Dear HAProxy-maintainers, As proposed by my colleague Christian Menges in [1], I’ve implemented support for fetching arbitrary TLV values for PROXY protocol V2 via a sample fetch. It can be used by calling ‘fc_pp_tlv’ with the numerical value of the desired TLV type. This also fixes issue [2].
Some design considerations for my approach: • *Do not break the existing API*: Keep methods for authority and unique ID, but refactor them internally with the updated, generified logic. • *Keep existing behavior and performance*: Pools for authority and unique ID are still used. Already implemented parsing logic is still applied. All information about a TLV payload that is already should be used for validation. • *Small memory footprint*: As there might be up to 50k connections, an array or hash map is too memory intensive. Therefore, a simple list is used. It is the best choice here in my opinion, as there are typically only a handful of TLVs. Additionally, memory pooling is used where possible. When TLV values become too large there is a fallback to ‘malloc’. Note that I choose to not overwrite existing TLVs in the list. This way, we return always the first found but would allow duplicate entries. This would be relevant when there are duplicate TLVs. Besides, I used ‘strtoul’ for the argument conversion to be consistent with other fetches that already use ‘strtoul’. If ‘strtoul’ is too slow for this use case, I am not opposed to reverting it to the more efficient HAProxy helper. *Important*: I will add the documentation after the code review, when the design is finalized. This email address is not subscribed to the list, please CC it when replying. Anyway, I would love to hear your feedback on this! Best Regards, Alexander Stephan SAP SE Germany PS: This is only the front-end part of my implementation, I will follow up with a backend implementation that allows to send user defined TLVs. I already implemented it, since SAP needs it any case. However, we are also very interested in contributing it. [1]: https://www.mail-archive.com/haproxy@formilux.org/msg43381.html [2]: https://github.com/haproxy/haproxy/issues/1947
0001-MEDIUM-sample-Implement-sample-fetch-for-arbitrary-P.patch
Description: 0001-MEDIUM-sample-Implement-sample-fetch-for-arbitrary-P.patch
