race condition in route_connected() leads to crash on startup/shutdown

Summary

Assertion failure in route_connected()->in ns_interfacemgr_attach():

#6  0x00007f901a31bab8 in ns_interfacemgr_attach (source=0x7f9015294000, target=0x7f901677aaf8) at interfacemgr.c:418
418		REQUIRE(NS_INTERFACEMGR_VALID(source));

BIND version used

• Affects v9.19 : v9_19_2
• Affects v9.18 : v9_18_4

It seems that v9.16 is not affected, or at least is not easily reproducible. I was not able to crash it after 2000 iterations and has given up.

Steps to reproduce

Easiest reproducer so far is this Bash loop:

for I in $(seq 1 1000); do /tmp/main/sbin/named -g -c /dev/null -n1 2>&1 & sleep 0.0$RANDOM; pkill named; done

What is the current bug behavior?

Crash after couple hundred iterations.

What is the expected correct behavior?

Well, no crash :-)

Relevant configuration files

None, see -c /dev/null.

Relevant logs and/or screenshots

gdb.log