[Feature] Add conditional compilation support for GetTCPInfo

Now there is functionality for conditionally supporting GetTCPInfo
depending on the platform. If the platform supports it, then the client
can call utilities.GetTCPInfo. In the case that the platform does not
support the GetTCPInfo function call, the result is an error of the type
`NotImplemented`.

5 files changed, 106 insertions, 66 deletions

diff --git a/lgc/lgc.go b/lgc/lgc.go
index 5b35fd1..fb51ec1 100644
--- a/lgc/lgc.go
+++ b/lgc/lgc.go
@@ -281,40 +281,40 @@ func (lgd *LoadGeneratingConnectionDownload) Start(
 	go lgd.doDownload(ctx)
 	return true
 }
-func (lbd *LoadGeneratingConnectionDownload) IsValid() bool {
-	return lbd.valid
+func (lgd *LoadGeneratingConnectionDownload) IsValid() bool {
+	return lgd.valid
 }
 
-func (lbd *LoadGeneratingConnectionDownload) Stats() *stats.TraceStats {
-	return &lbd.stats
+func (lgd *LoadGeneratingConnectionDownload) Stats() *stats.TraceStats {
+	return &lgd.stats
 }
 
-func (lbd *LoadGeneratingConnectionDownload) doDownload(ctx context.Context) {
+func (lgd *LoadGeneratingConnectionDownload) doDownload(ctx context.Context) {
 	var request *http.Request = nil
 	var get *http.Response = nil
 	var err error = nil
 
 	if request, err = http.NewRequestWithContext(
-		httptrace.WithClientTrace(ctx, lbd.tracer),
+		httptrace.WithClientTrace(ctx, lgd.tracer),
 		"GET",
-		lbd.Path,
+		lgd.Path,
 		nil,
 	); err != nil {
-		lbd.valid = false
+		lgd.valid = false
 		return
 	}
 
-	lbd.downloadStartTime = time.Now()
-	lbd.lastIntervalEnd = 0
+	lgd.downloadStartTime = time.Now()
+	lgd.lastIntervalEnd = 0
 
-	if get, err = lbd.client.Do(request); err != nil {
-		lbd.valid = false
+	if get, err = lgd.client.Do(request); err != nil {
+		lgd.valid = false
 		return
 	}
-	cr := &countingReader{n: &lbd.downloaded, ctx: ctx, readable: get.Body}
+	cr := &countingReader{n: &lgd.downloaded, ctx: ctx, readable: get.Body}
 	_, _ = io.Copy(ioutil.Discard, cr)
 	get.Body.Close()
-	if debug.IsDebug(lbd.debug) {
+	if debug.IsDebug(lgd.debug) {
 		fmt.Printf("Ending a load-generating download.\n")
 	}
 }
@@ -426,6 +426,7 @@ func (lgu *LoadGeneratingConnectionUpload) Start(
 	return true
 }
 
-func (lbd *LoadGeneratingConnectionUpload) Stats() *stats.TraceStats {
+func (lgu *LoadGeneratingConnectionUpload) Stats() *stats.TraceStats {
+	// Get all your stats from the download side of the LGC.
 	return nil
 }
diff --git a/networkQuality.go b/networkQuality.go
index 7593714..d9bdc94 100644
--- a/networkQuality.go
+++ b/networkQuality.go
@@ -336,7 +336,12 @@ func main() {
 				fmt.Printf("OOPS: Could not get the TCP info for the connection (not a TCP connection)!\n")
 			}
 			if info, err := utilities.GetTCPInfo(tcpConn); err != nil {
-				fmt.Printf("OOPS: Could not get the TCP info for the connection: %v!\n", err)
+				switch err.(type) {
+				case *utilities.NotImplemented:
+					fmt.Printf("GetTCPInfo not implemented on this platform.\n")
+				default:
+					fmt.Printf("OOPS: Could not get the TCP info for the connection: %v!\n", err)
+				}
 			} else {
 				utilities.PrintTCPInfo(info)
 			}
diff --git a/utilities/tcpinfo_other.go b/utilities/tcpinfo_other.go
new file mode 100644
index 0000000..8dd070b
--- /dev/null
+++ b/utilities/tcpinfo_other.go
@@ -0,0 +1,18 @@
+//go:build !darwin && !dragonfly && !freebsd && !linux && !netbsd && !openbsd
+// +build !darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd
+
+package utilities
+
+import (
+	"net"
+
+	"golang.org/x/sys/unix"
+)
+
+func GetTCPInfo(connection net.Conn) (*unix.TCPInfo, error) {
+	return nil, NotImplemented{Functionality: "GetTCPInfo"}
+}
+
+func PrintTCPInfo(info *unix.TCPInfo) {
+	return
+}
diff --git a/utilities/tcpinfo_unix.go b/utilities/tcpinfo_unix.go
new file mode 100644
index 0000000..b0b5252
--- /dev/null
+++ b/utilities/tcpinfo_unix.go
@@ -0,0 +1,62 @@
+//go:build darwin || dragonfly || freebsd || linux || netbsd || openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
+
+package utilities
+
+import (
+	"fmt"
+	"net"
+
+	"golang.org/x/sys/unix"
+)
+
+func GetTCPInfo(connection net.Conn) (*unix.TCPInfo, 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
+	}
+
+	var info *unix.TCPInfo = nil
+	rawConn.Control(func(fd uintptr) {
+		info, err = unix.GetsockoptTCPInfo(int(fd), unix.SOL_TCP, unix.TCP_INFO)
+	})
+	return info, err
+}
+
+func PrintTCPInfo(info *unix.TCPInfo) {
+	fmt.Printf("TCPInfo: \n")
+	fmt.Printf("	State: %v\n", info.State)
+	fmt.Printf("	Ca_state: %v\n", info.Ca_state)
+	fmt.Printf("	Retransmits: %v\n", info.Retransmits)
+	fmt.Printf("	Probes: %v\n", info.Probes)
+	fmt.Printf("	Backoff: %v\n", info.Backoff)
+	fmt.Printf("	Options: %v\n", info.Options)
+	fmt.Printf("	Rto: %v\n", info.Rto)
+	fmt.Printf("	Ato: %v\n", info.Ato)
+	fmt.Printf("	Snd_mss: %v\n", info.Snd_mss)
+	fmt.Printf("	Rcv_mss: %v\n", info.Rcv_mss)
+	fmt.Printf("	Unacked: %v\n", info.Unacked)
+	fmt.Printf("	Sacked: %v\n", info.Sacked)
+	fmt.Printf("	Lost: %v\n", info.Lost)
+	fmt.Printf("	Retrans: %v\n", info.Retrans)
+	fmt.Printf("	Fackets: %v\n", info.Fackets)
+	fmt.Printf("	Last_data_sent: %v\n", info.Last_data_sent)
+	fmt.Printf("	Last_ack_sent: %v\n", info.Last_ack_sent)
+	fmt.Printf("	Last_data_recv: %v\n", info.Last_data_recv)
+	fmt.Printf("	Last_ack_recv: %v\n", info.Last_ack_recv)
+	fmt.Printf("	Pmtu: %v\n", info.Pmtu)
+	fmt.Printf("	Rcv_ssthresh: %v\n", info.Rcv_ssthresh)
+	fmt.Printf("	Rtt: %v\n", info.Rtt)
+	fmt.Printf("	Rttvar: %v\n", info.Rttvar)
+	fmt.Printf("	Snd_ssthresh: %v\n", info.Snd_ssthresh)
+	fmt.Printf("	Snd_cwnd: %v\n", info.Snd_cwnd)
+	fmt.Printf("	Advmss: %v\n", info.Advmss)
+	fmt.Printf("	Reordering: %v\n", info.Reordering)
+	fmt.Printf("	Rcv_rtt: %v\n", info.Rcv_rtt)
+	fmt.Printf("	Rcv_space: %v\n", info.Rcv_space)
+	fmt.Printf("	Total_retrans: %v\n", info.Total_retrans)
+}
diff --git a/utilities/utilities.go b/utilities/utilities.go
index e4c8a0d..7e26ab9 100644
--- a/utilities/utilities.go
+++ b/utilities/utilities.go
@@ -18,13 +18,10 @@ import (
 	"fmt"
 	"math"
 	"math/rand"
-	"net"
 	"os"
 	"reflect"
 	"sync/atomic"
 	"time"
-
-	"golang.org/x/sys/unix"
 )
 
 func IsInterfaceNil(ifc interface{}) bool {
@@ -126,53 +123,10 @@ func RandBetween(max int) int {
 	return rand.New(rand.NewSource(int64(time.Now().Nanosecond()))).Int() % max
 }
 
-func GetTCPInfo(connection net.Conn) (*unix.TCPInfo, 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
-	}
-
-	var info *unix.TCPInfo = nil
-	rawConn.Control(func(fd uintptr) {
-		info, err = unix.GetsockoptTCPInfo(int(fd), unix.SOL_TCP, unix.TCP_INFO)
-	})
-	return info, err
+type NotImplemented struct {
+	Functionality string
 }
 
-func PrintTCPInfo(info *unix.TCPInfo) {
-	fmt.Printf("TCPInfo: \n")
-	fmt.Printf("	State: %v\n", info.State)
-	fmt.Printf("	Ca_state: %v\n", info.Ca_state)
-	fmt.Printf("	Retransmits: %v\n", info.Retransmits)
-	fmt.Printf("	Probes: %v\n", info.Probes)
-	fmt.Printf("	Backoff: %v\n", info.Backoff)
-	fmt.Printf("	Options: %v\n", info.Options)
-	fmt.Printf("	Rto: %v\n", info.Rto)
-	fmt.Printf("	Ato: %v\n", info.Ato)
-	fmt.Printf("	Snd_mss: %v\n", info.Snd_mss)
-	fmt.Printf("	Rcv_mss: %v\n", info.Rcv_mss)
-	fmt.Printf("	Unacked: %v\n", info.Unacked)
-	fmt.Printf("	Sacked: %v\n", info.Sacked)
-	fmt.Printf("	Lost: %v\n", info.Lost)
-	fmt.Printf("	Retrans: %v\n", info.Retrans)
-	fmt.Printf("	Fackets: %v\n", info.Fackets)
-	fmt.Printf("	Last_data_sent: %v\n", info.Last_data_sent)
-	fmt.Printf("	Last_ack_sent: %v\n", info.Last_ack_sent)
-	fmt.Printf("	Last_data_recv: %v\n", info.Last_data_recv)
-	fmt.Printf("	Last_ack_recv: %v\n", info.Last_ack_recv)
-	fmt.Printf("	Pmtu: %v\n", info.Pmtu)
-	fmt.Printf("	Rcv_ssthresh: %v\n", info.Rcv_ssthresh)
-	fmt.Printf("	Rtt: %v\n", info.Rtt)
-	fmt.Printf("	Rttvar: %v\n", info.Rttvar)
-	fmt.Printf("	Snd_ssthresh: %v\n", info.Snd_ssthresh)
-	fmt.Printf("	Snd_cwnd: %v\n", info.Snd_cwnd)
-	fmt.Printf("	Advmss: %v\n", info.Advmss)
-	fmt.Printf("	Reordering: %v\n", info.Reordering)
-	fmt.Printf("	Rcv_rtt: %v\n", info.Rcv_rtt)
-	fmt.Printf("	Rcv_space: %v\n", info.Rcv_space)
-	fmt.Printf("	Total_retrans: %v\n", info.Total_retrans)
+func (ni *NotImplemented) Error() string {
+	return fmt.Sprintf("%v not implemented.\n", ni.Functionality)
 }