macstealer: handle multiple DHCP offers

When multiple different DHCP offers arrive, the script would reply to
all of them. This confuses some DHCP servers. Prevent this by only
replying to the first offered IP address.

This should fix #6

research/macstealer.py

@@ -110,6 +110,7 @@ def __init__(self, iface, options):
 		self.bssid_victim=None
 
 		self.mac = get_macaddress(self.nic_iface)
+		self.offered_ip = None
 		self.clientip = None
 		self.routermac = None
 		self.routerip = None
@@ -398,9 +399,14 @@ def handle_eth_dhcp(self, p):
 
 		# DHCP Offer
 		if req_type == 2:
-			log(STATUS, f"Received DHCP offer for {p[BOOTP].yiaddr}, sending DHCP request.")
-			self.send_dhcp_request(p)
-			self.dhcp_offer_frame = p
+			offered_ip = p[BOOTP].yiaddr
+			if self.offered_ip != None and self.offered_ip != offered_ip:
+				log(WARNING, f"Ignoring DHCP offer for the different IP address {offered_ip}.")
+			else:
+				log(STATUS, f"Received DHCP offer for {offered_ip}, sending DHCP request.")
+				self.send_dhcp_request(p)
+				self.dhcp_offer_frame = p
+				self.offered_ip = offered_ip
 
 		# DHCP Ack
 		elif req_type == 5: