Error handling without silence

Treat errors as first-class: don’t blanket-suppress them with try?, try!, _ = result discards, or 2>/dev/null unless you can prove the failure is expected and harmless. For unexpected failures, either propagate (throw) or explicitly log and recover in a deterministic way.

Apply this rule:

• Narrow suppression only: when falling back for backward-compatibility, suppress only specific, expected cases (e.g. keyNotFound), and throw for malformed payloads.
• Check system/OS calls: capture return codes (and log warnings if you intentionally continue). Never ignore calls that can fail silently (e.g. setsockopt, iptables/systemctl).
• Preserve failure signals in tests/cleanup: don’t use try? where failures would corrupt subsequent state; either throw or record the failure.
• Validate preconditions early: ensure required inputs exist (e.g. “exactly one DNS question”, container running) and return an appropriate error/response variant.
• Avoid crashing on bad inputs: replace fatalError with typed thrown errors.

Example (narrow fallback instead of swallowing decode errors):

do {
  ipv4Address = try container.decode(CIDRv4.self, forKey: .ipv4Address)
} catch let DecodingError.keyNotFound(key, _) where key.stringValue == CodingKeys.address.stringValue {
  ipv4Address = try container.decode(CIDRv4.self, forKey: .address) // expected legacy fallback
}
// any other decoding error should be rethrown

Example (check OS call result / log warnings):

var sendSize = Self.socketSendBufferSize
let rc = setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &sendSize, socklen_t(MemoryLayout<Int32>.size))
if rc != 0 {
  log.warning("setsockopt(SO_SNDBUF) failed with errno \(errno)")
  // either throw or continue deliberately after logging
}

This standard reduces silent misconfiguration, hidden data corruption, and hard-to-debug runtime/test failures while still allowing intentional, documented recovery paths.