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net: cdc_ncm: respect operator preferred MTU reported by MBIM
According to "Universal Serial Bus Communications Class Subclass Specification for Mobile Broadband Interface Model, Revision 1.0, Errata-1" published by USB-IF, the wMTU field of the MBIM extended functional descriptor indicates the operator preferred MTU for IP data streams. This patch modifies cdc_ncm_setup to ensure that the MTU value set on the usbnet device does not exceed the operator preferred MTU indicated by wMTU if the MBIM device exposes a MBIM extended functional descriptor. Signed-off-by: Ben Chan <benchan@chromium.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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bfe9b3f8c5
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259fef033f
2 changed files with 18 additions and 0 deletions
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@ -74,6 +74,7 @@ static int cdc_ncm_setup(struct usbnet *dev)
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u8 iface_no;
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int err;
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int eth_hlen;
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u16 mbim_mtu;
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u16 ntb_fmt_supported;
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__le16 max_datagram_size;
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@ -261,6 +262,14 @@ static int cdc_ncm_setup(struct usbnet *dev)
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/* set MTU to max supported by the device if necessary */
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if (dev->net->mtu > ctx->max_datagram_size - eth_hlen)
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dev->net->mtu = ctx->max_datagram_size - eth_hlen;
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/* do not exceed operater preferred MTU */
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if (ctx->mbim_extended_desc) {
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mbim_mtu = le16_to_cpu(ctx->mbim_extended_desc->wMTU);
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if (mbim_mtu != 0 && mbim_mtu < dev->net->mtu)
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dev->net->mtu = mbim_mtu;
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}
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return 0;
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}
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@ -399,6 +408,14 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
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ctx->mbim_desc = (const struct usb_cdc_mbim_desc *)buf;
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break;
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case USB_CDC_MBIM_EXTENDED_TYPE:
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if (buf[0] < sizeof(*(ctx->mbim_extended_desc)))
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break;
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ctx->mbim_extended_desc =
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(const struct usb_cdc_mbim_extended_desc *)buf;
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break;
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default:
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break;
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}
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@ -93,6 +93,7 @@ struct cdc_ncm_ctx {
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const struct usb_cdc_ncm_desc *func_desc;
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const struct usb_cdc_mbim_desc *mbim_desc;
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const struct usb_cdc_mbim_extended_desc *mbim_extended_desc;
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const struct usb_cdc_ether_desc *ether_desc;
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struct usb_interface *control;
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