lwip.sys is the TCP/IP stack provider driver. It owns lwIP, tcpip_thread, netif attach, DNS, TCP, UDP, and the provider-side socket implementation.

The core kernel owns only:

NET_DEVICE registration and Ethernet frame transport
NET_STACK_PROVIDER registration
process-owned socket handles
syscall/user-memory boundaries

Build notes:

Do not use lwIP CMake.
build.bat compiles the sources listed in drivers/lwip/lwip_sources.txt.
Include directories:
- code/drivers/lwip/include
- code/third_party/lwip/src/include

Load order:

drivers.ini should load lwip.sys before NIC drivers so the provider is ready when the NIC registers. The kernel also supports provider-after-device registration, but provider-first keeps boot logs cleaner.