I'm using dhcpcd-10.1.0 and after restarting ppp, dhcpcd ends up in an infinite loop where it prints a ton of messages per second:
ppp0: carrier lost
br0: deleting address ...
br0: deleting route to ...
lo: deleting reject route to ...
ppp0: removing interface
ppp11: waiting for carrier
ppp11: carrier acquired
ppp11: IAID 00:00:00:3c
ppp11: carrier lost
ppp0: waiting for carrier
ppp0: removing interface
ppp0: IAID 70:70:70:30
ppp0: IA type 3 IAID 00:00:00:00
ppp0: IA type 25 IAID 00:00:00:00
ppp0: removing interface
...
Possibly related issues: #314 #359