GNU Zebra is free software that manages various IPv4 and IPv6 routing
protocols.

Currently GNU Zebra supports BGP4, BGP4+, OSPFv2, OSPFv3, RIPv1,
RIPv2, and RIPng.
  
See the file INSTALL for building and installation instructions.
  
See the file REPORTING-BUGS to report bugs.
  
GNU Zebra is free software. See the file COPYING for copying conditions.

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GNU zebra is an old free software and there is nobody maintain it.

But zebra is a very useful and cool product, I'm interested in its function and 

source code for a long time, when I maked it on my Ubuntu 14.04, I found a error 

about IPv6, and then I have to google the error. I modified the source code to

shot the bug.

Add a period of code in lib/zebra.h line 103

#ifdef GNU_LINUX 
#define  __USE_GNU 
#endif

Because zebra supports the IPv6, so we need to add the macro to use the structure 

'struct in6_pktinfo' in in.h in system.