wolfIP

Description and project goals

wolfIP is a TCP/IP stack with no dynamic memory allocations, designed to be used in resource-constrained embedded systems.

Endpoint only mode is supported, which means that wolfip can be used to establish network connections but it does not route traffic between different network interfaces.

A single network interface can be associated with the device.

Features supported

• ARP (RFC 826)
• IPv4 (RFC 791)
• ICMP (RFC 792): only ping replies
• DHCP (RFC 2131): client only
• DNS (RFC 1035): client only
• UDP (RFC 768): unicast only
• TCP (RFC 793)
  • TCP options supported: Timestamps, Maximum Segment Size
• BSD-like, non blocking socket API, with custom callbacks
• No dynamic memory allocation
  • Fixed number of concurrent sockets
  • Pre-allocated buffers for packet processing in static memory

Functional tests with LD_PRELOAD

The POSIX shim builds libwolfip.so, which can be injected in front of host tools so that calls to socket(2) and friends are redirected to the wolfIP stack and the TAP device (wtcp0). After running make:

sudo LD_PRELOAD=$PWD/libwolfip.so nc 10.10.10.2 80

The example above mirrors the existing nc-driven demos: any TCP sockets opened by the intercepted process are serviced by wolfIP instead of the host kernel.

Ping over the TAP device

ICMP datagram sockets can be validated the same way. With the TAP interface created automatically by the shim and the host endpoint configured in config.h (HOST_STACK_IP defaults to 10.10.10.1), run:

sudo LD_PRELOAD=$PWD/libwolfip.so ping -I wtcp0 -c5 10.10.10.1

The -I wtcp0 flag pins the test to the injected interface and -c5 generates five echo requests. Successful replies confirm the ICMP datagram socket support end-to-end through the tap device.

Copyright and License

wolfIP is licensed under the GPLv3 license. See the LICENSE file for details. Copyright (c) 2025 wolfSSL Inc.