cmd/mbf: optionally ignore reply

An acknowledgement is not always required in this use case. This change also adds 64 bits of connection configuration for future expansion.

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

cmd/mbf/daemon.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"encoding/binary"
 	"errors"
 	"io"
 	"log"
@@ -27,21 +28,28 @@ func daemonDeadline() time.Time {
 	return time.Now().Add(daemonTimeout)
 }
 
+const (
+	// remoteNoReply notifies that the client will not receive a cure reply.
+	remoteNoReply = 1 << iota
+)
+
 // cureFromIR services an IR curing request.
 func cureFromIR(
 	ctx context.Context,
 	cache *pkg.Cache,
 	conn net.Conn,
 ) (pkg.Artifact, error) {
-	go func() {
-		<-ctx.Done()
-		_ = conn.SetDeadline(time.Now())
-	}()
-
+	go func() { <-ctx.Done(); _ = conn.SetDeadline(time.Now()) }()
 	if err := conn.SetReadDeadline(daemonDeadline()); err != nil {
 		return nil, errors.Join(err, conn.Close())
 	}
 
+	var flagsWire [8]byte
+	if _, err := io.ReadFull(conn, flagsWire[:]); err != nil {
+		return nil, errors.Join(err, conn.Close())
+	}
+	flags := binary.LittleEndian.Uint64(flagsWire[:])
+
 	a, decodeErr := cache.NewDecoder(conn).Decode()
 	if decodeErr != nil {
 		_, err := conn.Write([]byte("\x00" + decodeErr.Error()))
@@ -49,10 +57,11 @@ func cureFromIR(
 	}
 
 	pathname, _, cureErr := cache.Cure(a)
+	if flags&remoteNoReply != 0 {
+		return a, errors.Join(cureErr, conn.Close())
+	}
 	if err := conn.SetWriteDeadline(daemonDeadline()); err != nil {
-		if !testing.Testing() || !errors.Is(err, io.ErrClosedPipe) {
-			return a, errors.Join(err, conn.Close())
-		}
+		return a, errors.Join(cureErr, err, conn.Close())
 	}
 	if cureErr != nil {
 		_, err := conn.Write([]byte("\x00" + cureErr.Error()))
@@ -66,7 +75,12 @@ func cureFromIR(
 }
 
 // serve services connections from a [net.UnixListener].
-func serve(ctx context.Context, log *log.Logger, cm *cache, ul *net.UnixListener) error {
+func serve(
+	ctx context.Context,
+	log *log.Logger,
+	cm *cache,
+	ul *net.UnixListener,
+) error {
 	ul.SetUnlinkOnClose(true)
 	if cm.c == nil {
 		if err := cm.open(); err != nil {
@@ -116,16 +130,19 @@ func cureRemote(
 	ctx context.Context,
 	addr *net.UnixAddr,
 	a pkg.Artifact,
+	flags uint64,
 ) (*check.Absolute, error) {
 	conn, err := net.DialUnix("unix", nil, addr)
 	if err != nil {
 		return nil, err
 	}
+	go func() { <-ctx.Done(); _ = conn.SetDeadline(time.Now()) }()
 
-	go func() {
-		<-ctx.Done()
-		_ = conn.SetDeadline(time.Now())
-	}()
+	if n, flagErr := conn.Write(binary.LittleEndian.AppendUint64(nil, flags)); flagErr != nil {
+		return nil, errors.Join(flagErr, conn.Close())
+	} else if n != 8 {
+		return nil, errors.Join(io.ErrShortWrite, conn.Close())
+	}
 
 	if err = pkg.NewIR().EncodeAll(conn, a); err != nil {
 		return nil, errors.Join(err, conn.Close())
@@ -133,6 +150,10 @@ func cureRemote(
 		return nil, errors.Join(err, conn.Close())
 	}
 
+	if flags&remoteNoReply != 0 {
+		return nil, conn.Close()
+	}
+
 	payload, recvErr := io.ReadAll(conn)
 	if err = errors.Join(recvErr, conn.Close()); err != nil {
 		if errors.Is(err, os.ErrDeadlineExceeded) {