[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`.

3 files changed, 84 insertions, 50 deletions

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)
 }