Same vendor-specific-option has been attached multiple times under option 17 if always-send flag is set true.

name: Bug report
about: Setting "always-send" flag to true results in multiple instances of vendor-specific-option attached. 
       Further, these instances keep on incrementing within subsequent frames.

Environment Specification

OS:     CentOS 7 Virtual Machine
Server: kea-server-1.8 hosted over CentOS 8 Container
Client: isc-dhclient-4.3.6 configured over CentOS 8 Container

Problem Description

I'm configuring dhcpv6 server with kea 1.8 stable version. I want to encapsulate vendor-specific information within option 17. I faced certain issues and came across a workaround which had success with some undesirable behaviour.

1. Option defined under vendor option space (Eg vendor-12345) is not being sent automatically as part of option 17.
2. Forcing these options resulted in attaching and incrementing that vendor-specific-option within subsequent frames.

Wireshark feeds

• Here, I have provided the snippet of Wireshark capture. The complete capture can be found in attachments.

Frame 4: 186 bytes on wire (1488 bits), 186 bytes captured (1488 bits)
Ethernet II, Src: 02:42:ac:12:00:02 (02:42:ac:12:00:02), Dst: 02:42:ac:12:00:03 (02:42:ac:12:00:03)
Internet Protocol Version 6, Src: fe80::42:acff:fe12:2, Dst: fe80::42:acff:fe12:3
User Datagram Protocol, Src Port: 547, Dst Port: 546
DHCPv6
    Message type: Advertise (2)
    Transaction ID: 0x01e550
    Vendor-specific Information
        Option: Vendor-specific Information (17)
        Length: 20
        Value: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
        Enterprise ID: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
        option
            Option code: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
            Option length: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
            Option data: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Frame 14: 202 bytes on wire (1616 bits), 202 bytes captured (1616 bits)
Ethernet II, Src: 02:42:ac:12:00:02 (02:42:ac:12:00:02), Dst: 02:42:ac:12:00:03 (02:42:ac:12:00:03)
Internet Protocol Version 6, Src: fe80::42:acff:fe12:2, Dst: fe80::42:acff:fe12:3
User Datagram Protocol, Src Port: 547, Dst Port: 546
DHCPv6
    Message type: Advertise (2)
    Transaction ID: 0x613d68
    Vendor-specific Information
        Option: Vendor-specific Information (17)
        Length: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
        Value: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
        Enterprise ID: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
        option
            Option code: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
            Option length: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
            Option data: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
        option
            Option code: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
            Option length: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
            Option data: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
        option
            Option code: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
            Option length: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
            Option data: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Configurations & logs

dhclient.conf

file-v2.pcap

kea-dhcp6.conf

Help required

• Filing this scenario as a bug since I could not find any documentation to resolve this issue or meet my requirements.
• I have attached the configuration files. Please verify the same; whether, I have wrongly configured any option or missing out any option, that has to be handled within the conf file.

PS: Testing env has been set up over container network. Logs/ Pcaps has been attached for the same.