[openssl-users] Help to understand WPACKET API

[Ananthaneni Saitejachowdary]

Hi,
I am trying to tweak openssl-master client to test a tls1.3 enabled server.

I want to club the client certificate, client key exchange , change cipher spec and certificate verify into single handshake message.( So that the record shows up as multiple handshake messages).

OpenSSL Version : OpenSSL 1.1.1-dev  xx XXX xxxx.

After going through the code I understand the new tls1.3 implemented OpenSSL code is using WPACKET API to frame the records. I need help in understanding what the following functions do. I am new to the mailing list, thanks in advance.

WPACKET_start_sub_packet_
WPACKET_allocate_bytes
WPACKET_sub_allocate_bytes__
WPACKET_reserve_bytes
WPACKET_start_sub_packet_len__
WPACKET_sub_memcpy__

Basically what does the word _sub_ mean in these functions and how do that differ from the non sub function say
Difference between WPACKET_sub_memcpy__ and WPACKET_memcpy__

Please feel free to reply if something is not understandable.

Thanks
Sate.

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