[FS#1327] dropbearkey hang on OpenWrt master (ar71xx - MIPS r2)

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Koen Vandeputte (xback) 

Attached to Project - OpenWrt/LEDE Project
Summary - dropbearkey hang on OpenWrt master (ar71xx - MIPS r2)
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - High
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - Hardware used:
- Ubiquiti Rocket M5 (ar7241 24Kc)  MIPS r2
- D-Link DIR-825 B2 (AR7xx 74Kc)

Both cpu's don't have a FPU.


On freshly installing/flashing OpenWrt trunk (kernel 4.9), the system is lacking a dropbear RSA host key and will generate one
as stated in /etc/init.d/dropbear.

The key generation hangs forever (100% cpu) causing dropbear to no work properly.

By default, a 1024 bit key is requested, but even manually generating a 512bit key causes it to hog the cpu.
Even after 3 days the cpu is still calculating the key.


17.01.04 releases **does not show** this problem and the key is generated within very reasonable time (few sec).

Reproducability: 100%

**Warning**: Make sure you have a serial link to your board before trying to reproduce it, as SSH access will be gone.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1327