Added as_path_get_first().

2 files changed, 29 insertions, 0 deletions

diff --git a/nest/a-path.c b/nest/a-path.c
index 0ea3e7b2..0c467551 100644
--- a/nest/a-path.c
+++ b/nest/a-path.c
@@ -103,6 +103,34 @@ as_path_getlen(struct adata *path)
   return res;
 }
 
+int
+as_path_get_first(struct adata *path)
+{
+  int res = -1;
+  u8 *p = path->data;
+  u8 *q = p+path->length;
+  int len;
+
+  while (p<q)
+    {
+      switch (*p++)
+	{
+	case AS_PATH_SET:
+	  if (len = *p++)
+	    res = get_u16(p);
+	  p += 2*len;
+	  break;
+	case AS_PATH_SEQUENCE:
+	  if (len = *p++)
+	    res = get_u16(p+2*(len-1));
+	  p += 2*len;
+	  break;
+	default: bug("as_path_get_first: Invalid path segment");
+	}
+    }
+  return res;
+}
+
 #define MASK_PLUS do { mask = mask->next; if (!mask) return next == q; \
 		       asterisk = (mask->val == PM_ANY); \
                        if (asterisk) { mask = mask->next; if (!mask) { return 1; } } \
diff --git a/nest/attrs.h b/nest/attrs.h
index 2618fa35..abd6b9e9 100644
--- a/nest/attrs.h
+++ b/nest/attrs.h
@@ -17,6 +17,7 @@
 struct adata *as_path_prepend(struct linpool *pool, struct adata *olda, int as);
 void as_path_format(struct adata *path, byte *buf, unsigned int size);
 int as_path_getlen(struct adata *path);
+int as_path_get_first(struct adata *path);
 
 struct f_path_mask {
   struct f_path_mask *next;