Why sending the message length(4 Byte) in a separate message when using TCP connection to send Kerberos packet

[Greg Hudson]

On 08/30/2016 10:40 PM, Sherry Yanmeng Tang (yanmtang) wrote:
> When kerberos are working on the tcp connection, it always send the message length of kerberos in one tcp message, and then send the following kerberos packet in another one or more messages.
> I wonder why not send the message length of the kerberos together with the real message body. Eg, even the packet is only 287 Bytes(tcp payload length), we need to send the 4 Bytes first, then send 283 Bytes.

We do send the length and message together, using
writev()(sendto_kdc.c:1099).  The code you pointed to at line 652 is
just setting up the iovs for a later call to writev().