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Bug#478532: marked as forwarded (dhcp3-server: dhcpd should ignore wron

Subject: Bug#478532: marked as forwarded dhcp3-server: dhcpd should ignore wrong udp checksums on loopback device
From: Debian Bug Tracking System
Date: Tue, 29 Apr 2008 17:33:05 +0000
Your message dated Wed, 30 Apr 2008 03:30:28 +1000
with message-id <[email protected]>
has caused the   report #478532,
regarding dhcp3-server: dhcpd should ignore wrong udp checksums on loopback 
device
to be marked as having been forwarded to the upstream software
author(s) [email protected]

(NB: If you are a system administrator and have no idea what this
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-- 
478532: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=478532
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Subject: Re: Bug#478532: dhcp3-server: dhcpd should ignore wrong udp checksums on loopback device
From: Andrew Pollock
Date: Wed, 30 Apr 2008 03:30:28 +1000
Hi,

This bug was submitted to Debian recently, and it's an upstream issue, so
I'm forwarding it on. Please maintain the Cc on replies to keep our bug
tracking system in the loop.

regards

Andrew

On Tue, Apr 29, 2008 at 05:54:42PM +0200, [email protected] wrote:
> Package: dhcp3-server
> Version: 3.0.4-13
> Severity: minor
> 
> 
> Hello,
> 
> since linux 2.6.24 no longer calculate the udp checksum for packages on
> the loopback device, dhcpd should ignore wrong checksums in packages
> coming from this device.
> 
> We use dhcping 1.2-3 running on the same host as dhcpd to check if
> dhcpd is still answering. This works great with linux 2.6.8 but fails
> with linux 2.6.24.
> 
> According to http://kerneltrap.org/mailarchive/linux-netdev/2007/9/23/272755
> the kernel no longer generates udp checksums for packets on localhost.
> Instead it sets a flag that signals that the udp checksum should be
> ignored.
> 
> Can you make dhcpd honoring this flag, please?
> 
> 
> Here some details from my setup. These hosts are the only linux hosts
> in their subnets, so I cannot run dhcping on another host.
> 
> --------------------------------------------
> # hostA working
> --------------------------------------------
> Related Packages:
>   dhcp-client               2.0pl5-19.1sarge3
>   dhcp3-common              3.0.1-2
>   dhcp3-server              3.0.1-2
>   dhcping                   1.2-2
>   kernel-image-2.6.8-4-686  2.6.8-16sarge7
> 
> 
> /etc/dhcp3/dhcpd.conf
>    ddns-update-style none;
>    log-facility local7;
>    default-lease-time 3600;
>    max-lease-time 86400;
>    not authoritative;
>    
>    subnet 192.XXX.XXX.0 netmask 255.255.255.0 {
>     ...
>    }
>    
>    subnet 127.0.0.0 netmask 255.0.0.0 {
>        host hostA {hardware ethernet 00:0E:0C:71:XX:XX; fixed-address 
> 192.XXX.XXX.1;}
>    }
> 
> 
> # /usr/sbin/dhcping -c 192.XXX.XXX.1 -s 192.XXX.XXX.1 -h 00:0E:0C:71:XX:XX
> Got answer from: 192.XXX.XXX.1   
> 
> 
> # tethereal -V -i lo udp
> Capturing on lo
> Frame 1 (292 bytes on wire, 292 bytes captured)
> ...
> User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
>     Source port: bootpc (68)
>     Destination port: bootps (67)
>     Length: 258
>     Checksum: 0xc4c8 (correct)
> 
> 
> #-------------------------------------------
> # hostB not working
> #-------------------------------------------
> Related Packages:
>   dhcp3-common              3.0.4-13
>   dhcp3-server              3.0.4-13
>   dhcping                   1.2-3
>   linux-image-2.6.24-1-686  2.6.24-5
> 
> 
> /etc/dhcp3/dhcpd.conf
>    ddns-update-style none;
>    log-facility local7;
>    default-lease-time 3600;
>    max-lease-time 86400;
>    not authoritative;
>    
>    subnet 192.YYY.YYY.0 netmask 255.255.255.0 {
>    ...
>    }
>    
>    subnet 127.0.0.0 netmask 255.0.0.0 {
>        host hostB  {hardware ethernet 00:1F:29:C3:YY:YY; fixed-address 
> 192.YYY.YYY.1;}
>    }
> 
> 
> # /usr/sbin/dhcping -c 192.YYY.YYY.1 -s 192.YYY.YYY.1 -h 00:1F:29:C3:YY:YY
> no answer
> 
> 
> # tshark -V -i lo udp
> Capturing on lo
> Frame 1 (292 bytes on wire, 292 bytes captured)
> ...
> User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
>     Source port: bootpc (68)
>     Destination port: bootps (67)
>     Length: 258
>     Checksum: 0xfc66 [incorrect, should be 0xb39c]              !!!!
> 
> --------------------------------------------------
> 
> 
> Thanks, 
> Martin
> 
> 

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