3 files changed, 20 insertions, 4 deletions
diff --git a/sysdep/bsd/krt-sock.c b/sysdep/bsd/krt-sock.c
index 4817df39..12ebe6de 100644
--- a/sysdep/bsd/krt-sock.c
+++ b/sysdep/bsd/krt-sock.c
@@ -546,7 +546,17 @@ krt_read_addr(struct ks_msg *msg)
 #endif
 
   if (iface->flags & IF_MULTIACCESS)
+  {
     ifa.prefix = ipa_and(ifa.ip, ipa_mkmask(masklen));
+
+    if (i->ifa_prefixlen == BITS_PER_IP_ADDRESS - 1)
+      ifa.opposite = ipa_opposite_m1(ifa.ip);
+
+#ifndef IPV6
+    if (i->ifa_prefixlen == BITS_PER_IP_ADDRESS - 2)
+      ifa.opposite = ipa_opposite_m2(ifa.ip);
+#endif
+  }
   else         /* PtP iface */
   {
     ifa.flags |= IA_UNNUMBERED;
diff --git a/sysdep/linux/netlink/netlink.c b/sysdep/linux/netlink/netlink.c
index aa0f2c45..72f06cc2 100644
--- a/sysdep/linux/netlink/netlink.c
+++ b/sysdep/linux/netlink/netlink.c
@@ -390,9 +390,13 @@ nl_parse_addr(struct nlmsghdr *h)
       ip_addr netmask = ipa_mkmask(ifa.pxlen);
       ifa.prefix = ipa_and(ifa.ip, netmask);
       ifa.brd = ipa_or(ifa.ip, ipa_not(netmask));
+      if (i->ifa_prefixlen == BITS_PER_IP_ADDRESS - 1)
+	ifa.opposite = ipa_opposite_m1(ifa.ip);
+
 #ifndef IPV6
       if (i->ifa_prefixlen == BITS_PER_IP_ADDRESS - 2)
-	ifa.opposite = ipa_opposite(ifa.ip, i->ifa_prefixlen);
+	ifa.opposite = ipa_opposite_m2(ifa.ip);
+
       if ((ifi->flags & IF_BROADCAST) && a[IFA_BROADCAST])
 	{
 	  ip_addr xbrd;
diff --git a/sysdep/unix/krt-iface.c b/sysdep/unix/krt-iface.c
index e0158b6b..5fda0d1d 100644
--- a/sysdep/unix/krt-iface.c
+++ b/sysdep/unix/krt-iface.c
@@ -89,7 +89,7 @@ scan_ifs(struct ifreq *r, int cnt)
 	{ err = "SIOCGIFNETMASK"; goto faulty; }
       get_sockaddr((struct sockaddr_in *) &r->ifr_addr, &netmask, NULL, 0);
       l = ipa_mklen(netmask);
-      if (l < 0 || l == 31)
+      if (l < 0)
 	{
 	  log(L_ERR "%s: Invalid netmask (%x)", i.name, netmask);
 	  goto bad;
@@ -139,8 +139,10 @@ scan_ifs(struct ifreq *r, int cnt)
 	    i.flags |= IF_BROADCAST;
 	  if (a.pxlen < 30)
 	    i.flags |= IF_MULTIACCESS;
-	  else
-	    a.opposite = ipa_opposite(a.ip, a.pxlen);
+	  if (a.pxlen == 30)
+	    ifa.opposite = ipa_opposite_m2(ifa.ip);
+	  if (a.pxlen == 31)
+	    ifa.opposite = ipa_opposite_m1(ifa.ip);
 	}
       else
 	a.brd = a.opposite;