func (fs FS) NetTCP() (NetTCP, error) {
	return newNetTCP(fs.proc.Path("net/tcp"))
}
NetTCP returns the IPv4 kernel/networking statistics for TCP datagrams
read from /proc/net/tcp.
package procfs
type (
	NetTCP []*netIPSocketLine
	NetTCPSummary NetIPSocketSummary
)