fix getSysConn to work with TLS (#918)

`tls.Conn` by default doesn't implement `syscall.Conn` and hence tchannel emits `onnection does not implement SyscallConn.` log a lot. 

Since go 1.18, `tls.Conn` exposes method `NetConn()` to expose raw underlying TCP connection. This is used for getting the `syscall.Conn`.

connection.go

@@ -21,6 +21,7 @@
 package tchannel
 
 import (
+	"crypto/tls"
 	"errors"
 	"fmt"
 	"io"
@@ -971,7 +972,18 @@ func (c *Connection) getLastActivityWriteTime() time.Time {
 }
 
 func getSysConn(conn net.Conn, log Logger) syscall.RawConn {
-	connSyscall, ok := conn.(syscall.Conn)
+	var (
+		connSyscall syscall.Conn
+		ok          bool
+	)
+	switch v := conn.(type) {
+	case syscall.Conn:
+		connSyscall = v
+		ok = true
+	case *tls.Conn:
+		connSyscall, ok = v.NetConn().(syscall.Conn)
+	}
+
 	if !ok {
 		log.WithFields(LogField{"connectionType", fmt.Sprintf("%T", conn)}).
 			Error("Connection does not implement SyscallConn.")

connection_internal_test.go

@@ -22,7 +22,9 @@ package tchannel
 
 import (
 	"bytes"
+	"crypto/tls"
 	"net"
+	"net/http/httptest"
 	"syscall"
 	"testing"
 
@@ -79,4 +81,45 @@ func TestGetSysConn(t *testing.T) {
 		require.NotNil(t, sysConn)
 		assert.Empty(t, loggerBuf.String(), "expected no logs on success")
 	})
+
+	t.Run("SyscallConn is successful with TLS", func(t *testing.T) {
+		var (
+			loggerBuf = &bytes.Buffer{}
+			logger    = NewLogger(loggerBuf)
+			server    = httptest.NewTLSServer(nil)
+		)
+		defer server.Close()
+
+		conn, err := tls.Dial("tcp", server.Listener.Addr().String(), &tls.Config{InsecureSkipVerify: true})
+		require.NoError(t, err, "failed to dial")
+		defer conn.Close()
+
+		sysConn := getSysConn(conn, logger)
+		require.NotNil(t, sysConn)
+		assert.Empty(t, loggerBuf.String(), "expected no logs on success")
+	})
+
+	t.Run("no SyscallConn - nil net.Conn", func(t *testing.T) {
+		var (
+			loggerBuf   = &bytes.Buffer{}
+			logger      = NewLogger(loggerBuf)
+			syscallConn = getSysConn(nil /* conn */, logger)
+		)
+
+		require.Nil(t, syscallConn, "expected no syscall.RawConn to be returned")
+		assert.Contains(t, loggerBuf.String(), "Connection does not implement SyscallConn", "missing log")
+		assert.Contains(t, loggerBuf.String(), "{connectionType <nil>}", "missing type in log")
+	})
+
+	t.Run("no SyscallConn - TLS with no net.Conn", func(t *testing.T) {
+		var (
+			loggerBuf   = &bytes.Buffer{}
+			logger      = NewLogger(loggerBuf)
+			syscallConn = getSysConn(&tls.Conn{}, logger)
+		)
+
+		require.Nil(t, syscallConn, "expected no syscall.RawConn to be returned")
+		assert.Contains(t, loggerBuf.String(), "Connection does not implement SyscallConn", "missing log")
+		assert.Contains(t, loggerBuf.String(), "{connectionType *tls.Conn}", "missing type in log")
+	})
 }