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1/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com2 *3 * This program is free software; you can redistribute it and/or4 * modify it under the terms of version 2 of the GNU General Public5 * 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 ABI15 * 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 meaningful18 */19SEC("kprobe.multi/__netif_receive_skb_core*")20int bpf_prog1(struct pt_regs *ctx)21{22 /* attaches to kprobe __netif_receive_skb_core,23 * looks for packets on loobpack device and prints them24 * (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 46char _license[] SEC("license") = "GPL";47u32 _version SEC("version") = LINUX_VERSION_CODE;48