[lwip-devel] [bug #20409] Add netif callback function for link change event

[Frédéric Bernon]

Follow-up Comment #12, bug #20409 (project lwip):

For the last four states you give, I'm agree with you. In cases where LINK
DOWN, this is because the "link_output" will return an error that the "core"
know there is a problem.

>status_callback goes to application, not driver. Driver runs the same
regardless of whether its netif is UP or DOWN.

Agree with you

>driver signals link change back to the stack (via one of the methods you
mention)

When the link go from DOWN to UP state, it will be good to do some stack
actions (ARP gratuitous, DHCP/AUTOIP renew). So the problem is here: found a
way to communicate from driver to stack (actually, only link_output return
code, and netif->input are available). 

1/ I think we have to define - or recommend - exactly what codes to return
when the link is down, and when the MAC buffers are all full.

2/ I think we could something like netif->linkstatus (on the same idea than
netif->input) to be able to work on all design cases (NO_SYS=0/1 with/without
tcpip.c...). We could define inside tcpip.c a new function like
tcpip_linkstatus using perhaps tcpip_callback or the "lock". The idea is to
reinitialize any stack state to respect RFC 3220 "IP Mobility Support for
IPv4" (or other).





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