MRT: Fix IPv6 table dumps

Add fake MP_REACH_NLRI attribute with BGP next hop when encoding MRT
table dumps for IPv6 routes. That is necessary to encode next hop as
NEXT_HOP attribute is not used for MP-BGP.

Thanks to Santiago Aggio for the bugreport.

2 files changed, 32 insertions, 0 deletions

diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c
index b2c37301..6752cb7f 100644
--- a/proto/bgp/attrs.c
+++ b/proto/bgp/attrs.c
@@ -683,6 +683,37 @@ bgp_format_cluster_list(const eattr *a, byte *buf, uint size)
 }
 
 
+int
+bgp_encode_mp_reach_mrt(struct bgp_write_state *s UNUSED, eattr *a, byte *buf, uint size)
+{
+  /*
+   *	Limited version of MP_REACH_NLRI used for MRT table dumps (IPv6 only):
+   *
+   *	3 B	MP_REACH_NLRI header
+   *	1 B	MP_REACH_NLRI data - Length of Next Hop Network Address
+   *	var	MP_REACH_NLRI data - Network Address of Next Hop
+   */
+
+  ip_addr *nh = (void *) a->u.ptr->data;
+  uint len = a->u.ptr->length;
+
+  ASSERT((len == 16) || (len == 32));
+
+  if (size < (3+1+len))
+    return -1;
+
+  bgp_put_attr_hdr3(buf, BA_MP_REACH_NLRI, BAF_OPTIONAL, 1+len);
+  buf[3] = len;
+  buf += 4;
+
+  put_ip6(buf, ipa_to_ip6(nh[0]));
+
+  if (len == 32)
+    put_ip6(buf+16, ipa_to_ip6(nh[1]));
+
+  return 3+1+len;
+}
+
 static inline u32
 get_af3(byte *buf)
 {
diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index 5cabd327..dd7dc28f 100644
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -559,6 +559,7 @@ static inline void
 bgp_unset_attr(ea_list **to, struct linpool *pool, uint code)
 { eattr *e = bgp_set_attr(to, pool, code, 0, 0); e->type = EAF_TYPE_UNDEF; }
 
+int bgp_encode_mp_reach_mrt(struct bgp_write_state *s, eattr *a, byte *buf, uint size);
 
 int bgp_encode_attrs(struct bgp_write_state *s, ea_list *attrs, byte *buf, byte *end);
 ea_list * bgp_decode_attrs(struct bgp_parse_state *s, byte *data, uint len);