nsapi - Add optional API for static configuration of network interfaces

[geky]

This is a proposal to add static configuration to network interfaces.

This accomplishes two things:

1. Provides a simple route for adding static IP address support to the base NetworkInterface
2. Provides a simple route for adding configurability to network interfaces and unifies the network interface to consistent connect call, allowing network interfaces to be passed around abstractly

Additional functions:

int NetworkInterface::set_network(const char *ip_address, const char *netmask, const char *gateway);
int NetworkInterface::set_dhcp(bool dhcp);
int WiFiInterface::set_credentials(const char *ssid, const char *pass);
int CellularInterface::set_credentials(const char *apn, const char *user, const char *pass);

Let me know any concerns

related discussion #2627
should resolve #2649
cc @bulislaw, @sg-, @c1728p9

[bulislaw]

User can still provide credential directly to the connect, which is all right, but in case user calls set_credentials first and then 'full' connect we won't update credentials data in the object (_ssid, _pass, _security) ending up, correctly, connected to different network than we have info stored. We could call the set_credentials in the connect to update network info.

[geky]

That is a good idea. Unfortunately we can't control the connect function since it is overriden by the WiFi implementation. I'm open to ideas if you think we can work around this.

It would be better if the set_credentials was overridden by the interface (similarly to the set_network function), but this would break existing implementations.

[sg-]

@geky needs some conflicts resolved.

[sg-]

Looks like dhcp defaults to false, is that right? That would be a breaking change for all existing applications unless dhcp happens when mask and gateway are null?

[geky]

Looks like dhcp defaults to false, is that right?

You are absolutely correct, dhcp should default to true. Not sure how this was missed.

[geky]

/morph test

[mbed-bot]

Result: SUCCESS

Your command has finished executing! Here's what you wrote!

/morph test

Output

mbed Build Number: 933

All builds and test passed!

[kristofmulier]

Does anyone have an example code to get a simple UDP packet transferred to a PC, with static IP addresses?

[bridadan]

@kristofmulier you can start with the sockets example here: https://github.com/ARMmbed/mbed-os-example-sockets