[Dnsmasq-discuss] iptables configuration drops packets

Adam Hardy adam.ant at cyberspaceroad.com
Fri May 16 23:10:54 BST 2008


Simon Kelley on 16/05/08 19:48, wrote:
> Adam Hardy wrote:
>> Hi,
>>
>> I set up iptables myself today after using an obtusely written script 
>> for some time.
>>
>> I am trying to work out whether everything is in order and I am seeing 
>> logs from iptables saying that it is dropping packets from the machine 
>> every 12 minutes, which doesn't make sense - here's a line from the log:
>>
>> May 16 19:21:10 isengard kernel: dropped from OUTPUT IN= OUT=eth1 
>> SRC=192.168.0.2 DST=192.168.0.255 LEN=237 TOS=0x00 PREC=0x00 TTL=64 
>> ID=0 DF PROTO=UDP SPT=138 DPT=138 LEN=217
>>
>>
> Are you running Samba?
> 
> thekelleys:~# grep 138 /etc/services
> netbios-dgm     138/tcp                # NETBIOS Datagram Service
> netbios-dgm     138/udp

Yes indeed. I see. OK. I can't see any reference to 192.168.0.255 in the samba 
config. Before you say it, I guess my config is slightly wrong. I just twigged 
that since 192.168.0.255 is configured as the broadcast address for the NIC on 
the LAN, samba must see that, as does every NIC on the LAN and so I have to 
enable the LAN to broadcast to the gateway, and in fact the gateway to broadcast 
to the LAN ... which must require an OUTPUT rule to let it through.

Thanks for the clue,

regards
Adam




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