Podman 5 machine config file - Step 1

The following PR is the very first step in what will a series of steps
to apply a "common" machine configuration file to all providers.
Function names, method names, struct names, and field names are all up
for debate.  The purpose of this PR is to offer a glimpse at the
direction we intend to take.

This PR also contains temporary structs (i.e. aThing) that are not
exported.  These are merely placeholders.

The configuration work in this PR is also unused of yet.  But the code
is compiled.  Once merged, we can begin the next step of development.

[NO NEW TESTS NEEDED]

Signed-off-by: Brent Baude <bbaude@redhat.com>

pkg/machine/sockets/sockets.go

@@ -0,0 +1,93 @@
+package sockets
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"net"
+	"path/filepath"
+	"time"
+
+	"github.com/containers/podman/v4/pkg/machine/define"
+)
+
+// SetSocket creates a new machine file for the socket and assigns it to
+// `socketLoc`
+func SetSocket(socketLoc *define.VMFile, path string, symlink *string) error {
+	socket, err := define.NewMachineFile(path, symlink)
+	if err != nil {
+		return err
+	}
+	*socketLoc = *socket
+	return nil
+}
+
+// ReadySocketPath returns the filepath for the ready socket
+func ReadySocketPath(runtimeDir, machineName string) string {
+	return filepath.Join(runtimeDir, fmt.Sprintf("%s_ready.sock", machineName))
+}
+
+// ListenAndWaitOnSocket waits for a new connection to the listener and sends
+// any error back through the channel. ListenAndWaitOnSocket is intended to be
+// used as a goroutine
+func ListenAndWaitOnSocket(errChan chan<- error, listener net.Listener) {
+	conn, err := listener.Accept()
+	if err != nil {
+		errChan <- err
+		return
+	}
+	_, err = bufio.NewReader(conn).ReadString('\n')
+
+	if closeErr := conn.Close(); closeErr != nil {
+		errChan <- closeErr
+		return
+	}
+
+	errChan <- err
+}
+
+// DialSocketWithBackoffs attempts to connect to the socket in maxBackoffs attempts
+func DialSocketWithBackoffs(maxBackoffs int, backoff time.Duration, socketPath string) (conn net.Conn, err error) {
+	for i := 0; i < maxBackoffs; i++ {
+		if i > 0 {
+			time.Sleep(backoff)
+			backoff *= 2
+		}
+		conn, err = net.Dial("unix", socketPath)
+		if err == nil {
+			return conn, nil
+		}
+	}
+	return nil, err
+}
+
+// DialSocketWithBackoffsAndProcCheck attempts to connect to the socket in
+// maxBackoffs attempts. After every failure to connect, it makes sure the
+// specified process is alive
+func DialSocketWithBackoffsAndProcCheck(
+	maxBackoffs int,
+	backoff time.Duration,
+	socketPath string,
+	checkProccessStatus func(string, int, *bytes.Buffer) error,
+	procHint string,
+	procPid int,
+	errBuf *bytes.Buffer,
+) (conn net.Conn, err error) {
+	for i := 0; i < maxBackoffs; i++ {
+		if i > 0 {
+			time.Sleep(backoff)
+			backoff *= 2
+		}
+		conn, err = net.Dial("unix", socketPath)
+		if err == nil {
+			return conn, nil
+		}
+
+		// check to make sure process denoted by procHint is alive
+		err = checkProccessStatus(procHint, procPid, errBuf)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return nil, err
+}