dhclient doing DISCOVER with bad IP checksum - bge (7.1 show stopper??)

Jonathan Feally vulture at netvulture.com
Tue Dec 2 09:40:53 PST 2008


I will try another em card in that server to confirm/rule out the nic 
driver. I am seeing the same checksum number on both the source machine, 
the dhcp server machine, and a 3rd windows xp machine sniffing the 
traffic with etherreal/wireshark. The windows xp box is running an intel 
nic as well, and those 0.0.0.0.67 -> 255.255.255.255.68 packets as seen 
by the server do have the correct checksum. After the nic test, if no 
change from one driver to the other, then I'll try to un-patch the bpf.c 
change.

At this point it is acting like the checksum offloading (which I did 
disable on both the client and server) just isn't working.

Will let you know.

-Jon

Danny Braniss wrote:
>> Can someone please confirm or rule out my issue with dhclient sending 
>> bad IP checksum packets. It would really suck if 7.1 was released with a 
>> broken DHCP client.
>>
>>     
> I've had many problems lately, but none involved checksum nor the dhcpd
> (btw, I assume that you are seeing bad checksum on the receiving server)
> could you add a nic to your PE1750? 
>
> danny
>
>
>   
>> Jonathan Feally wrote:
>>     
>>> Sorry for the cross-post, but this could be either lists problem.
>>>
>>> I have 2 boxes running 7-STABLE as of 20081130, both i386 SMP. One is 
>>> running ISC DHCPD 3.0.x from recent ports, and the other dhclient from 
>>> make world.
>>>
>>> The server is refusing to answer the DISCOVER request, as it thinks 
>>> the IP checksum is wrong, which tcpdump also confirms. Other DHCP 
>>> clients are working fine on this network, so I do not believe it to be 
>>> the network, server or dhcpd.
>>>
>>> Server is running a 2 Port Intel card - em driver.
>>>
>>> Client is a Dell PE1750 with 2 onboard NIC's - bge driver.
>>>
>>> I have tried turning off both RXCSUM and TXCSUM on both the client and 
>>> server machines with no luck. I also tried the second NIC on the 
>>> server with the same result.
>>>
>>> This setup was working just a couple of weeks ago, and the only thing 
>>> that has changed is updating the src for a make world. PXE booting 
>>> this server does result in an IP being issued, so it is pointing 
>>> towards something new/changed in 7-STABLE.
>>>
>>> I have attached a 3 packet dump of the DISCOVER requests.
>>>
>>> Can anybody shed some light on this for me?
>>>
>>> Thanks, -Jon
>>>
>>> ------------------------------------------------------------------------
>>>
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>
>
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