Create separate option for bridging mcast and hw can

[bugobliterator]

• Bridging between mcast CAN and HW CAN needs to be turned off by default. The reason is if there are more than 2 devices on the same HW CAN and Ethernet network that will cause network loops and potentially choke the CAN bus.
• Bridging needs to be always turned off for Bootloaders, and in the case of AP_Periph and ardupilot, it should be enabled by the user.

Changes done:

• Change option name from CAN1_MCAST_GATEWAY to CAN1_MCAST_ENDPOINT in NET_OPTIONS.
• Adds another option CAN1_MCAST_BRIDGED to enable bridging between MCAST and Hw CAN.
• Bridging option can be changed and will take effect on the same run, reboot is not required.

[tridge]

why do we need these disable flags? if we want to disable, why don't we just call unregister_frame_callback()?

[bugobliterator]

@tridge the disable is only to remove calling on rx, but we still call the callback on tx from CANIface. Basically we don't forward what we receive from CAN Bus, but we still transmit frames that are to be sent out. That's how we leave the interaction with the device itself functional. Unregistering will remove the call from both tx and rx.

[tridge]

@bugobliterator could this be handled in the callback in the AP_Networking layer?

[bugobliterator]

@bugobliterator could this be handled in the callback in the AP_Networking layer?

I don't think there's a way to do this without changes to CANIface, there's a common callback for both RX and TX. We have to either pass the direction as callback parameter, make it part of each frame or the way I have done which is to have the direction selection per callback. First method will require wider changes, second one costs more memory and third one I think is a happy middle.

[tridge]

adding an bool is_send as an additional field in the callback
maybe change

    FUNCTOR_TYPEDEF(FrameCb, void, uint8_t, const AP_HAL::CANFrame &);

to this:

    FUNCTOR_TYPEDEF(FrameCb, void, uint8_t, const AP_HAL::CANFrame &, uint8_t flags);

[tridge]

or could be a bool

[bugobliterator]

Moved to using CANIOFlags actually to keep things consistent.

Also changed IsMAVCAN flag to IsForwardedFrame. This flag is then used to check if the frame was forwarded from different physical iface.

[bugobliterator]

requested changes made

[tridge]

this looks much better, thank you!
just the one trivial fix needed then should be merged

[tridge]

I think we need parentheses around the bitmask test, or some compilers will complain