Understanding ICMP: How to Send and Receive ICMP Messages in Go

The term "ping" is commonly used in gaming to measure the round-trip time it takes for a packet to travel from a device to a game server and back, which is a key component of network latency. Ping relies on the Internet Control Message Protocol (ICMP), a protocol used for network diagnostics and error reporting. ICMP messages are used to test connectivity and trace the route of packets across a network, and can indicate unreachable destinations, packet loss, or excessive delays. ICMP packets have a specific structure, which includes a type field that specifies the message type, a code field that provides additional information, a checksum field used for error-checking, an identifier field that helps match requests with replies, a sequence number field that tracks the order of packets, and a data field that contains the payload. The article demonstrates how to send and receive ICMP messages using the Go programming language, specifically the Echo and Echo Reply messages, which have types 8 and 0 respectively. The Go icmp package provides structs for ICMP messages, allowing developers to avoid crafting the packets manually. To use the code, you must start the Docker containers, which include a client and server application. The client application sends ICMP Echo requests to the server, which responds with ICMP Echo replies. The client determines the latency by calculating the elapsed time between the echo and the echo reply. The implementation details of the code are provided, including the functions to send Echo requests to a server and to receive those ICMP requests and send them back to the sender. The code uses the Go icmp package to parse and marshal ICMP messages, and to calculate the elapsed time between the echo and the echo reply. The article also notes that ICMP can be exploited for network attacks, such as ICMP flood or smurf attacks, leading to its restriction or filtering in certain environments. However, when used correctly, ICMP remains a vital tool for understanding and maintaining network health.