Counter-Strike: Global Offensive: Reverse Engineering Valve's P2P Networking System
Overview CSGO’s lobby architecture implements a decentralized peer-to-peer topology, where clients establish direct connections to exchange game state and synchronize player actions. This design exposes the underlying ISteamNetworking interface, which leaks remote peer IPv4 addresses through the P2PSessionState_t structure. This enables trivial IP enumeration of all players in an active lobby. Architecture Analysis Steam Networking Stack CSGO leverages Valve’s proprietary Steam networking layer built atop the Source engine. The P2P system abstracts away NAT traversal through a combination of direct connections and relay servers, exposing the following critical structures via the Source SDK: ...