Show HN: Implementing ping from the Ethernet layer (ARP,IPv4,ICMP in user space)

github.com

5 points by ibuki256 11 hours ago

I built a user-space implementation of ping that constructs Ethernet frames, performs ARP resolution, builds IPv4 headers, and sends ICMP echo requests manually using AF_PACKET.

- ARP (packet format, cache with aging, re-ARP, conflict handling) - IPv4 header construction and checksum - DF handling and ICMP Fragmentation Needed (Type 3 Code 4) - IP fragment reassembly - ICMP echo request/reply parsing - A basic ping loop with loss statistics

The goal was to understand how packets actually move from Layer 2 upward.

enjoykaz - 11 hours ago

Fragment reassembly in user space is the part most toy implementations skip. Handling the DF bit and ICMP Fragmentation Needed (Type 3/4) means it actually deals with path MTU discovery scenarios. Most stop at basic echo/reply.