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From: Yuri Pankov <freebsd@irbis.net.ru>
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Date: Sun, 28 Aug 2005 04:18:26 +0400
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Subject: libpcap and interface with no IPv4 address
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Hi,

tcpdump (and other programs using libpcap with IP proto filter) behaves strangely (as it seems to me) on an interface with no IPv4 address assigned..

tcpdump -ni xl0
tcpdump: WARNING: xl0: no IPv4 address assigned
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on xl0, link-type EN10MB (Ethernet), capture size 96 bytes
04:08:01.207673 IP 62.183.127.130.49192 > 85.118.141.1.80: . ack 4143124359 win 33304 <nop,nop,timestamp 460213338 604944>
04:08:01.209350 IP 62.183.127.130.49192 > 85.118.141.1.80: P 0:609(609) ack 1 win 33304 <nop,nop,timestamp 460213338 604944>
04:08:01.415512 IP 62.183.127.130.49192 > 85.118.141.1.80: . ack 989 win 33060 <nop,nop,timestamp 460213358 604944>
04:08:01.418589 IP 62.183.127.130.49192 > 85.118.141.1.80: . ack 1989 win 33054 <nop,nop,timestamp 460213359 604944>
04:08:01.421370 IP 62.183.127.130.49192 > 85.118.141.1.80: . ack 2989 win 33054 <nop,nop,timestamp 460213359 604944>
04:08:01.424297 IP 62.183.127.130.49192 > 85.118.141.1.80: . ack 3989 win 33054 <nop,nop,timestamp 460213359 604944>
etc.

and using tcpdump -ni xl0 ip (any IP proto related filter here) gives no output at all besides the warning line and info.

host must just collect IP packets, which are copied to this interface from another port.
can this be solved? and any reason if not.

FreeBSD-5 with tcpdump version 3.8.3 +libpcap version 0.8.3
FreeBSD-6 with tcpdump version 3.9.1 + libpcap version 0.9.1