Rumprun issue with Kubernetes /32 networks with ARP proxying

[lumjjb]

We run into an error where the CNI is configured to use ARP proxying. Rumprun gives an error rumprun: gw "169.254.1.1" addition failed. Changing the mask to 1 makes this possible. Thus, the hypothesis is that rumprun checks if the GW is in the same subnet as the ip specified.

We will need to remove this check in rumprun to allow such network configurations.

            |      ___|
  __|  _ \  |  _ \ __ \
\__ \ (   | | (   |  ) |
____/\___/ _|\___/____/
Solo5: Memory map: 512 MB addressable:
Solo5:     unused @ (0x0 - 0xfffff)
Solo5:       text @ (0x100000 - 0xaed6f7)
Solo5:     rodata @ (0xaed6f8 - 0xda55b7)
Solo5:       data @ (0xda55b8 - 0xfdbea7)
Solo5:       heap >= 0xfdc000 < stack < 0x20000000
rump kernel bare metal bootstrap

Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
    2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016
    The NetBSD Foundation, Inc.  All rights reserved.
Copyright (c) 1982, 1986, 1989, 1991, 1993
    The Regents of the University of California.  All rights reserved.

NetBSD 7.99.34 (RUMP-ROAST)
total memory = 247 MB
timecounter: Timecounters tick every 10.000 msec
timecounter: Timecounter "clockinterrupt" frequency 100 Hz quality 0
cpu0 at thinair0: rump virtual cpu
root file system type: rumpfs
kern.module.path=/stand/amd64/7.99.34/modules
mainbus0 (root)
timecounter: Timecounter "bmktc" frequency 1000000000 Hz quality 100
ukvmif0: Ethernet address 26:df:ef:a8:1b:d6
rumprun: gw "169.254.1.1" addition failed```