/* 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, * 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 */ skb = (struct sk_buff *) 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;