PXE Error: Only absolute filenames allowed

[TJ]

Binary package hint: tftp-hpa

I've just upgraded a rarp/bootp/tftp PXE server that hosts bootable images for the LAN from Karmic to Lucid using:

do-release-upgrade -d

Prior to the upgrade it worked fine. After the upgrade PXE clients report:

Only absolute filename allowed
TFTP Error - Access Violation

Running a network sniffing session I see:

sudo tcpdump -ni eth0 -v -T tftp 'udp'
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
18:14:33.056751 IP (tos 0x0, ttl 20, id 2, offset 0, flags [none], proto UDP (17), length 55)
    10.254.251.95.2070 > 10.254.251.2.69: 27 RRQ "pxelinux.0" octet tsize 0
18:14:33.062219 IP (tos 0x0, ttl 64, id 9743, offset 0, flags [none], proto UDP (17), length 64)
    10.254.251.2.48777 > 10.254.251.95.2070: 36 ERROR EACCESS "Only absolute filenames allowed"
18:14:33.063885 IP (tos 0x0, ttl 20, id 3, offset 0, flags [none], proto UDP (17), length 60)
    10.254.251.95.2071 > 10.254.251.2.69: 32 RRQ "pxelinux.0" octet blksize 1456
18:14:33.069505 IP (tos 0x0, ttl 64, id 9744, offset 0, flags [none], proto UDP (17), length 64)
    10.254.251.2.39907 > 10.254.251.95.2071: 36 ERROR EACCESS "Only absolute filenames allowed"

[TJ (tj)]

The issue is caused because the tftpd-hpa --secure flag is not being used. I've added it to /etc/default/tftpd-hpa:

TFTP_OPTIONS="-s"

Now I see:

sudo tcpdump -ni eth0 -v -T tftp 'udp'
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
18:25:50.528436 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 47)
    10.254.251.51.42972 > 10.254.251.2.69: 19 RRQ "pxelinux.0" octet
18:25:50.551265 IP (tos 0x0, ttl 64, id 31434, offset 0, flags [none], proto UDP (17), length 544)
    10.254.251.2.44414 > 10.254.251.51.42972: 516 DATA block 1
18:25:50.553521 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 32)
    10.254.251.51.42972 > 10.254.251.2.44414: 4 ACK block 1
...

[helix84 (helix84)]

Thanks for identifying the issue and suggesting the fix. I'd consider this a regression - PXE boot stopped working and this must be fixed on the server side - one cannot change the PXE client which is usually in firmware. Could this be SRU-ed?

[Tim (tc0nn)]

Ubuntu 10.4.4 - in /etc/defaut/tftpd-hpa the option is actually TFTP_OPTIONS="-s", the default config has OPTIONS="....." but that is not the same.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.