bin/56129: ftp(1) should keep control session during large xfer

[Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>]

>Number:         56129
>Category:       bin
>Synopsis:       ftp(1) should keep control session during large xfer
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Sun Apr 25 15:05:00 +0000 2021
>Originator:     Izumi Tsutsui
>Release:        NetBSD 9.1
>Organization:
>Environment:
System: NetBSD mirage 9.1 NetBSD 9.1 (GENERIC) #0: Sun Oct 18 19:24:30 UTC 2020 mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/i386/compile/GENERIC i386
Architecture: i386
Machine: i386
>Description:
During ftp installation using miniroot on slow hp300 and sun3 etc.,
the install script in miniroot use ftp(1) to get binary sets.
However it takes more than 5 minites (300 seconds) to get large sets
like base.tgz and comp.tgz etc., then ftp(1) command complains

---
250 CWD command successful.
local: INSTALL/base.tgz remote: base.tgz
227 Entering Passive Mode (199,233,217,201,203,31)
100% |************************************| 40035KiB  104.99 KiB/s    00:00 ETA

421 Service not available, remote server timed out. Connection closed.
40995866 bytes received in 07:21 (90.60 KiB/s)
ftp: No control connection for command
Extracting base.tgz:

---

I've fixed miniroot script to use auto-fetching with URL per each set
 https://mail-index.netbsd.org/source-changes/2020/12/12/msg125060.html
 http://cvsweb.netbsd.org/cgi-bin/cvsweb.cgi/src/distrib/miniroot/install.sub.diff?r1=1.58&r2=1.59
so installation now works, but ftp(1) command still comlains as above.

Several ftp clients keep control sessions by sending NOOP or PWD etc.
during large tranfers, so it's worth to add similar mechanism to
NetBSD's ftp(1).

>How-To-Repeat:
See above.
Or downloader comp.tgz on slow machines or via poor network.

>Fix:
N/A