[dir_bcast] Fix issue of dir_bcast testing#771

Merged

lguohan merged 3 commits intosonic-net:masterfrom

wangxin:dir-bcast

Mar 22, 2019

Commits on Jan 14, 2019

[dir_bcast] Replace injected BOOTP UDP packet with ordinary IP packet
Xin Wang
committed
[dir_bcast] Use an obviously unused source IP address 1.1.1.1
Xin Wang
committed

Commits on Feb 20, 2019

[dir_bcast] Add checking directed broadcast of DHCP packets
Xin Wang
committed