struct timeval udp_reply_sent; /* Last time a (gratuitous) UDP probe reply was sent */
struct timeval udp_ping_sent; /* Last time a UDP probe was sent */
+ int udp_ping_rtt; /* Round trip time of UDP ping (in microseconds; or -1 if !status.udp_confirmed) */
timeout_t udp_ping_timeout; /* Ping timeout event */
struct timeval mtu_ping_sent; /* Last time a MTU probe was sent */