lib: fix incorrect comment re. ZAPI encoding

The comment was incorrectly stating that there's a byte length field
after the address, with an example "4" for IPv4.  It's a prefix length
field.  Also add it for the destination prefix.

Signed-off-by: David 'equinox' Lamparter <equinox@opensourcerouting.org>

Author: eqvinox

lib/zclient.c

@@ -3185,12 +3185,14 @@ size_t zebra_interface_link_params_write(struct stream *s,
  * :               :
  * |               |
  * +-+-+-+-+-+-+-+-+
- * |    addr_len   |  len of addr. E.g., addr_len = 4 for ipv4 addrs.
+ * |   addr_plen   |  prefixlen of addr.
  * +-+-+-+-+-+-+-+-+
- * |     daddr..   |
+ * |    daddr..    |  (zeroes if no destination/peer prefix)
  * :               :
  * |               |
  * +-+-+-+-+-+-+-+-+
+ * |   daddr_plen  |  prefixlen of daddr.
+ * +-+-+-+-+-+-+-+-+
  */
 
 static int memconstant(const void *s, int c, size_t n)