routing: fix support for default gateway

[ChrisMuc]

Issues #147 and #240 complain about a non working default gateway feature. I had the same issue and tried to find solutions.

Routes with a netmask of /1 or larger are working, wheres routes with a netmask of /0 are accepted but not used when it comes to selecting the next hop.

• Option A: Use separate routes with a netmask of "/1" or larger.
  e.g. 0.0.0.0/1 and 128.0.0.0/1
• Option B: Fix the code
  The proposed fix initializes nh (i.e. next hop) with tree->root->data[0] (i.e. mtrie leaf for 0.0.0.0) and resets this to NULL, if this is not a gateway (i.e. OFP_RTL_FLAGS_GATEWAY not set).
  This way, if (elem->masklen == 0) return nh; will return the default gateway instead of NULL.

[bogdanPricope]

Hi @ChrisMuc,

Sorry to bring the bad news but there are no active maintainers for this repo. Both Nokia and Enea have lost interest and stopped contributing. There is no one to review and merge the fixes.

The 'default route' functionality is missing and I plan to implement it at some point in my own version of OFP.
Out of curiosity, what are you trying to achieve with OFP and what other features would you like to see in OFP?

Best regards,
Bogdan