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/* 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 "vmlinux.h"
#include "net_shared.h"
#include <linux/version.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_core_read.h>
#include <bpf/bpf_tracing.h>
/* 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.multi/__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
* (wildcard is used for avoiding symbol mismatch due to optimization)
*/
char devname[IFNAMSIZ];
struct net_device *dev;
struct sk_buff *skb;
int len;
bpf_core_read(&skb, sizeof(skb), (void *)PT_REGS_PARM1(ctx));
dev = BPF_CORE_READ(skb, dev);
len = BPF_CORE_READ(skb, len);
BPF_CORE_READ_STR_INTO(&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;
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