smoltcp is a standalone, event-driven TCP/IP stack that is designed for bare-metal, real-time systems. Its design goals are simplicity and robustness. Its design anti-goals include complicated compile-time computations, such as macro or type tricks, even at cost of performance degradation.
smoltcp does not need heap allocation at all, is extensively documented, and compiles on stable Rust 1.20 and later. It is used in embedded systems such as the ARTIQ core device and ionpak.
smoltcp achieves ~Gbps of throughput when tested against the Linux TCP stack in loopback mode.
The source code is available on GitHub.