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Investigation · Part 8 of 10 · Following a TCP connection
How a Name Becomes an Address: What getaddrinfo Really Does
Connecting to localhost took 77 microseconds and connecting to 127.0.0.1 took 12, to the same server. I followed getaddrinfo with strace: four sources tried in order, files read on every call, answers sorted with IPv6 first, and a lookup that blocks the thread.