What is the exact meaning of "On Commit" in ISC DHCP server configuration?

Elon20

10/16/22, 1:28 AM

I know there are three kinds of events we can use for scripting in ISC dhcpd -- commit, expire and lease. My problem is, I am having a little problem in understanding the "commit" event. I know "commit" event means when the server has made a commitment of a certain lease to a client. But it would be easier to understand this in DORA context.

That means, when the "commit" event will trigger in ISC DHCP server? Is it when the dhcpd is ready to offer a lease to a client? or after it has leased IP to a client?

For example, in the following configuration -

on commit {
    set ClientIP = binary-to-ascii(10, 8, ".", leased-address);
    set ClientMac = binary-to-ascii(16, 8, ":", substring(hardware, 1, 6));
    execute("/usr/sbin/test.py", "commit", ClientIP, ClientMac);
}

when exactly will the test.py script will execute? Before the DHCP ACK packet exits from DHCP server or after DHCP OFFER packet exits from DHCP server?

Thanks in advance. Cheers :)

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anx

10/16/22, 2:44 AM

Looks like `execute_statements(on_commit)` precedes `send_packet*` in `server/dhcp*.c`. You can probably prove it works the way you want by prefixing your test command with a `sleep()` and noting the delay on sending the packet.

Elon20

10/16/22, 7:46 PM

Thanks for your comment @anx. I downloaded the dhcp-4.4.2b1, but couldn't find " _execute_statements(on_commit)_" or " _send_packet*_" string in **server/dhcp.c** or **server/dhcpd.c** . Can you mention which c file you are referring to in the server directory?

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: What is the exact meaning of "On Commit" in ISC DHCP server configuration?

TH: ความหมายที่แท้จริงของ "On Commit" ในการกำหนดค่าเซิร์ฟเวอร์ ISC DHCP คืออะไร

RO: Care este semnificația exactă a „On Commit” în configurația serverului ISC DHCP?

RU: Каково точное значение «On Commit» в конфигурации DHCP-сервера ISC?

VI: Ý nghĩa chính xác của "Đang cam kết" trong cấu hình máy chủ ISC DHCP là gì?

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