internal/pipewire: hold socket fd directly

The interface provided by net is not used here and is a leftover from a previous implementation. This change removes it.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pipewire/pipewire.go

@@ -19,7 +19,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"net"
 	"os"
 	"path"
 	"runtime"
@@ -144,14 +143,11 @@ func New(conn Conn, props SPADict) (*Context, error) {
 	return &ctx, nil
 }
 
-// A SyscallConnCloser is a [syscall.Conn] that implements [io.Closer].
-type SyscallConnCloser interface {
-	syscall.Conn
-	io.Closer
-}
+// unixConn is an implementation of the [Conn] interface for connections
+// to Unix domain sockets.
+type unixConn struct {
+	fd int
 
-// A SyscallConn is a [Conn] adapter for [syscall.Conn].
-type SyscallConn struct {
 	// Whether creation of a new epoll instance was attempted.
 	epoll bool
 	// File descriptor referring to the new epoll instance.
@@ -164,20 +160,31 @@ type SyscallConn struct {
 
 	// If non-zero, next call is treated as a blocking call.
 	timeout time.Duration
-
-	SyscallConnCloser
 }
 
-// MightBlock implements [Conn.MightBlock].
-func (conn *SyscallConn) MightBlock(timeout time.Duration) {
+// Dial connects to a Unix domain socket described by name.
+func Dial(name string) (Conn, error) {
+	if fd, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_CLOEXEC|syscall.SOCK_NONBLOCK, 0); err != nil {
+		return nil, os.NewSyscallError("socket", err)
+	} else if err = syscall.Connect(fd, &syscall.SockaddrUnix{Name: name}); err != nil {
+		_ = syscall.Close(fd)
+		return nil, os.NewSyscallError("connect", err)
+	} else {
+		return &unixConn{fd: fd}, nil
+	}
+}
+
+// MightBlock informs the implementation that the next call
+// might block for a non-zero timeout.
+func (conn *unixConn) MightBlock(timeout time.Duration) {
 	if timeout < 0 {
 		timeout = 0
 	}
 	conn.timeout = timeout
 }
 
-// wantsEpoll is called at the beginning of any method that wants to use epoll.
-func (conn *SyscallConn) wantsEpoll() error {
+// wantsEpoll is called at the beginning of any method that might use epoll.
+func (conn *unixConn) wantsEpoll() error {
 	if !conn.epoll {
 		conn.epoll = true
 		conn.epollFd, conn.epollErr = syscall.EpollCreate1(syscall.EPOLL_CLOEXEC)
@@ -185,24 +192,24 @@ func (conn *SyscallConn) wantsEpoll() error {
 	return conn.epollErr
 }
 
-// wait waits for a specific I/O event for a fd passed for [syscall.Conn.SyscallConn]
-// and returns a function that should be deferred by the caller regardless of error.
-func (conn *SyscallConn) wait(fd int, event uint32, errP *error) (cleanupFunc func()) {
+// wait waits for a specific I/O event on fd and returns a function
+// that must be deferred by the caller regardless of error.
+func (conn *unixConn) wait(event uint32, errP *error) (cleanupFunc func()) {
 	if conn.timeout == 0 {
 		return func() {}
 	}
 	deadline := time.Now().Add(conn.timeout)
 	conn.timeout = 0
 
-	if *errP = syscall.EpollCtl(conn.epollFd, syscall.EPOLL_CTL_ADD, fd, &syscall.EpollEvent{
+	if *errP = syscall.EpollCtl(conn.epollFd, syscall.EPOLL_CTL_ADD, conn.fd, &syscall.EpollEvent{
 		Events: event | syscall.EPOLLERR | syscall.EPOLLHUP,
-		Fd:     int32(fd),
+		Fd:     int32(conn.fd),
 	}); *errP != nil {
 		return func() {}
 	} else {
 		cleanupFunc = func() {
 			// fd is guaranteed to remain valid while f executes but not after f returns
-			if epDelErr := syscall.EpollCtl(conn.epollFd, syscall.EPOLL_CTL_DEL, fd, nil); epDelErr != nil && *errP == nil {
+			if epDelErr := syscall.EpollCtl(conn.epollFd, syscall.EPOLL_CTL_DEL, conn.fd, nil); epDelErr != nil && *errP == nil {
 				*errP = epDelErr
 				return
 			}
@@ -216,7 +223,7 @@ func (conn *SyscallConn) wait(fd int, event uint32, errP *error) (cleanupFunc fu
 		} else {
 			switch n {
 			case 1: // only the socket fd is ever added
-				if conn.epollBuf[0].Fd != int32(fd) { // unreachable
+				if conn.epollBuf[0].Fd != int32(conn.fd) { // unreachable
 					err = syscall.ENOTRECOVERABLE
 					break
 				}
@@ -243,62 +250,40 @@ func (conn *SyscallConn) wait(fd int, event uint32, errP *error) (cleanupFunc fu
 	return
 }
 
-// Recvmsg implements [Conn.Recvmsg] via [syscall.Conn.SyscallConn].
-func (conn *SyscallConn) Recvmsg(p, oob []byte, flags int) (n, oobn, recvflags int, err error) {
+// Recvmsg calls syscall.Recvmsg on the underlying socket.
+func (conn *unixConn) Recvmsg(p, oob []byte, flags int) (n, oobn, recvflags int, err error) {
 	if err = conn.wantsEpoll(); err != nil {
 		return
 	}
-
-	var rc syscall.RawConn
-	if rc, err = conn.SyscallConn(); err != nil {
+	defer conn.wait(syscall.EPOLLIN, &err)()
+	if err != nil {
 		return
 	}
 
-	if controlErr := rc.Control(func(fd uintptr) {
-		defer conn.wait(int(fd), syscall.EPOLLIN, &err)()
-		if err != nil {
-			return
-		}
-
-		n, oobn, recvflags, _, err = syscall.Recvmsg(int(fd), p, oob, flags)
-
-	}); controlErr != nil && err == nil {
-		err = controlErr
-	}
+	n, oobn, recvflags, _, err = syscall.Recvmsg(conn.fd, p, oob, flags)
 	return
 }
 
-// Sendmsg implements [Conn.Sendmsg] via [syscall.Conn.SyscallConn].
-func (conn *SyscallConn) Sendmsg(p, oob []byte, flags int) (n int, err error) {
+// Sendmsg calls syscall.Sendmsg on the underlying socket.
+func (conn *unixConn) Sendmsg(p, oob []byte, flags int) (n int, err error) {
 	if err = conn.wantsEpoll(); err != nil {
 		return
 	}
-
-	var rc syscall.RawConn
-	if rc, err = conn.SyscallConn(); err != nil {
+	defer conn.wait(syscall.EPOLLOUT, &err)()
+	if err != nil {
 		return
 	}
 
-	if controlErr := rc.Control(func(fd uintptr) {
-		defer conn.wait(int(fd), syscall.EPOLLOUT, &err)()
-		if err != nil {
-			return
-		}
-
-		n, err = syscall.SendmsgN(int(fd), p, oob, nil, flags)
-	}); controlErr != nil && err == nil {
-		err = controlErr
-	}
+	n, err = syscall.SendmsgN(conn.fd, p, oob, nil, flags)
 	return
 }
 
-// Close implements [Conn.Close] via [syscall.Conn.Close] but also
-// closes the epoll fd if populated.
-func (conn *SyscallConn) Close() (err error) {
+// Close closes the underlying socket and the epoll fd if populated.
+func (conn *unixConn) Close() (err error) {
 	if conn.epoll && conn.epollErr == nil {
 		conn.epollErr = syscall.Close(conn.epollFd)
 	}
-	if err = conn.SyscallConnCloser.Close(); err != nil {
+	if err = syscall.Close(conn.fd); err != nil {
 		return
 	}
 	return conn.epollErr
@@ -992,14 +977,14 @@ const Remote = "PIPEWIRE_REMOTE"
 
 const DEFAULT_SYSTEM_RUNTIME_DIR = "/run/pipewire"
 
-// connectName connects to a PipeWire remote by name and returns the [net.UnixConn].
-func connectName(name string, manager bool) (conn *net.UnixConn, err error) {
+// connectName connects to a PipeWire remote by name and returns the resulting [Conn].
+func connectName(name string, manager bool) (conn Conn, err error) {
 	if manager && !strings.HasSuffix(name, "-manager") {
 		return connectName(name+"-manager", false)
 	}
 
 	if path.IsAbs(name) || (len(name) > 0 && name[0] == '@') {
-		return net.DialUnix("unix", nil, &net.UnixAddr{Name: name, Net: "unix"})
+		return Dial(name)
 	} else {
 		runtimeDir, ok := os.LookupEnv("PIPEWIRE_RUNTIME_DIR")
 		if !ok || !path.IsAbs(runtimeDir) {
@@ -1014,7 +999,7 @@ func connectName(name string, manager bool) (conn *net.UnixConn, err error) {
 		if !ok || !path.IsAbs(runtimeDir) {
 			runtimeDir = DEFAULT_SYSTEM_RUNTIME_DIR
 		}
-		return net.DialUnix("unix", nil, &net.UnixAddr{Name: path.Join(runtimeDir, name), Net: "unix"})
+		return Dial(path.Join(runtimeDir, name))
 	}
 }
 
@@ -1032,12 +1017,10 @@ func ConnectName(name string, manager bool, props SPADict) (ctx *Context, err er
 		}
 	}
 
-	var unixConn *net.UnixConn
-	if unixConn, err = connectName(name, manager); err != nil {
+	var conn Conn
+	if conn, err = connectName(name, manager); err != nil {
 		return
 	}
-
-	conn := &SyscallConn{SyscallConnCloser: unixConn}
 	if ctx, err = New(conn, props); err != nil {
 		ctx = nil
 		_ = conn.Close()