Change the default value of synchronous_dhclient to NO.

To preserve the existing behavior of etc/rc.d/netif, add code to wait
up to if_up_delay seconds (30 seconds by default) for a default route to
be configured if there are any dhcp interfaces.  This should be extended
to test that the interface is actually up.

X-MFC after:

1 files changed, 6 insertions, 2 deletions

diff --git a/share/man/man5/rc.conf.5 b/share/man/man5/rc.conf.5
index cf291a5..49f030e 100644
--- a/share/man/man5/rc.conf.5
+++ b/share/man/man5/rc.conf.5
@@ -393,10 +393,10 @@ only.
 .It Va synchronous_dhclient
 .Pq Bt bool
 Set to
-.Dq Li NO
+.Dq Li YES
 to start
 .Xr dhclient 8
-only in response to interface events and not synchronously at startup.
+synchronously at startup.
 This behavior can be overridden on a per-interface basis by replacing
 the
 .Dq Li DHCP
@@ -406,6 +406,10 @@ variable with
 .Dq Li SYNCDHCP
 or
 .Dq Li NOSYNCDHCP .
+.It Va if_up_delay
+.Pq Vt int
+When set to a positive value, wait up to this long after configuring
+DHCP interfaces at startup to give the interfaces time to receive a lease.
 .It Va firewall_enable
 .Pq Vt bool
 Set to