[lwip-users] DHCP renewing/ rebinding and on going connexions

[PELISSIER Christophe]

Hi all,

i am using lwip V1.2 on a blackfin CPU. the lwip port has been made by Analog 
Device. I have not a long experience in lwip use. 
Looking at the DHCP client, i was wondering how on going connection are managed 
during an IP address change.

For example, during the IP renewing phase if the client receives a DHCPNAK (or 
never receives a DHCPACK), it should stop using its current IP address. The 
RFC2131adds on page 41 that it "MUST immediately stop any other network 
processing and requests network initialization parameters...".

In the current dhcp code, i have seen that in such cases a dhcp_release is 
performed. This shutdown the NETIF flags but for my understanding nothing is 
done for the connexions currently in use.

Do i miss something? Is shutting down on going connection not required? That is 
the behaviour of opened sockets in such cases?
If shutting down is required, does this action have to be performed by the 
stack? By the application level?
If this action is related to application level, is there any call-back 
mechanism available to inform the application when these events are raised?

In the same way, RFC2131 says page 41, during a renewing phase,  "if the client 
is given a new network address, it MUST NOT continue using the previous network 
address and SHOULD notify le local users of the problem".

For me the local users is stand for "application level". Here again, i haven't 
seen in the DHCP client code, any comparison between old and new address in the 
renewing phase (and any call-back mechanism to inform the application level of 
this issue). 

Do I miss something else?

Thanks for your support.
Regards,

Christophe