[lwip-users] DHCP on multiple interfaces

[Toby Duckworth]

Hi,

I am updating our code to support multiple simultaneous network interfaces,
and have a question relating to DHCP.

Before calling dhcp_start(...) we call netif_set_default(...) - Is this
strictly necessary?

If I remove the call to netif_set_default, then DHCP doesn't appear to work
correctly.

With the net_set_default(..) call in place, DHCP works correctly, but
(perhaps obviously) only on one interface at a time. Furthermore, having
obtained an IP address, we then go on to call netconn_new(...) to create a
Netconn on it, and find that unless netconn_bind_if(...) is called on the
created netconn, then subsequent attempts to DHCP on a different interface
cause problems for that netconn.

I would like to understand better the expected behaviour of LWIP with
respect to multiple network interfaces. and in particular how the DHCP
process is meant to work:

1) Is a call to netif_set_default(..) required before calling
dhcp_start(..)?
2) Is it possible for multiple network interfaces to DHCP simultaneously?
3) Is a call to netconn_bind_if(...) necessary if we want to guarantee that
packets are sent and received using a particular network interface?

Thanks,
Toby



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