rtsol/rtsold: Add option to skip random delay

[cperciva]

Summary

In accordance with a SHOULD in RFC 4861, rtsol and rtsold wait a random time between
zero and one (aka MAX_RTR_SOLICITATION_DELAY) seconds before sending a Router
Solicitation, in order to avoid network congestion if many hosts come online at once. (The
question of how many hosts would be required to cause congestion by each sending a
single packet on a Gbps+ network is left to the reader.)

The new option -i disables this wait and instructs rtsol and rtsold to send the Router
Solicitation immediately.

[kp]

LGTM. The man page date will want to be bumped up.

[allanjude]

usr.sbin/rtsold/rtsold.c

724–727

This if makes a double negative, I feel like this if would read better the other way around...

		if (no_solicitation_delay == 1)
			interval = 0;
		else
			interval = arc4random_uniform(MAX_RTR_SOLICITATION_DELAY * MILLION);

[cperciva]

Bumped man page date & adjusted if logic to avoid double-negative.

[bz]

usr.sbin/rtsold/rtsold.c

102

bool given we have that these days (as opposed to 25 years ago)?

[bz]

Apart from that this seems fine to me.

[cperciva]

usr.sbin/rtsold/rtsold.c

102

I considered that, but figured that it made sense to keep style consistency with the surrounding code.

(For the same reason, I didn't wrap the interval = arc4random_uniform(MAX_RTR_SOLICITATION_DELAY * MILLION); -- it's a long line, but it was *already* >80 characters before this change...)