55 lines
1.8 KiB
C
55 lines
1.8 KiB
C
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/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*/
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#include <linux/skbuff.h>
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#include <linux/netdevice.h>
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#include <uapi/linux/bpf.h>
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#include <linux/version.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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#define _(P) \
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({ \
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typeof(P) val = 0; \
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bpf_probe_read_kernel(&val, sizeof(val), &(P)); \
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val; \
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})
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/* kprobe is NOT a stable ABI
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* kernel functions can be removed, renamed or completely change semantics.
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* Number of arguments and their positions can change, etc.
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* In such case this bpf+kprobe example will no longer be meaningful
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*/
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SEC("kprobe/__netif_receive_skb_core")
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int bpf_prog1(struct pt_regs *ctx)
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{
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/* attaches to kprobe __netif_receive_skb_core,
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* looks for packets on loobpack device and prints them
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*/
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char devname[IFNAMSIZ];
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struct net_device *dev;
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struct sk_buff *skb;
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int len;
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/* non-portable! works for the given kernel only */
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bpf_probe_read_kernel(&skb, sizeof(skb), (void *)PT_REGS_PARM1(ctx));
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dev = _(skb->dev);
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len = _(skb->len);
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bpf_probe_read_kernel(devname, sizeof(devname), dev->name);
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if (devname[0] == 'l' && devname[1] == 'o') {
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char fmt[] = "skb %p len %d\n";
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/* using bpf_trace_printk() for DEBUG ONLY */
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bpf_trace_printk(fmt, sizeof(fmt), skb, len);
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}
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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u32 _version SEC("version") = LINUX_VERSION_CODE;
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