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 "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 ABI 15 * 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 meaningful 18 */ 19 SEC("kprobe.multi/__netif_receive_skb_core*") 20 int bpf_prog1(struct pt_regs *ctx) 21 { 22 /* attaches to kprobe __netif_receive_skb_core, 23 * looks for packets on loobpack device and prints them 24 * (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 46 char _license[] SEC("license") = "GPL"; 47 u32 _version SEC("version") = LINUX_VERSION_CODE; 48