Merge pull request #4773 from thozza/31-prefix-bcast-addr

ipv4_broadcast_addr() didn't comply with RFC3021

diff --cc lib/prefix.c
Simple merge

diff --cc lib/prefix.h
index 667627ddfe804aa10e8b577ffdf622ada2942a89,7a7e13518a1fd91b957dea67235b2fb54279949f..fb80c4ca6cab9430f7bc3ceeb6b00ce49a1a5a91
--- 1/lib/prefix.h
--- 2/lib/prefix.h
+++ b/lib/prefix.h
@@@ -449,10 -447,11 +449,9 @@@ extern void apply_classful_mask_ipv4(st
  
  extern uint8_t ip_masklen(struct in_addr);
  extern void masklen2ip(const int, struct in_addr *);
 -/* returns the network portion of the host address */
 -extern in_addr_t ipv4_network_addr(in_addr_t hostaddr, int masklen);
  /* given the address of a host on a network and the network mask length,
   * calculate the broadcast address for that network;
-  * special treatment for /31: returns the address of the other host
-  * on the network by flipping the host bit */
+  * special treatment for /31 according to RFC3021 section 3.3 */
  extern in_addr_t ipv4_broadcast_addr(in_addr_t hostaddr, int masklen);
  
  extern int netmask_str2prefix_str(const char *, const char *, char *);