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Old 17th September 2011
badguy badguy is offline
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Join Date: Jul 2009
Location: MD, USA
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Default Trying to understand routing with openbsd

Hi guys, i am looking for help understanding a couple of things.

My network
Open BSD box serving as a router/gateway to internet with IPs below
| em0 |---> ISP
| em1 |---> (Wired LAN)
| em2 |---> (Wireless AP)

root ~ # cat /etc/hostname.em1                                                                                                                                                        
inet NONE
#!route add -net
#!route add -net

root ~ # cat /etc/hostname.ural0                                                                                                                                                       
inet NONE autoselect mode 11g mediaopt hostap nwid an0nym0us chan 11 wpa wpaprotos wpa2 wpaakms psk wpapsk lol 

root ~ # cat /etc/sysctl.conf |grep net.inet.ip.forwarding 
net.inet.ip.forwarding=1        # 1=Permit forwarding (routing) of IPv4 packets

root ~ # pfctl -sr                                                                                                                                                                     
anchor "miniupnpd" all
match out log on egress inet from ! (egress) to any nat-to (egress:0) round-robin
block drop in log quick on ! em1 inet from to any
block drop in log quick inet from to any
block drop in log quick on ! em0 from (em0:network) to any
block drop in log quick from (em0) to any
block drop in log quick on re0 inet6 from fe80::e291:f5ff:fe20:3eb0 to any
pass out quick all flags S/SA keep state
pass in quick all flags S/SA keep state
The problem.
random client (connected to wireless ap) is unable to ping random client (connected to switch on em1). I added the commented static routes in hostname.em1 and still same problem.

one thing i noticed when i did a tcpdump on the openbsd box is that i got this. dont know if i is the reason.

root ~ # tcpdump -n -vvv -i re0 host         
tcpdump: listening on re0, link-type EN10MB
21:17:15.985288 > icmp: echo request (id:c624 seq:10) (ttl 63, id 46271, len 84, bad cksum 0! differs by 421d)
21:17:16.994790 > icmp: echo request (id:c624 seq:11) (ttl 63, id 65157, len 84, bad cksum 0! differs by f856)
21:17:16.995493 arp who-has tell
21:17:17.987041 > icmp: echo request (id:c624 seq:12) (ttl 63, id 37534, len 84, bad cksum 0! differs by 643e)
21:17:17.995391 arp who-has tell
21:17:18.995221 arp who-has tell
and on the host i get

root ~ # tcpdump -vvvttt host
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
00:00:00.000000 IP (tos 0x0, ttl 63, id 27416, offset 0, flags [none], proto ICMP (1), length 84) > ICMP echo request, id 3621, seq 78, length 64
00:00:00.003411 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has tell, length 28
00:00:00.997995 IP (tos 0x0, ttl 63, id 36710, offset 0, flags [none], proto ICMP (1), length 84) > ICMP echo request, id 3621, seq 79, length 64

Can it be PF? since i am still a noob with PF so i have allowed all in and out just to make sure it is not because of PF.

pass out quick
pass in quick

by the way how will you check specific packets dropped by PF? do a tcpdump on pflog?

Thanks in advance

Last edited by badguy; 17th September 2011 at 01:45 AM.
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