RADIX_MPATH not defined in sys/netinet/ip_input.c on FreeBSD (10.4/12.1)

[Foster, Greg]

FreeBSD,

I've been looking at some issues related to multipath routing on a system running FreeBSD 10.4
and came across what looks like a bug/inconsistency in the kernel networking code.

sys/netinet/ip_output.c:

  *   Includes the "opt_mpath.h" header file via the line  "#include "opt_mpath.h".


When ip_output.c is compiled the #define RADIX_MPATH will be defined and the code
used will be within the "#ifdef RADIX_MPATH" section of the #ifdef statement.

sys/netinet/ip_input.c:

  *   Does NOT include the "opt_mpath.h" header file.

When ip_input.c is compiled the #define RADIX_MPATH will NOT be defined and the code
used will be within the "#else" section of the "#ifdef RADIX_MPATH" statement.

FreeBSD 12.1 was checked and it has the same inconsistency.

Is this a BUG or is there an explanation why the difference?

Thanks
Greg