33 lines
1.6 KiB
Text
33 lines
1.6 KiB
Text
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$Id: README.bsd,v 1.1 2000/02/19 21:54:07 guy Exp $
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In order to capture packets (with Ethereal/Tethereal, tcpdump, or any
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other packet capture program) on a Linux system, your kernel must have
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the Berkeley packet Filter mechanism enabled. On some BSDs (recent
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versions of FreeBSD, for example), it's enabled by default in the
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generic kernel; it's not enabled by default in older FreeBSD kernels,
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and might not be enabled by default in other kernels.
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The entry in the FreeBSD 3.4 i386 GENERIC configuration file for it is:
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# The `bpfilter' pseudo-device enables the Berkeley Packet Filter.
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# Be aware of the administrative consequences of enabling this!
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# The number of devices determines the maximum number of
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# simultaneous BPF clients programs runnable.
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pseudo-device bpfilter 1 #Berkeley packet filter
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To enable BPF, add "pseudo-device" line such as the last line there to
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your configuration file, re-run "config", rebuild the kernel, install
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the new kernel, and reboot.
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Note that some daemons, or other applications, may be BPF clients, i.e.
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may use the BPF mechanism to see link-layer traffic coming into the
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machine and send link-layer traffic from the machine; for example, if
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the number in the "pseudo-device bpfilter" line is 1, and such a daemon
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or application is running, a packet-capture program will not be able to
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do packet capture, as the one and only BPF device will already be in
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use. You may therefore need to increase the number of BPF devices, by
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increasing the number in the "pseudo-device bpfilter" line, re-running
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"config", rebuilding the kernel, installing the new kernel, and
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rebooting.
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