Capturing redirected packets?

Hi!

I have PF rules redirecting packets to an IP on one interface (rdomain 1) to the IP of another interface (rdomain 0):

pass in log on rdomain 1 inet proto tcp to $ipv4b port 80 rdr-to $ipv4a port 8080 rtable 0
pass in log on rdomain 1 inet6 proto tcp to $ipv6b port 80 rdr-to $ipv6a port 8080 rtable 0

These rules work for IPv4 but initially not for IPv6. (That problem is now solved.) I was trying to figure out why and started using tcpdump(8).

em0 has the IPs: ipv4a and ipv6a.
em1 is in rdomain 1 and has the IPs: ipv4b and ipv6b.
Both are connected to the same LAN.

httpd(8) is configured to listen on ipv4a:80, ipv6a:80 with one (virtual) server and on ipv4a:8080, ipv6a:8080 with another, each serving a very simple index.html file that shows which server is responding.

To debug I started:
# tcpdump -n -e -ttt -l -i em0 'port 80 or 8080'

# tcpdump -n -e -ttt -l -i em1 'port 80 or 8080'

(Both in separate terminal windows at the same time.)

Now from a second machine I access the web server:
$ curl --url 'http://<ipv4a>'
Works fine, I see traffic in the tcpdump(8) for em0.

$ curl --url 'http://<ipv4b>'
Works fine, I see traffic in the tcpdump(8) for em1 but not for em0.

$ curl --url 'http://[<ipv6a>]'
Works fine, I see traffic in the tcpdump(8) for em0.

$ curl --url 'http://[<ipv6b>]'
Timeout! I see traffic in the tcpdump(8) for em1 but not for em0.
This was the one I was ultimately trying to debug but as the trace on the IPv4 version doesn't work as expected I was momentarily at a loss.
I have since solved the actual problem by setting:
# sysctl net.inet6.ip6.forwarding=1
But I still don't see the redirected traffic in the tcpdump(8) for em0.


I don't understand the second and fourth results. Why does the tcpdump(8) for em0 not show the redirected packets?

I am likely missing something obvious here. How can I capture the redirected packets?


Thanks!

Mike