usb-mtp: Introduce write support for MTP objects

Allow write operations on behalf of the initiator. The
precursor to write is the sending of the write metadata
that consists of the ObjectInfo dataset. This patch introduces
a flag that is set when the responder is ready to receive
write data based on a previous SendObjectInfo operation by
the initiator (The SendObjectInfo implementation is in a
later patch)

Signed-off-by: Bandan Das <bsd@redhat.com>
Message-id: 20180223164829.29683-5-bsd@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/usb/dev-mtp.c

@@ -47,6 +47,7 @@ enum mtp_code {
     CMD_GET_OBJECT_INFO            = 0x1008,
     CMD_GET_OBJECT                 = 0x1009,
     CMD_DELETE_OBJECT              = 0x100b,
+    CMD_SEND_OBJECT                = 0x100d,
     CMD_GET_PARTIAL_OBJECT         = 0x101b,
     CMD_GET_OBJECT_PROPS_SUPPORTED = 0x9801,
     CMD_GET_OBJECT_PROP_DESC       = 0x9802,
@@ -63,9 +64,11 @@ enum mtp_code {
     RES_INVALID_STORAGE_ID         = 0x2008,
     RES_INVALID_OBJECT_HANDLE      = 0x2009,
     RES_INVALID_OBJECT_FORMAT_CODE = 0x200b,
+    RES_STORE_FULL                 = 0x200c,
     RES_STORE_READ_ONLY            = 0x200e,
     RES_PARTIAL_DELETE             = 0x2012,
     RES_SPEC_BY_FORMAT_UNSUPPORTED = 0x2014,
+    RES_INVALID_OBJECTINFO         = 0x2015,
     RES_INVALID_PARENT_OBJECT      = 0x201a,
     RES_INVALID_PARAMETER          = 0x201d,
     RES_SESSION_ALREADY_OPEN       = 0x201e,
@@ -183,6 +186,14 @@ struct MTPState {
     int          inotifyfd;
     QTAILQ_HEAD(events, MTPMonEntry) events;
 #endif
+    /* Responder is expecting a write operation */
+    bool write_pending;
+    struct {
+        uint32_t parent_handle;
+        uint16_t format;
+        uint32_t size;
+        char *filename;
+    } dataset;
 };
 
 #define TYPE_USB_MTP "usb-mtp"
@@ -804,6 +815,7 @@ static MTPData *usb_mtp_get_device_info(MTPState *s, MTPControl *c)
         CMD_GET_OBJECT_HANDLES,
         CMD_GET_OBJECT_INFO,
         CMD_DELETE_OBJECT,
+        CMD_SEND_OBJECT,
         CMD_GET_OBJECT,
         CMD_GET_PARTIAL_OBJECT,
         CMD_GET_OBJECT_PROPS_SUPPORTED,
@@ -1378,6 +1390,19 @@ static void usb_mtp_command(MTPState *s, MTPControl *c)
         nres = 1;
         res0 = data_in->length;
         break;
+    case CMD_SEND_OBJECT:
+        if (!FLAG_SET(s, MTP_FLAG_WRITABLE)) {
+            usb_mtp_queue_result(s, RES_STORE_READ_ONLY,
+                                 c->trans, 0, 0, 0, 0);
+            return;
+        }
+        if (!s->write_pending) {
+            usb_mtp_queue_result(s, RES_INVALID_OBJECTINFO,
+                                 c->trans, 0, 0, 0, 0);
+            return;
+        }
+        s->data_out = usb_mtp_data_alloc(c);
+        return;
     case CMD_GET_OBJECT_PROPS_SUPPORTED:
         if (c->argv[0] != FMT_UNDEFINED_OBJECT &&
             c->argv[0] != FMT_ASSOCIATION) {
@@ -1472,12 +1497,126 @@ static void usb_mtp_cancel_packet(USBDevice *dev, USBPacket *p)
     fprintf(stderr, "%s\n", __func__);
 }
 
+static void usb_mtp_write_data(MTPState *s)
+{
+    MTPData *d = s->data_out;
+    MTPObject *parent =
+        usb_mtp_object_lookup(s, s->dataset.parent_handle);
+    char *path = NULL;
+    int rc = -1;
+    mode_t mask = 0644;
+
+    assert(d != NULL);
+
+    if (parent == NULL || !s->write_pending) {
+        usb_mtp_queue_result(s, RES_INVALID_OBJECTINFO, d->trans,
+                             0, 0, 0, 0);
+        return;
+    }
+
+    if (s->dataset.filename) {
+        path = g_strdup_printf("%s/%s", parent->path, s->dataset.filename);
+        if (s->dataset.format == FMT_ASSOCIATION) {
+            d->fd = mkdir(path, mask);
+            goto free;
+        }
+        if (s->dataset.size < d->length) {
+            usb_mtp_queue_result(s, RES_STORE_FULL, d->trans,
+                                 0, 0, 0, 0);
+            goto done;
+        }
+        d->fd = open(path, O_CREAT | O_WRONLY, mask);
+        if (d->fd == -1) {
+            usb_mtp_queue_result(s, RES_STORE_FULL, d->trans,
+                                 0, 0, 0, 0);
+            goto done;
+        }
+
+        /*
+         * Return success if initiator sent 0 sized data
+         */
+        if (!s->dataset.size) {
+            goto success;
+        }
+
+        rc = write(d->fd, d->data, s->dataset.size);
+        if (rc == -1) {
+            usb_mtp_queue_result(s, RES_STORE_FULL, d->trans,
+                                 0, 0, 0, 0);
+            goto done;
+            }
+        if (rc != s->dataset.size) {
+            usb_mtp_queue_result(s, RES_INCOMPLETE_TRANSFER, d->trans,
+                                 0, 0, 0, 0);
+            goto done;
+        }
+    }
+
+success:
+    usb_mtp_queue_result(s, RES_OK, d->trans,
+                         0, 0, 0, 0);
+
+done:
+    /*
+     * The write dataset is kept around and freed only
+     * on success or if another write request comes in
+     */
+    if (d->fd != -1) {
+        close(d->fd);
+    }
+free:
+    g_free(s->dataset.filename);
+    g_free(path);
+    s->write_pending = false;
+}
+
+static void usb_mtp_get_data(MTPState *s, mtp_container *container,
+                             USBPacket *p)
+{
+    MTPData *d = s->data_out;
+    uint64_t dlen;
+    uint32_t data_len = p->iov.size;
+
+    if (d->first) {
+        /* Total length of incoming data */
+        d->length = cpu_to_le32(container->length) - sizeof(mtp_container);
+        /* Length of data in this packet */
+        data_len -= sizeof(mtp_container);
+        usb_mtp_realloc(d, d->length);
+        d->offset = 0;
+        d->first = false;
+    }
+
+    if (d->length - d->offset > data_len) {
+        dlen = data_len;
+    } else {
+        dlen = d->length - d->offset;
+    }
+
+    switch (d->code) {
+    case CMD_SEND_OBJECT:
+        usb_packet_copy(p, d->data + d->offset, dlen);
+        d->offset += dlen;
+        if (d->offset == d->length) {
+            usb_mtp_write_data(s);
+            usb_mtp_data_free(s->data_out);
+            s->data_out = NULL;
+            return;
+        }
+        break;
+    default:
+        p->status = USB_RET_STALL;
+        return;
+    }
+}
+
 static void usb_mtp_handle_data(USBDevice *dev, USBPacket *p)
 {
     MTPState *s = USB_MTP(dev);
     MTPControl cmd;
     mtp_container container;
     uint32_t params[5];
+    uint16_t container_type;
     int i, rc;
 
     switch (p->ep->nr) {
@@ -1567,8 +1706,13 @@ static void usb_mtp_handle_data(USBDevice *dev, USBPacket *p)
             p->status = USB_RET_STALL;
             return;
         }
-        usb_packet_copy(p, &container, sizeof(container));
-        switch (le16_to_cpu(container.type)) {
+        if (s->data_out && !s->data_out->first) {
+            container_type = TYPE_DATA;
+        } else {
+            usb_packet_copy(p, &container, sizeof(container));
+            container_type = le16_to_cpu(container.type);
+        }
+        switch (container_type) {
         case TYPE_COMMAND:
             if (s->data_in || s->data_out || s->result) {
                 trace_usb_mtp_stall(s->dev.addr, "transaction inflight");
@@ -1599,6 +1743,15 @@ static void usb_mtp_handle_data(USBDevice *dev, USBPacket *p)
                                   (cmd.argc > 4) ? cmd.argv[4] : 0);
             usb_mtp_command(s, &cmd);
             break;
+        case TYPE_DATA:
+            /* One of the previous transfers has already errored but the
+             * responder is still sending data associated with it
+             */
+            if (s->result != NULL) {
+                return;
+            }
+            usb_mtp_get_data(s, &container, p);
+            break;
         default:
             /* not needed as long as the mtp device is read-only */
             p->status = USB_RET_STALL;