Bug 22234

Summary:	When using tun interface (user PPP), tcpdump does not show incoming packets when used with a filter expression
Product:	Base System	Reporter:	Stanley.Hopcroft <Stanley.Hopcroft>
Component:	misc	Assignee:	freebsd-bugs (Nobody) <bugs>
Status:	Closed FIXED
Severity:	Affects Only Me
Priority:	Normal
Version:	4.1-RELEASE
Hardware:	Any
OS:	Any

Description Stanley.Hopcroft 2000-10-23 07:00:01 UTC

tcpdump -itunX filter_expression shows only outgoing (from localhost)
packets.

It does not show any incoming packets.

Problem machine has only one serial interface.

Ethereal 8.xbehaves the same way.

Ethernet interfaces are not affected.

No NAT or IPFW or IPFILTER in place.

Fix: 

Same behaviour under 4.0-RELEASE.

Downgrade to 3.x I suspect.
How-To-Repeat: tcpdump -itunX port telnet

when you have an open telnet connection shows only
the telnet client packets; there are no server reply packets.

tcpdump -itunX <Null_Filter_Expression ie Null String works fine but you get everything.

Comment 1 Brian Somers freebsd_committer

2000-10-31 23:56:53 UTC

State Changed
From-To: open->closed

Fixed in -current, and just commited to -stable (net/if_tun.c 1.74.2.2)