1 files changed, 81 insertions, 1 deletions

diff --git a/bgpd/bgp_aspath.c b/bgpd/bgp_aspath.c
index d7e985d4..38c9caa6 100644
--- a/bgpd/bgp_aspath.c
+++ b/bgpd/bgp_aspath.c
@@ -1225,6 +1225,81 @@ aspath_prepend (struct aspath *as1, struct aspath *as2)
   /* Not reached */
 }
 
+/* Iterate over AS_PATH segments and wipe all occurences of the
+ * listed AS numbers. Hence some segments may lose some or even
+ * all data on the way, the operation is implemented as a smarter
+ * version of aspath_dup(), which allocates memory to hold the new
+ * data, not the original. The new AS path is returned.
+ */
+struct aspath *
+aspath_filter_exclude (struct aspath * source, struct aspath * exclude_list)
+{
+  struct assegment * srcseg, * exclseg, * lastseg;
+  struct aspath * newpath;
+
+  newpath = aspath_new();
+  lastseg = NULL;
+
+  for (srcseg = source->segments; srcseg; srcseg = srcseg->next)
+  {
+    unsigned i, y, newlen = 0, done = 0, skip_as;
+    struct assegment * newseg;
+
+    /* Find out, how much ASns are we going to pick from this segment.
+     * We can't perform filtering right inline, because the size of
+     * the new segment isn't known at the moment yet.
+     */
+    for (i = 0; i < srcseg->length; i++)
+    {
+      skip_as = 0;
+      for (exclseg = exclude_list->segments; exclseg && !skip_as; exclseg = exclseg->next)
+        for (y = 0; y < exclseg->length; y++)
+          if (srcseg->as[i] == exclseg->as[y])
+          {
+            skip_as = 1;
+            // There's no sense in testing the rest of exclusion list, bail out.
+            break;
+          }
+      if (!skip_as)
+        newlen++;
+    }
+    /* newlen is now the number of ASns to copy */
+    if (!newlen)
+      continue;
+
+    /* Actual copying. Allocate memory and iterate once more, performing filtering. */
+    newseg = assegment_new (srcseg->type, newlen);
+    for (i = 0; i < srcseg->length; i++)
+    {
+      skip_as = 0;
+      for (exclseg = exclude_list->segments; exclseg && !skip_as; exclseg = exclseg->next)
+        for (y = 0; y < exclseg->length; y++)
+          if (srcseg->as[i] == exclseg->as[y])
+          {
+            skip_as = 1;
+            break;
+          }
+      if (skip_as)
+        continue;
+      newseg->as[done++] = srcseg->as[i];
+    }
+    /* At his point newlen must be equal to done, and both must be positive. Append
+     * the filtered segment to the gross result. */
+    if (!lastseg)
+      newpath->segments = newseg;
+    else
+      lastseg->next = newseg;
+    lastseg = newseg;
+  }
+  aspath_str_update (newpath);
+  /* We are happy returning even an empty AS_PATH, because the administrator
+   * might expect this very behaviour. There's a mean to avoid this, if necessary,
+   * by having a match rule against certain AS_PATH regexps in the route-map index.
+   */
+  aspath_free (source);
+  return newpath;
+}
+
 /* Add specified AS to the leftmost of aspath. */
 static struct aspath *
 aspath_add_one_as (struct aspath *aspath, as_t asno, u_char type)
@@ -1741,11 +1816,16 @@ aspath_print (struct aspath *as)
 }
 
 /* Printing functions */
+/* Feed the AS_PATH to the vty; the suffix string follows it only in case
+ * AS_PATH wasn't empty.
+ */
 void
-aspath_print_vty (struct vty *vty, const char *format, struct aspath *as)
+aspath_print_vty (struct vty *vty, const char *format, struct aspath *as, const char * suffix)
 {
   assert (format);
   vty_out (vty, format, as->str);
+  if (strlen (as->str) && strlen (suffix))
+    vty_out (vty, "%s", suffix);
 }
 
 static void