install/56219: sysinst ftp(1) gets Interrupted system call on fetching set via http

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

>Number:         56219
>Category:       install
>Synopsis:       sysinst ftp(1) gets Interrupted system call on fetching set via http
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun May 30 11:35:00 +0000 2021
>Originator:     Izumi Tsutsui
>Release:        NetBSD 9.2
>Organization:
>Environment:
System: NetBSD lunatic 9.2 NetBSD 9.2 (INSTALL) #0: Wed May 12 13:15:55 UTC 2021
        mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/luna68k/compile/INSTALL
Architecture: m68k
Machine: luna68k (maybe other slow 68030 machines?)
>Description:
During upgrade from NetBSD/luna68k 9.1 to 9.2,
crunched ftp(1) fetching binary sets via http from cdn.NetBSD.org
get Interrupted system call (EINTR) and fails to fetch and extract sets.

Note this is only seen on LUNA-I (M68030 20MHz / 16MB RAM),
and isn't seen on LUNA-II (M68040 25MHz / 64MB RAM).

We cannot choose fetch via ftp(1) due to another problem
(ftp control session timeout on fetching large sets, as per PR/56129)

>How-To-Repeat:
Perform upgrade install to NetBSD to 9.2 (only on slow 68030 machines?).

Sysinst comptails:
---
/binary/sets/kern-GENERIC.tgz

     Hit enter to continue

Requesting http://cdn.NetBSD/org/pub/NetBSD/NetBSD-9.2/luna68k/binary/sets/kern-GENERIC.tgz
 97% | ********************************  |  1248 KiB   83.01 KiB/s    00:00 ETAftp: Reading file: Interrupted system call
---

https://pbs.twimg.com/media/E2nBohKUYAA44Ur.jpg
https://pbs.twimg.com/media/E2nHfHDVkAAXoAo.jpg
https://pbs.twimg.com/media/E2nm5h0UcAc9w7V.jpg
https://pbs.twimg.com/media/E2npjw4VUAYx839.jpg
etc.

Note1: IIRC this problem didn't happen on 9.0 and 9.1 upgrade.
Note2: This also happens on fetching from not only cdn.NetBSD.org but 
       also ftp.netbsd.org, ftp4.jp.netbsd.org, ftp6.jp.netbsd.org, and
       ftp7.jp.netbsd.org etc. so it doesn't look server side problem.

>Fix:
Check all possible EINTR errors and handle it properly?

For fetching via ftp protocol we also fix for PR/56129
(ftp(1) should keep control session during large xfer)
https://pbs.twimg.com/media/E2nuME0UUAAkeo1.jpg

---
Izumi Tsutsui