In order to mitigate the problem of having no internet at all, we got a SIM-Card for LTE/4Ǵ. At the same time the Telekom Speedstick V LTE (which is basically a rebranded Huawei 3372s) became available and not too expensive. A little research showed that it should be really easy to deploy this stick, when flashing a Non-HiLink Firmware (⇐21.xxx), when the Stick could be used just like old modems, with at commands but without the dependency to run pppd/wvdial like in the old modem or even 3G days. You just have to

$ echo "AT^NDISDUP=1,1,"internet.eplus.de" > /dev/ttyUSB1
$ udhcpc wwan0

and should be done with it. In reality this became quite a quest but with combined efforts we managed to get it to work and created a patch for current kernels (tested 3.18.[11-18]. If you also have this stick and are unable to get an IP via dhcp, this patch might be for you.

$ make clean
$ make target/linux/{clean,prepare} V=s QUILT=1
$ cd build_dir/target-mips_34kc_musl-1.1.10/linux-ar71xx_generic/linux-3.18.18/
$ patch -p1 -i /path/to/patchfile/fix-cdc-ncm-huawei-3372s.patch

diff -u a/drivers/net/usb/cdc_mbim.c b/drivers/net/usb/cdc_mbim.c
--- a/drivers/net/usb/cdc_mbim.c	2015-06-28 17:40:40.000000000 +0000
+++ b/drivers/net/usb/cdc_mbim.c	2015-07-04 15:05:14.546901702 +0000
@@ -158,7 +158,7 @@
 	if (!cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting))
 		goto err;

-	ret = cdc_ncm_bind_common(dev, intf, data_altsetting);
+	ret = cdc_ncm_bind_common(dev, intf, data_altsetting, 0);
 	if (ret)
 		goto err;

diff -u a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
--- a/drivers/net/usb/cdc_ncm.c	2015-06-28 17:40:40.000000000 +0000
+++ b/drivers/net/usb/cdc_ncm.c	2015-07-09 08:43:01.658770535 +0000
@@ -684,10 +684,11 @@
 		ctx->tx_curr_skb = NULL;
 	}

+	kfree(ctx->delayed_ndp16);
 	kfree(ctx);
 }

-int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_altsetting)
+int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_altsetting, int drvflags)
 {
 	const struct usb_cdc_union_desc *union_desc = NULL;
 	struct cdc_ncm_ctx *ctx;
@@ -855,6 +856,17 @@
 	/* finish setting up the device specific data */
 	cdc_ncm_setup(dev);

+	/* Device-specific flags */
+	ctx->drvflags = drvflags;
+
+	/* Allocate the delayed NDP if needed. */
+	if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END) {
+		ctx->delayed_ndp16 = kzalloc(ctx->max_ndp_size, GFP_KERNEL);
+		if (!ctx->delayed_ndp16)
+			goto error2;
+		dev_info(&intf->dev, "NDP will be placed at end of frame for this device.");
+	}
+
 	/* override ethtool_ops */
 	dev->net->ethtool_ops = &cdc_ncm_ethtool_ops;
@@ -954,8 +966,11 @@
 	if (cdc_ncm_select_altsetting(intf) != CDC_NCM_COMM_ALTSETTING_NCM)
 		return -ENODEV;

-	/* The NCM data altsetting is fixed */
-	ret = cdc_ncm_bind_common(dev, intf, CDC_NCM_DATA_ALTSETTING_NCM);
+	/* The NCM data altsetting is fixed, so we hard-coded it.
+	 * Additionally, generic NCM devices are assumed to accept arbitrarily
+	 * placed NDP.
+	 */
+	ret = cdc_ncm_bind_common(dev, intf, CDC_NCM_DATA_ALTSETTING_NCM, 0);

 	/*
 	 * We should get an event when network connection is "connected" or
@@ -986,6 +1001,14 @@
 	struct usb_cdc_ncm_nth16 *nth16 = (void *)skb->data;
 	size_t ndpoffset = le16_to_cpu(nth16->wNdpIndex);

+	/* If NDP should be moved to the end of the NCM package, we can't follow the
+	* NTH16 header as we would normally do. NDP isn't written to the SKB yet, and
+	* the wNdpIndex field in the header is actually not consistent with reality. It will be later.
+	*/
+	if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END)
+		if (ctx->delayed_ndp16->dwSignature == sign)
+			return ctx->delayed_ndp16;
+
 	/* follow the chain of NDPs, looking for a match */
 	while (ndpoffset) {
 		ndp16 = (struct usb_cdc_ncm_ndp16 *)(skb->data + ndpoffset);
@@ -995,7 +1018,8 @@
 	}

 	/* align new NDP */
-	cdc_ncm_align_tail(skb, ctx->tx_ndp_modulus, 0, ctx->tx_max);
+	if (!(ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END))
+		cdc_ncm_align_tail(skb, ctx->tx_ndp_modulus, 0, ctx->tx_max);

 	/* verify that there is room for the NDP and the datagram (reserve) */
 	if ((ctx->tx_max - skb->len - reserve) < ctx->max_ndp_size)
@@ -1008,7 +1032,11 @@
 		nth16->wNdpIndex = cpu_to_le16(skb->len);

 	/* push a new empty NDP */
-	ndp16 = (struct usb_cdc_ncm_ndp16 *)memset(skb_put(skb, ctx->max_ndp_size), 0, ctx->max_ndp_size);
+	if (!(ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END))
+		ndp16 = (struct usb_cdc_ncm_ndp16 *)memset(skb_put(skb, ctx->max_ndp_size), 0, ctx->max_ndp_size);
+	else
+		ndp16 = ctx->delayed_ndp16;
+
 	ndp16->dwSignature = sign;
 	ndp16->wLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_ndp16) + sizeof(struct usb_cdc_ncm_dpe16));
 	return ndp16;
@@ -1023,6 +1051,15 @@
 	struct sk_buff *skb_out;
 	u16 n = 0, index, ndplen;
 	u8 ready2send = 0;
+	u32 delayed_ndp_size;
+
+	/* When our NDP gets written in cdc_ncm_ndp(), then skb_out->len gets updated
+	 * accordingly. Otherwise, we should check here.
+	 */
+	if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END)
+		delayed_ndp_size = ctx->max_ndp_size;
+	else
+		delayed_ndp_size = 0;

 	/* if there is a remaining skb, it gets priority */
 	if (skb != NULL) {
@@ -1077,7 +1114,7 @@
 		cdc_ncm_align_tail(skb_out,  ctx->tx_modulus, ctx->tx_remainder, ctx->tx_max);

 		/* check if we had enough room left for both NDP and frame */
-		if (!ndp16 || skb_out->len + skb->len > ctx->tx_max) {
+		if (!ndp16 || skb_out->len + skb->len + delayed_ndp_size > ctx->tx_max) {
 			if (n == 0) {
 				/* won't fit, MTU problem? */
 				dev_kfree_skb_any(skb);

@@ -1150,6 +1187,17 @@
 		/* variables will be reset at next call */
 	}

+	/* If requested, put NDP at end of frame. */
+	if (ctx->drvflags & CDC_NCM_FLAG_NDP_TO_END) {
+		nth16 = (struct usb_cdc_ncm_nth16 *)skb_out->data;
+		cdc_ncm_align_tail(skb_out, ctx->tx_ndp_modulus, 0, ctx->tx_max);
+		nth16->wNdpIndex = cpu_to_le16(skb_out->len);
+		memcpy(skb_put(skb_out, ctx->max_ndp_size), ctx->delayed_ndp16, ctx->max_ndp_size);
+
+		/* Zero out delayed NDP - signature checking will naturally fail. */
+		ndp16 = memset(ctx->delayed_ndp16, 0, ctx->max_ndp_size);
+	}
+
 	/* If collected data size is less or equal ctx->min_tx_pkt
 	 * bytes, we send buffers as it is. If we get more data, it
 	 * would be more efficient for USB HS mobile device with DMA
diff -u a/drivers/net/usb/huawei_cdc_ncm.c b/drivers/net/usb/huawei_cdc_ncm.c
--- a/drivers/net/usb/huawei_cdc_ncm.c	2015-06-28 17:40:40.000000000 +0000
+++ b/drivers/net/usb/huawei_cdc_ncm.c	2015-07-04 15:23:25.779014586 +0000
@@ -73,11 +73,14 @@
 	struct usb_driver *subdriver = ERR_PTR(-ENODEV);
 	int ret = -ENODEV;
 	struct huawei_cdc_ncm_state *drvstate = (void *)&usbnet_dev->data;
+	int drvflags = 0;

 	/* altsetting should always be 1 for NCM devices - so we hard-coded
-	 * it here
+	 * it here. Some huawei devices will need the NDP part of the NCM package to
+	 * be at the end of the frame.
 	 */
-	ret = cdc_ncm_bind_common(usbnet_dev, intf, 1);
+	drvflags |= CDC_NCM_FLAG_NDP_TO_END;
+	ret = cdc_ncm_bind_common(usbnet_dev, intf, 1, drvflags);
 	if (ret)
 		goto err;

diff -u a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
--- a/include/linux/usb/cdc_ncm.h	2015-06-28 17:40:40.000000000 +0000
+++ b/include/linux/usb/cdc_ncm.h	2015-07-04 15:27:52.171388014 +0000
@@ -80,6 +80,9 @@
 #define CDC_NCM_TIMER_INTERVAL_MIN		5UL
 #define CDC_NCM_TIMER_INTERVAL_MAX		(U32_MAX / NSEC_PER_USEC)

+/* Driver flags */
+#define CDC_NCM_FLAG_NDP_TO_END			0x02	/* NDP is placed at end of frame */
+
 #define cdc_ncm_comm_intf_is_mbim(x)  ((x)->desc.bInterfaceSubClass == USB_CDC_SUBCLASS_MBIM && \
 				       (x)->desc.bInterfaceProtocol == USB_CDC_PROTO_NONE)
 #define cdc_ncm_data_intf_is_mbim(x)  ((x)->desc.bInterfaceProtocol == USB_CDC_MBIM_PROTO_NTB)
@@ -103,9 +106,11 @@

 	spinlock_t mtx;
 	atomic_t stop;
+	int drvflags;

 	u32 timer_interval;
 	u32 max_ndp_size;
+	struct usb_cdc_ncm_ndp16 *delayed_ndp16;

 	u32 tx_timer_pending;
 	u32 tx_curr_frame_num;
@@ -133,7 +138,7 @@
 };

 u8 cdc_ncm_select_altsetting(struct usb_interface *intf);
-int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_altsetting);
+int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_altsetting, int drvflags);
 void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf);
 struct sk_buff *cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign);
 int cdc_ncm_rx_verify_nth16(struct cdc_ncm_ctx *ctx, struct sk_buff *skb_in);