Sends out a TFTP READ REQ but all DATA packets coming in are subsequently blocked by UFW

[jean-christophe manciot]

Ubuntu Server 15.04 - 3.19.0-25-generic - atftp 0.7 or tftp-hda 5.2
ufw 0.34~rc-0ubuntu5
---------------------------------------------------------------------
I'm trying to get a file from a virtual router running on my host using TFTP through one tap interface. A READ request is sent through tap0 and subsequent data packets are received on the same interface (confirmed by wireshark); however, they never make it to the TFTP client due ufw blocking all of them.

In the Syslog:

Aug 13 15:21:17 msi-ge60 kernel: [ 4121.438888] [UFW ALLOW] IN= OUT=tap0 SRC=192.168.137.1 DST=109.65.200.241 LEN=59 TOS=0x00 PREC=0x00 TTL=64 ID=31061 DF PROTO=UDP SPT=53067 DPT=69 LEN=39
Aug 13 15:21:17 msi-ge60 kernel: [ 4121.527317] [UFW BLOCK] IN=tap0 OUT= MAC=9a:41:f1:65:57:20:ca:07:2e:65:00:08:08:00 SRC=109.65.200.241 DST=192.168.137.1 LEN=544 TOS=0x00 PREC=0x00 TTL=251 ID=0 PROTO=UDP SPT=60728 DPT=53067 LEN=524

I have not setup any rule which would block incoming TFTP on any interface.

Let me know if you need any more information to debug this issue.

[jean-christophe manciot (manciot-jeanchristophe)]

If I add a rule explicitly allowing incoming traffic from that virtual router, the DATA transfer takes place.
This shouldn't be needed when a request first gets out.

[Jamie Strandboge (jdstrand)]

Thank you for using ufw and filing a bug. You probably want to use the tftp connection tracking module. See IPT_MODULES in /etc/default/ufw for details.