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open netlink
determine if specified interface exists
if not, complain and exit
determine type of interface
if loopback, pointopoint, something without arp
or a slave interface, complain and exit
if not ethernet, complain and exit
get MAC address
open arp socket to interface
ask netlink for link, address (and route?) events on inteface
poll waiting for arp or netlink event
if arp event:
set link up
store received arp packet
if netlink event:
validate event is for us (size, interface index)
if RTM_NEWLINK, see if the interface index matches
what we have on file. If so, re-grab flags and hwaddress
/*
* a bad idea because we could 'follow' interfaces around too much.
* consider interface 'wlan0' is interface 2. It is subsequantly renamed
* to 'eth2'. Then the PCMCIA wireless card is removed and a USB fixed
* ethernet card is inserted which also get the name 'eth2'. Inteface
* indexes are never reused in Linux, but we would be pick up the new
* one and it might be one the user does not want us to follow that
* device.
if RTM_NEWLINK, if interface index does not match, check
attribute data to see if name matches; If so, re-grab flags,
index and hwaddress.
*/
if RTM_NEWLINK and IFF_RUNNING flag is not set
set state to ADDR_INIT and resume polling
depending on state:
ADDR_INIT: (2.2.1)
wait PROBE_WAIT time
reset probe, conflict and claim counters
goto ADDR_PROBE
ADDR_PROBE: (2.2.1)
if ARP packet received and it conflicts then
increment conflict count
reset probe count to 0
endif
pick random address
send out probe and increment probe counter
wait for ARP packet or timeout
if number of probes >= PROBE_NUM then
goto ADDR_CLAIM
endif
if conflict count > MAX_CONFLICTS then
wait RATE_LIMIT_INTERVAL time
else
wait (PROBE_MAX - PROBE_MIN) time
endif
goto ADDR_PROBE
ADDR_CLAIM: (2.4)
wait for ARP packet or ANNOUNCE_WAIT (or remainder) time
if ARP packet && NOT conflict
goto ADDR_CLAIM
endif
send out claim && increment claim counter
wait for ARP packet or ANNOUNCE_INTERVAL time
if ARP packet && conflict
goto ADDR_PROBE
endif
if number of claims >= ANNOUNCE_NUM
goto ADDR_TAKE
endif
goto ADDR_CLAIM
ADDR_TAKE:
configure ip address
goto ADDR_DEFEND
ADDR_DEFEND:(2.5)
wait for ARP packet
if ARP packet && conflict then
send ARP Defend
goto ADDR_FINAL
endif
goto ADDR_DEFEND
ADDR_FINAL: (2.5)
wait for ARP packet or DEFEND_INTERVAL timeout
if ARP packet && conflict
goto ADDR_RELEASE
endif
if timeout
goto ADDR_DEFEND
endif
goto ADDR_FINAL
ADDR_RELEASE:
deconfigure ip address
<reset any connections?>
goto ADDR_INIT
---
ARP Probe:
arp request
sender IP address: 0.0.0.0
sender HW address: MAC address
target IP address: <probe addr>
target HW address: 00:00:00:00:00:00
ARP Claim:
arp request
sender IP address: <claim addr>
sender HW address: MAC address
target IP address: <claim addr>
target HW address: 00:00:00:00:00:00
ARP Defend:
arp reply
sender IP address: <claim addr>
sender HW address: MAC address
target IP address: <claim addr>
target HW address: 00:00:00:00:00:00
It is expected that the kernel will notice that in all cases the
target HW address is all-zeros and will convert that to the link-layer
broadcast address when sending out the ARP packet. In the case of
Ethernet that should mean the Ethernet link-layer broadcast address of
FF:FF:FF:FF:FF:FF is used.
pick random address:
address range is 169.254.1.0 - 169.254.254.255 (inc.)
pick random number between (0 - 65023) + 256
convert into 16 bits and create address
if ARP packet:
2.2.1 ARP packet (request or reply)
sender IP address: <probe addr>
=> conflict has occurred
2.2.1 ARP request (ARP Probe)
sender HW address: NOT MAC address
target IP address: <probe addr>
=> conflict has occurred
2.5 ARP packet (request or reply)
sender HW address: NOT MAC address
sender IP address: <claim addr>
=> conflict has occurred
"strict" mode, which deconfigures the 169.254.0.0/16 address when a
routable address is assigned.
=> wake from sleep requires reconfiguration (while link up...)
=> association requires reconfiguration
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