/*
 * Copyright (c) 2012  Smith Micro Software, Inc.
 * Copyright (c) 2012  Bjørn Mork <bjorn@mork.no>
 *
 * This driver is based on and reuse most of cdc_ncm, which is
 * Copyright (C) ST-Ericsson 2010-2012
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/ethtool.h>
#include <linux/if_vlan.h>
#include <linux/ip.h>
#include <linux/mii.h>
#include <linux/usb.h>
#include <linux/usb/cdc.h>
#include <linux/usb/usbnet.h>
#include <linux/usb/cdc-wdm.h>
#include <linux/usb/cdc_ncm.h>
#include <net/ipv6.h>
#include <net/addrconf.h>

/* alternative VLAN for IP session 0 if not untagged */
#define MBIM_IPS0_VID   4094

/* driver specific data - must match cdc_ncm usage */
struct cdc_mbim_state {
        struct cdc_ncm_ctx *ctx;
        atomic_t pmcount;
        struct usb_driver *subdriver;
        unsigned long _unused;
        unsigned long flags;
};

/* flags for the cdc_mbim_state.flags field */
enum cdc_mbim_flags {
        FLAG_IPS0_VLAN = 1 << 0,        /* IP session 0 is tagged  */
};

/* using a counter to merge subdriver requests with our own into a combined state */
static int cdc_mbim_manage_power(struct usbnet *dev, int on)
{
        struct cdc_mbim_state *info = (void *)&dev->data;
        int rv = 0;

        dev_dbg(&dev->intf->dev, "%s() pmcount=%d, on=%d\n", __func__, atomic_read(&info->pmcount), on);

        if ((on && atomic_add_return(1, &info->pmcount) == 1) || (!on && atomic_dec_and_test(&info->pmcount))) {
                /* need autopm_get/put here to ensure the usbcore sees the new value */
                rv = usb_autopm_get_interface(dev->intf);
                dev->intf->needs_remote_wakeup = on;
                if (!rv)
                        usb_autopm_put_interface(dev->intf);
        }
        return 0;
}

static int cdc_mbim_wdm_manage_power(struct usb_interface *intf, int status)
{
        struct usbnet *dev = usb_get_intfdata(intf);

        /* can be called while disconnecting */
        if (!dev)
                return 0;

        return cdc_mbim_manage_power(dev, status);
}

static int cdc_mbim_rx_add_vid(struct net_device *netdev, __be16 proto, u16 vid)
{
        struct usbnet *dev = netdev_priv(netdev);
        struct cdc_mbim_state *info = (void *)&dev->data;

        /* creation of this VLAN is a request to tag IP session 0 */
        if (vid == MBIM_IPS0_VID)
                info->flags |= FLAG_IPS0_VLAN;
        else
                if (vid >= 512) /* we don't map these to MBIM session */
                        return -EINVAL;
        return 0;
}

static int cdc_mbim_rx_kill_vid(struct net_device *netdev, __be16 proto, u16 vid)
{
        struct usbnet *dev = netdev_priv(netdev);
        struct cdc_mbim_state *info = (void *)&dev->data;

        /* this is a request for an untagged IP session 0 */
        if (vid == MBIM_IPS0_VID)
                info->flags &= ~FLAG_IPS0_VLAN;
        return 0;
}

static const struct net_device_ops cdc_mbim_netdev_ops = {
        .ndo_open             = usbnet_open,
        .ndo_stop             = usbnet_stop,
        .ndo_start_xmit       = usbnet_start_xmit,
        .ndo_tx_timeout       = usbnet_tx_timeout,
        .ndo_change_mtu       = cdc_ncm_change_mtu,
        .ndo_set_mac_address  = eth_mac_addr,
        .ndo_validate_addr    = eth_validate_addr,
        .ndo_vlan_rx_add_vid  = cdc_mbim_rx_add_vid,
        .ndo_vlan_rx_kill_vid = cdc_mbim_rx_kill_vid,
};

/* Change the control interface altsetting and update the .driver_info
 * pointer if the matching entry after changing class codes points to
 * a different struct
 */
static int cdc_mbim_set_ctrlalt(struct usbnet *dev, struct usb_interface *intf, u8 alt)
{
        struct usb_driver *driver = to_usb_driver(intf->dev.driver);
        const struct usb_device_id *id;
        struct driver_info *info;
        int ret;

        ret = usb_set_interface(dev->udev,
                                intf->cur_altsetting->desc.bInterfaceNumber,
                                alt);
        if (ret)
                return ret;

        id = usb_match_id(intf, driver->id_table);
        if (!id)
                return -ENODEV;

        info = (struct driver_info *)id->driver_info;
        if (info != dev->driver_info) {
                dev_dbg(&intf->dev, "driver_info updated to '%s'\n",
                        info->description);
                dev->driver_info = info;
        }
        return 0;
}

static int cdc_mbim_bind(struct usbnet *dev, struct usb_interface *intf)
{
        struct cdc_ncm_ctx *ctx;
        struct usb_driver *subdriver = ERR_PTR(-ENODEV);
        int ret = -ENODEV;
        u8 data_altsetting = 1;
        struct cdc_mbim_state *info = (void *)&dev->data;

        /* should we change control altsetting on a NCM/MBIM function? */
        if (cdc_ncm_select_altsetting(intf) == CDC_NCM_COMM_ALTSETTING_MBIM) {
                data_altsetting = CDC_NCM_DATA_ALTSETTING_MBIM;
                ret = cdc_mbim_set_ctrlalt(dev, intf, CDC_NCM_COMM_ALTSETTING_MBIM);
                if (ret)
                        goto err;
                ret = -ENODEV;
        }

        /* we will hit this for NCM/MBIM functions if prefer_mbim is false */
        if (!cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting))
                goto err;

        ret = cdc_ncm_bind_common(dev, intf, data_altsetting, dev->driver_info->data);
        if (ret)
                goto err;

        ctx = info->ctx;

        /* The MBIM descriptor and the status endpoint are required */
        if (ctx->mbim_desc && dev->status)
                subdriver = usb_cdc_wdm_register(ctx->control,
                                                 &dev->status->desc,
                                                 le16_to_cpu(ctx->mbim_desc->wMaxControlMessage),
                                                 cdc_mbim_wdm_manage_power);
        if (IS_ERR(subdriver)) {
                ret = PTR_ERR(subdriver);
                cdc_ncm_unbind(dev, intf);
                goto err;
        }

        /* can't let usbnet use the interrupt endpoint */
        dev->status = NULL;
        info->subdriver = subdriver;

        /* MBIM cannot do ARP */
        dev->net->flags |= IFF_NOARP;

        /* no need to put the VLAN tci in the packet headers */
        dev->net->features |= NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_CTAG_FILTER;

        /* monitor VLAN additions and removals */
        dev->net->netdev_ops = &cdc_mbim_netdev_ops;
err:
        return ret;
}

static void cdc_mbim_unbind(struct usbnet *dev, struct usb_interface *intf)
{
        struct cdc_mbim_state *info = (void *)&dev->data;
        struct cdc_ncm_ctx *ctx = info->ctx;

        /* disconnect subdriver from control interface */
        if (info->subdriver && info->subdriver->disconnect)
                info->subdriver->disconnect(ctx->control);
        info->subdriver = NULL;

        /* let NCM unbind clean up both control and data interface */
        cdc_ncm_unbind(dev, intf);
}

/* verify that the ethernet protocol is IPv4 or IPv6 */
static bool is_ip_proto(__be16 proto)
{
        switch (proto) {
        case htons(ETH_P_IP):
        case htons(ETH_P_IPV6):
                return true;
        }
        return false;
}

static struct sk_buff *cdc_mbim_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
{
        struct sk_buff *skb_out;
        struct cdc_mbim_state *info = (void *)&dev->data;
        struct cdc_ncm_ctx *ctx = info->ctx;
        __le32 sign = cpu_to_le32(USB_CDC_MBIM_NDP16_IPS_SIGN);
        u16 tci = 0;
        bool is_ip;
        u8 *c;

        if (!ctx)
                goto error;

        if (skb) {
                if (skb->len <= ETH_HLEN)
                        goto error;

                /* Some applications using e.g. packet sockets will
                 * bypass the VLAN acceleration and create tagged
                 * ethernet frames directly.  We primarily look for
                 * the accelerated out-of-band tag, but fall back if
                 * required
                 */
                skb_reset_mac_header(skb);
                if (vlan_get_tag(skb, &tci) < 0 && skb->len > VLAN_ETH_HLEN &&
                    __vlan_get_tag(skb, &tci) == 0) {
                        is_ip = is_ip_proto(vlan_eth_hdr(skb)->h_vlan_encapsulated_proto);
                        skb_pull(skb, VLAN_ETH_HLEN);
                } else {
                        is_ip = is_ip_proto(eth_hdr(skb)->h_proto);
                        skb_pull(skb, ETH_HLEN);
                }

                /* Is IP session <0> tagged too? */
                if (info->flags & FLAG_IPS0_VLAN) {
                        /* drop all untagged packets */
                        if (!tci)
                                goto error;
                        /* map MBIM_IPS0_VID to IPS<0> */
                        if (tci == MBIM_IPS0_VID)
                                tci = 0;
                }

                /* mapping VLANs to MBIM sessions:
                 *   no tag     => IPS session <0> if !FLAG_IPS0_VLAN
                 *   1 - 255    => IPS session <vlanid>
                 *   256 - 511  => DSS session <vlanid - 256>
                 *   512 - 4093 => unsupported, drop
                 *   4094       => IPS session <0> if FLAG_IPS0_VLAN
                 */

                switch (tci & 0x0f00) {
                case 0x0000: /* VLAN ID 0 - 255 */
                        if (!is_ip)
                                goto error;
                        c = (u8 *)&sign;
                        c[3] = tci;
                        break;
                case 0x0100: /* VLAN ID 256 - 511 */
                        if (is_ip)
                                goto error;
                        sign = cpu_to_le32(USB_CDC_MBIM_NDP16_DSS_SIGN);
                        c = (u8 *)&sign;
                        c[3] = tci;
                        break;
                default:
                        netif_err(dev, tx_err, dev->net,
                                  "unsupported tci=0x%04x\n", tci);
                        goto error;
                }
        }

        spin_lock_bh(&ctx->mtx);
        skb_out = cdc_ncm_fill_tx_frame(dev, skb, sign);
        spin_unlock_bh(&ctx->mtx);
        return skb_out;

error:
        if (skb)
                dev_kfree_skb_any(skb);

        return NULL;
}

/* Some devices are known to send Neigbor Solicitation messages and
 * require Neigbor Advertisement replies.  The IPv6 core will not
 * respond since IFF_NOARP is set, so we must handle them ourselves.
 */
static void do_neigh_solicit(struct usbnet *dev, u8 *buf, u16 tci)
{
        struct ipv6hdr *iph = (void *)buf;
        struct nd_msg *msg = (void *)(iph + 1);
        struct net_device *netdev;
        struct inet6_dev *in6_dev;
        bool is_router;

        /* we'll only respond to requests from unicast addresses to
         * our solicited node addresses.
         */
        if (!ipv6_addr_is_solict_mult(&iph->daddr) ||
            !(ipv6_addr_type(&iph->saddr) & IPV6_ADDR_UNICAST))
                return;

        /* need to send the NA on the VLAN dev, if any */
        rcu_read_lock();
        if (tci) {
                netdev = __vlan_find_dev_deep_rcu(dev->net, htons(ETH_P_8021Q),
                                                  tci);
                if (!netdev) {
                        rcu_read_unlock();
                        return;
                }
        } else {
                netdev = dev->net;
        }
        dev_hold(netdev);
        rcu_read_unlock();

        in6_dev = in6_dev_get(netdev);
        if (!in6_dev)
                goto out;
        is_router = !!in6_dev->cnf.forwarding;
        in6_dev_put(in6_dev);

        /* ipv6_stub != NULL if in6_dev_get returned an inet6_dev */
        ipv6_stub->ndisc_send_na(netdev, &iph->saddr, &msg->target,
                                 is_router /* router */,
                                 true /* solicited */,
                                 false /* override */,
                                 true /* inc_opt */);
out:
        dev_put(netdev);
}

static bool is_neigh_solicit(u8 *buf, size_t len)
{
        struct ipv6hdr *iph = (void *)buf;
        struct nd_msg *msg = (void *)(iph + 1);

        return (len >= sizeof(struct ipv6hdr) + sizeof(struct nd_msg) &&
                iph->nexthdr == IPPROTO_ICMPV6 &&
                msg->icmph.icmp6_code == 0 &&
                msg->icmph.icmp6_type == NDISC_NEIGHBOUR_SOLICITATION);
}


static struct sk_buff *cdc_mbim_process_dgram(struct usbnet *dev, u8 *buf, size_t len, u16 tci)
{
        __be16 proto = htons(ETH_P_802_3);
        struct sk_buff *skb = NULL;

        if (tci < 256 || tci == MBIM_IPS0_VID) { /* IPS session? */
                if (len < sizeof(struct iphdr))
                        goto err;

                switch (*buf & 0xf0) {
                case 0x40:
                        proto = htons(ETH_P_IP);
                        break;
                case 0x60:
                        if (is_neigh_solicit(buf, len))
                                do_neigh_solicit(dev, buf, tci);
                        proto = htons(ETH_P_IPV6);
                        break;
                default:
                        goto err;
                }
        }

        skb = netdev_alloc_skb_ip_align(dev->net,  len + ETH_HLEN);
        if (!skb)
                goto err;

        /* add an ethernet header */
        skb_put(skb, ETH_HLEN);
        skb_reset_mac_header(skb);
        eth_hdr(skb)->h_proto = proto;
        eth_zero_addr(eth_hdr(skb)->h_source);
        memcpy(eth_hdr(skb)->h_dest, dev->net->dev_addr, ETH_ALEN);

        /* add datagram */
        memcpy(skb_put(skb, len), buf, len);

        /* map MBIM session to VLAN */
        if (tci)
                __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), tci);
err:
        return skb;
}

static int cdc_mbim_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in)
{
        struct sk_buff *skb;
        struct cdc_mbim_state *info = (void *)&dev->data;
        struct cdc_ncm_ctx *ctx = info->ctx;
        int len;
        int nframes;
        int x;
        int offset;
        struct usb_cdc_ncm_ndp16 *ndp16;
        struct usb_cdc_ncm_dpe16 *dpe16;
        int ndpoffset;
        int loopcount = 50; /* arbitrary max preventing infinite loop */
        u32 payload = 0;
        u8 *c;
        u16 tci;

        ndpoffset = cdc_ncm_rx_verify_nth16(ctx, skb_in);
        if (ndpoffset < 0)
                goto error;

next_ndp:
        nframes = cdc_ncm_rx_verify_ndp16(skb_in, ndpoffset);
        if (nframes < 0)
                goto error;

        ndp16 = (struct usb_cdc_ncm_ndp16 *)(skb_in->data + ndpoffset);

        switch (ndp16->dwSignature & cpu_to_le32(0x00ffffff)) {
        case cpu_to_le32(USB_CDC_MBIM_NDP16_IPS_SIGN):
                c = (u8 *)&ndp16->dwSignature;
                tci = c[3];
                /* tag IPS<0> packets too if MBIM_IPS0_VID exists */
                if (!tci && info->flags & FLAG_IPS0_VLAN)
                        tci = MBIM_IPS0_VID;
                break;
        case cpu_to_le32(USB_CDC_MBIM_NDP16_DSS_SIGN):
                c = (u8 *)&ndp16->dwSignature;
                tci = c[3] + 256;
                break;
        default:
                netif_dbg(dev, rx_err, dev->net,
                          "unsupported NDP signature <0x%08x>\n",
                          le32_to_cpu(ndp16->dwSignature));
                goto err_ndp;

        }

        dpe16 = ndp16->dpe16;
        for (x = 0; x < nframes; x++, dpe16++) {
                offset = le16_to_cpu(dpe16->wDatagramIndex);
                len = le16_to_cpu(dpe16->wDatagramLength);

                /*
                 * CDC NCM ch. 3.7
                 * All entries after first NULL entry are to be ignored
                 */
                if ((offset == 0) || (len == 0)) {
                        if (!x)
                                goto err_ndp; /* empty NTB */
                        break;
                }

                /* sanity checking */
                if (((offset + len) > skb_in->len) || (len > ctx->rx_max)) {
                        netif_dbg(dev, rx_err, dev->net,
                                  "invalid frame detected (ignored) offset[%u]=%u, length=%u, skb=%p\n",
                                  x, offset, len, skb_in);
                        if (!x)
                                goto err_ndp;
                        break;
                } else {
                        skb = cdc_mbim_process_dgram(dev, skb_in->data + offset, len, tci);
                        if (!skb)
                                goto error;
                        usbnet_skb_return(dev, skb);
                        payload += len; /* count payload bytes in this NTB */
                }
        }
err_ndp:
        /* are there more NDPs to process? */
        ndpoffset = le16_to_cpu(ndp16->wNextNdpIndex);
        if (ndpoffset && loopcount--)
                goto next_ndp;

        /* update stats */
        ctx->rx_overhead += skb_in->len - payload;
        ctx->rx_ntbs++;

        return 1;
error:
        return 0;
}

static int cdc_mbim_suspend(struct usb_interface *intf, pm_message_t message)
{
        int ret = -ENODEV;
        struct usbnet *dev = usb_get_intfdata(intf);
        struct cdc_mbim_state *info = (void *)&dev->data;
        struct cdc_ncm_ctx *ctx = info->ctx;

        if (!ctx)
                goto error;

        /*
         * Both usbnet_suspend() and subdriver->suspend() MUST return 0
         * in system sleep context, otherwise, the resume callback has
         * to recover device from previous suspend failure.
         */
        ret = usbnet_suspend(intf, message);
        if (ret < 0)
                goto error;

        if (intf == ctx->control && info->subdriver && info->subdriver->suspend)
                ret = info->subdriver->suspend(intf, message);
        if (ret < 0)
                usbnet_resume(intf);

error:
        return ret;
}

static int cdc_mbim_resume(struct usb_interface *intf)
{
        int  ret = 0;
        struct usbnet *dev = usb_get_intfdata(intf);
        struct cdc_mbim_state *info = (void *)&dev->data;
        struct cdc_ncm_ctx *ctx = info->ctx;
        bool callsub = (intf == ctx->control && info->subdriver && info->subdriver->resume);

        if (callsub)
                ret = info->subdriver->resume(intf);
        if (ret < 0)
                goto err;
        ret = usbnet_resume(intf);
        if (ret < 0 && callsub)
                info->subdriver->suspend(intf, PMSG_SUSPEND);
err:
        return ret;
}

static const struct driver_info cdc_mbim_info = {
        .description = "CDC MBIM",
        .flags = FLAG_NO_SETINT | FLAG_MULTI_PACKET | FLAG_WWAN,
        .bind = cdc_mbim_bind,
        .unbind = cdc_mbim_unbind,
        .manage_power = cdc_mbim_manage_power,
        .rx_fixup = cdc_mbim_rx_fixup,
        .tx_fixup = cdc_mbim_tx_fixup,
};

/* MBIM and NCM devices should not need a ZLP after NTBs with
 * dwNtbOutMaxSize length. Nevertheless, a number of devices from
 * different vendor IDs will fail unless we send ZLPs, forcing us
 * to make this the default.
 *
 * This default may cause a performance penalty for spec conforming
 * devices wanting to take advantage of optimizations possible without
 * ZLPs.  A whitelist is added in an attempt to avoid this for devices
 * known to conform to the MBIM specification.
 *
 * All known devices supporting NCM compatibility mode are also
 * conforming to the NCM and MBIM specifications. For this reason, the
 * NCM subclass entry is also in the ZLP whitelist.
 */
static const struct driver_info cdc_mbim_info_zlp = {
        .description = "CDC MBIM",
        .flags = FLAG_NO_SETINT | FLAG_MULTI_PACKET | FLAG_WWAN | FLAG_SEND_ZLP,
        .bind = cdc_mbim_bind,
        .unbind = cdc_mbim_unbind,
        .manage_power = cdc_mbim_manage_power,
        .rx_fixup = cdc_mbim_rx_fixup,
        .tx_fixup = cdc_mbim_tx_fixup,
};

/* The spefication explicitly allows NDPs to be placed anywhere in the
 * frame, but some devices fail unless the NDP is placed after the IP
 * packets.  Using the CDC_NCM_FLAG_NDP_TO_END flags to force this
 * behaviour.
 *
 * Note: The current implementation of this feature restricts each NTB
 * to a single NDP, implying that multiplexed sessions cannot share an
 * NTB. This might affect performace for multiplexed sessions.
 */
static const struct driver_info cdc_mbim_info_ndp_to_end = {
        .description = "CDC MBIM",
        .flags = FLAG_NO_SETINT | FLAG_MULTI_PACKET | FLAG_WWAN,
        .bind = cdc_mbim_bind,
        .unbind = cdc_mbim_unbind,
        .manage_power = cdc_mbim_manage_power,
        .rx_fixup = cdc_mbim_rx_fixup,
        .tx_fixup = cdc_mbim_tx_fixup,
        .data = CDC_NCM_FLAG_NDP_TO_END,
};

static const struct usb_device_id mbim_devs[] = {
        /* This duplicate NCM entry is intentional. MBIM devices can
         * be disguised as NCM by default, and this is necessary to
         * allow us to bind the correct driver_info to such devices.
         *
         * bind() will sort out this for us, selecting the correct
         * entry and reject the other
         */
        { USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&cdc_mbim_info,
        },
        /* ZLP conformance whitelist: All Ericsson MBIM devices */
        { USB_VENDOR_AND_INTERFACE_INFO(0x0bdb, USB_CLASS_COMM, USB_CDC_SUBCLASS_MBIM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&cdc_mbim_info,
        },
        /* Huawei E3372 fails unless NDP comes after the IP packets */
        { USB_DEVICE_AND_INTERFACE_INFO(0x12d1, 0x157d, USB_CLASS_COMM, USB_CDC_SUBCLASS_MBIM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&cdc_mbim_info_ndp_to_end,
        },
        /* default entry */
        { USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_MBIM, USB_CDC_PROTO_NONE),
          .driver_info = (unsigned long)&cdc_mbim_info_zlp,
        },
        {
        },
};
MODULE_DEVICE_TABLE(usb, mbim_devs);

static struct usb_driver cdc_mbim_driver = {
        .name = "cdc_mbim",
        .id_table = mbim_devs,
        .probe = usbnet_probe,
        .disconnect = usbnet_disconnect,
        .suspend = cdc_mbim_suspend,
        .resume = cdc_mbim_resume,
        .reset_resume = cdc_mbim_resume,
        .supports_autosuspend = 1,
        .disable_hub_initiated_lpm = 1,
};
module_usb_driver(cdc_mbim_driver);

MODULE_AUTHOR("Greg Suarez <gsuarez@smithmicro.com>");
MODULE_AUTHOR("Bjørn Mork <bjorn@mork.no>");
MODULE_DESCRIPTION("USB CDC MBIM host driver");
MODULE_LICENSE("GPL");