std::string src; // Can be empty.
uint32_t pacing_rate; // In bytes per second. Default is ~0U (no limit).
int ttl; // Default is -1 (use operating system default).
std::string src; // Can be empty.
uint32_t pacing_rate; // In bytes per second. Default is ~0U (no limit).
int ttl; // Default is -1 (use operating system default).