If you want an FPGA tied to a SolarFlare NIC, that's been available for years as a finished product under the name "Application Onload Engine". News article:
Yes, but the Solarflare ApplicationOnload Engine has several issues (e.g. limited Altera FPGA, inflexible architecture, logic on a separate ASIC that must communicate with the FPGA, and still uses a host CPU for the networking stack), which should be resolved by fully integrating with the Xilinx Ultrascale+ technology and putting all networking and decision logic on one chip. The result should be a much faster, much more flexible, and much more powerful solution.
https://www.theregister.co.uk/2012/02/08/solarflare_applicat...
Whitepapers:
* https://solarflare.com/wp-content/uploads/2018/11/SF-114649-...
* https://solarflare.com/wp-content/uploads/2018/11/SF-114903-...