Implement as path prepends. At least one prepend is needed for ebgp

neighbors. Fix a bug in the update generation. If no path attributes are
available e.g. a packet with only withdraws we need to set (and write) the
bgp path attribute field to zero. With this change we are able to send
valid updates to our neighbors with one exception: the nexthop field which
needs to be changed for ebgp neighbors.
OK henning@

1 files changed, 77 insertions, 1 deletions

diff --git a/usr.sbin/bgpd/rde_rib.c b/usr.sbin/bgpd/rde_rib.c
index 097d18e02e6..f4712ffef3b 100644
--- a/usr.sbin/bgpd/rde_rib.c
+++ b/usr.sbin/bgpd/rde_rib.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rde_rib.c,v 1.15 2004/01/10 16:20:29 claudio Exp $ */
+/*	$OpenBSD: rde_rib.c,v 1.16 2004/01/10 22:25:42 claudio Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Claudio Jeker <claudio@openbsd.org>
@@ -297,6 +297,82 @@ aspath_create(void *data, u_int16_t len)
 	return aspath;
 }
 
+int
+aspath_write(void *p, u_int16_t len, struct aspath *aspath, u_int16_t myAS,
+    int prepend)
+{
+	u_char		*b = p;
+	int		 tot_len, as_len, size, wpos = 0;
+	u_int16_t	 tmp;
+	u_int8_t	 type, attr_flag = ATTR_WELL_KNOWN;
+
+	if (prepend > 255)
+		/* lunatic prepends need to be blocked in the parser */
+		return (-1);
+
+	/* first calculate new size */
+	type = aspath->data[0];
+	size = aspath->data[1];
+	if (prepend == 0)
+		as_len = aspath->hdr.len;
+	else if (type == AS_SET || size + prepend > 255)
+		/* need to attach a new AS_SEQUENCE */
+		as_len = 2 + prepend * 2 + aspath->hdr.len;
+	else
+		as_len = prepend * 2 + aspath->hdr.len;
+
+	/* check buffer size */
+	tot_len = 2 + as_len;
+	if (as_len > 255) {
+		attr_flag |= ATTR_EXTLEN;
+		tot_len += 2;
+	} else
+		tot_len += 1;
+
+	if (tot_len > len)
+		return (-1);
+
+	/* header */
+	b[wpos++] = attr_flag;
+	b[wpos++] = ATTR_ASPATH;
+	if (as_len > 0xff) {
+		tmp = as_len;
+		tmp = htons(tmp);
+		memcpy(b, &tmp, 2);
+		wpos += 2;
+	} else
+		b[wpos++] = (u_char)(as_len & 0xff);
+
+	/* first prepends */
+	myAS = htons(myAS);
+	if (type == AS_SET) {
+		b[wpos++] = AS_SEQUENCE;
+		b[wpos++] = prepend;
+		for (; prepend > 0; prepend--) {
+			memcpy(b + wpos, &myAS, 2);
+			wpos += 2;
+		}
+		memcpy(b + wpos, aspath->data, aspath->hdr.len);
+	} else {
+		if (size + prepend > 255) {
+			b[wpos++] = AS_SEQUENCE;
+			b[wpos++] = size + prepend - 255;
+			for (; prepend + size > 255; prepend--) {
+				memcpy(b + wpos, &myAS, 2);
+				wpos += 2;
+			}
+		}
+		b[wpos++] = AS_SEQUENCE;
+		b[wpos++] = size + prepend;
+		for (; prepend > 0; prepend--) {
+			memcpy(b + wpos, &myAS, 2);
+			wpos += 2;
+		}
+		memcpy(b + wpos, aspath->data + 2, aspath->hdr.len - 2);
+	}
+	return (tot_len);
+}
+
 void
 aspath_destroy(struct aspath *aspath)
 {