Really fix ftp loop

[richcarl]

The previous fix in 9a1c36c was not sufficient, and the code was still looping, eventually consuming all available memory. This new patch has been verified in production running many thousands of ftp transfers with no problems.

This test code can be used to reproduce a case where this happens, with a mimic of a broken control sequence:

{ok, P} = gen_tcp:listen(0,[]).
rr(ftp).
ftp:handle_info({tcp, P, <<$\r>>}, #state{csock={tcp,P}, ctrl_data={<<$\r, $\n, 0,0,2>>,[],{2,0,0}}} ).

[HansN]

Thanks for the PR! I've rebased and merged it to maint and master so it will appear in 22.2 and 23.0.
It will also be released in 21.3.8.11

[richcarl]

This patch is in 21 and master but never made it to maint-22, so it's not yet been included in any OTP 22 release.

[HansN]

It is available also in maint (as all maint-* patches) and will therefor be released in OTP-22.2, planned to be released 2019-12-11.