Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph...

[people/ms/linux.git] / net / rxrpc / ar-ack.c

/* 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 (dhowells@redhat.com)
 *
 * 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"

/*
 * How long to wait before scheduling ACK generation after seeing a
 * packet with RXRPC_REQUEST_ACK set (in jiffies).
 */
unsigned rxrpc_requested_ack_delay = 1;

/*
 * How long to wait before scheduling an ACK with subtype DELAY (in jiffies).
 *
 * We use this when we've received new data packets.  If those packets aren't
 * all consumed within this time we will send a DELAY ACK if an ACK was not
 * requested to let the sender know it doesn't need to resend.
 */
unsigned rxrpc_soft_ack_delay = 1 * HZ;

/*
 * How long to wait before scheduling an ACK with subtype IDLE (in jiffies).
 *
 * We use this when we've consumed some previously soft-ACK'd packets when
 * further packets aren't immediately received to decide when to send an IDLE
 * ACK let the other end know that it can free up its Tx buffer space.
 */
unsigned rxrpc_idle_ack_delay = 0.5 * HZ;

/*
 * Receive window size in packets.  This indicates the maximum number of
 * unconsumed received packets we're willing to retain in memory.  Once this
 * limit is hit, we should generate an EXCEEDS_WINDOW ACK and discard further
 * packets.
 */
unsigned rxrpc_rx_window_size = 32;

/*
 * Maximum Rx MTU size.  This indicates to the sender the size of jumbo packet
 * made by gluing normal packets together that we're willing to handle.
 */
unsigned rxrpc_rx_mtu = 5692;

/*
 * The maximum number of fragments in a received jumbo packet that we tell the
 * sender that we're willing to handle.
 */
unsigned rxrpc_rx_jumbo_max = 4;

static const char *rxrpc_acks(u8 reason)
{
        static const char *const str[] = {
                "---", "REQ", "DUP", "OOS", "WIN", "MEM", "PNG", "PNR", "DLY",
                "IDL", "-?-"
        };

        if (reason >= ARRAY_SIZE(str))
                reason = ARRAY_SIZE(str) - 1;
        return str[reason];
}

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");
                expiry = rxrpc_soft_ack_delay;
                goto run_timer;

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

        case RXRPC_ACK_REQUESTED:
                expiry = rxrpc_requested_ack_delay;
                if (!expiry)
                        goto cancel_timer;
                if (!immediate || serial == cpu_to_be32(1)) {
                        _debug("run defer timer");
                        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;
        bool stop;
        int loop;
        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 = false;
        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 = true;
                                sp->resend_at = jiffies + 3;
                        } else {
                                sp->resend_at =
                                        jiffies + rxrpc_resend_timeout;
                        }
                }

                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) {
                                call->acks_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(rxrpc_rx_window_size);

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

        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;
}