[strongSwan] DHCP plugin + freeradius - strange behavior when no proposals

[Kamil Jońca]

Disclaimer: I do not know if it is bug or feature, and what should be
changed: freeradius or dhcp plugin.

I have configured dhcp plugin:

--8<---------------cut here---------------start------------->8---
dhcp {
    force_server_address = yes
    identity_lease = yes
    interface = eth0
    load = yes
	server=192.168.200.200
}
--8<---------------cut here---------------end--------------->8---

as a DHCP server act  freeradius.
Adresses are statically asigned.
strange thing happen when plugin asks for unknown mac, freeradius send
this message:

Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Relay-IP-Address = 192.168.200.200
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Message-Type = DHCP-Offer
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Domain-Name-Server = 192.168.200.200
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Subnet-Mask = 255.255.255.0
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Router-Address = 192.168.200.218
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-IP-Address-Lease-Time = 86400
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-DHCP-Server-Identifier = 192.168.200.200
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Domain-Name = "kjonca"
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Server-IP-Address = 192.168.200.200
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Time-Server = 192.168.200.200
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Opcode = Server-Message
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Hardware-Type = Ethernet
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Hardware-Address-Length = 6
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Hop-Count = 0
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Transaction-Id = 1809418123
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Flags = 0
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Client-IP-Address = 0.0.0.0
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Gateway-IP-Address = 192.168.200.200
Sun Oct 14 19:27:57 2018 : Debug: (35)   DHCP-Client-Hardware-Address = 7a:a7:86:29:f1:72

so dhcp servers offer 0.0.0.0 as address 
dhcp plugins requests this address:
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Opcode = Client-Message
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Hardware-Type = Ethernet
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Hardware-Address-Length = 6
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Hop-Count = 0
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Transaction-Id = 1809418123
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Number-of-Seconds = 0
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Flags = 0
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Client-IP-Address = 0.0.0.0
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Your-IP-Address = 0.0.0.0
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Server-IP-Address = 0.0.0.0
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Gateway-IP-Address = 192.168.200.200
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Client-Hardware-Address = 7a:a7:86:29:f1:72
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Message-Type = DHCP-Request
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Hostname = "sikorka.kjonca"
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Client-Identifier = 0x73696b6f726b612e6b6a6f6e6361
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Requested-IP-Address = 0.0.0.0
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-DHCP-Server-Identifier = 192.168.200.200
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Parameter-Request-List = DHCP-Domain-Name-Server
Sun Oct 14 19:27:57 2018 : Debug: (41)   DHCP-Parameter-Request-List = DHCP-NETBIOS-Name-Servers

and received dhcp-ack.
And ... again send dhcp-request, received dhcp-ack, and we end with
infinite loop.

Now I (temporarily) configure dhcp server not to send offer for unknown
client but I am not sure if it is proper solution.

1. what should do dhcp server when receives dhcp-discover via gateway,
when there is no proposals? should it send any answer?
2. what should do dhcp-plugin when receives dhcp-offer with address like
0.0.0.0?

KJ




-- 
http://wolnelektury.pl/wesprzyj/teraz/
Work expands to fill the time available.
		-- Cyril Northcote Parkinson, "The Economist", 1955