49 lines
1.5 KiB
C
49 lines
1.5 KiB
C
/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
|
|
*
|
|
* 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.
|
|
*/
|
|
#include <linux/skbuff.h>
|
|
#include <linux/netdevice.h>
|
|
#include <uapi/linux/bpf.h>
|
|
#include <linux/version.h>
|
|
#include "bpf_helpers.h"
|
|
|
|
#define _(P) ({typeof(P) val = 0; bpf_probe_read(&val, sizeof(val), &P); val;})
|
|
|
|
/* kprobe is NOT a stable ABI
|
|
* kernel functions can be removed, renamed or completely change semantics.
|
|
* Number of arguments and their positions can change, etc.
|
|
* In such case this bpf+kprobe example will no longer be meaningful
|
|
*/
|
|
SEC("kprobe/__netif_receive_skb_core")
|
|
int bpf_prog1(struct pt_regs *ctx)
|
|
{
|
|
/* attaches to kprobe __netif_receive_skb_core,
|
|
* looks for packets on loobpack device and prints them
|
|
*/
|
|
char devname[IFNAMSIZ];
|
|
struct net_device *dev;
|
|
struct sk_buff *skb;
|
|
int len;
|
|
|
|
/* non-portable! works for the given kernel only */
|
|
bpf_probe_read_kernel(&skb, sizeof(skb), (void *)PT_REGS_PARM1(ctx));
|
|
dev = _(skb->dev);
|
|
len = _(skb->len);
|
|
|
|
bpf_probe_read(devname, sizeof(devname), dev->name);
|
|
|
|
if (devname[0] == 'l' && devname[1] == 'o') {
|
|
char fmt[] = "skb %p len %d\n";
|
|
/* using bpf_trace_printk() for DEBUG ONLY */
|
|
bpf_trace_printk(fmt, sizeof(fmt), skb, len);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
char _license[] SEC("license") = "GPL";
|
|
u32 _version SEC("version") = LINUX_VERSION_CODE;
|