1 files changed, 148 insertions, 0 deletions
diff --git a/extendedstats/windows.go b/extendedstats/windows.go
new file mode 100644
index 0000000..cc2fca7
--- /dev/null
+++ b/extendedstats/windows.go
@@ -0,0 +1,148 @@
+//go:build windows
+// +build windows
+
+package extendedstats
+
+import (
+	"crypto/tls"
+	"fmt"
+	"net"
+	"unsafe"
+
+	"github.com/network-quality/goresponsiveness/utilities"
+	"golang.org/x/sys/windows"
+)
+
+type ExtendedStats struct {
+	MaxMss                  uint64
+	TotalBytesSent          uint64
+	TotalBytesReceived      uint64
+	TotalBytesReordered     uint64
+	TotalBytesRetransmitted uint64
+
+	RetransmitRatio  float64
+	AverageRtt       float64
+	rtt_measurements uint64
+	total_rtt        float64
+}
+
+type TCPINFO_BASE struct {
+	State             uint32
+	Mss               uint32
+	ConnectionTimeMs  uint64
+	TimestampsEnabled bool
+	RttUs             uint32
+	MinRttUs          uint32
+	BytesInFlight     uint32
+	Cwnd              uint32
+	SndWnd            uint32
+	RcvWnd            uint32
+	RcvBuf            uint32
+	BytesOut          uint64
+	BytesIn           uint64
+	BytesReordered    uint32
+	BytesRetrans      uint32
+	FastRetrans       uint32
+	DupAcksIn         uint32
+	TimeoutEpisodes   uint32
+	SynRetrans        byte // UCHAR
+}
+
+// https://github.com/tpn/winsdk-10/blob/9b69fd26ac0c7d0b83d378dba01080e93349c2ed/Include/10.0.16299.0/shared/mstcpip.h#L289
+type TCPINFO_V0 struct {
+	TCPINFO_BASE
+}
+
+// https://docs.microsoft.com/en-us/windows/win32/api/mstcpip/ns-mstcpip-tcp_info_v1
+type TCPINFO_V1 struct {
+	TCPINFO_BASE
+	SndLimTransRwin uint32
+	SndLimTimeRwin  uint32
+	SndLimBytesRwin uint64
+	SndLimTransCwnd uint32
+	SndLimTimeCwnd  uint32
+	SndLimBytesCwnd uint64
+	SndLimTransSnd  uint32
+	SndLimTimeSnd   uint32
+	SndLimBytesSnd  uint64
+}
+
+func (es *ExtendedStats) IncorporateConnectionStats(rawConn net.Conn) error {
+	tlsConn, ok := rawConn.(*tls.Conn)
+	if !ok {
+		return fmt.Errorf("OOPS: Could not get the TCP info for the connection (not a TLS connection)")
+	}
+	tcpConn, ok := tlsConn.NetConn().(*net.TCPConn)
+	if !ok {
+		return fmt.Errorf("OOPS: Could not get the TCP info for the connection (not a TCP connection)")
+	}
+	if info, err := getTCPInfo(tcpConn); err != nil {
+		return fmt.Errorf("OOPS: Could not get the TCP info for the connection: %v", err)
+	} else {
+		es.MaxMss = utilities.Max(es.MaxMss, uint64(info.Mss))
+		es.TotalBytesReordered += uint64(info.BytesReordered)
+		es.TotalBytesRetransmitted += uint64(info.BytesRetrans)
+		es.TotalBytesSent += info.BytesOut
+		es.TotalBytesReceived += info.BytesIn
+
+		es.total_rtt += float64(info.RttUs)
+		es.rtt_measurements += 1
+		es.AverageRtt = es.total_rtt / float64(es.rtt_measurements)
+		es.RetransmitRatio = (float64(es.TotalBytesRetransmitted) / float64(es.TotalBytesSent)) * 100.0
+	}
+	return nil
+}
+
+func (es *ExtendedStats) Repr() string {
+	return fmt.Sprintf(`Extended Statistics:
+	Maximum Segment Size: %v
+	Total Bytes Retransmitted: %v
+	Retransmission Ratio: %.2f%%
+	Total Bytes Reordered: %v
+	Average RTT: %v
+`, es.MaxMss, es.TotalBytesRetransmitted, es.RetransmitRatio, es.TotalBytesReordered, es.AverageRtt)
+}
+
+func ExtendedStatsAvailable() bool {
+	return true
+}
+
+func getTCPInfo(connection net.Conn) (*TCPINFO_V1, error) {
+	tcpConn, ok := connection.(*net.TCPConn)
+	if !ok {
+		return nil, fmt.Errorf("connection is not a net.TCPConn")
+	}
+	rawConn, err := tcpConn.SyscallConn()
+	if err != nil {
+		return nil, err
+	}
+
+	// SIO_TCP_INFO
+	// https://docs.microsoft.com/en-us/windows/win32/winsock/sio-tcp-info
+	// https://github.com/tpn/winsdk-10/blob/master/Include/10.0.16299.0/shared/mstcpip.h
+	iocc := uint32(windows.IOC_INOUT | windows.IOC_VENDOR | 39)
+
+	// Should be a DWORD, 0 for version 0, 1 for version 1 tcp_info:
+	// 0: https://docs.microsoft.com/en-us/windows/win32/api/mstcpip/ns-mstcpip-tcp_info_v0
+	// 1: https://docs.microsoft.com/en-us/windows/win32/api/mstcpip/ns-mstcpip-tcp_info_v1
+	inbuf := uint32(1)
+
+	// Size of the inbuf variable
+	cbif := uint32(4)
+
+	outbuf := TCPINFO_V1{}
+
+	cbob := uint32(unsafe.Sizeof(outbuf)) // Size = 136 for V1 and 88 for V0
+
+	// Size pointer of return object
+	cbbr := uint32(0)
+
+	overlapped := windows.Overlapped{}
+
+	completionRoutine := uintptr(0)
+
+	rawConn.Control(func(fd uintptr) {
+		err = windows.WSAIoctl(windows.Handle(fd), iocc, (*byte)(unsafe.Pointer(&inbuf)), cbif, (*byte)(unsafe.Pointer(&outbuf)), cbob, &cbbr, &overlapped, completionRoutine)
+	})
+	return &outbuf, err
+}