nf_nat_tftp broken in 4.8?

[Florian Fainelli <f.fainelli@gmail.com>]

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Hi,

After updating my workstation from 4.4 to 4.8, which also serves as a
NAT gateway for local machines, I noticed that TFTP across this NAT box
broke:

- TFTP read request to the server, source port 3534
- server replies with a data packet to dst port 3534
- gateway sends an ICMP destination unreachable with port unreachable
along with the UDP data packet

I am currently bisecting this, but it is taking a lot longer to build
than I thought. Attached is the non-working case PCAP file for you to
look at.

There has not been a lot happening for net/netfilter/*tftp* between v4.4
and 4.8, so can you think about something in particular that could cause
that?

Thanks!
--
Florian

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