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Mike Pennington
Asked: 2012-09-30 13:00:47 +0800 CST

CentOS tftp server is broken

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I'm trying to run tftpd from xinetd on CentOS 6; however, I can only tftp from localhost.

I have a file in /opt/tftpboot/fw.test.conf that I can retrieve if I tftp to localhost:

[mpenning@localhost ~]$ tftp localhost
tftp> get fw.test.conf
tftp> quit
[mpenning@localhost ~]$ ls
fw.test.conf
[mpenning@localhost ~]$

However, I cannot receive this file if I tftp to eth1 on this server (the address on eth1 is 172.16.1.4).

[mpenning@localhost ~]$ sudo tshark -i eth1 udp and host 172.16.1.5
Running as user "root" and group "root". This could be dangerous.
Capturing on eth1
  0.000000   172.16.1.5 -> 172.16.1.4   TFTP Read Request, File: fw.test.conf\000, Transfer type: netascii\000
  5.000133   172.16.1.5 -> 172.16.1.4   TFTP Read Request, File: fw.test.conf\000, Transfer type: netascii\000
 10.000184   172.16.1.5 -> 172.16.1.4   TFTP Read Request, File: fw.test.conf\000, Transfer type: netascii\000
 15.000297   172.16.1.5 -> 172.16.1.4   TFTP Read Request, File: fw.test.conf\000, Transfer type: netascii\000
 20.000331   172.16.1.5 -> 172.16.1.4   TFTP Read Request, File: fw.test.conf\000, Transfer type: netascii\000
^C5 packets captured
[mpenning@localhost ~]$

I have the following xinetd configuration:

[root@localhost mpenning]# cat /etc/xinetd.d/tftp
# default: off
# description: The tftp server serves files using the trivial file transfer \
#       protocol.  The tftp protocol is often used to boot diskless \
#       workstations, download configuration files to network-aware printers, \
#       and to start the installation process for some operating systems.
service tftp
{
        socket_type             = dgram
        protocol                = udp
        wait                    = yes
        user                    = root
        server                  = /usr/sbin/in.tftpd
        server_args             = -s /opt/tftpboot
        disable                 = no
        per_source              = 11
        cps                     = 100 2
        flags                   = IPv4
}
[root@localhost mpenning]#
linux

2 Answers

  1. Best Answer

    In a production environment you would want to specifically allow TFTP through the firewall. This can be done by running system-config-firewall-tui, customising the firewall, and selecting the "TFTP" service.

    • 2

  2. CentOS blocks inbound UDP tftp requests with iptables on ethernet interfaces by default... disabling the iptables service fixed the problem (this is a lab machine, so disabling iptables is ok).

    [root@localhost mpenning]# chkconfig iptables off
[root@localhost mpenning]# /etc/init.d/iptables stop
[root@localhost mpenning]#
    • 0