ar-ack.c

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/* Management of Tx window, Tx resend, ACKs and out-of-sequence reception
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/circ_buf.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/udp.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "ar-internal.h"

static unsigned int rxrpc_ack_defer = 1;

static const char *const rxrpc_acks[] = {
    "---", "REQ", "DUP", "OOS", "WIN", "MEM", "PNG", "PNR", "DLY", "IDL",
    "-?-"
};

static const s8 rxrpc_ack_priority[] = {
    [0]             = 0,
    [RXRPC_ACK_DELAY]       = 1,
    [RXRPC_ACK_REQUESTED]       = 2,
    [RXRPC_ACK_IDLE]        = 3,
    [RXRPC_ACK_PING_RESPONSE]   = 4,
    [RXRPC_ACK_DUPLICATE]       = 5,
    [RXRPC_ACK_OUT_OF_SEQUENCE] = 6,
    [RXRPC_ACK_EXCEEDS_WINDOW]  = 7,
    [RXRPC_ACK_NOSPACE]     = 8,
};

/*
 * propose an ACK be sent
 */
void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
             __be32 serial, bool immediate)
{
    unsigned long expiry;
    s8 prior = rxrpc_ack_priority[ack_reason];

    ASSERTCMP(prior, >, 0);

    _enter("{%d},%s,%%%x,%u",
           call->debug_id, rxrpc_acks[ack_reason], ntohl(serial),
           immediate);

    if (prior < rxrpc_ack_priority[call->ackr_reason]) {
        if (immediate)
            goto cancel_timer;
        return;
    }

    /* update DELAY, IDLE, REQUESTED and PING_RESPONSE ACK serial
     * numbers */
    if (prior == rxrpc_ack_priority[call->ackr_reason]) {
        if (prior <= 4)
            call->ackr_serial = serial;
        if (immediate)
            goto cancel_timer;
        return;
    }

    call->ackr_reason = ack_reason;
    call->ackr_serial = serial;

    switch (ack_reason) {
    case RXRPC_ACK_DELAY:
        _debug("run delay timer");
        call->ack_timer.expires = jiffies + rxrpc_ack_timeout * HZ;
        add_timer(&call->ack_timer);
        return;

    case RXRPC_ACK_IDLE:
        if (!immediate) {
            _debug("run defer timer");
            expiry = 1;
            goto run_timer;
        }
        goto cancel_timer;

    case RXRPC_ACK_REQUESTED:
        if (!rxrpc_ack_defer)
            goto cancel_timer;
        if (!immediate || serial == cpu_to_be32(1)) {
            _debug("run defer timer");
            expiry = rxrpc_ack_defer;
            goto run_timer;
        }

    default:
        _debug("immediate ACK");
        goto cancel_timer;
    }

run_timer:
    expiry += jiffies;
    if (!timer_pending(&call->ack_timer) ||
        time_after(call->ack_timer.expires, expiry))
        mod_timer(&call->ack_timer, expiry);
    return;

cancel_timer:
    _debug("cancel timer %%%u", ntohl(serial));
    try_to_del_timer_sync(&call->ack_timer);
    read_lock_bh(&call->state_lock);
    if (call->state <= RXRPC_CALL_COMPLETE &&
        !test_and_set_bit(RXRPC_CALL_ACK, &call->events))
        rxrpc_queue_call(call);
    read_unlock_bh(&call->state_lock);
}

/*
 * propose an ACK be sent, locking the call structure
 */
void rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
               __be32 serial, bool immediate)
{
    s8 prior = rxrpc_ack_priority[ack_reason];

    if (prior > rxrpc_ack_priority[call->ackr_reason]) {
        spin_lock_bh(&call->lock);
        __rxrpc_propose_ACK(call, ack_reason, serial, immediate);
        spin_unlock_bh(&call->lock);
    }
}

/*
 * set the resend timer
 */
static void rxrpc_set_resend(struct rxrpc_call *call, u8 resend,
                 unsigned long resend_at)
{
    read_lock_bh(&call->state_lock);
    if (call->state >= RXRPC_CALL_COMPLETE)
        resend = 0;

    if (resend & 1) {
        _debug("SET RESEND");
        set_bit(RXRPC_CALL_RESEND, &call->events);
    }

    if (resend & 2) {
        _debug("MODIFY RESEND TIMER");
        set_bit(RXRPC_CALL_RUN_RTIMER, &call->flags);
        mod_timer(&call->resend_timer, resend_at);
    } else {
        _debug("KILL RESEND TIMER");
        del_timer_sync(&call->resend_timer);
        clear_bit(RXRPC_CALL_RESEND_TIMER, &call->events);
        clear_bit(RXRPC_CALL_RUN_RTIMER, &call->flags);
    }
    read_unlock_bh(&call->state_lock);
}

/*
 * resend packets
 */
static void rxrpc_resend(struct rxrpc_call *call)
{
    struct rxrpc_skb_priv *sp;
    struct rxrpc_header *hdr;
    struct sk_buff *txb;
    unsigned long *p_txb, resend_at;
    int loop, stop;
    u8 resend;

    _enter("{%d,%d,%d,%d},",
           call->acks_hard, call->acks_unacked,
           atomic_read(&call->sequence),
           CIRC_CNT(call->acks_head, call->acks_tail, call->acks_winsz));

    stop = 0;
    resend = 0;
    resend_at = 0;

    for (loop = call->acks_tail;
         loop != call->acks_head || stop;
         loop = (loop + 1) &  (call->acks_winsz - 1)
         ) {
        p_txb = call->acks_window + loop;
        smp_read_barrier_depends();
        if (*p_txb & 1)
            continue;

        txb = (struct sk_buff *) *p_txb;
        sp = rxrpc_skb(txb);

        if (sp->need_resend) {
            sp->need_resend = false;

            /* each Tx packet has a new serial number */
            sp->hdr.serial =
                htonl(atomic_inc_return(&call->conn->serial));

            hdr = (struct rxrpc_header *) txb->head;
            hdr->serial = sp->hdr.serial;

            _proto("Tx DATA %%%u { #%d }",
                   ntohl(sp->hdr.serial), ntohl(sp->hdr.seq));
            if (rxrpc_send_packet(call->conn->trans, txb) < 0) {
                stop = 0;
                sp->resend_at = jiffies + 3;
            } else {
                sp->resend_at =
                    jiffies + rxrpc_resend_timeout * HZ;
            }
        }

        if (time_after_eq(jiffies + 1, sp->resend_at)) {
            sp->need_resend = true;
            resend |= 1;
        } else if (resend & 2) {
            if (time_before(sp->resend_at, resend_at))
                resend_at = sp->resend_at;
        } else {
            resend_at = sp->resend_at;
            resend |= 2;
        }
    }

    rxrpc_set_resend(call, resend, resend_at);
    _leave("");
}

/*
 * handle resend timer expiry
 */
static void rxrpc_resend_timer(struct rxrpc_call *call)
{
    struct rxrpc_skb_priv *sp;
    struct sk_buff *txb;
    unsigned long *p_txb, resend_at;
    int loop;
    u8 resend;

    _enter("%d,%d,%d",
           call->acks_tail, call->acks_unacked, call->acks_head);

    if (call->state >= RXRPC_CALL_COMPLETE)
        return;

    resend = 0;
    resend_at = 0;

    for (loop = call->acks_unacked;
         loop != call->acks_head;
         loop = (loop + 1) &  (call->acks_winsz - 1)
         ) {
        p_txb = call->acks_window + loop;
        smp_read_barrier_depends();
        txb = (struct sk_buff *) (*p_txb & ~1);
        sp = rxrpc_skb(txb);

        ASSERT(!(*p_txb & 1));

        if (sp->need_resend) {
            ;
        } else if (time_after_eq(jiffies + 1, sp->resend_at)) {
            sp->need_resend = true;
            resend |= 1;
        } else if (resend & 2) {
            if (time_before(sp->resend_at, resend_at))
                resend_at = sp->resend_at;
        } else {
            resend_at = sp->resend_at;
            resend |= 2;
        }
    }

    rxrpc_set_resend(call, resend, resend_at);
    _leave("");
}

/*
 * process soft ACKs of our transmitted packets
 * - these indicate packets the peer has or has not received, but hasn't yet
 *   given to the consumer, and so can still be discarded and re-requested
 */
static int rxrpc_process_soft_ACKs(struct rxrpc_call *call,
                   struct rxrpc_ackpacket *ack,
                   struct sk_buff *skb)
{
    struct rxrpc_skb_priv *sp;
    struct sk_buff *txb;
    unsigned long *p_txb, resend_at;
    int loop;
    u8 sacks[RXRPC_MAXACKS], resend;

    _enter("{%d,%d},{%d},",
           call->acks_hard,
           CIRC_CNT(call->acks_head, call->acks_tail, call->acks_winsz),
           ack->nAcks);

    if (skb_copy_bits(skb, 0, sacks, ack->nAcks) < 0)
        goto protocol_error;

    resend = 0;
    resend_at = 0;
    for (loop = 0; loop < ack->nAcks; loop++) {
        p_txb = call->acks_window;
        p_txb += (call->acks_tail + loop) & (call->acks_winsz - 1);
        smp_read_barrier_depends();
        txb = (struct sk_buff *) (*p_txb & ~1);
        sp = rxrpc_skb(txb);

        switch (sacks[loop]) {
        case RXRPC_ACK_TYPE_ACK:
            sp->need_resend = false;
            *p_txb |= 1;
            break;
        case RXRPC_ACK_TYPE_NACK:
            sp->need_resend = true;
            *p_txb &= ~1;
            resend = 1;
            break;
        default:
            _debug("Unsupported ACK type %d", sacks[loop]);
            goto protocol_error;
        }
    }

    smp_mb();
    call->acks_unacked = (call->acks_tail + loop) & (call->acks_winsz - 1);

    /* anything not explicitly ACK'd is implicitly NACK'd, but may just not
     * have been received or processed yet by the far end */
    for (loop = call->acks_unacked;
         loop != call->acks_head;
         loop = (loop + 1) &  (call->acks_winsz - 1)
         ) {
        p_txb = call->acks_window + loop;
        smp_read_barrier_depends();
        txb = (struct sk_buff *) (*p_txb & ~1);
        sp = rxrpc_skb(txb);

        if (*p_txb & 1) {
            /* packet must have been discarded */
            sp->need_resend = true;
            *p_txb &= ~1;
            resend |= 1;
        } else if (sp->need_resend) {
            ;
        } else if (time_after_eq(jiffies + 1, sp->resend_at)) {
            sp->need_resend = true;
            resend |= 1;
        } else if (resend & 2) {
            if (time_before(sp->resend_at, resend_at))
                resend_at = sp->resend_at;
        } else {
            resend_at = sp->resend_at;
            resend |= 2;
        }
    }

    rxrpc_set_resend(call, resend, resend_at);
    _leave(" = 0");
    return 0;

protocol_error:
    _leave(" = -EPROTO");
    return -EPROTO;
}

/*
 * discard hard-ACK'd packets from the Tx window
 */
static void rxrpc_rotate_tx_window(struct rxrpc_call *call, u32 hard)
{
    unsigned long _skb;
    int tail = call->acks_tail, old_tail;
    int win = CIRC_CNT(call->acks_head, tail, call->acks_winsz);

    _enter("{%u,%u},%u", call->acks_hard, win, hard);

    ASSERTCMP(hard - call->acks_hard, <=, win);

    while (call->acks_hard < hard) {
        smp_read_barrier_depends();
        _skb = call->acks_window[tail] & ~1;
        rxrpc_free_skb((struct sk_buff *) _skb);
        old_tail = tail;
        tail = (tail + 1) & (call->acks_winsz - 1);
        call->acks_tail = tail;
        if (call->acks_unacked == old_tail)
            call->acks_unacked = tail;
        call->acks_hard++;
    }

    wake_up(&call->tx_waitq);
}

/*
 * clear the Tx window in the event of a failure
 */
static void rxrpc_clear_tx_window(struct rxrpc_call *call)
{
    rxrpc_rotate_tx_window(call, atomic_read(&call->sequence));
}

/*
 * drain the out of sequence received packet queue into the packet Rx queue
 */
static int rxrpc_drain_rx_oos_queue(struct rxrpc_call *call)
{
    struct rxrpc_skb_priv *sp;
    struct sk_buff *skb;
    bool terminal;
    int ret;

    _enter("{%d,%d}", call->rx_data_post, call->rx_first_oos);

    spin_lock_bh(&call->lock);

    ret = -ECONNRESET;
    if (test_bit(RXRPC_CALL_RELEASED, &call->flags))
        goto socket_unavailable;

    skb = skb_dequeue(&call->rx_oos_queue);
    if (skb) {
        sp = rxrpc_skb(skb);

        _debug("drain OOS packet %d [%d]",
               ntohl(sp->hdr.seq), call->rx_first_oos);

        if (ntohl(sp->hdr.seq) != call->rx_first_oos) {
            skb_queue_head(&call->rx_oos_queue, skb);
            call->rx_first_oos = ntohl(rxrpc_skb(skb)->hdr.seq);
            _debug("requeue %p {%u}", skb, call->rx_first_oos);
        } else {
            skb->mark = RXRPC_SKB_MARK_DATA;
            terminal = ((sp->hdr.flags & RXRPC_LAST_PACKET) &&
                !(sp->hdr.flags & RXRPC_CLIENT_INITIATED));
            ret = rxrpc_queue_rcv_skb(call, skb, true, terminal);
            BUG_ON(ret < 0);
            _debug("drain #%u", call->rx_data_post);
            call->rx_data_post++;

            /* find out what the next packet is */
            skb = skb_peek(&call->rx_oos_queue);
            if (skb)
                call->rx_first_oos =
                    ntohl(rxrpc_skb(skb)->hdr.seq);
            else
                call->rx_first_oos = 0;
            _debug("peek %p {%u}", skb, call->rx_first_oos);
        }
    }

    ret = 0;
socket_unavailable:
    spin_unlock_bh(&call->lock);
    _leave(" = %d", ret);
    return ret;
}

/*
 * insert an out of sequence packet into the buffer
 */
static void rxrpc_insert_oos_packet(struct rxrpc_call *call,
                    struct sk_buff *skb)
{
    struct rxrpc_skb_priv *sp, *psp;
    struct sk_buff *p;
    u32 seq;

    sp = rxrpc_skb(skb);
    seq = ntohl(sp->hdr.seq);
    _enter(",,{%u}", seq);

    skb->destructor = rxrpc_packet_destructor;
    ASSERTCMP(sp->call, ==, NULL);
    sp->call = call;
    rxrpc_get_call(call);

    /* insert into the buffer in sequence order */
    spin_lock_bh(&call->lock);

    skb_queue_walk(&call->rx_oos_queue, p) {
        psp = rxrpc_skb(p);
        if (ntohl(psp->hdr.seq) > seq) {
            _debug("insert oos #%u before #%u",
                   seq, ntohl(psp->hdr.seq));
            skb_insert(p, skb, &call->rx_oos_queue);
            goto inserted;
        }
    }

    _debug("append oos #%u", seq);
    skb_queue_tail(&call->rx_oos_queue, skb);
inserted:

    /* we might now have a new front to the queue */
    if (call->rx_first_oos == 0 || seq < call->rx_first_oos)
        call->rx_first_oos = seq;

    read_lock(&call->state_lock);
    if (call->state < RXRPC_CALL_COMPLETE &&
        call->rx_data_post == call->rx_first_oos) {
        _debug("drain rx oos now");
        set_bit(RXRPC_CALL_DRAIN_RX_OOS, &call->events);
    }
    read_unlock(&call->state_lock);

    spin_unlock_bh(&call->lock);
    _leave(" [stored #%u]", call->rx_first_oos);
}

/*
 * clear the Tx window on final ACK reception
 */
static void rxrpc_zap_tx_window(struct rxrpc_call *call)
{
    struct rxrpc_skb_priv *sp;
    struct sk_buff *skb;
    unsigned long _skb, *acks_window;
    u8 winsz = call->acks_winsz;
    int tail;

    acks_window = call->acks_window;
    call->acks_window = NULL;

    while (CIRC_CNT(call->acks_head, call->acks_tail, winsz) > 0) {
        tail = call->acks_tail;
        smp_read_barrier_depends();
        _skb = acks_window[tail] & ~1;
        smp_mb();
        call->acks_tail = (call->acks_tail + 1) & (winsz - 1);

        skb = (struct sk_buff *) _skb;
        sp = rxrpc_skb(skb);
        _debug("+++ clear Tx %u", ntohl(sp->hdr.seq));
        rxrpc_free_skb(skb);
    }

    kfree(acks_window);
}

/*
 * process the extra information that may be appended to an ACK packet
 */
static void rxrpc_extract_ackinfo(struct rxrpc_call *call, struct sk_buff *skb,
                  unsigned int latest, int nAcks)
{
    struct rxrpc_ackinfo ackinfo;
    struct rxrpc_peer *peer;
    unsigned int mtu;

    if (skb_copy_bits(skb, nAcks + 3, &ackinfo, sizeof(ackinfo)) < 0) {
        _leave(" [no ackinfo]");
        return;
    }

    _proto("Rx ACK %%%u Info { rx=%u max=%u rwin=%u jm=%u }",
           latest,
           ntohl(ackinfo.rxMTU), ntohl(ackinfo.maxMTU),
           ntohl(ackinfo.rwind), ntohl(ackinfo.jumbo_max));

    mtu = min(ntohl(ackinfo.rxMTU), ntohl(ackinfo.maxMTU));

    peer = call->conn->trans->peer;
    if (mtu < peer->maxdata) {
        spin_lock_bh(&peer->lock);
        peer->maxdata = mtu;
        peer->mtu = mtu + peer->hdrsize;
        spin_unlock_bh(&peer->lock);
        _net("Net MTU %u (maxdata %u)", peer->mtu, peer->maxdata);
    }
}

/*
 * process packets in the reception queue
 */
static int rxrpc_process_rx_queue(struct rxrpc_call *call,
                  u32 *_abort_code)
{
    struct rxrpc_ackpacket ack;
    struct rxrpc_skb_priv *sp;
    struct sk_buff *skb;
    bool post_ACK;
    int latest;
    u32 hard, tx;

    _enter("");

process_further:
    skb = skb_dequeue(&call->rx_queue);
    if (!skb)
        return -EAGAIN;

    _net("deferred skb %p", skb);

    sp = rxrpc_skb(skb);

    _debug("process %s [st %d]", rxrpc_pkts[sp->hdr.type], call->state);

    post_ACK = false;

    switch (sp->hdr.type) {
        /* data packets that wind up here have been received out of
         * order, need security processing or are jumbo packets */
    case RXRPC_PACKET_TYPE_DATA:
        _proto("OOSQ DATA %%%u { #%u }",
               ntohl(sp->hdr.serial), ntohl(sp->hdr.seq));

        /* secured packets must be verified and possibly decrypted */
        if (rxrpc_verify_packet(call, skb, _abort_code) < 0)
            goto protocol_error;

        rxrpc_insert_oos_packet(call, skb);
        goto process_further;

        /* partial ACK to process */
    case RXRPC_PACKET_TYPE_ACK:
        if (skb_copy_bits(skb, 0, &ack, sizeof(ack)) < 0) {
            _debug("extraction failure");
            goto protocol_error;
        }
        if (!skb_pull(skb, sizeof(ack)))
            BUG();

        latest = ntohl(sp->hdr.serial);
        hard = ntohl(ack.firstPacket);
        tx = atomic_read(&call->sequence);

        _proto("Rx ACK %%%u { m=%hu f=#%u p=#%u s=%%%u r=%s n=%u }",
               latest,
               ntohs(ack.maxSkew),
               hard,
               ntohl(ack.previousPacket),
               ntohl(ack.serial),
               rxrpc_acks[ack.reason],
               ack.nAcks);

        rxrpc_extract_ackinfo(call, skb, latest, ack.nAcks);

        if (ack.reason == RXRPC_ACK_PING) {
            _proto("Rx ACK %%%u PING Request", latest);
            rxrpc_propose_ACK(call, RXRPC_ACK_PING_RESPONSE,
                      sp->hdr.serial, true);
        }

        /* discard any out-of-order or duplicate ACKs */
        if (latest - call->acks_latest <= 0) {
            _debug("discard ACK %d <= %d",
                   latest, call->acks_latest);
            goto discard;
        }
        call->acks_latest = latest;

        if (call->state != RXRPC_CALL_CLIENT_SEND_REQUEST &&
            call->state != RXRPC_CALL_CLIENT_AWAIT_REPLY &&
            call->state != RXRPC_CALL_SERVER_SEND_REPLY &&
            call->state != RXRPC_CALL_SERVER_AWAIT_ACK)
            goto discard;

        _debug("Tx=%d H=%u S=%d", tx, call->acks_hard, call->state);

        if (hard > 0) {
            if (hard - 1 > tx) {
                _debug("hard-ACK'd packet %d not transmitted"
                       " (%d top)",
                       hard - 1, tx);
                goto protocol_error;
            }

            if ((call->state == RXRPC_CALL_CLIENT_AWAIT_REPLY ||
                 call->state == RXRPC_CALL_SERVER_AWAIT_ACK) &&
                hard > tx)
                goto all_acked;

            smp_rmb();
            rxrpc_rotate_tx_window(call, hard - 1);
        }

        if (ack.nAcks > 0) {
            if (hard - 1 + ack.nAcks > tx) {
                _debug("soft-ACK'd packet %d+%d not"
                       " transmitted (%d top)",
                       hard - 1, ack.nAcks, tx);
                goto protocol_error;
            }

            if (rxrpc_process_soft_ACKs(call, &ack, skb) < 0)
                goto protocol_error;
        }
        goto discard;

        /* complete ACK to process */
    case RXRPC_PACKET_TYPE_ACKALL:
        goto all_acked;

        /* abort and busy are handled elsewhere */
    case RXRPC_PACKET_TYPE_BUSY:
    case RXRPC_PACKET_TYPE_ABORT:
        BUG();

        /* connection level events - also handled elsewhere */
    case RXRPC_PACKET_TYPE_CHALLENGE:
    case RXRPC_PACKET_TYPE_RESPONSE:
    case RXRPC_PACKET_TYPE_DEBUG:
        BUG();
    }

    /* if we've had a hard ACK that covers all the packets we've sent, then
     * that ends that phase of the operation */
all_acked:
    write_lock_bh(&call->state_lock);
    _debug("ack all %d", call->state);

    switch (call->state) {
    case RXRPC_CALL_CLIENT_AWAIT_REPLY:
        call->state = RXRPC_CALL_CLIENT_RECV_REPLY;
        break;
    case RXRPC_CALL_SERVER_AWAIT_ACK:
        _debug("srv complete");
        call->state = RXRPC_CALL_COMPLETE;
        post_ACK = true;
        break;
    case RXRPC_CALL_CLIENT_SEND_REQUEST:
    case RXRPC_CALL_SERVER_RECV_REQUEST:
        goto protocol_error_unlock; /* can't occur yet */
    default:
        write_unlock_bh(&call->state_lock);
        goto discard; /* assume packet left over from earlier phase */
    }

    write_unlock_bh(&call->state_lock);

    /* if all the packets we sent are hard-ACK'd, then we can discard
     * whatever we've got left */
    _debug("clear Tx %d",
           CIRC_CNT(call->acks_head, call->acks_tail, call->acks_winsz));

    del_timer_sync(&call->resend_timer);
    clear_bit(RXRPC_CALL_RUN_RTIMER, &call->flags);
    clear_bit(RXRPC_CALL_RESEND_TIMER, &call->events);

    if (call->acks_window)
        rxrpc_zap_tx_window(call);

    if (post_ACK) {
        /* post the final ACK message for userspace to pick up */
        _debug("post ACK");
        skb->mark = RXRPC_SKB_MARK_FINAL_ACK;
        sp->call = call;
        rxrpc_get_call(call);
        spin_lock_bh(&call->lock);
        if (rxrpc_queue_rcv_skb(call, skb, true, true) < 0)
            BUG();
        spin_unlock_bh(&call->lock);
        goto process_further;
    }

discard:
    rxrpc_free_skb(skb);
    goto process_further;

protocol_error_unlock:
    write_unlock_bh(&call->state_lock);
protocol_error:
    rxrpc_free_skb(skb);
    _leave(" = -EPROTO");
    return -EPROTO;
}

/*
 * post a message to the socket Rx queue for recvmsg() to pick up
 */
static int rxrpc_post_message(struct rxrpc_call *call, u32 mark, u32 error,
                  bool fatal)
{
    struct rxrpc_skb_priv *sp;
    struct sk_buff *skb;
    int ret;

    _enter("{%d,%lx},%u,%u,%d",
           call->debug_id, call->flags, mark, error, fatal);

    /* remove timers and things for fatal messages */
    if (fatal) {
        del_timer_sync(&call->resend_timer);
        del_timer_sync(&call->ack_timer);
        clear_bit(RXRPC_CALL_RUN_RTIMER, &call->flags);
    }

    if (mark != RXRPC_SKB_MARK_NEW_CALL &&
        !test_bit(RXRPC_CALL_HAS_USERID, &call->flags)) {
        _leave("[no userid]");
        return 0;
    }

    if (!test_bit(RXRPC_CALL_TERMINAL_MSG, &call->flags)) {
        skb = alloc_skb(0, GFP_NOFS);
        if (!skb)
            return -ENOMEM;

        rxrpc_new_skb(skb);

        skb->mark = mark;

        sp = rxrpc_skb(skb);
        memset(sp, 0, sizeof(*sp));
        sp->error = error;
        sp->call = call;
        rxrpc_get_call(call);

        spin_lock_bh(&call->lock);
        ret = rxrpc_queue_rcv_skb(call, skb, true, fatal);
        spin_unlock_bh(&call->lock);
        BUG_ON(ret < 0);
    }

    return 0;
}

/*
 * handle background processing of incoming call packets and ACK / abort
 * generation
 */
void rxrpc_process_call(struct work_struct *work)
{
    struct rxrpc_call *call =
        container_of(work, struct rxrpc_call, processor);
    struct rxrpc_ackpacket ack;
    struct rxrpc_ackinfo ackinfo;
    struct rxrpc_header hdr;
    struct msghdr msg;
    struct kvec iov[5];
    unsigned long bits;
    __be32 data, pad;
    size_t len;
    int genbit, loop, nbit, ioc, ret, mtu;
    u32 abort_code = RX_PROTOCOL_ERROR;
    u8 *acks = NULL;

    //printk("\n--------------------\n");
    _enter("{%d,%s,%lx} [%lu]",
           call->debug_id, rxrpc_call_states[call->state], call->events,
           (jiffies - call->creation_jif) / (HZ / 10));

    if (test_and_set_bit(RXRPC_CALL_PROC_BUSY, &call->flags)) {
        _debug("XXXXXXXXXXXXX RUNNING ON MULTIPLE CPUS XXXXXXXXXXXXX");
        return;
    }

    /* there's a good chance we're going to have to send a message, so set
     * one up in advance */
    msg.msg_name    = &call->conn->trans->peer->srx.transport.sin;
    msg.msg_namelen = sizeof(call->conn->trans->peer->srx.transport.sin);
    msg.msg_control = NULL;
    msg.msg_controllen = 0;
    msg.msg_flags   = 0;

    hdr.epoch   = call->conn->epoch;
    hdr.cid     = call->cid;
    hdr.callNumber  = call->call_id;
    hdr.seq     = 0;
    hdr.type    = RXRPC_PACKET_TYPE_ACK;
    hdr.flags   = call->conn->out_clientflag;
    hdr.userStatus  = 0;
    hdr.securityIndex = call->conn->security_ix;
    hdr._rsvd   = 0;
    hdr.serviceId   = call->conn->service_id;

    memset(iov, 0, sizeof(iov));
    iov[0].iov_base = &hdr;
    iov[0].iov_len  = sizeof(hdr);

    /* deal with events of a final nature */
    if (test_bit(RXRPC_CALL_RELEASE, &call->events)) {
        rxrpc_release_call(call);
        clear_bit(RXRPC_CALL_RELEASE, &call->events);
    }

    if (test_bit(RXRPC_CALL_RCVD_ERROR, &call->events)) {
        int error;

        clear_bit(RXRPC_CALL_CONN_ABORT, &call->events);
        clear_bit(RXRPC_CALL_REJECT_BUSY, &call->events);
        clear_bit(RXRPC_CALL_ABORT, &call->events);

        error = call->conn->trans->peer->net_error;
        _debug("post net error %d", error);

        if (rxrpc_post_message(call, RXRPC_SKB_MARK_NET_ERROR,
                       error, true) < 0)
            goto no_mem;
        clear_bit(RXRPC_CALL_RCVD_ERROR, &call->events);
        goto kill_ACKs;
    }

    if (test_bit(RXRPC_CALL_CONN_ABORT, &call->events)) {
        ASSERTCMP(call->state, >, RXRPC_CALL_COMPLETE);

        clear_bit(RXRPC_CALL_REJECT_BUSY, &call->events);
        clear_bit(RXRPC_CALL_ABORT, &call->events);

        _debug("post conn abort");

        if (rxrpc_post_message(call, RXRPC_SKB_MARK_LOCAL_ERROR,
                       call->conn->error, true) < 0)
            goto no_mem;
        clear_bit(RXRPC_CALL_CONN_ABORT, &call->events);
        goto kill_ACKs;
    }

    if (test_bit(RXRPC_CALL_REJECT_BUSY, &call->events)) {
        hdr.type = RXRPC_PACKET_TYPE_BUSY;
        genbit = RXRPC_CALL_REJECT_BUSY;
        goto send_message;
    }

    if (test_bit(RXRPC_CALL_ABORT, &call->events)) {
        ASSERTCMP(call->state, >, RXRPC_CALL_COMPLETE);

        if (rxrpc_post_message(call, RXRPC_SKB_MARK_LOCAL_ERROR,
                       ECONNABORTED, true) < 0)
            goto no_mem;
        hdr.type = RXRPC_PACKET_TYPE_ABORT;
        data = htonl(call->abort_code);
        iov[1].iov_base = &data;
        iov[1].iov_len = sizeof(data);
        genbit = RXRPC_CALL_ABORT;
        goto send_message;
    }

    if (test_bit(RXRPC_CALL_ACK_FINAL, &call->events)) {
        genbit = RXRPC_CALL_ACK_FINAL;

        ack.bufferSpace = htons(8);
        ack.maxSkew = 0;
        ack.serial  = 0;
        ack.reason  = RXRPC_ACK_IDLE;
        ack.nAcks   = 0;
        call->ackr_reason = 0;

        spin_lock_bh(&call->lock);
        ack.serial = call->ackr_serial;
        ack.previousPacket = call->ackr_prev_seq;
        ack.firstPacket = htonl(call->rx_data_eaten + 1);
        spin_unlock_bh(&call->lock);

        pad = 0;

        iov[1].iov_base = &ack;
        iov[1].iov_len  = sizeof(ack);
        iov[2].iov_base = &pad;
        iov[2].iov_len  = 3;
        iov[3].iov_base = &ackinfo;
        iov[3].iov_len  = sizeof(ackinfo);
        goto send_ACK;
    }

    if (call->events & ((1 << RXRPC_CALL_RCVD_BUSY) |
                (1 << RXRPC_CALL_RCVD_ABORT))
        ) {
        u32 mark;

        if (test_bit(RXRPC_CALL_RCVD_ABORT, &call->events))
            mark = RXRPC_SKB_MARK_REMOTE_ABORT;
        else
            mark = RXRPC_SKB_MARK_BUSY;

        _debug("post abort/busy");
        rxrpc_clear_tx_window(call);
        if (rxrpc_post_message(call, mark, ECONNABORTED, true) < 0)
            goto no_mem;

        clear_bit(RXRPC_CALL_RCVD_BUSY, &call->events);
        clear_bit(RXRPC_CALL_RCVD_ABORT, &call->events);
        goto kill_ACKs;
    }

    if (test_and_clear_bit(RXRPC_CALL_RCVD_ACKALL, &call->events)) {
        _debug("do implicit ackall");
        rxrpc_clear_tx_window(call);
    }

    if (test_bit(RXRPC_CALL_LIFE_TIMER, &call->events)) {
        write_lock_bh(&call->state_lock);
        if (call->state <= RXRPC_CALL_COMPLETE) {
            call->state = RXRPC_CALL_LOCALLY_ABORTED;
            call->abort_code = RX_CALL_TIMEOUT;
            set_bit(RXRPC_CALL_ABORT, &call->events);
        }
        write_unlock_bh(&call->state_lock);

        _debug("post timeout");
        if (rxrpc_post_message(call, RXRPC_SKB_MARK_LOCAL_ERROR,
                       ETIME, true) < 0)
            goto no_mem;

        clear_bit(RXRPC_CALL_LIFE_TIMER, &call->events);
        goto kill_ACKs;
    }

    /* deal with assorted inbound messages */
    if (!skb_queue_empty(&call->rx_queue)) {
        switch (rxrpc_process_rx_queue(call, &abort_code)) {
        case 0:
        case -EAGAIN:
            break;
        case -ENOMEM:
            goto no_mem;
        case -EKEYEXPIRED:
        case -EKEYREJECTED:
        case -EPROTO:
            rxrpc_abort_call(call, abort_code);
            goto kill_ACKs;
        }
    }

    /* handle resending */
    if (test_and_clear_bit(RXRPC_CALL_RESEND_TIMER, &call->events))
        rxrpc_resend_timer(call);
    if (test_and_clear_bit(RXRPC_CALL_RESEND, &call->events))
        rxrpc_resend(call);

    /* consider sending an ordinary ACK */
    if (test_bit(RXRPC_CALL_ACK, &call->events)) {
        _debug("send ACK: window: %d - %d { %lx }",
               call->rx_data_eaten, call->ackr_win_top,
               call->ackr_window[0]);

        if (call->state > RXRPC_CALL_SERVER_ACK_REQUEST &&
            call->ackr_reason != RXRPC_ACK_PING_RESPONSE) {
            /* ACK by sending reply DATA packet in this state */
            clear_bit(RXRPC_CALL_ACK, &call->events);
            goto maybe_reschedule;
        }

        genbit = RXRPC_CALL_ACK;

        acks = kzalloc(call->ackr_win_top - call->rx_data_eaten,
                   GFP_NOFS);
        if (!acks)
            goto no_mem;

        //hdr.flags = RXRPC_SLOW_START_OK;
        ack.bufferSpace = htons(8);
        ack.maxSkew = 0;
        ack.serial  = 0;
        ack.reason  = 0;

        spin_lock_bh(&call->lock);
        ack.reason = call->ackr_reason;
        ack.serial = call->ackr_serial;
        ack.previousPacket = call->ackr_prev_seq;
        ack.firstPacket = htonl(call->rx_data_eaten + 1);

        ack.nAcks = 0;
        for (loop = 0; loop < RXRPC_ACKR_WINDOW_ASZ; loop++) {
            nbit = loop * BITS_PER_LONG;
            for (bits = call->ackr_window[loop]; bits; bits >>= 1
                 ) {
                _debug("- l=%d n=%d b=%lx", loop, nbit, bits);
                if (bits & 1) {
                    acks[nbit] = RXRPC_ACK_TYPE_ACK;
                    ack.nAcks = nbit + 1;
                }
                nbit++;
            }
        }
        call->ackr_reason = 0;
        spin_unlock_bh(&call->lock);

        pad = 0;

        iov[1].iov_base = &ack;
        iov[1].iov_len  = sizeof(ack);
        iov[2].iov_base = acks;
        iov[2].iov_len  = ack.nAcks;
        iov[3].iov_base = &pad;
        iov[3].iov_len  = 3;
        iov[4].iov_base = &ackinfo;
        iov[4].iov_len  = sizeof(ackinfo);

        switch (ack.reason) {
        case RXRPC_ACK_REQUESTED:
        case RXRPC_ACK_DUPLICATE:
        case RXRPC_ACK_OUT_OF_SEQUENCE:
        case RXRPC_ACK_EXCEEDS_WINDOW:
        case RXRPC_ACK_NOSPACE:
        case RXRPC_ACK_PING:
        case RXRPC_ACK_PING_RESPONSE:
            goto send_ACK_with_skew;
        case RXRPC_ACK_DELAY:
        case RXRPC_ACK_IDLE:
            goto send_ACK;
        }
    }

    /* handle completion of security negotiations on an incoming
     * connection */
    if (test_and_clear_bit(RXRPC_CALL_SECURED, &call->events)) {
        _debug("secured");
        spin_lock_bh(&call->lock);

        if (call->state == RXRPC_CALL_SERVER_SECURING) {
            _debug("securing");
            write_lock(&call->conn->lock);
            if (!test_bit(RXRPC_CALL_RELEASED, &call->flags) &&
                !test_bit(RXRPC_CALL_RELEASE, &call->events)) {
                _debug("not released");
                call->state = RXRPC_CALL_SERVER_ACCEPTING;
                list_move_tail(&call->accept_link,
                           &call->socket->acceptq);
            }
            write_unlock(&call->conn->lock);
            read_lock(&call->state_lock);
            if (call->state < RXRPC_CALL_COMPLETE)
                set_bit(RXRPC_CALL_POST_ACCEPT, &call->events);
            read_unlock(&call->state_lock);
        }

        spin_unlock_bh(&call->lock);
        if (!test_bit(RXRPC_CALL_POST_ACCEPT, &call->events))
            goto maybe_reschedule;
    }

    /* post a notification of an acceptable connection to the app */
    if (test_bit(RXRPC_CALL_POST_ACCEPT, &call->events)) {
        _debug("post accept");
        if (rxrpc_post_message(call, RXRPC_SKB_MARK_NEW_CALL,
                       0, false) < 0)
            goto no_mem;
        clear_bit(RXRPC_CALL_POST_ACCEPT, &call->events);
        goto maybe_reschedule;
    }

    /* handle incoming call acceptance */
    if (test_and_clear_bit(RXRPC_CALL_ACCEPTED, &call->events)) {
        _debug("accepted");
        ASSERTCMP(call->rx_data_post, ==, 0);
        call->rx_data_post = 1;
        read_lock_bh(&call->state_lock);
        if (call->state < RXRPC_CALL_COMPLETE)
            set_bit(RXRPC_CALL_DRAIN_RX_OOS, &call->events);
        read_unlock_bh(&call->state_lock);
    }

    /* drain the out of sequence received packet queue into the packet Rx
     * queue */
    if (test_and_clear_bit(RXRPC_CALL_DRAIN_RX_OOS, &call->events)) {
        while (call->rx_data_post == call->rx_first_oos)
            if (rxrpc_drain_rx_oos_queue(call) < 0)
                break;
        goto maybe_reschedule;
    }

    /* other events may have been raised since we started checking */
    goto maybe_reschedule;

send_ACK_with_skew:
    ack.maxSkew = htons(atomic_read(&call->conn->hi_serial) -
                ntohl(ack.serial));
send_ACK:
    mtu = call->conn->trans->peer->if_mtu;
    mtu -= call->conn->trans->peer->hdrsize;
    ackinfo.maxMTU  = htonl(mtu);
    ackinfo.rwind   = htonl(32);

    /* permit the peer to send us jumbo packets if it wants to */
    ackinfo.rxMTU   = htonl(5692);
    ackinfo.jumbo_max = htonl(4);

    hdr.serial = htonl(atomic_inc_return(&call->conn->serial));
    _proto("Tx ACK %%%u { m=%hu f=#%u p=#%u s=%%%u r=%s n=%u }",
           ntohl(hdr.serial),
           ntohs(ack.maxSkew),
           ntohl(ack.firstPacket),
           ntohl(ack.previousPacket),
           ntohl(ack.serial),
           rxrpc_acks[ack.reason],
           ack.nAcks);

    del_timer_sync(&call->ack_timer);
    if (ack.nAcks > 0)
        set_bit(RXRPC_CALL_TX_SOFT_ACK, &call->flags);
    goto send_message_2;

send_message:
    _debug("send message");

    hdr.serial = htonl(atomic_inc_return(&call->conn->serial));
    _proto("Tx %s %%%u", rxrpc_pkts[hdr.type], ntohl(hdr.serial));
send_message_2:

    len = iov[0].iov_len;
    ioc = 1;
    if (iov[4].iov_len) {
        ioc = 5;
        len += iov[4].iov_len;
        len += iov[3].iov_len;
        len += iov[2].iov_len;
        len += iov[1].iov_len;
    } else if (iov[3].iov_len) {
        ioc = 4;
        len += iov[3].iov_len;
        len += iov[2].iov_len;
        len += iov[1].iov_len;
    } else if (iov[2].iov_len) {
        ioc = 3;
        len += iov[2].iov_len;
        len += iov[1].iov_len;
    } else if (iov[1].iov_len) {
        ioc = 2;
        len += iov[1].iov_len;
    }

    ret = kernel_sendmsg(call->conn->trans->local->socket,
                 &msg, iov, ioc, len);
    if (ret < 0) {
        _debug("sendmsg failed: %d", ret);
        read_lock_bh(&call->state_lock);
        if (call->state < RXRPC_CALL_DEAD)
            rxrpc_queue_call(call);
        read_unlock_bh(&call->state_lock);
        goto error;
    }

    switch (genbit) {
    case RXRPC_CALL_ABORT:
        clear_bit(genbit, &call->events);
        clear_bit(RXRPC_CALL_RCVD_ABORT, &call->events);
        goto kill_ACKs;

    case RXRPC_CALL_ACK_FINAL:
        write_lock_bh(&call->state_lock);
        if (call->state == RXRPC_CALL_CLIENT_FINAL_ACK)
            call->state = RXRPC_CALL_COMPLETE;
        write_unlock_bh(&call->state_lock);
        goto kill_ACKs;

    default:
        clear_bit(genbit, &call->events);
        switch (call->state) {
        case RXRPC_CALL_CLIENT_AWAIT_REPLY:
        case RXRPC_CALL_CLIENT_RECV_REPLY:
        case RXRPC_CALL_SERVER_RECV_REQUEST:
        case RXRPC_CALL_SERVER_ACK_REQUEST:
            _debug("start ACK timer");
            rxrpc_propose_ACK(call, RXRPC_ACK_DELAY,
                      call->ackr_serial, false);
        default:
            break;
        }
        goto maybe_reschedule;
    }

kill_ACKs:
    del_timer_sync(&call->ack_timer);
    if (test_and_clear_bit(RXRPC_CALL_ACK_FINAL, &call->events))
        rxrpc_put_call(call);
    clear_bit(RXRPC_CALL_ACK, &call->events);

maybe_reschedule:
    if (call->events || !skb_queue_empty(&call->rx_queue)) {
        read_lock_bh(&call->state_lock);
        if (call->state < RXRPC_CALL_DEAD)
            rxrpc_queue_call(call);
        read_unlock_bh(&call->state_lock);
    }

    /* don't leave aborted connections on the accept queue */
    if (call->state >= RXRPC_CALL_COMPLETE &&
        !list_empty(&call->accept_link)) {
        _debug("X unlinking once-pending call %p { e=%lx f=%lx c=%x }",
               call, call->events, call->flags,
               ntohl(call->conn->cid));

        read_lock_bh(&call->state_lock);
        if (!test_bit(RXRPC_CALL_RELEASED, &call->flags) &&
            !test_and_set_bit(RXRPC_CALL_RELEASE, &call->events))
            rxrpc_queue_call(call);
        read_unlock_bh(&call->state_lock);
    }

error:
    clear_bit(RXRPC_CALL_PROC_BUSY, &call->flags);
    kfree(acks);

    /* because we don't want two CPUs both processing the work item for one
     * call at the same time, we use a flag to note when it's busy; however
     * this means there's a race between clearing the flag and setting the
     * work pending bit and the work item being processed again */
    if (call->events && !work_pending(&call->processor)) {
        _debug("jumpstart %x", ntohl(call->conn->cid));
        rxrpc_queue_call(call);
    }

    _leave("");
    return;

no_mem:
    _debug("out of memory");
    goto maybe_reschedule;
}