Implement proper LSA ID generation.

3 files changed, 66 insertions, 11 deletions

diff --git a/proto/ospf/ospf.c b/proto/ospf/ospf.c
index dafb607e..0c4d673b 100644
--- a/proto/ospf/ospf.c
+++ b/proto/ospf/ospf.c
@@ -605,7 +605,9 @@ ospf_reconfigure(struct proto *p, struct proto_config *c)
   struct area_net_config *anc;
   struct area_net *an;
 
-  po->rfc1583 = new->rfc1583;
+  if (po->rfc1583 != new->rfc1583)
+    return 0;
+
   schedule_rtcalc(po);
 
   po->tick = new->tick;
diff --git a/proto/ospf/rt.c b/proto/ospf/rt.c
index 416223f3..68b6c821 100644
--- a/proto/ospf/rt.c
+++ b/proto/ospf/rt.c
@@ -18,7 +18,7 @@ static void ospf_ext_spf(struct proto_ospf *po);
 static void rt_sync(struct proto_ospf *po);
 
 /* In ospf_area->rtr we store paths to routers, but we use RID (and not IP address)
-   as index, so we need to encapsulate RID to IP addresss */
+   as index, so we need to encapsulate RID to IP address */
 #ifdef OSPFv2
 #define ipa_from_rid(x) _MI(x)
 #else /* OSPFv3 */
diff --git a/proto/ospf/topology.c b/proto/ospf/topology.c
index 182f644a..6f7905bc 100644
--- a/proto/ospf/topology.c
+++ b/proto/ospf/topology.c
@@ -30,11 +30,64 @@ void flush_prefix_net_lsa(struct ospf_iface *ifa);
 #define ipa_to_rid(x) _I3(x)
 #endif
 
-/* FIXME very ugly hack */
+
 #ifdef OSPFv2
-#define ipa_to_lsaid(x) _I(x)
+static inline u32
+fibnode_to_lsaid(struct proto_ospf *po, struct fib_node *fn)
+{
+  /* We have to map IP prefixes to u32 in such manner that resulting
+     u32 interpreted as IP address is a member of given
+     prefix. Therefore, /32 prefix have to be mapped on itself.
+     All received prefixes have to be mapped on different u32s.
+
+     We have an assumption that if there is nontrivial (non-/32)
+     network prefix, then there is not /32 prefix for the first
+     and the last IP address of the network (these are usually
+     reserved, therefore it is not an important restriction).
+     The network prefix is mapped to the first or the last
+     IP address in the manner that disallow collisions - we
+     use IP address that cannot be used by parent prefix.
+
+     For example:
+     192.168.0.0/24 maps to 192.168.0.255
+     192.168.1.0/24 maps to 192.168.1.0
+     because 192.168.0.0 and 192.168.1.255 might be used by
+     192.168.0.0/23 .
+
+     This is not compatible with older RFC 1583, so we have an option
+     to the RFC 1583 compatible assignment (that always uses the first
+     address) which disallows subnetting.
+
+     Appendig E of RFC 2328 suggests different algorithm, that tries
+     to maximize both compatibility and subnetting. But as it is not
+     possible to have both reliably and the suggested algorithm was
+     unnecessary complicated and it does crazy things like changing
+     LSA ID for a network because different network appeared, we
+     choose a different way. */
+
+  u32 id = _I(fn->prefix);
+
+  if ((po->rfc1583) || (fn->pxlen == 0) || (fn->pxlen == 32))
+    return id;
+
+  if (id & (1 << (32 - fn->pxlen)))
+    return id;
+  else
+    return id | ~u32_mkmask(fn->pxlen);
+}
+
 #else /* OSPFv3 */
-#define ipa_to_lsaid(x) _I0(x) ^ _I1(x) ^ _I2(x) ^ _I3(x)
+
+static inline u32
+fibnode_to_lsaid(struct proto_ospf *po, struct fib_node *fn)
+{
+  /* In OSPFv3, it is simpler. There is not a requirement
+     for membership of the result in input network, so we
+     just use hash-based unique ID. */
+
+  return fn->uid;
+}
+
 #endif
 
 
@@ -660,8 +713,7 @@ originate_sum_lsa(struct ospf_area *oa, struct fib_node *fn, int type, int metri
 
   if (type == ORT_NET)
     {
-      /* FIXME proper handling of LSA IDs and check for the same network */
-      lsa.id = ipa_to_lsaid(fn->prefix);
+      lsa.id = fibnode_to_lsaid(po, fn);
       lsa.type = LSA_T_SUM_NET;
     }
   else
@@ -710,8 +762,7 @@ flush_sum_lsa(struct ospf_area *oa, struct fib_node *fn, int type)
   lsa.rt = rid;
   if (type == ORT_NET)
     {
-      /* FIXME proper handling of LSA IDs and check for the same network */
-      lsa.id = ipa_to_lsaid(fn->prefix);
+      lsa.id = fibnode_to_lsaid(po, fn);
       lsa.type = LSA_T_SUM_NET;
     }
   else
@@ -721,6 +772,8 @@ flush_sum_lsa(struct ospf_area *oa, struct fib_node *fn, int type)
       lsa.type = LSA_T_SUM_RT;
     }
 
+  /* FIXME check for the same network */
+
   if ((en = ospf_hash_find_header(po->gr, oa->areaid, &lsa)) != NULL)
     {
       struct ospf_lsa_sum *sum = en->lsa_body;
@@ -892,7 +945,7 @@ originate_ext_lsa(net * n, rte * e, struct proto_ospf *po,
 #endif
 
   /* FIXME proper handling of LSA IDs and check for the same network */
-  lsa.id = ipa_to_lsaid(n->n.prefix);
+  lsa.id = fibnode_to_lsaid(po, &n->n);
 
   if ((en = ospf_hash_find_header(po->gr, 0, &lsa)) != NULL)
     {
@@ -927,7 +980,7 @@ flush_ext_lsa(net *n, struct proto_ospf *po)
 	     n->n.prefix, n->n.pxlen);
 
   /* FIXME proper handling of LSA IDs and check for the same network */
-  u32 lsaid = ipa_to_lsaid(n->n.prefix);
+  u32 lsaid = fibnode_to_lsaid(po, &n->n);
 
   if (en = ospf_hash_find(po->gr, 0, lsaid, rid, LSA_T_EXT))
     {