add ntp request size option

RIPE-NCC / ripe-atlas-probe-measurements

RIPE Atlas probe measurement source code

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add ntp request size option #6

Closed ddrown closed 2 years ago

ddrown commented 2 years ago

Some providers are now filtering ntp traffic on size in response to ddos attacks. This provides a way to test those filters in order to make decisions about NTPv5 and NTS protocol design.

PhilipHomburg commented 2 years ago

One comment, is it possible to avoid using a code point from the experimental range? In my opinion it is not nice to use those code point for production traffic. Maybe there is some existing field that can be send safely?

Otherwise it looks good.

ddrown commented 2 years ago

Switched to autokey's no-op request from RFC5906

how popular servers respond:

chrony 4.1 = accepts and ignores (48 byte response)
ntpsec 1.2.1 = drops request (looks like extens_server_recv drops every non-NTS extension)
ntpd 4.2.8p15 = accepts and responds with "key id" (52 byte response)

michel-stam commented 2 years ago

Hi Daniel,

I've pulled in your change for the next release. I've made 2 small changes, one being a cast to prevent a compiler warning, the other to use #defines to indicate the message type rather than hardcoded values.

Regards,

Michel

michel-stam commented 2 years ago

Did a quick test:

Cisco 2901 responds with a total IP packet size of up to 500 bytes. This for me meant -s 452
Like wise for the Cisco Catalyst 3750X Cheers,

Michel