bab2f42d8d
[ Upstream commit 31642e7089df8fd3f54ca7843f7ee2952978cad1 ]
Simon Kapadia reported the following issue:
<quote>
The Online Amateur Radio Community (OARC) has recently been experimenting
with building a nationwide packet network in the UK.
As part of our experimentation, we have been testing out packet on 300bps HF,
and playing with net/rom. For HF packet at this baud rate you really need
to make sure that your MTU is relatively low; AX.25 suggests a PACLEN of 60,
and a net/rom PACLEN of 40 to go with that.
However the Linux net/rom support didn't work with a low PACLEN;
the mkiss module would truncate packets if you set the PACLEN below about 200 or so, e.g.:
Apr 19 14:00:51 radio kernel: [12985.747310] mkiss: ax1: truncating oversized transmit packet!
This didn't make any sense to me (if the packets are smaller why would they
be truncated?) so I started investigating.
I looked at the packets using ethereal, and found that many were just huge
compared to what I would expect.
A simple net/rom connection request packet had the request and then a bunch
of what appeared to be random data following it:
</quote>
Simon provided a patch that I slightly revised:
Not only we must not use skb_tailroom(), we also do
not want to count NR_NETWORK_LEN twice.
Fixes:
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|---|---|---|
| .. | ||
| af_netrom.c | ||
| Makefile | ||
| nr_dev.c | ||
| nr_in.c | ||
| nr_loopback.c | ||
| nr_out.c | ||
| nr_route.c | ||
| nr_subr.c | ||
| nr_timer.c | ||
| sysctl_net_netrom.c | ||