XDP (eXpress Data Path)

XDP (eXpress Data Path) is a high-performance data path framework within the Linux kernel that enables programmable packet processing at the earliest possible point—directly within the network driver. By executing lightweight eBPF (extended Berkeley Packet Filter) programs before packets enter the main kernel networking stack, XDP bypasses significant processing overhead, allowing for operations like dropping, forwarding, or modifying packets at near line-rate speeds. This makes it an exceptionally powerful technology for building high-speed network functions such as DDoS mitigation systems, efficient load balancers, and advanced firewalls, where processing millions of packets per second is critical.

1. Introduction to High-Performance Networking
   1. Network Performance Challenges
      1. Traditional Networking Limitations
      2. Scalability Requirements
      3. Latency Sensitivity
   2. Linux Kernel Networking Stack
      1. OSI Model in Linux Context
      2. Traditional Packet Processing Path
         1. Network Interface Card Reception
         2. Interrupt Handling
         3. Packet Buffer Allocation
         4. Protocol Stack Traversal
         5. Userspace Delivery
      3. Performance Bottlenecks
         1. Context Switch Overhead
         2. Memory Copy Operations
         3. Lock Contention
         4. Interrupt Processing Delays
         5. Packet Drop Scenarios
   3. Alternative High-Performance Approaches
      1. Kernel Bypass Techniques
         1. DPDK Overview
         2. Netmap Overview
         3. PF_RING Overview
      2. Programmable Data Planes
         1. Software-Defined Networking Context
         2. In-kernel Programmability
         3. eBPF Introduction