[quagga-dev 7043] [RESEND] [PATCH] 6/7 isisd Wrong next-hops from SPF

Fritz Reichmann fritz at reichmann.nl
Thu Aug 6 20:45:48 BST 2009


From http://lists.quagga.net/pipermail/quagga-dev/2009-April/006512.html.

Author: Peter Szilagyi <peszilagyi at gmail.com>
Date:   Apr 13 13:31:14 IST 2009

    [isisd] The forwarding table was filled with wrong next-hops, and which is even worse, it was done in a totally non-deterministic way. The next-hop set for an IP prefix by isisd was the neighbor IS from which the flooded LSP about the IP prefix was arrived. So, if an IS received all the LSPs through its, say, eth0 interface, all entries in the forwarding table contained the next IS reachable via eth0 as the next-hop. The solution is to propagate the correct next-hop further from node to node as the SPF algorithm traverses the graph and selects the next node to be added to the set of already covered nodes.

Also, the construction of the tentative node list (the nodes where the shortest path is not known yet) was buggy: if a node was already a member of this list with a certain path cost, and an alternative path was found to it with a lower cost while processing a pseudo-node LSP, it was not added to the list. This way, the path selected by isisd for a certain prefix was the first one it encountered during the LSDB processing.

Index: isisd/isis_spf.c
===================================================================
--- isisd/isis_spf.c    (revision 401)
+++ isisd/isis_spf.c    (working copy)
@@ -405,12 +405,13 @@

   if (adj)
     listnode_add (vertex->Adj_N, adj);
+
 #ifdef EXTREME_DEBUG
   zlog_debug ("ISIS-Spf: add to TENT  %s %s depth %d dist %d",
              vtype2string (vertex->type), vid2string (vertex, buff),
              vertex->depth, vertex->d_N);
 #endif /* EXTREME_DEBUG */
-  listnode_add (spftree->tents, vertex);
+
   if (list_isempty (spftree->tents))
     {
       listnode_add (spftree->tents, vertex);
@@ -549,7 +550,8 @@
  */
 static int
 isis_spf_process_lsp (struct isis_spftree *spftree, struct isis_lsp *lsp,
-                     uint32_t cost, uint16_t depth, int family)
+                     uint32_t cost, uint16_t depth, int family,
+                      struct isis_adjacency *adj)
 {
   struct listnode *node, *fragnode = NULL;
   u_int16_t dist;
@@ -563,9 +565,6 @@
   struct ipv6_reachability *ip6reach;
 #endif /* HAVE_IPV6 */

-
-  if (!lsp->adj)
-    return ISIS_WARNING;
   if (lsp->tlv_data.nlpids == NULL || !speaks (lsp->tlv_data.nlpids, family))
     return ISIS_OK;

@@ -591,7 +590,7 @@
              vtype = LSP_PSEUDO_ID (is_neigh->neigh_id) ? VTYPE_PSEUDO_IS
                : VTYPE_NONPSEUDO_IS;
              process_N (spftree, vtype, (void *) is_neigh->neigh_id, dist,
-                        depth + 1, lsp->adj, family);
+                        depth + 1, adj, family);
            }
        }
       if (lsp->tlv_data.te_is_neighs)
@@ -607,7 +606,7 @@
              vtype = LSP_PSEUDO_ID (te_is_neigh->neigh_id) ? VTYPE_PSEUDO_TE_IS
                : VTYPE_NONPSEUDO_TE_IS;
              process_N (spftree, vtype, (void *) te_is_neigh->neigh_id, dist,
-                        depth + 1, lsp->adj, family);
+                        depth + 1, adj, family);
            }
        }
       if (family == AF_INET && lsp->tlv_data.ipv4_int_reachs)
@@ -621,7 +620,7 @@
              prefix.u.prefix4 = ipreach->prefix;
              prefix.prefixlen = ip_masklen (ipreach->mask);
              process_N (spftree, vtype, (void *) &prefix, dist, depth + 1,
-                        lsp->adj, family);
+                        adj, family);
            }
        }

@@ -636,7 +635,7 @@
              prefix.u.prefix4 = ipreach->prefix;
              prefix.prefixlen = ip_masklen (ipreach->mask);
              process_N (spftree, vtype, (void *) &prefix, dist, depth + 1,
-                        lsp->adj, family);
+                        adj, family);
            }
        }
       if (family == AF_INET && lsp->tlv_data.te_ipv4_reachs)
@@ -651,7 +650,7 @@
                                                   te_ipv4_reach->control);
              prefix.prefixlen = (te_ipv4_reach->control & 0x3F);
              process_N (spftree, vtype, (void *) &prefix, dist, depth + 1,
-                        lsp->adj, family);
+                        adj, family);
            }
        }
 #ifdef HAVE_IPV6
@@ -668,7 +667,7 @@
              memcpy (&prefix.u.prefix6.s6_addr, ip6reach->prefix,
                      PSIZE (ip6reach->prefix_len));
              process_N (spftree, vtype, (void *) &prefix, dist, depth + 1,
-                        lsp->adj, family);
+                        adj, family);
            }
        }
 #endif /* HAVE_IPV6 */
@@ -691,7 +690,8 @@
 static int
 isis_spf_process_pseudo_lsp (struct isis_spftree *spftree,
                             struct isis_lsp *lsp, uint16_t cost,
-                            uint16_t depth, int family)
+                            uint16_t depth, int family,
+                             struct isis_adjacency *adj)
 {
   struct listnode *node, *fragnode = NULL;
   struct is_neigh *is_neigh;
@@ -715,13 +715,13 @@
        /* Two way connectivity */
        if (!memcmp (is_neigh->neigh_id, isis->sysid, ISIS_SYS_ID_LEN))
          continue;
-       if (isis_find_vertex
-           (spftree->tents, (void *) is_neigh->neigh_id, vtype) == NULL
+       if ((depth > 0 || isis_find_vertex
+             (spftree->tents, (void *) is_neigh->neigh_id, vtype) == NULL)
            && isis_find_vertex (spftree->paths, (void *) is_neigh->neigh_id,
                               vtype) == NULL)
          {
            /* C.2.5 i) */
-           isis_spf_add2tent (spftree, vtype, is_neigh->neigh_id, lsp->adj,
+           isis_spf_add2tent (spftree, vtype, is_neigh->neigh_id, adj,
                             cost, depth, family);
          }
       }
@@ -733,13 +733,13 @@
        /* Two way connectivity */
        if (!memcmp (te_is_neigh->neigh_id, isis->sysid, ISIS_SYS_ID_LEN))
          continue;
-       if (isis_find_vertex
-           (spftree->tents, (void *) te_is_neigh->neigh_id, vtype) == NULL
+       if ((depth > 0 || isis_find_vertex
+             (spftree->tents, (void *) te_is_neigh->neigh_id, vtype) == NULL)
            && isis_find_vertex (spftree->paths, (void *) te_is_neigh->neigh_id,
                                 vtype) == NULL)
          {
            /* C.2.5 i) */
-           isis_spf_add2tent (spftree, vtype, te_is_neigh->neigh_id, lsp->adj,
+           isis_spf_add2tent (spftree, vtype, te_is_neigh->neigh_id, adj,
                               cost, depth, family);
          }
       }
@@ -860,9 +860,6 @@
                  lsp = lsp_search (lsp_id, area->lspdb[level - 1]);
                  if (!lsp)
                    zlog_warn ("No lsp found for IS adjacency");
-                 /*          else {
-                    isis_spf_process_lsp (spftree, lsp, vertex->d_N, 1, family);
-                    } */
                  break;
                case ISIS_SYSTYPE_UNKNOWN:
                default:
@@ -885,14 +882,14 @@
            {
              zlog_warn ("ISIS-Spf: No adjacency found for DR");
            }
-         if (lsp == NULL || lsp->lsp_header->rem_lifetime == 0)
+         else if (lsp == NULL || lsp->lsp_header->rem_lifetime == 0)
            {
              zlog_warn ("ISIS-Spf: No lsp found for DR");
            }
          else
            {
              isis_spf_process_pseudo_lsp (spftree, lsp,
-                                 circuit->te_metric[level - 1], 0, family);
+                                           circuit->te_metric[level - 1], 0, family, adj);

            }
        }
@@ -982,6 +979,7 @@
   struct isis_spftree *spftree = NULL;
   u_char lsp_id[ISIS_SYS_ID_LEN + 2];
   struct isis_lsp *lsp;
+  struct isis_adjacency *adj = NULL;
   struct route_table *table = NULL;
   struct route_node *rode;
   struct isis_route_info *rinfo;
@@ -1042,6 +1040,11 @@
       if (vertex->type == VTYPE_PSEUDO_IS ||
          vertex->type == VTYPE_NONPSEUDO_IS)
        {
+          if (listcount(vertex->Adj_N) == 0) {
+            continue;
+          }
+          adj = listgetdata(vertex->Adj_N->head);
+
          memcpy (lsp_id, vertex->N.id, ISIS_SYS_ID_LEN + 1);
          LSP_FRAGMENT (lsp_id) = 0;
          lsp = lsp_search (lsp_id, area->lspdb[level - 1]);
@@ -1050,13 +1053,13 @@
              if (LSP_PSEUDO_ID (lsp_id))
                {
                  isis_spf_process_pseudo_lsp (spftree, lsp, vertex->d_N,
-                                              vertex->depth, family);
+                                              vertex->depth, family, adj);

                }
              else
                {
                  isis_spf_process_lsp (spftree, lsp, vertex->d_N,
-                                       vertex->depth, family);
+                                       vertex->depth, family, adj);
                }
            }
          else
Index: isisd/isis_pdu.c
===================================================================
--- isisd/isis_pdu.c    (revision 401)
+++ isisd/isis_pdu.c    (working copy)
@@ -1222,7 +1222,6 @@
                                     ntohs (hdr->pdu_len), lsp0,
                                     circuit->area);
          lsp->level = level;
-         lsp->adj = adj;
          lsp_insert (lsp, circuit->area->lspdb[level - 1]);
          /* ii */
          ISIS_FLAGS_SET_ALL (lsp->SRMflags);
@@ -1254,8 +1253,7 @@
          ISIS_CLEAR_FLAG (lsp->SSNflags, circuit);
        }
     }
-  if (lsp)
-    lsp->adj = adj;
+
   return retval;
 }

Index: isisd/isis_lsp.h
===================================================================
--- isisd/isis_lsp.h    (revision 401)
+++ isisd/isis_lsp.h    (working copy)
@@ -58,7 +58,6 @@
 #endif
   /* used for 60 second counting when rem_lifetime is zero */
   int age_out;
-  struct isis_adjacency *adj;
   /* FIXME: For now only topology LSP's use this. Is it helpful for others? */
   struct isis_area *area;
   struct tlvs tlv_data;                /* Simplifies TLV access */



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