ospfd: fix regression in recent commit

commit '717750433839762d23a5f8d88fe0b4d57c8d490a' causes SEGV error,
when 'oi = ospf_if_lookup_recv_if (ospf, iph->ip_src, ifp);' returns
NULL.

* ospf_packet.c
  * ospf_read(): change a place of calling 'ospf_verify_header()'

1 files changed, 15 insertions, 10 deletions

diff --git a/ospfd/ospf_packet.c b/ospfd/ospf_packet.c
index 489b928c..c347f31d 100644
--- a/ospfd/ospf_packet.c
+++ b/ospfd/ospf_packet.c
@@ -2392,16 +2392,10 @@ ospf_read (struct thread *thread)
   /* associate packet with ospf interface */
   oi = ospf_if_lookup_recv_if (ospf, iph->ip_src, ifp);
 
-  /* Verify header fields before any further processing. */
-  ret = ospf_verify_header (ibuf, oi, iph, ospfh);
-  if (ret < 0)
-  {
-    if (IS_DEBUG_OSPF_PACKET (0, RECV))
-      zlog_debug ("ospf_read[%s]: Header check failed, "
-                  "dropping.",
-                  inet_ntoa (iph->ip_src));
-    return ret;
-  }
+  /* ospf_verify_header() relies on a valid "oi" and thus can be called only
+     after the passive/backbone/other checks below are passed. These checks
+     in turn access the fields of unverified "ospfh" structure for their own
+     purposes and must remain very accurate in doing this. */
 
   /* If incoming interface is passive one, ignore it. */
   if (oi && OSPF_IF_PASSIVE_STATUS (oi) == OSPF_IF_PASSIVE)
@@ -2493,6 +2487,17 @@ ospf_read (struct thread *thread)
       return 0;
     }
 
+  /* Verify more OSPF header fields. */
+  ret = ospf_verify_header (ibuf, oi, iph, ospfh);
+  if (ret < 0)
+  {
+    if (IS_DEBUG_OSPF_PACKET (0, RECV))
+      zlog_debug ("ospf_read[%s]: Header check failed, "
+                  "dropping.",
+                  inet_ntoa (iph->ip_src));
+    return ret;
+  }
+
   /* Show debug receiving packet. */
   if (IS_DEBUG_OSPF_PACKET (ospfh->type - 1, RECV))
     {