CVS commit: src/sys

["Roy Marples" <roy%netbsd.org@localhost>]

Module Name:    src
Committed By:   roy
Date:           Tue Sep 15 10:05:37 UTC 2020

Modified Files:
        src/sys/net: nd.c nd.h
        src/sys/netinet: if_arp.c
        src/sys/netinet6: nd6.c

Log Message:
Implement RFC 7048, making Neighbor Unreachability Detection less impatient

RFC 7048 Section 3 says in the UNREACHABLE state packets continue to be
sent to the link-layer address and then backoff exponentially.
We adjust this slightly and move to the INCOMPLETE state after
`nd_mmaxtries` probes and then start backing off.

This results in simpler code whilst providing a more robust model which
doubles the time to failure over what we did before.
We don't want to be back to the old ARP model where no unreachability
errors are returned because very few applications would look at
unreachability hints provided such as ND_LLINFO_UNREACHABLE or RTM_MISS.


To generate a diff of this commit:
cvs rdiff -u -r1.2 -r1.3 src/sys/net/nd.c src/sys/net/nd.h
cvs rdiff -u -r1.296 -r1.297 src/sys/netinet/if_arp.c
cvs rdiff -u -r1.273 -r1.274 src/sys/netinet6/nd6.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.