misc/122685: It is not visible passing packets in tcpdump

[Sergey Zabolotny]

>Number:         122685
>Category:       misc
>Synopsis:       It is not visible passing packets in tcpdump
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Apr 12 09:30:02 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     Sergey Zabolotny
>Release:        7.0
>Organization:
>Environment:
FreeBSD gw.deadnet.net 7.0-RELEASE FreeBSD 7.0-RELEASE #10: Fri Apr 11 20:47:03 EEST 2008     Zuram at gw.deadnet.net:/usr/src/sys/i386/compile/gw.deadnet.net  i386

>Description:
There are two channels in the Internet. Default gateway through iface1.

There is a rule in firewall:

fwd ip_gw_iface2 ip from ip_iface2 to any out xmit iface1

do ping -S ip_iface1 mail.ru answers is, tcpdumpd shows sending requests and replays on the interface iface1.

do ping -S ip_iface2 mail.ru answers is, tcpdumpd shows only answers on the interface iface2. requests I do not see neither on iface1 nor on iface2.
>How-To-Repeat:
ifconfig fxp0 inet 192.168.1.254/24
ifconfig fxp1 inet 192.168.2.254/24
route add default 192.168.1.1

ipfw add 1 fwd 192.168.2.1 ip from 192.168.2.254 to any out xmit fxp0
ipfw add 2 allow ip from any to any

ping -S 192.168.2.254 mail.ru >/dev/null &

tcpdump -ni fxp1 icmp
tcpdump -ni fxp2 icmp
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: