A machine with Wi-Fi, a VPN and a container bridge has several addresses, and a hostname lookup can return the wrong one. Connecting a UDP socket to a destination makes the kernel pick the source address it would use, and getsockname() reads it back without a single packet being sent. Checked on Linux with three interfaces: five destinations, five answers, no IPv4 or ARP frames on the wire.
Five techniques from a polyglot codebase: rolling out golangci-lint on existing Go code, running the race detector in CI, bounding subprocess lifetimes, re-registering launchd services without the bootout race, and choosing PostgreSQL row-lock strength around foreign keys.
A machine with Wi-Fi, a VPN and a container bridge has several addresses, and a hostname lookup can return the wrong one. Connecting a UDP socket to a destination makes the kernel pick the source address it would use, and getsockname() reads it back without a single packet being sent. Checked on Linux with three interfaces: five destinations, five answers, no IPv4 or ARP frames on the wire.
Five techniques from a polyglot codebase: rolling out golangci-lint on existing Go code, running the race detector in CI, bounding subprocess lifetimes, re-registering launchd services without the bootout race, and choosing PostgreSQL row-lock strength around foreign keys.