ipsec_subnetof(3) given Internet address and subnet mask return subnet number, host part, broadcast address

Other Alias

ipsec_hostof, ipsec_broadcastof


#include <freeswan.h>

struct in_addr subnetof(struct in_addr addr,
  struct in_addr mask);
struct in_addr hostof(struct in_addr addr,
  struct in_addr mask);
struct in_addr broadcastof(struct in_addr addr,
  struct in_addr mask);


These functions are obsolete; see ipsec_networkof(3) for their replacements.

Subnetof takes an Internet address and a subnet mask and returns the network part of the address (all in network byte order). Hostof similarly returns the host part, and broadcastof returns the broadcast address (all-1s convention) for the network.

These functions are provided to hide the Internet bit-munging inside an API, in hopes of easing the eventual transition to IPv6.


Written for the FreeS/WAN project by Henry Spencer.


Calling functions for this is more costly than doing it yourself.