 | |
| 40 | if (devname[0] == 'l' && devname[1] == 'o') { |
| 41 | char fmt[] = "skb %p len %d\n"; |
| 42 | /* using bpf_trace_printk() for DEBUG ONLY */ |
| 43 | bpf_trace_printk(fmt, sizeof(fmt), skb, len); |
| 44 | } |
| 45 | |
| 46 | return 0; |
| 47 | } |
| 48 | |
| 49 | char _license[] SEC("license") = "GPL"; |
| 50 | u32 _version SEC("version") = LINUX_VERSION_CODE; |