I got some point from others.I already red and debug network.c . Now I now the basic logic behind that. But still I'm confused by arithmetic. I find some comments on that , I need some one's help.
/*
* int
* bitncmp(l, r, n)
*compare bit masks l and r, for n bits.
* return:
*-1, 1, or 0 in the libc tradition.
* note:
*network byte order assumed. this means 192.5.5.240/28 has
