/*
 * Back-end of the driver for virtual network devices. This portion of the
 * driver exports a 'unified' network-device interface that can be accessed
 * by any operating system that implements a compatible front end. A
 * reference front-end implementation can be found in:
 *  drivers/net/xen-netfront.c
 *
 * Copyright (c) 2002-2005, K A Fraser
 *
 * 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; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "common.h"

#include <linux/kthread.h>
#include <linux/if_vlan.h>
#include <linux/udp.h>
#include <linux/highmem.h>

#include <net/tcp.h>

#include <xen/xen.h>
#include <xen/events.h>
#include <xen/interface/memory.h>

#include <asm/xen/hypercall.h>
#include <asm/xen/page.h>

/* Provide an option to disable split event channels at load time as
 * event channels are limited resource. Split event channels are
 * enabled by default.
 */
bool separate_tx_rx_irq = 1;
module_param(separate_tx_rx_irq, bool, 0644);

/* When guest ring is filled up, qdisc queues the packets for us, but we have
 * to timeout them, otherwise other guests' packets can get stuck there
 */
unsigned int rx_drain_timeout_msecs = 10000;
module_param(rx_drain_timeout_msecs, uint, 0444);
unsigned int rx_drain_timeout_jiffies;

/*
 * This is the maximum slots a skb can have. If a guest sends a skb
 * which exceeds this limit it is considered malicious.
 */
#define FATAL_SKB_SLOTS_DEFAULT 20
static unsigned int fatal_skb_slots = FATAL_SKB_SLOTS_DEFAULT;
module_param(fatal_skb_slots, uint, 0444);

static void xenvif_idx_release(struct xenvif *vif, u16 pending_idx,
                               u8 status);

static void make_tx_response(struct xenvif *vif,
                             struct xen_netif_tx_request *txp,
                             s8       st);

static inline int tx_work_todo(struct xenvif *vif);
static inline int rx_work_todo(struct xenvif *vif);

static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif,
                                             u16      id,
                                             s8       st,
                                             u16      offset,
                                             u16      size,
                                             u16      flags);

static inline unsigned long idx_to_pfn(struct xenvif *vif,
                                       u16 idx)
{
        return page_to_pfn(vif->mmap_pages[idx]);
}

static inline unsigned long idx_to_kaddr(struct xenvif *vif,
                                         u16 idx)
{
        return (unsigned long)pfn_to_kaddr(idx_to_pfn(vif, idx));
}

#define callback_param(vif, pending_idx) \
        (vif->pending_tx_info[pending_idx].callback_struct)

/* Find the containing VIF's structure from a pointer in pending_tx_info array
 */
static inline struct xenvif *ubuf_to_vif(const struct ubuf_info *ubuf)
{
        u16 pending_idx = ubuf->desc;
        struct pending_tx_info *temp =
                container_of(ubuf, struct pending_tx_info, callback_struct);
        return container_of(temp - pending_idx,
                            struct xenvif,
                            pending_tx_info[0]);
}

/* This is a miniumum size for the linear area to avoid lots of
 * calls to __pskb_pull_tail() as we set up checksum offsets. The
 * value 128 was chosen as it covers all IPv4 and most likely
 * IPv6 headers.
 */
#define PKT_PROT_LEN 128

static u16 frag_get_pending_idx(skb_frag_t *frag)
{
        return (u16)frag->page_offset;
}

static void frag_set_pending_idx(skb_frag_t *frag, u16 pending_idx)
{
        frag->page_offset = pending_idx;
}

static inline pending_ring_idx_t pending_index(unsigned i)
{
        return i & (MAX_PENDING_REQS-1);
}

bool xenvif_rx_ring_slots_available(struct xenvif *vif, int needed)
{
        RING_IDX prod, cons;

        do {
                prod = vif->rx.sring->req_prod;
                cons = vif->rx.req_cons;

                if (prod - cons >= needed)
                        return true;

                vif->rx.sring->req_event = prod + 1;

                /* Make sure event is visible before we check prod
                 * again.
                 */
                mb();
        } while (vif->rx.sring->req_prod != prod);

        return false;
}

/*
 * Returns true if we should start a new receive buffer instead of
 * adding 'size' bytes to a buffer which currently contains 'offset'
 * bytes.
 */
static bool start_new_rx_buffer(int offset, unsigned long size, int head)
{
        /* simple case: we have completely filled the current buffer. */
        if (offset == MAX_BUFFER_OFFSET)
                return true;

        /*
         * complex case: start a fresh buffer if the current frag
         * would overflow the current buffer but only if:
         *     (i)   this frag would fit completely in the next buffer
         * and (ii)  there is already some data in the current buffer
         * and (iii) this is not the head buffer.
         *
         * Where:
         * - (i) stops us splitting a frag into two copies
         *   unless the frag is too large for a single buffer.
         * - (ii) stops us from leaving a buffer pointlessly empty.
         * - (iii) stops us leaving the first buffer
         *   empty. Strictly speaking this is already covered
         *   by (ii) but is explicitly checked because
         *   netfront relies on the first buffer being
         *   non-empty and can crash otherwise.
         *
         * This means we will effectively linearise small
         * frags but do not needlessly split large buffers
         * into multiple copies tend to give large frags their
         * own buffers as before.
         */
        BUG_ON(size > MAX_BUFFER_OFFSET);
        if ((offset + size > MAX_BUFFER_OFFSET) && offset && !head)
                return true;

        return false;
}

struct netrx_pending_operations {
        unsigned copy_prod, copy_cons;
        unsigned meta_prod, meta_cons;
        struct gnttab_copy *copy;
        struct xenvif_rx_meta *meta;
        int copy_off;
        grant_ref_t copy_gref;
};

static struct xenvif_rx_meta *get_next_rx_buffer(struct xenvif *vif,
                                                 struct netrx_pending_operations *npo)
{
        struct xenvif_rx_meta *meta;
        struct xen_netif_rx_request *req;

        req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);

        meta = npo->meta + npo->meta_prod++;
        meta->gso_type = XEN_NETIF_GSO_TYPE_NONE;
        meta->gso_size = 0;
        meta->size = 0;
        meta->id = req->id;

        npo->copy_off = 0;
        npo->copy_gref = req->gref;

        return meta;
}

/*
 * Set up the grant operations for this fragment. If it's a flipping
 * interface, we also set up the unmap request from here.
 */
static void xenvif_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb,
                                 struct netrx_pending_operations *npo,
                                 struct page *page, unsigned long size,
                                 unsigned long offset, int *head,
                                 struct xenvif *foreign_vif,
                                 grant_ref_t foreign_gref)
{
        struct gnttab_copy *copy_gop;
        struct xenvif_rx_meta *meta;
        unsigned long bytes;
        int gso_type = XEN_NETIF_GSO_TYPE_NONE;

        /* Data must not cross a page boundary. */
        BUG_ON(size + offset > PAGE_SIZE<<compound_order(page));

        meta = npo->meta + npo->meta_prod - 1;

        /* Skip unused frames from start of page */
        page += offset >> PAGE_SHIFT;
        offset &= ~PAGE_MASK;

        while (size > 0) {
                BUG_ON(offset >= PAGE_SIZE);
                BUG_ON(npo->copy_off > MAX_BUFFER_OFFSET);

                bytes = PAGE_SIZE - offset;

                if (bytes > size)
                        bytes = size;

                if (start_new_rx_buffer(npo->copy_off, bytes, *head)) {
                        /*
                         * Netfront requires there to be some data in the head
                         * buffer.
                         */
                        BUG_ON(*head);

                        meta = get_next_rx_buffer(vif, npo);
                }

                if (npo->copy_off + bytes > MAX_BUFFER_OFFSET)
                        bytes = MAX_BUFFER_OFFSET - npo->copy_off;

                copy_gop = npo->copy + npo->copy_prod++;
                copy_gop->flags = GNTCOPY_dest_gref;
                copy_gop->len = bytes;

                if (foreign_vif) {
                        copy_gop->source.domid = foreign_vif->domid;
                        copy_gop->source.u.ref = foreign_gref;
                        copy_gop->flags |= GNTCOPY_source_gref;
                } else {
                        copy_gop->source.domid = DOMID_SELF;
                        copy_gop->source.u.gmfn =
                                virt_to_mfn(page_address(page));
                }
                copy_gop->source.offset = offset;

                copy_gop->dest.domid = vif->domid;
                copy_gop->dest.offset = npo->copy_off;
                copy_gop->dest.u.ref = npo->copy_gref;

                npo->copy_off += bytes;
                meta->size += bytes;

                offset += bytes;
                size -= bytes;

                /* Next frame */
                if (offset == PAGE_SIZE && size) {
                        BUG_ON(!PageCompound(page));
                        page++;
                        offset = 0;
                }

                /* Leave a gap for the GSO descriptor. */
                if (skb_is_gso(skb)) {
                        if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
                                gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
                        else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
                                gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
                }

                if (*head && ((1 << gso_type) & vif->gso_mask))
                        vif->rx.req_cons++;

                *head = 0; /* There must be something in this buffer now. */

        }
}

/*
 * Find the grant ref for a given frag in a chain of struct ubuf_info's
 * skb: the skb itself
 * i: the frag's number
 * ubuf: a pointer to an element in the chain. It should not be NULL
 *
 * Returns a pointer to the element in the chain where the page were found. If
 * not found, returns NULL.
 * See the definition of callback_struct in common.h for more details about
 * the chain.
 */
static const struct ubuf_info *xenvif_find_gref(const struct sk_buff *const skb,
                                                const int i,
                                                const struct ubuf_info *ubuf)
{
        struct xenvif *foreign_vif = ubuf_to_vif(ubuf);

        do {
                u16 pending_idx = ubuf->desc;

                if (skb_shinfo(skb)->frags[i].page.p ==
                    foreign_vif->mmap_pages[pending_idx])
                        break;
                ubuf = (struct ubuf_info *) ubuf->ctx;
        } while (ubuf);

        return ubuf;
}

/*
 * Prepare an SKB to be transmitted to the frontend.
 *
 * This function is responsible for allocating grant operations, meta
 * structures, etc.
 *
 * It returns the number of meta structures consumed. The number of
 * ring slots used is always equal to the number of meta slots used
 * plus the number of GSO descriptors used. Currently, we use either
 * zero GSO descriptors (for non-GSO packets) or one descriptor (for
 * frontend-side LRO).
 */
static int xenvif_gop_skb(struct sk_buff *skb,
                          struct netrx_pending_operations *npo)
{
        struct xenvif *vif = netdev_priv(skb->dev);
        int nr_frags = skb_shinfo(skb)->nr_frags;
        int i;
        struct xen_netif_rx_request *req;
        struct xenvif_rx_meta *meta;
        unsigned char *data;
        int head = 1;
        int old_meta_prod;
        int gso_type;
        const struct ubuf_info *ubuf = skb_shinfo(skb)->destructor_arg;
        const struct ubuf_info *const head_ubuf = ubuf;

        old_meta_prod = npo->meta_prod;

        gso_type = XEN_NETIF_GSO_TYPE_NONE;
        if (skb_is_gso(skb)) {
                if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
                        gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
                else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
                        gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
        }

        /* Set up a GSO prefix descriptor, if necessary */
        if ((1 << gso_type) & vif->gso_prefix_mask) {
                req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
                meta = npo->meta + npo->meta_prod++;
                meta->gso_type = gso_type;
                meta->gso_size = skb_shinfo(skb)->gso_size;
                meta->size = 0;
                meta->id = req->id;
        }

        req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
        meta = npo->meta + npo->meta_prod++;

        if ((1 << gso_type) & vif->gso_mask) {
                meta->gso_type = gso_type;
                meta->gso_size = skb_shinfo(skb)->gso_size;
        } else {
                meta->gso_type = XEN_NETIF_GSO_TYPE_NONE;
                meta->gso_size = 0;
        }

        meta->size = 0;
        meta->id = req->id;
        npo->copy_off = 0;
        npo->copy_gref = req->gref;

        data = skb->data;
        while (data < skb_tail_pointer(skb)) {
                unsigned int offset = offset_in_page(data);
                unsigned int len = PAGE_SIZE - offset;

                if (data + len > skb_tail_pointer(skb))
                        len = skb_tail_pointer(skb) - data;

                xenvif_gop_frag_copy(vif, skb, npo,
                                     virt_to_page(data), len, offset, &head,
                                     NULL,
                                     0);
                data += len;
        }

        for (i = 0; i < nr_frags; i++) {
                /* This variable also signals whether foreign_gref has a real
                 * value or not.
                 */
                struct xenvif *foreign_vif = NULL;
                grant_ref_t foreign_gref;

                if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) &&
                        (ubuf->callback == &xenvif_zerocopy_callback)) {
                        const struct ubuf_info *const startpoint = ubuf;

                        /* Ideally ubuf points to the chain element which
                         * belongs to this frag. Or if frags were removed from
                         * the beginning, then shortly before it.
                         */
                        ubuf = xenvif_find_gref(skb, i, ubuf);

                        /* Try again from the beginning of the list, if we
                         * haven't tried from there. This only makes sense in
                         * the unlikely event of reordering the original frags.
                         * For injected local pages it's an unnecessary second
                         * run.
                         */
                        if (unlikely(!ubuf) && startpoint != head_ubuf)
                                ubuf = xenvif_find_gref(skb, i, head_ubuf);

                        if (likely(ubuf)) {
                                u16 pending_idx = ubuf->desc;

                                foreign_vif = ubuf_to_vif(ubuf);
                                foreign_gref = foreign_vif->pending_tx_info[pending_idx].req.gref;
                                /* Just a safety measure. If this was the last
                                 * element on the list, the for loop will
                                 * iterate again if a local page were added to
                                 * the end. Using head_ubuf here prevents the
                                 * second search on the chain. Or the original
                                 * frags changed order, but that's less likely.
                                 * In any way, ubuf shouldn't be NULL.
                                 */
                                ubuf = ubuf->ctx ?
                                        (struct ubuf_info *) ubuf->ctx :
                                        head_ubuf;
                        } else
                                /* This frag was a local page, added to the
                                 * array after the skb left netback.
                                 */
                                ubuf = head_ubuf;
                }
                xenvif_gop_frag_copy(vif, skb, npo,
                                     skb_frag_page(&skb_shinfo(skb)->frags[i]),
                                     skb_frag_size(&skb_shinfo(skb)->frags[i]),
                                     skb_shinfo(skb)->frags[i].page_offset,
                                     &head,
                                     foreign_vif,
                                     foreign_vif ? foreign_gref : UINT_MAX);
        }

        return npo->meta_prod - old_meta_prod;
}

/*
 * This is a twin to xenvif_gop_skb.  Assume that xenvif_gop_skb was
 * used to set up the operations on the top of
 * netrx_pending_operations, which have since been done.  Check that
 * they didn't give any errors and advance over them.
 */
static int xenvif_check_gop(struct xenvif *vif, int nr_meta_slots,
                            struct netrx_pending_operations *npo)
{
        struct gnttab_copy     *copy_op;
        int status = XEN_NETIF_RSP_OKAY;
        int i;

        for (i = 0; i < nr_meta_slots; i++) {
                copy_op = npo->copy + npo->copy_cons++;
                if (copy_op->status != GNTST_okay) {
                        netdev_dbg(vif->dev,
                                   "Bad status %d from copy to DOM%d.\n",
                                   copy_op->status, vif->domid);
                        status = XEN_NETIF_RSP_ERROR;
                }
        }

        return status;
}

static void xenvif_add_frag_responses(struct xenvif *vif, int status,
                                      struct xenvif_rx_meta *meta,
                                      int nr_meta_slots)
{
        int i;
        unsigned long offset;

        /* No fragments used */
        if (nr_meta_slots <= 1)
                return;

        nr_meta_slots--;

        for (i = 0; i < nr_meta_slots; i++) {
                int flags;
                if (i == nr_meta_slots - 1)
                        flags = 0;
                else
                        flags = XEN_NETRXF_more_data;

                offset = 0;
                make_rx_response(vif, meta[i].id, status, offset,
                                 meta[i].size, flags);
        }
}

struct xenvif_rx_cb {
        int meta_slots_used;
};

#define XENVIF_RX_CB(skb) ((struct xenvif_rx_cb *)(skb)->cb)

void xenvif_kick_thread(struct xenvif *vif)
{
        wake_up(&vif->wq);
}

static void xenvif_rx_action(struct xenvif *vif)
{
        s8 status;
        u16 flags;
        struct xen_netif_rx_response *resp;
        struct sk_buff_head rxq;
        struct sk_buff *skb;
        LIST_HEAD(notify);
        int ret;
        unsigned long offset;
        bool need_to_notify = false;

        struct netrx_pending_operations npo = {
                .copy  = vif->grant_copy_op,
                .meta  = vif->meta,
        };

        skb_queue_head_init(&rxq);

        while ((skb = skb_dequeue(&vif->rx_queue)) != NULL) {
                RING_IDX max_slots_needed;
                RING_IDX old_req_cons;
                RING_IDX ring_slots_used;
                int i;

                /* We need a cheap worse case estimate for the number of
                 * slots we'll use.
                 */

                max_slots_needed = DIV_ROUND_UP(offset_in_page(skb->data) +
                                                skb_headlen(skb),
                                                PAGE_SIZE);
                for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                        unsigned int size;
                        unsigned int offset;

                        size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
                        offset = skb_shinfo(skb)->frags[i].page_offset;

                        /* For a worse-case estimate we need to factor in
                         * the fragment page offset as this will affect the
                         * number of times xenvif_gop_frag_copy() will
                         * call start_new_rx_buffer().
                         */
                        max_slots_needed += DIV_ROUND_UP(offset + size,
                                                         PAGE_SIZE);
                }

                /* To avoid the estimate becoming too pessimal for some
                 * frontends that limit posted rx requests, cap the estimate
                 * at MAX_SKB_FRAGS.
                 */
                if (max_slots_needed > MAX_SKB_FRAGS)
                        max_slots_needed = MAX_SKB_FRAGS;

                /* We may need one more slot for GSO metadata */
                if (skb_is_gso(skb) &&
                   (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4 ||
                    skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6))
                        max_slots_needed++;

                /* If the skb may not fit then bail out now */
                if (!xenvif_rx_ring_slots_available(vif, max_slots_needed)) {
                        skb_queue_head(&vif->rx_queue, skb);
                        need_to_notify = true;
                        vif->rx_last_skb_slots = max_slots_needed;
                        break;
                } else
                        vif->rx_last_skb_slots = 0;

                old_req_cons = vif->rx.req_cons;
                XENVIF_RX_CB(skb)->meta_slots_used = xenvif_gop_skb(skb, &npo);
                ring_slots_used = vif->rx.req_cons - old_req_cons;

                BUG_ON(ring_slots_used > max_slots_needed);

                __skb_queue_tail(&rxq, skb);
        }

        BUG_ON(npo.meta_prod > ARRAY_SIZE(vif->meta));

        if (!npo.copy_prod)
                goto done;

        BUG_ON(npo.copy_prod > MAX_GRANT_COPY_OPS);
        gnttab_batch_copy(vif->grant_copy_op, npo.copy_prod);

        while ((skb = __skb_dequeue(&rxq)) != NULL) {

                if ((1 << vif->meta[npo.meta_cons].gso_type) &
                    vif->gso_prefix_mask) {
                        resp = RING_GET_RESPONSE(&vif->rx,
                                                 vif->rx.rsp_prod_pvt++);

                        resp->flags = XEN_NETRXF_gso_prefix | XEN_NETRXF_more_data;

                        resp->offset = vif->meta[npo.meta_cons].gso_size;
                        resp->id = vif->meta[npo.meta_cons].id;
                        resp->status = XENVIF_RX_CB(skb)->meta_slots_used;

                        npo.meta_cons++;
                        XENVIF_RX_CB(skb)->meta_slots_used--;
                }


                vif->dev->stats.tx_bytes += skb->len;
                vif->dev->stats.tx_packets++;

                status = xenvif_check_gop(vif,
                                          XENVIF_RX_CB(skb)->meta_slots_used,
                                          &npo);

                if (XENVIF_RX_CB(skb)->meta_slots_used == 1)
                        flags = 0;
                else
                        flags = XEN_NETRXF_more_data;

                if (skb->ip_summed == CHECKSUM_PARTIAL) /* local packet? */
                        flags |= XEN_NETRXF_csum_blank | XEN_NETRXF_data_validated;
                else if (skb->ip_summed == CHECKSUM_UNNECESSARY)
                        /* remote but checksummed. */
                        flags |= XEN_NETRXF_data_validated;

                offset = 0;
                resp = make_rx_response(vif, vif->meta[npo.meta_cons].id,
                                        status, offset,
                                        vif->meta[npo.meta_cons].size,
                                        flags);

                if ((1 << vif->meta[npo.meta_cons].gso_type) &
                    vif->gso_mask) {
                        struct xen_netif_extra_info *gso =
                                (struct xen_netif_extra_info *)
                                RING_GET_RESPONSE(&vif->rx,
                                                  vif->rx.rsp_prod_pvt++);

                        resp->flags |= XEN_NETRXF_extra_info;

                        gso->u.gso.type = vif->meta[npo.meta_cons].gso_type;
                        gso->u.gso.size = vif->meta[npo.meta_cons].gso_size;
                        gso->u.gso.pad = 0;
                        gso->u.gso.features = 0;

                        gso->type = XEN_NETIF_EXTRA_TYPE_GSO;
                        gso->flags = 0;
                }

                xenvif_add_frag_responses(vif, status,
                                          vif->meta + npo.meta_cons + 1,
                                          XENVIF_RX_CB(skb)->meta_slots_used);

                RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->rx, ret);

                need_to_notify |= !!ret;

                npo.meta_cons += XENVIF_RX_CB(skb)->meta_slots_used;
                dev_kfree_skb(skb);
        }

done:
        if (need_to_notify)
                notify_remote_via_irq(vif->rx_irq);
}

void xenvif_napi_schedule_or_enable_events(struct xenvif *vif)
{
        int more_to_do;

        RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, more_to_do);

        if (more_to_do)
                napi_schedule(&vif->napi);
}

static void tx_add_credit(struct xenvif *vif)
{
        unsigned long max_burst, max_credit;

        /*
         * Allow a burst big enough to transmit a jumbo packet of up to 128kB.
         * Otherwise the interface can seize up due to insufficient credit.
         */
        max_burst = RING_GET_REQUEST(&vif->tx, vif->tx.req_cons)->size;
        max_burst = min(max_burst, 131072UL);
        max_burst = max(max_burst, vif->credit_bytes);

        /* Take care that adding a new chunk of credit doesn't wrap to zero. */
        max_credit = vif->remaining_credit + vif->credit_bytes;
        if (max_credit < vif->remaining_credit)
                max_credit = ULONG_MAX; /* wrapped: clamp to ULONG_MAX */

        vif->remaining_credit = min(max_credit, max_burst);
}

static void tx_credit_callback(unsigned long data)
{
        struct xenvif *vif = (struct xenvif *)data;
        tx_add_credit(vif);
        xenvif_napi_schedule_or_enable_events(vif);
}

static void xenvif_tx_err(struct xenvif *vif,
                          struct xen_netif_tx_request *txp, RING_IDX end)
{
        RING_IDX cons = vif->tx.req_cons;
        unsigned long flags;

        do {
                spin_lock_irqsave(&vif->response_lock, flags);
                make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR);
                spin_unlock_irqrestore(&vif->response_lock, flags);
                if (cons == end)
                        break;
                txp = RING_GET_REQUEST(&vif->tx, cons++);
        } while (1);
        vif->tx.req_cons = cons;
}

static void xenvif_fatal_tx_err(struct xenvif *vif)
{
        netdev_err(vif->dev, "fatal error; disabling device\n");
        vif->disabled = true;
        xenvif_kick_thread(vif);
}

static int xenvif_count_requests(struct xenvif *vif,
                                 struct xen_netif_tx_request *first,
                                 struct xen_netif_tx_request *txp,
                                 int work_to_do)
{
        RING_IDX cons = vif->tx.req_cons;
        int slots = 0;
        int drop_err = 0;
        int more_data;

        if (!(first->flags & XEN_NETTXF_more_data))
                return 0;

        do {
                struct xen_netif_tx_request dropped_tx = { 0 };

                if (slots >= work_to_do) {
                        netdev_err(vif->dev,
                                   "Asked for %d slots but exceeds this limit\n",
                                   work_to_do);
                        xenvif_fatal_tx_err(vif);
                        return -ENODATA;
                }

                /* This guest is really using too many slots and
                 * considered malicious.
                 */
                if (unlikely(slots >= fatal_skb_slots)) {
                        netdev_err(vif->dev,
                                   "Malicious frontend using %d slots, threshold %u\n",
                                   slots, fatal_skb_slots);
                        xenvif_fatal_tx_err(vif);
                        return -E2BIG;
                }

                /* Xen network protocol had implicit dependency on
                 * MAX_SKB_FRAGS. XEN_NETBK_LEGACY_SLOTS_MAX is set to
                 * the historical MAX_SKB_FRAGS value 18 to honor the
                 * same behavior as before. Any packet using more than
                 * 18 slots but less than fatal_skb_slots slots is
                 * dropped
                 */
                if (!drop_err && slots >= XEN_NETBK_LEGACY_SLOTS_MAX) {
                        if (net_ratelimit())
                                netdev_dbg(vif->dev,
                                           "Too many slots (%d) exceeding limit (%d), dropping packet\n",
                                           slots, XEN_NETBK_LEGACY_SLOTS_MAX);
                        drop_err = -E2BIG;
                }

                if (drop_err)
                        txp = &dropped_tx;

                memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),
                       sizeof(*txp));

                /* If the guest submitted a frame >= 64 KiB then
                 * first->size overflowed and following slots will
                 * appear to be larger than the frame.
                 *
                 * This cannot be fatal error as there are buggy
                 * frontends that do this.
                 *
                 * Consume all slots and drop the packet.
                 */
                if (!drop_err && txp->size > first->size) {
                        if (net_ratelimit())
                                netdev_dbg(vif->dev,
                                           "Invalid tx request, slot size %u > remaining size %u\n",
                                           txp->size, first->size);
                        drop_err = -EIO;
                }

                first->size -= txp->size;
                slots++;

                if (unlikely((txp->offset + txp->size) > PAGE_SIZE)) {
                        netdev_err(vif->dev, "Cross page boundary, txp->offset: %x, size: %u\n",
                                 txp->offset, txp->size);
                        xenvif_fatal_tx_err(vif);
                        return -EINVAL;
                }

                more_data = txp->flags & XEN_NETTXF_more_data;

                if (!drop_err)
                        txp++;

        } while (more_data);

        if (drop_err) {
                xenvif_tx_err(vif, first, cons + slots);
                return drop_err;
        }

        return slots;
}


struct xenvif_tx_cb {
        u16 pending_idx;
};

#define XENVIF_TX_CB(skb) ((struct xenvif_tx_cb *)(skb)->cb)

static inline void xenvif_tx_create_map_op(struct xenvif *vif,
                                          u16 pending_idx,
                                          struct xen_netif_tx_request *txp,
                                          struct gnttab_map_grant_ref *mop)
{
        vif->pages_to_map[mop-vif->tx_map_ops] = vif->mmap_pages[pending_idx];
        gnttab_set_map_op(mop, idx_to_kaddr(vif, pending_idx),
                          GNTMAP_host_map | GNTMAP_readonly,
                          txp->gref, vif->domid);

        memcpy(&vif->pending_tx_info[pending_idx].req, txp,
               sizeof(*txp));
}

static inline struct sk_buff *xenvif_alloc_skb(unsigned int size)
{
        struct sk_buff *skb =
                alloc_skb(size + NET_SKB_PAD + NET_IP_ALIGN,
                          GFP_ATOMIC | __GFP_NOWARN);
        if (unlikely(skb == NULL))
                return NULL;

        /* Packets passed to netif_rx() must have some headroom. */
        skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);

        /* Initialize it here to avoid later surprises */
        skb_shinfo(skb)->destructor_arg = NULL;

        return skb;
}

static struct gnttab_map_grant_ref *xenvif_get_requests(struct xenvif *vif,
                                                        struct sk_buff *skb,
                                                        struct xen_netif_tx_request *txp,
                                                        struct gnttab_map_grant_ref *gop)
{
        struct skb_shared_info *shinfo = skb_shinfo(skb);
        skb_frag_t *frags = shinfo->frags;
        u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
        int start;
        pending_ring_idx_t index;
        unsigned int nr_slots, frag_overflow = 0;

        /* At this point shinfo->nr_frags is in fact the number of
         * slots, which can be as large as XEN_NETBK_LEGACY_SLOTS_MAX.
         */
        if (shinfo->nr_frags > MAX_SKB_FRAGS) {
                frag_overflow = shinfo->nr_frags - MAX_SKB_FRAGS;
                BUG_ON(frag_overflow > MAX_SKB_FRAGS);
                shinfo->nr_frags = MAX_SKB_FRAGS;
        }
        nr_slots = shinfo->nr_frags;

        /* Skip first skb fragment if it is on same page as header fragment. */
        start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);

        for (shinfo->nr_frags = start; shinfo->nr_frags < nr_slots;
             shinfo->nr_frags++, txp++, gop++) {
                index = pending_index(vif->pending_cons++);
                pending_idx = vif->pending_ring[index];
                xenvif_tx_create_map_op(vif, pending_idx, txp, gop);
                frag_set_pending_idx(&frags[shinfo->nr_frags], pending_idx);
        }

        if (frag_overflow) {
                struct sk_buff *nskb = xenvif_alloc_skb(0);
                if (unlikely(nskb == NULL)) {
                        if (net_ratelimit())
                                netdev_err(vif->dev,
                                           "Can't allocate the frag_list skb.\n");
                        return NULL;
                }

                shinfo = skb_shinfo(nskb);
                frags = shinfo->frags;

                for (shinfo->nr_frags = 0; shinfo->nr_frags < frag_overflow;
                     shinfo->nr_frags++, txp++, gop++) {
                        index = pending_index(vif->pending_cons++);
                        pending_idx = vif->pending_ring[index];
                        xenvif_tx_create_map_op(vif, pending_idx, txp, gop);
                        frag_set_pending_idx(&frags[shinfo->nr_frags],
                                             pending_idx);
                }

                skb_shinfo(skb)->frag_list = nskb;
        }

        return gop;
}

static inline void xenvif_grant_handle_set(struct xenvif *vif,
                                           u16 pending_idx,
                                           grant_handle_t handle)
{
        if (unlikely(vif->grant_tx_handle[pending_idx] !=
                     NETBACK_INVALID_HANDLE)) {
                netdev_err(vif->dev,
                           "Trying to overwrite active handle! pending_idx: %x\n",
                           pending_idx);
                BUG();
        }
        vif->grant_tx_handle[pending_idx] = handle;
}

static inline void xenvif_grant_handle_reset(struct xenvif *vif,
                                             u16 pending_idx)
{
        if (unlikely(vif->grant_tx_handle[pending_idx] ==
                     NETBACK_INVALID_HANDLE)) {
                netdev_err(vif->dev,
                           "Trying to unmap invalid handle! pending_idx: %x\n",
                           pending_idx);
                BUG();
        }
        vif->grant_tx_handle[pending_idx] = NETBACK_INVALID_HANDLE;

}

static int xenvif_tx_check_gop(struct xenvif *vif,
                               struct sk_buff *skb,
                               struct gnttab_map_grant_ref **gopp_map,
                               struct gnttab_copy **gopp_copy)
{
        struct gnttab_map_grant_ref *gop_map = *gopp_map;
        u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
        struct skb_shared_info *shinfo = skb_shinfo(skb);
        int nr_frags = shinfo->nr_frags;
        int i, err;
        struct sk_buff *first_skb = NULL;

        /* Check status of header. */
        err = (*gopp_copy)->status;
        (*gopp_copy)++;
        if (unlikely(err)) {
                if (net_ratelimit())
                        netdev_dbg(vif->dev,
                                   "Grant copy of header failed! status: %d pending_idx: %u ref: %u\n",
                                   (*gopp_copy)->status,
                                   pending_idx,
                                   (*gopp_copy)->source.u.ref);
                xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);
        }

check_frags:
        for (i = 0; i < nr_frags; i++, gop_map++) {
                int j, newerr;

                pending_idx = frag_get_pending_idx(&shinfo->frags[i]);

                /* Check error status: if okay then remember grant handle. */
                newerr = gop_map->status;

                if (likely(!newerr)) {
                        xenvif_grant_handle_set(vif,
                                                pending_idx,
                                                gop_map->handle);
                        /* Had a previous error? Invalidate this fragment. */
                        if (unlikely(err))
                                xenvif_idx_unmap(vif, pending_idx);
                        continue;
                }

                /* Error on this fragment: respond to client with an error. */
                if (net_ratelimit())
                        netdev_dbg(vif->dev,
                                   "Grant map of %d. frag failed! status: %d pending_idx: %u ref: %u\n",
                                   i,
                                   gop_map->status,
                                   pending_idx,
                                   gop_map->ref);
                xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);

                /* Not the first error? Preceding frags already invalidated. */
                if (err)
                        continue;
                /* First error: invalidate preceding fragments. */
                for (j = 0; j < i; j++) {
                        pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
                        xenvif_idx_unmap(vif, pending_idx);
                }

                /* Remember the error: invalidate all subsequent fragments. */
                err = newerr;
        }

        if (skb_has_frag_list(skb)) {
                first_skb = skb;
                skb = shinfo->frag_list;
                shinfo = skb_shinfo(skb);
                nr_frags = shinfo->nr_frags;

                goto check_frags;
        }

        /* There was a mapping error in the frag_list skb. We have to unmap
         * the first skb's frags
         */
        if (first_skb && err) {
                int j;
                shinfo = skb_shinfo(first_skb);
                for (j = 0; j < shinfo->nr_frags; j++) {
                        pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
                        xenvif_idx_unmap(vif, pending_idx);
                }
        }

        *gopp_map = gop_map;
        return err;
}

static void xenvif_fill_frags(struct xenvif *vif, struct sk_buff *skb)
{
        struct skb_shared_info *shinfo = skb_shinfo(skb);
        int nr_frags = shinfo->nr_frags;
        int i;
        u16 prev_pending_idx = INVALID_PENDING_IDX;

        for (i = 0; i < nr_frags; i++) {
                skb_frag_t *frag = shinfo->frags + i;
                struct xen_netif_tx_request *txp;
                struct page *page;
                u16 pending_idx;

                pending_idx = frag_get_pending_idx(frag);

                /* If this is not the first frag, chain it to the previous*/
                if (prev_pending_idx == INVALID_PENDING_IDX)
                        skb_shinfo(skb)->destructor_arg =
                                &callback_param(vif, pending_idx);
                else
                        callback_param(vif, prev_pending_idx).ctx =
                                &callback_param(vif, pending_idx);

                callback_param(vif, pending_idx).ctx = NULL;
                prev_pending_idx = pending_idx;

                txp = &vif->pending_tx_info[pending_idx].req;
                page = virt_to_page(idx_to_kaddr(vif, pending_idx));
                __skb_fill_page_desc(skb, i, page, txp->offset, txp->size);
                skb->len += txp->size;
                skb->data_len += txp->size;
                skb->truesize += txp->size;

                /* Take an extra reference to offset network stack's put_page */
                get_page(vif->mmap_pages[pending_idx]);
        }
        /* FIXME: __skb_fill_page_desc set this to true because page->pfmemalloc
         * overlaps with "index", and "mapping" is not set. I think mapping
         * should be set. If delivered to local stack, it would drop this
         * skb in sk_filter unless the socket has the right to use it.
         */
        skb->pfmemalloc = false;
}

static int xenvif_get_extras(struct xenvif *vif,
                                struct xen_netif_extra_info *extras,
                                int work_to_do)
{
        struct xen_netif_extra_info extra;
        RING_IDX cons = vif->tx.req_cons;

        do {
                if (unlikely(work_to_do-- <= 0)) {
                        netdev_err(vif->dev, "Missing extra info\n");
                        xenvif_fatal_tx_err(vif);
                        return -EBADR;
                }

                memcpy(&extra, RING_GET_REQUEST(&vif->tx, cons),
                       sizeof(extra));
                if (unlikely(!extra.type ||
                             extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
                        vif->tx.req_cons = ++cons;
                        netdev_err(vif->dev,
                                   "Invalid extra type: %d\n", extra.type);
                        xenvif_fatal_tx_err(vif);
                        return -EINVAL;
                }

                memcpy(&extras[extra.type - 1], &extra, sizeof(extra));
                vif->tx.req_cons = ++cons;
        } while (extra.flags & XEN_NETIF_EXTRA_FLAG_MORE);

        return work_to_do;
}

static int xenvif_set_skb_gso(struct xenvif *vif,
                              struct sk_buff *skb,
                              struct xen_netif_extra_info *gso)
{
        if (!gso->u.gso.size) {
                netdev_err(vif->dev, "GSO size must not be zero.\n");
                xenvif_fatal_tx_err(vif);
                return -EINVAL;
        }

        switch (gso->u.gso.type) {
        case XEN_NETIF_GSO_TYPE_TCPV4:
                skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
                break;
        case XEN_NETIF_GSO_TYPE_TCPV6:
                skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
                break;
        default:
                netdev_err(vif->dev, "Bad GSO type %d.\n", gso->u.gso.type);
                xenvif_fatal_tx_err(vif);
                return -EINVAL;
        }

        skb_shinfo(skb)->gso_size = gso->u.gso.size;
        /* gso_segs will be calculated later */

        return 0;
}

static int checksum_setup(struct xenvif *vif, struct sk_buff *skb)
{
        bool recalculate_partial_csum = false;

        /* A GSO SKB must be CHECKSUM_PARTIAL. However some buggy
         * peers can fail to set NETRXF_csum_blank when sending a GSO
         * frame. In this case force the SKB to CHECKSUM_PARTIAL and
         * recalculate the partial checksum.
         */
        if (skb->ip_summed != CHECKSUM_PARTIAL && skb_is_gso(skb)) {
                vif->rx_gso_checksum_fixup++;
                skb->ip_summed = CHECKSUM_PARTIAL;
                recalculate_partial_csum = true;
        }

        /* A non-CHECKSUM_PARTIAL SKB does not require setup. */
        if (skb->ip_summed != CHECKSUM_PARTIAL)
                return 0;

        return skb_checksum_setup(skb, recalculate_partial_csum);
}

static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
{
        u64 now = get_jiffies_64();
        u64 next_credit = vif->credit_window_start +
                msecs_to_jiffies(vif->credit_usec / 1000);

        /* Timer could already be pending in rare cases. */
        if (timer_pending(&vif->credit_timeout))
                return true;

        /* Passed the point where we can replenish credit? */
        if (time_after_eq64(now, next_credit)) {
                vif->credit_window_start = now;
                tx_add_credit(vif);
        }

        /* Still too big to send right now? Set a callback. */
        if (size > vif->remaining_credit) {
                vif->credit_timeout.data     =
                        (unsigned long)vif;
                vif->credit_timeout.function =
                        tx_credit_callback;
                mod_timer(&vif->credit_timeout,
                          next_credit);
                vif->credit_window_start = next_credit;

                return true;
        }

        return false;
}

static void xenvif_tx_build_gops(struct xenvif *vif,
                                     int budget,
                                     unsigned *copy_ops,
                                     unsigned *map_ops)
{
        struct gnttab_map_grant_ref *gop = vif->tx_map_ops, *request_gop;
        struct sk_buff *skb;
        int ret;

        while (skb_queue_len(&vif->tx_queue) < budget) {
                struct xen_netif_tx_request txreq;
                struct xen_netif_tx_request txfrags[XEN_NETBK_LEGACY_SLOTS_MAX];
                struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX-1];
                u16 pending_idx;
                RING_IDX idx;
                int work_to_do;
                unsigned int data_len;
                pending_ring_idx_t index;

                if (vif->tx.sring->req_prod - vif->tx.req_cons >
                    XEN_NETIF_TX_RING_SIZE) {
                        netdev_err(vif->dev,
                                   "Impossible number of requests. "
                                   "req_prod %d, req_cons %d, size %ld\n",
                                   vif->tx.sring->req_prod, vif->tx.req_cons,
                                   XEN_NETIF_TX_RING_SIZE);
                        xenvif_fatal_tx_err(vif);
                        break;
                }

                work_to_do = RING_HAS_UNCONSUMED_REQUESTS(&vif->tx);
                if (!work_to_do)
                        break;

                idx = vif->tx.req_cons;
                rmb(); /* Ensure that we see the request before we copy it. */
                memcpy(&txreq, RING_GET_REQUEST(&vif->tx, idx), sizeof(txreq));

                /* Credit-based scheduling. */
                if (txreq.size > vif->remaining_credit &&
                    tx_credit_exceeded(vif, txreq.size))
                        break;

                vif->remaining_credit -= txreq.size;

                work_to_do--;
                vif->tx.req_cons = ++idx;

                memset(extras, 0, sizeof(extras));
                if (txreq.flags & XEN_NETTXF_extra_info) {
                        work_to_do = xenvif_get_extras(vif, extras,
                                                       work_to_do);
                        idx = vif->tx.req_cons;
                        if (unlikely(work_to_do < 0))
                                break;
                }

                ret = xenvif_count_requests(vif, &txreq, txfrags, work_to_do);
                if (unlikely(ret < 0))
                        break;

                idx += ret;

                if (unlikely(txreq.size < ETH_HLEN)) {
                        netdev_dbg(vif->dev,
                                   "Bad packet size: %d\n", txreq.size);
                        xenvif_tx_err(vif, &txreq, idx);
                        break;
                }

                /* No crossing a page as the payload mustn't fragment. */
                if (unlikely((txreq.offset + txreq.size) > PAGE_SIZE)) {
                        netdev_err(vif->dev,
                                   "txreq.offset: %x, size: %u, end: %lu\n",
                                   txreq.offset, txreq.size,
                                   (txreq.offset&~PAGE_MASK) + txreq.size);
                        xenvif_fatal_tx_err(vif);
                        break;
                }

                index = pending_index(vif->pending_cons);
                pending_idx = vif->pending_ring[index];

                data_len = (txreq.size > PKT_PROT_LEN &&
                            ret < XEN_NETBK_LEGACY_SLOTS_MAX) ?
                        PKT_PROT_LEN : txreq.size;

                skb = xenvif_alloc_skb(data_len);
                if (unlikely(skb == NULL)) {
                        netdev_dbg(vif->dev,
                                   "Can't allocate a skb in start_xmit.\n");
                        xenvif_tx_err(vif, &txreq, idx);
                        break;
                }

                if (extras[XEN_NETIF_EXTRA_TYPE_GSO - 1].type) {
                        struct xen_netif_extra_info *gso;
                        gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1];

                        if (xenvif_set_skb_gso(vif, skb, gso)) {
                                /* Failure in xenvif_set_skb_gso is fatal. */
                                kfree_skb(skb);
                                break;
                        }
                }

                XENVIF_TX_CB(skb)->pending_idx = pending_idx;

                __skb_put(skb, data_len);
                vif->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
                vif->tx_copy_ops[*copy_ops].source.domid = vif->domid;
                vif->tx_copy_ops[*copy_ops].source.offset = txreq.offset;

                vif->tx_copy_ops[*copy_ops].dest.u.gmfn =
                        virt_to_mfn(skb->data);
                vif->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
                vif->tx_copy_ops[*copy_ops].dest.offset =
                        offset_in_page(skb->data);

                vif->tx_copy_ops[*copy_ops].len = data_len;
                vif->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;

                (*copy_ops)++;

                skb_shinfo(skb)->nr_frags = ret;
                if (data_len < txreq.size) {
                        skb_shinfo(skb)->nr_frags++;
                        frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
                                             pending_idx);
                        xenvif_tx_create_map_op(vif, pending_idx, &txreq, gop);
                        gop++;
                } else {
                        frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
                                             INVALID_PENDING_IDX);
                        memcpy(&vif->pending_tx_info[pending_idx].req, &txreq,
                               sizeof(txreq));
                }

                vif->pending_cons++;

                request_gop = xenvif_get_requests(vif, skb, txfrags, gop);
                if (request_gop == NULL) {
                        kfree_skb(skb);
                        xenvif_tx_err(vif, &txreq, idx);
                        break;
                }
                gop = request_gop;

                __skb_queue_tail(&vif->tx_queue, skb);

                vif->tx.req_cons = idx;

                if (((gop-vif->tx_map_ops) >= ARRAY_SIZE(vif->tx_map_ops)) ||
                    (*copy_ops >= ARRAY_SIZE(vif->tx_copy_ops)))
                        break;
        }

        (*map_ops) = gop - vif->tx_map_ops;
        return;
}

/* Consolidate skb with a frag_list into a brand new one with local pages on
 * frags. Returns 0 or -ENOMEM if can't allocate new pages.
 */
static int xenvif_handle_frag_list(struct xenvif *vif, struct sk_buff *skb)
{
        unsigned int offset = skb_headlen(skb);
        skb_frag_t frags[MAX_SKB_FRAGS];
        int i;
        struct ubuf_info *uarg;
        struct sk_buff *nskb = skb_shinfo(skb)->frag_list;

        vif->tx_zerocopy_sent += 2;
        vif->tx_frag_overflow++;

        xenvif_fill_frags(vif, nskb);
        /* Subtract frags size, we will correct it later */
        skb->truesize -= skb->data_len;
        skb->len += nskb->len;
        skb->data_len += nskb->len;

        /* create a brand new frags array and coalesce there */
        for (i = 0; offset < skb->len; i++) {
                struct page *page;
                unsigned int len;

                BUG_ON(i >= MAX_SKB_FRAGS);
                page = alloc_page(GFP_ATOMIC|__GFP_COLD);
                if (!page) {
                        int j;
                        skb->truesize += skb->data_len;
                        for (j = 0; j < i; j++)
                                put_page(frags[j].page.p);
                        return -ENOMEM;
                }

                if (offset + PAGE_SIZE < skb->len)
                        len = PAGE_SIZE;
                else
                        len = skb->len - offset;
                if (skb_copy_bits(skb, offset, page_address(page), len))
                        BUG();

                offset += len;
                frags[i].page.p = page;
                frags[i].page_offset = 0;
                skb_frag_size_set(&frags[i], len);
        }
        /* swap out with old one */
        memcpy(skb_shinfo(skb)->frags,
               frags,
               i * sizeof(skb_frag_t));
        skb_shinfo(skb)->nr_frags = i;
        skb->truesize += i * PAGE_SIZE;

        /* remove traces of mapped pages and frag_list */
        skb_frag_list_init(skb);
        uarg = skb_shinfo(skb)->destructor_arg;
        uarg->callback(uarg, true);
        skb_shinfo(skb)->destructor_arg = NULL;

        skb_shinfo(nskb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
        kfree_skb(nskb);

        return 0;
}

static int xenvif_tx_submit(struct xenvif *vif)
{
        struct gnttab_map_grant_ref *gop_map = vif->tx_map_ops;
        struct gnttab_copy *gop_copy = vif->tx_copy_ops;
        struct sk_buff *skb;
        int work_done = 0;

        while ((skb = __skb_dequeue(&vif->tx_queue)) != NULL) {
                struct xen_netif_tx_request *txp;
                u16 pending_idx;
                unsigned data_len;

                pending_idx = XENVIF_TX_CB(skb)->pending_idx;
                txp = &vif->pending_tx_info[pending_idx].req;

                /* Check the remap error code. */
                if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map, &gop_copy))) {
                        skb_shinfo(skb)->nr_frags = 0;
                        kfree_skb(skb);
                        continue;
                }

                data_len = skb->len;
                callback_param(vif, pending_idx).ctx = NULL;
                if (data_len < txp->size) {
                        /* Append the packet payload as a fragment. */
                        txp->offset += data_len;
                        txp->size -= data_len;
                } else {
                        /* Schedule a response immediately. */
                        xenvif_idx_release(vif, pending_idx,
                                           XEN_NETIF_RSP_OKAY);
                }

                if (txp->flags & XEN_NETTXF_csum_blank)
                        skb->ip_summed = CHECKSUM_PARTIAL;
                else if (txp->flags & XEN_NETTXF_data_validated)
                        skb->ip_summed = CHECKSUM_UNNECESSARY;

                xenvif_fill_frags(vif, skb);

                if (unlikely(skb_has_frag_list(skb))) {
                        if (xenvif_handle_frag_list(vif, skb)) {
                                if (net_ratelimit())
                                        netdev_err(vif->dev,
                                                   "Not enough memory to consolidate frag_list!\n");
                                skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
                                kfree_skb(skb);
                                continue;
                        }
                }

                if (skb_is_nonlinear(skb) && skb_headlen(skb) < PKT_PROT_LEN) {
                        int target = min_t(int, skb->len, PKT_PROT_LEN);
                        __pskb_pull_tail(skb, target - skb_headlen(skb));
                }

                skb->dev      = vif->dev;
                skb->protocol = eth_type_trans(skb, skb->dev);
                skb_reset_network_header(skb);

                if (checksum_setup(vif, skb)) {
                        netdev_dbg(vif->dev,
                                   "Can't setup checksum in net_tx_action\n");
                        /* We have to set this flag to trigger the callback */
                        if (skb_shinfo(skb)->destructor_arg)
                                skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
                        kfree_skb(skb);
                        continue;
                }

                skb_probe_transport_header(skb, 0);

                /* If the packet is GSO then we will have just set up the
                 * transport header offset in checksum_setup so it's now
                 * straightforward to calculate gso_segs.
                 */
                if (skb_is_gso(skb)) {
                        int mss = skb_shinfo(skb)->gso_size;
                        int hdrlen = skb_transport_header(skb) -
                                skb_mac_header(skb) +
                                tcp_hdrlen(skb);

                        skb_shinfo(skb)->gso_segs =
                                DIV_ROUND_UP(skb->len - hdrlen, mss);
                }

                vif->dev->stats.rx_bytes += skb->len;
                vif->dev->stats.rx_packets++;

                work_done++;

                /* Set this flag right before netif_receive_skb, otherwise
                 * someone might think this packet already left netback, and
                 * do a skb_copy_ubufs while we are still in control of the
                 * skb. E.g. the __pskb_pull_tail earlier can do such thing.
                 */
                if (skb_shinfo(skb)->destructor_arg) {
                        skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
                        vif->tx_zerocopy_sent++;
                }

                netif_receive_skb(skb);
        }

        return work_done;
}

void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success)
{
        unsigned long flags;
        pending_ring_idx_t index;
        struct xenvif *vif = ubuf_to_vif(ubuf);

        /* This is the only place where we grab this lock, to protect callbacks
         * from each other.
         */
        spin_lock_irqsave(&vif->callback_lock, flags);
        do {
                u16 pending_idx = ubuf->desc;
                ubuf = (struct ubuf_info *) ubuf->ctx;
                BUG_ON(vif->dealloc_prod - vif->dealloc_cons >=
                        MAX_PENDING_REQS);
                index = pending_index(vif->dealloc_prod);
                vif->dealloc_ring[index] = pending_idx;
                /* Sync with xenvif_tx_dealloc_action:
                 * insert idx then incr producer.
                 */
                smp_wmb();
                vif->dealloc_prod++;
        } while (ubuf);
        wake_up(&vif->dealloc_wq);
        spin_unlock_irqrestore(&vif->callback_lock, flags);

        if (likely(zerocopy_success))
                vif->tx_zerocopy_success++;
        else
                vif->tx_zerocopy_fail++;
}

static inline void xenvif_tx_dealloc_action(struct xenvif *vif)
{
        struct gnttab_unmap_grant_ref *gop;
        pending_ring_idx_t dc, dp;
        u16 pending_idx, pending_idx_release[MAX_PENDING_REQS];
        unsigned int i = 0;

        dc = vif->dealloc_cons;
        gop = vif->tx_unmap_ops;

        /* Free up any grants we have finished using */
        do {
                dp = vif->dealloc_prod;

                /* Ensure we see all indices enqueued by all
                 * xenvif_zerocopy_callback().
                 */
                smp_rmb();

                while (dc != dp) {
                        BUG_ON(gop - vif->tx_unmap_ops > MAX_PENDING_REQS);
                        pending_idx =
                                vif->dealloc_ring[pending_index(dc++)];

                        pending_idx_release[gop-vif->tx_unmap_ops] =
                                pending_idx;
                        vif->pages_to_unmap[gop-vif->tx_unmap_ops] =
                                vif->mmap_pages[pending_idx];
                        gnttab_set_unmap_op(gop,
                                            idx_to_kaddr(vif, pending_idx),
                                            GNTMAP_host_map,
                                            vif->grant_tx_handle[pending_idx]);
                        xenvif_grant_handle_reset(vif, pending_idx);
                        ++gop;
                }

        } while (dp != vif->dealloc_prod);

        vif->dealloc_cons = dc;

        if (gop - vif->tx_unmap_ops > 0) {
                int ret;
                ret = gnttab_unmap_refs(vif->tx_unmap_ops,
                                        NULL,
                                        vif->pages_to_unmap,
                                        gop - vif->tx_unmap_ops);
                if (ret) {
                        netdev_err(vif->dev, "Unmap fail: nr_ops %tx ret %d\n",
                                   gop - vif->tx_unmap_ops, ret);
                        for (i = 0; i < gop - vif->tx_unmap_ops; ++i) {
                                if (gop[i].status != GNTST_okay)
                                        netdev_err(vif->dev,
                                                   " host_addr: %llx handle: %x status: %d\n",
                                                   gop[i].host_addr,
                                                   gop[i].handle,
                                                   gop[i].status);
                        }
                        BUG();
                }
        }

        for (i = 0; i < gop - vif->tx_unmap_ops; ++i)
                xenvif_idx_release(vif, pending_idx_release[i],
                                   XEN_NETIF_RSP_OKAY);
}


/* Called after netfront has transmitted */
int xenvif_tx_action(struct xenvif *vif, int budget)
{
        unsigned nr_mops, nr_cops = 0;
        int work_done, ret;

        if (unlikely(!tx_work_todo(vif)))
                return 0;

        xenvif_tx_build_gops(vif, budget, &nr_cops, &nr_mops);

        if (nr_cops == 0)
                return 0;

        gnttab_batch_copy(vif->tx_copy_ops, nr_cops);
        if (nr_mops != 0) {
                ret = gnttab_map_refs(vif->tx_map_ops,
                                      NULL,
                                      vif->pages_to_map,
                                      nr_mops);
                BUG_ON(ret);
        }

        work_done = xenvif_tx_submit(vif);

        return work_done;
}

static void xenvif_idx_release(struct xenvif *vif, u16 pending_idx,
                               u8 status)
{
        struct pending_tx_info *pending_tx_info;
        pending_ring_idx_t index;
        unsigned long flags;

        pending_tx_info = &vif->pending_tx_info[pending_idx];
        spin_lock_irqsave(&vif->response_lock, flags);
        make_tx_response(vif, &pending_tx_info->req, status);
        index = pending_index(vif->pending_prod);
        vif->pending_ring[index] = pending_idx;
        /* TX shouldn't use the index before we give it back here */
        mb();
        vif->pending_prod++;
        spin_unlock_irqrestore(&vif->response_lock, flags);
}


static void make_tx_response(struct xenvif *vif,
                             struct xen_netif_tx_request *txp,
                             s8       st)
{
        RING_IDX i = vif->tx.rsp_prod_pvt;
        struct xen_netif_tx_response *resp;
        int notify;

        resp = RING_GET_RESPONSE(&vif->tx, i);
        resp->id     = txp->id;
        resp->status = st;

        if (txp->flags & XEN_NETTXF_extra_info)
                RING_GET_RESPONSE(&vif->tx, ++i)->status = XEN_NETIF_RSP_NULL;

        vif->tx.rsp_prod_pvt = ++i;
        RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->tx, notify);
        if (notify)
                notify_remote_via_irq(vif->tx_irq);
}

static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif,
                                             u16      id,
                                             s8       st,
                                             u16      offset,
                                             u16      size,
                                             u16      flags)
{
        RING_IDX i = vif->rx.rsp_prod_pvt;
        struct xen_netif_rx_response *resp;

        resp = RING_GET_RESPONSE(&vif->rx, i);
        resp->offset     = offset;
        resp->flags      = flags;
        resp->id         = id;
        resp->status     = (s16)size;
        if (st < 0)
                resp->status = (s16)st;

        vif->rx.rsp_prod_pvt = ++i;

        return resp;
}

void xenvif_idx_unmap(struct xenvif *vif, u16 pending_idx)
{
        int ret;
        struct gnttab_unmap_grant_ref tx_unmap_op;

        gnttab_set_unmap_op(&tx_unmap_op,
                            idx_to_kaddr(vif, pending_idx),
                            GNTMAP_host_map,
                            vif->grant_tx_handle[pending_idx]);
        xenvif_grant_handle_reset(vif, pending_idx);

        ret = gnttab_unmap_refs(&tx_unmap_op, NULL,
                                &vif->mmap_pages[pending_idx], 1);
        if (ret) {
                netdev_err(vif->dev,
                           "Unmap fail: ret: %d pending_idx: %d host_addr: %llx handle: %x status: %d\n",
                           ret,
                           pending_idx,
                           tx_unmap_op.host_addr,
                           tx_unmap_op.handle,
                           tx_unmap_op.status);
                BUG();
        }

        xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_OKAY);
}

static inline int rx_work_todo(struct xenvif *vif)
{
        return (!skb_queue_empty(&vif->rx_queue) &&
               xenvif_rx_ring_slots_available(vif, vif->rx_last_skb_slots)) ||
               vif->rx_queue_purge;
}

static inline int tx_work_todo(struct xenvif *vif)
{

        if (likely(RING_HAS_UNCONSUMED_REQUESTS(&vif->tx)))
                return 1;

        return 0;
}

static inline bool tx_dealloc_work_todo(struct xenvif *vif)
{
        return vif->dealloc_cons != vif->dealloc_prod;
}

void xenvif_unmap_frontend_rings(struct xenvif *vif)
{
        if (vif->tx.sring)
                xenbus_unmap_ring_vfree(xenvif_to_xenbus_device(vif),
                                        vif->tx.sring);
        if (vif->rx.sring)
                xenbus_unmap_ring_vfree(xenvif_to_xenbus_device(vif),
                                        vif->rx.sring);
}

int xenvif_map_frontend_rings(struct xenvif *vif,
                              grant_ref_t tx_ring_ref,
                              grant_ref_t rx_ring_ref)
{
        void *addr;
        struct xen_netif_tx_sring *txs;
        struct xen_netif_rx_sring *rxs;

        int err = -ENOMEM;

        err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(vif),
                                     tx_ring_ref, &addr);
        if (err)
                goto err;

        txs = (struct xen_netif_tx_sring *)addr;
        BACK_RING_INIT(&vif->tx, txs, PAGE_SIZE);

        err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(vif),
                                     rx_ring_ref, &addr);
        if (err)
                goto err;

        rxs = (struct xen_netif_rx_sring *)addr;
        BACK_RING_INIT(&vif->rx, rxs, PAGE_SIZE);

        return 0;

err:
        xenvif_unmap_frontend_rings(vif);
        return err;
}

void xenvif_stop_queue(struct xenvif *vif)
{
        if (!vif->can_queue)
                return;

        netif_stop_queue(vif->dev);
}

static void xenvif_start_queue(struct xenvif *vif)
{
        if (xenvif_schedulable(vif))
                netif_wake_queue(vif->dev);
}

int xenvif_kthread_guest_rx(void *data)
{
        struct xenvif *vif = data;
        struct sk_buff *skb;

        while (!kthread_should_stop()) {
                wait_event_interruptible(vif->wq,
                                         rx_work_todo(vif) ||
                                         vif->disabled ||
                                         kthread_should_stop());

                /* This frontend is found to be rogue, disable it in
                 * kthread context. Currently this is only set when
                 * netback finds out frontend sends malformed packet,
                 * but we cannot disable the interface in softirq
                 * context so we defer it here.
                 */
                if (unlikely(vif->disabled && netif_carrier_ok(vif->dev)))
                        xenvif_carrier_off(vif);

                if (kthread_should_stop())
                        break;

                if (vif->rx_queue_purge) {
                        skb_queue_purge(&vif->rx_queue);
                        vif->rx_queue_purge = false;
                }

                if (!skb_queue_empty(&vif->rx_queue))
                        xenvif_rx_action(vif);

                if (skb_queue_empty(&vif->rx_queue) &&
                    netif_queue_stopped(vif->dev)) {
                        del_timer_sync(&vif->wake_queue);
                        xenvif_start_queue(vif);
                }

                cond_resched();
        }

        /* Bin any remaining skbs */
        while ((skb = skb_dequeue(&vif->rx_queue)) != NULL)
                dev_kfree_skb(skb);

        return 0;
}

int xenvif_dealloc_kthread(void *data)
{
        struct xenvif *vif = data;

        while (!kthread_should_stop()) {
                wait_event_interruptible(vif->dealloc_wq,
                                         tx_dealloc_work_todo(vif) ||
                                         kthread_should_stop());
                if (kthread_should_stop())
                        break;

                xenvif_tx_dealloc_action(vif);
                cond_resched();
        }

        /* Unmap anything remaining*/
        if (tx_dealloc_work_todo(vif))
                xenvif_tx_dealloc_action(vif);

        return 0;
}

static int __init netback_init(void)
{
        int rc = 0;

        if (!xen_domain())
                return -ENODEV;

        if (fatal_skb_slots < XEN_NETBK_LEGACY_SLOTS_MAX) {
                pr_info("fatal_skb_slots too small (%d), bump it to XEN_NETBK_LEGACY_SLOTS_MAX (%d)\n",
                        fatal_skb_slots, XEN_NETBK_LEGACY_SLOTS_MAX);
                fatal_skb_slots = XEN_NETBK_LEGACY_SLOTS_MAX;
        }

        rc = xenvif_xenbus_init();
        if (rc)
                goto failed_init;

        rx_drain_timeout_jiffies = msecs_to_jiffies(rx_drain_timeout_msecs);

        return 0;

failed_init:
        return rc;
}

module_init(netback_init);

static void __exit netback_fini(void)
{
        xenvif_xenbus_fini();
}
module_exit(netback_fini);

MODULE_LICENSE("Dual BSD/GPL");
MODULE_ALIAS("xen-backend:vif");