Welcome to GTP-Guard
GTP-Guard is a routing daemon written in C that implements the GTP protocol (GPRS Tunneling Protocol), the tunneling layer that carries user traffic across mobile core networks. It covers pGW functions for 4G and UPF functions for 5G, acting as the border element between the mobile core and the external IP network.
Three internal frameworks handle the main forwarding roles. The Proxy framework intercepts and tweaks data-plane traffic in flight. The Routing framework manages encapsulation, interconnection, and layer-3 forwarding between network segments. The Firewall framework filters, rewrites, and redirects packets according to policy.
The data-plane runs through the Linux XDP framework via eBPF programs, which process packets directly in the driver interrupt handler before they reach the kernel network stack. Configuration and monitoring use a standard VTY terminal interface.
GTP-Guard is free software distributed under the GNU Affero General Public License v3.
Last Updates
- April 2026 - Per-Core CPU Load Measurement
- Standard
/procinterfaces miss inline NAPI softirq work that XDP runs outside the scheduler. This article explains whyPERF_COUNT_HW_REF_CPU_CYCLESwas selected as the load metric, and describes the two measurement modes (TSC and calibrated) exposed bylib/cpu.c. - March 2026 - 5G UPF: Pump Up the Volume!
- Hardware selection, system tuning, and TEID-based flow steering with range partitioning to route each UE session to a dedicated core. The design targets ~800 Gbps on a single 1RU commodity server using ConnectX-7 NICs and XDP.