tftp - bad checksum error? can't transfer file

Anton Shterenlikht mexas at bristol.ac.uk
Fri Jul 8 09:08:48 UTC 2011


> ----- Original Message -----
> From: Anton Shterenlikht [mailto:mexas at bristol.ac.uk]
> Sent: Thursday, July 07, 2011 05:44 PM
> To: freebsd-questions at freebsd.org <freebsd-questions at freebsd.org>
> Subject: tftp - bad checksum error? can't transfer file
> 
> I'm trying to troubleshoot tftpd(8).
> 
> % grep boot /etc/inetd.conf
> tftp   dgram udp  wait root /usr/libexec/tftpd  tftpd -dd -l -s /tftpboot
> tftp   dgram udp  wait root /usr/libexec/tftpd  tftpd -dd -l -s /tftpboot
> bootps dgram udp  wait root /usr/libexec/bootpd bootpd -d4 -t0 /etc/bootptab
> %
> 
> I'm trying to boot another node via bootp/tftp.
> 
> I'm monitoring what's going on with tcpdump -vv.
> 
> bootpd starts fine, and seems to read /etc/bootptab
> correctly.
> 
> But after that nothing happens, and after a few minutes
> I get on the console of the host which I want to boot:
> 
> > bootp()/bsd.rd.IP32
> Unable to execute bootp()/bsd.rd.IP32:  invalid argument
> >
> 
> 
> Does this tcpdump fragment help to understand where
> the problem is:
> 
>     192.168.232.10.15388 > buzi.tftp: [no cksum]  25 RRQ "/bsd.rd.IP32" octet (
> o
> 23:25:21.024160 IP (tos 0x0, ttl 64, id 56, offset 0, flags [none], proto UDP (1
> 7), length 30, bad cksum 0 (->293a)!)
>     buzi.19330 > 192.168.232.10.15388: [udp sum ok] UDP, length 2
> 23:25:51.013759 IP (tos 0x0, ttl 255, id 256, offset 0, flags [none], proto UDP
> (17), length 53)
> 
> I'm happy to provide more detailed information
> on the settings I use and a longer tcpdump output,
> if this helps.
> 

On Thu, Jul 07, 2011 at 05:54:38PM -0500, Gary Gatten wrote:
> >From my experience tcpdump is misleading re udp fragments and chksums.
>  If the packet gets fragmented, udp will report bad chksums at some point.
> 
> Check your file names (case), perms, etc.
> 90% of time I typo a name or forget to chmod the files;

% ls -al /tftpboot/bsd.rd.IP32 
-rwxrwxrwx  1 root  wheel  9646005 Jul  7 21:02 /tftpboot/bsd.rd.IP32
%
% cat /etc/bootptab 
o2:\
        :ht=ether:\
        :ha=0800690c0e3f:\
        :sm=255.255.255.0:\
        :ip=192.168.232.10:\
        :td=/tftpboot:bf=bsd.rd.IP32:
%

Does this look ok?


Many thanks
Anton

-- 
Anton Shterenlikht
Room 2.6, Queen's Building
Mech Eng Dept
Bristol University
University Walk, Bristol BS8 1TR, UK
Tel: +44 (0)117 331 5944
Fax: +44 (0)117 929 4423


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