spit. not so much polish.

net/uring/io_uring.c

@@ -48,7 +48,7 @@ struct req {
 
 typedef struct req goreq;
 
-static struct req *initializeReq(size_t sz, int ipVersion) {
+static struct req *initializeReq(size_t sz, int ipLen) {
     struct req *r = malloc(sizeof(struct req));
     memset(r, 0, sizeof(*r));
     r->buf = malloc(sz);
@@ -57,12 +57,12 @@ static struct req *initializeReq(size_t sz, int ipVersion) {
     r->iov.iov_len = sz;
     r->hdr.msg_iov = &r->iov;
     r->hdr.msg_iovlen = 1;
-    switch(ipVersion) {
+    switch(ipLen) {
         case 4:
             r->hdr.msg_name = &r->sa;
             r->hdr.msg_namelen = sizeof(r->sa);
             break;
-        case 6:
+        case 16:
             r->hdr.msg_name = &r->sa6;
             r->hdr.msg_namelen = sizeof(r->sa6);
             break;

net/uring/io_uring_linux.go

@@ -45,6 +45,11 @@ type UDPConn struct {
 	// closed is an atomic variable that indicates whether the connection has been closed.
 	// TODO: Make an atomic bool type that we can use here.
 	closed uint32
+	// shutdown is a sequence of funcs to be called when the UDPConn closes.
+	shutdown []func()
+
+	// file is the os file underlying this connection.
+	file *os.File
 
 	// local is the local address of this UDPConn.
 	local net.Addr
@@ -61,7 +66,8 @@ type UDPConn struct {
 	// sendReqC is a channel containing indices into sendReqs
 	// that are free to use (that is, not in the kernel).
 	sendReqC chan int
-	is4      bool
+	// is4 indicates whether the conn is an IPv4 connection.
+	is4 bool
 	// reads counts the number of outstanding read requests.
 	// It is accessed atomically.
 	reads int32
@@ -72,52 +78,64 @@ func NewUDPConn(pconn net.PacketConn) (*UDPConn, error) {
 	if !ok {
 		return nil, fmt.Errorf("cannot use io_uring with conn of type %T", pconn)
 	}
-	// this is dumb
-	local := conn.LocalAddr().String()
-	ip, err := netaddr.ParseIPPort(local)
-	if err != nil {
-		return nil, fmt.Errorf("failed to parse UDPConn local addr %s as IP: %w", local, err)
-	}
-	ipVersion := 6
-	if ip.IP().Is4() {
-		ipVersion = 4
+	local := conn.LocalAddr()
+	udpAddr, ok := local.(*net.UDPAddr)
+	if !ok {
+		return nil, fmt.Errorf("cannot use io_uring with conn.LocalAddr of type %T", local)
 	}
+
 	// TODO: probe for system capabilities: https://unixism.net/loti/tutorial/probe_liburing.html
+
 	file, err := conn.File()
 	if err != nil {
 		return nil, err
 	}
 	// conn.File dup'd the conn's fd. We no longer need the original conn.
 	conn.Close()
-	recvRing := new(C.go_uring)
-	sendRing := new(C.go_uring)
+
+	u := &UDPConn{
+		recvRing: new(C.go_uring),
+		sendRing: new(C.go_uring),
+		file:     file,
+		local:    local,
+		is4:      len(udpAddr.IP) == 4,
+	}
 
 	fd := file.Fd()
-	for _, r := range []*C.go_uring{recvRing, sendRing} {
-		ret := C.initialize(r, C.int(fd))
-		if ret < 0 {
-			// TODO: free recvRing if sendRing initialize failed
-			return nil, fmt.Errorf("uring initialization failed: %d", ret)
-		}
+	u.shutdown = append(u.shutdown, func() { file.Close() })
+
+	if ret := C.initialize(u.recvRing, C.int(fd)); ret < 0 {
+		u.doShutdown()
+		return nil, fmt.Errorf("recvRing initialization failed: %w", syscall.Errno(-ret))
 	}
-	u := &UDPConn{
-		recvRing: recvRing,
-		sendRing: sendRing,
-		local:    conn.LocalAddr(),
-		is4:      ipVersion == 4,
+	u.shutdown = append(u.shutdown, func() { C.io_uring_queue_exit(u.recvRing) })
+
+	if ret := C.initialize(u.sendRing, C.int(fd)); ret < 0 {
+		u.doShutdown()
+		return nil, fmt.Errorf("sendRing initialization failed: %w", syscall.Errno(-ret))
 	}
+	u.shutdown = append(u.shutdown, func() { C.io_uring_queue_exit(u.sendRing) })
 
 	// Initialize buffers
-	for _, reqs := range []*[8]*C.goreq{&u.recvReqs, &u.sendReqs} {
-		for i := range reqs {
-			reqs[i] = C.initializeReq(bufferSize, C.int(ipVersion))
-		}
+	for i := range u.recvReqs {
+		u.recvReqs[i] = C.initializeReq(bufferSize, C.int(len(udpAddr.IP)))
 	}
+	for i := range u.sendReqs {
+		u.sendReqs[i] = C.initializeReq(bufferSize, C.int(len(udpAddr.IP)))
+	}
+	u.shutdown = append(u.shutdown, func() {
+		for _, r := range u.recvReqs {
+			C.freeReq(r)
+		}
+		for _, r := range u.sendReqs {
+			C.freeReq(r)
+		}
+	})
 
 	// Initialize recv half.
 	for i := range u.recvReqs {
 		if err := u.submitRecvRequest(i); err != nil {
-			u.Close() // TODO: will this crash?
+			u.doShutdown()
 			return nil, err
 		}
 	}
@@ -233,20 +251,17 @@ func (u *UDPConn) Close() error {
 		}
 		// TODO: block until no one else uses our rings.
 		// (Or is that unnecessary now?)
-		C.io_uring_queue_exit(u.recvRing)
-		C.io_uring_queue_exit(u.sendRing)
-
-		// Free buffers
-		for _, r := range u.recvReqs {
-			C.freeReq(r)
-		}
-		for _, r := range u.sendReqs {
-			C.freeReq(r)
-		}
+		u.doShutdown()
 	})
 	return nil
 }
 
+func (u *UDPConn) doShutdown() {
+	for _, fn := range u.shutdown {
+		fn()
+	}
+}
+
 // Implement net.PacketConn, for convenience integrating with magicsock.
 
 var _ net.PacketConn = (*UDPConn)(nil)