qemu/net/colo-compare.c

/*
 * COarse-grain LOck-stepping Virtual Machines for Non-stop Service (COLO)
 * (a.k.a. Fault Tolerance or Continuous Replication)
 *
 * Copyright (c) 2016 HUAWEI TECHNOLOGIES CO., LTD.
 * Copyright (c) 2016 FUJITSU LIMITED
 * Copyright (c) 2016 Intel Corporation
 *
 * Author: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or
 * later.  See the COPYING file in the top-level directory.
 */

#include "qemu/osdep.h"
#include "qemu-common.h"
#include "qemu/error-report.h"
#include "trace.h"
#include "qapi/error.h"
#include "net/net.h"
#include "net/eth.h"
#include "qom/object_interfaces.h"
#include "qemu/iov.h"
#include "qom/object.h"
#include "net/queue.h"
#include "chardev/char-fe.h"
#include "qemu/sockets.h"
#include "colo.h"
#include "sysemu/iothread.h"
#include "net/colo-compare.h"
#include "migration/colo.h"
#include "migration/migration.h"
#include "util.h"

#include "block/aio-wait.h"
#include "qemu/coroutine.h"

#define TYPE_COLO_COMPARE "colo-compare"
typedef struct CompareState CompareState;
DECLARE_INSTANCE_CHECKER(CompareState, COLO_COMPARE,
                         TYPE_COLO_COMPARE)

static QTAILQ_HEAD(, CompareState) net_compares =
       QTAILQ_HEAD_INITIALIZER(net_compares);

static NotifierList colo_compare_notifiers =
    NOTIFIER_LIST_INITIALIZER(colo_compare_notifiers);

#define COMPARE_READ_LEN_MAX NET_BUFSIZE
#define MAX_QUEUE_SIZE 1024

#define COLO_COMPARE_FREE_PRIMARY     0x01
#define COLO_COMPARE_FREE_SECONDARY   0x02

#define REGULAR_PACKET_CHECK_MS 1000
#define DEFAULT_TIME_OUT_MS 3000

/* #define DEBUG_COLO_PACKETS */

static QemuMutex colo_compare_mutex;
static bool colo_compare_active;
static QemuMutex event_mtx;
static QemuCond event_complete_cond;
static int event_unhandled_count;
static uint32_t max_queue_size;

/*
 *  + CompareState ++
 *  |               |
 *  +---------------+   +---------------+         +---------------+
 *  |   conn list   + - >      conn     + ------- >      conn     + -- > ......
 *  +---------------+   +---------------+         +---------------+
 *  |               |     |           |             |          |
 *  +---------------+ +---v----+  +---v----+    +---v----+ +---v----+
 *                    |primary |  |secondary    |primary | |secondary
 *                    |packet  |  |packet  +    |packet  | |packet  +
 *                    +--------+  +--------+    +--------+ +--------+
 *                        |           |             |          |
 *                    +---v----+  +---v----+    +---v----+ +---v----+
 *                    |primary |  |secondary    |primary | |secondary
 *                    |packet  |  |packet  +    |packet  | |packet  +
 *                    +--------+  +--------+    +--------+ +--------+
 *                        |           |             |          |
 *                    +---v----+  +---v----+    +---v----+ +---v----+
 *                    |primary |  |secondary    |primary | |secondary
 *                    |packet  |  |packet  +    |packet  | |packet  +
 *                    +--------+  +--------+    +--------+ +--------+
 */

typedef struct SendCo {
    Coroutine *co;
    struct CompareState *s;
    CharBackend *chr;
    GQueue send_list;
    bool notify_remote_frame;
    bool done;
    int ret;
} SendCo;

typedef struct SendEntry {
    uint32_t size;
    uint32_t vnet_hdr_len;
    uint8_t *buf;
} SendEntry;

struct CompareState {
    Object parent;

    char *pri_indev;
    char *sec_indev;
    char *outdev;
    char *notify_dev;
    CharBackend chr_pri_in;
    CharBackend chr_sec_in;
    CharBackend chr_out;
    CharBackend chr_notify_dev;
    SocketReadState pri_rs;
    SocketReadState sec_rs;
    SocketReadState notify_rs;
    SendCo out_sendco;
    SendCo notify_sendco;
    bool vnet_hdr;
    uint64_t compare_timeout;
    uint32_t expired_scan_cycle;

    /*
     * Record the connection that through the NIC
     * Element type: Connection
     */
    GQueue conn_list;
    /* Record the connection without repetition */
    GHashTable *connection_track_table;

    IOThread *iothread;
    GMainContext *worker_context;
    QEMUTimer *packet_check_timer;

    QEMUBH *event_bh;
    enum colo_event event;

    QTAILQ_ENTRY(CompareState) next;
};

typedef struct CompareClass {
    ObjectClass parent_class;
} CompareClass;

enum {
    PRIMARY_IN = 0,
    SECONDARY_IN,
};

static const char *colo_mode[] = {
    [PRIMARY_IN] = "primary",
    [SECONDARY_IN] = "secondary",
};

static int compare_chr_send(CompareState *s,
                            uint8_t *buf,
                            uint32_t size,
                            uint32_t vnet_hdr_len,
                            bool notify_remote_frame,
                            bool zero_copy);

static bool packet_matches_str(const char *str,
                               const uint8_t *buf,
                               uint32_t packet_len)
{
    if (packet_len != strlen(str)) {
        return false;
    }

    return !memcmp(str, buf, strlen(str));
}

static void notify_remote_frame(CompareState *s)
{
    char msg[] = "DO_CHECKPOINT";
    int ret = 0;

    ret = compare_chr_send(s, (uint8_t *)msg, strlen(msg), 0, true, false);
    if (ret < 0) {
        error_report("Notify Xen COLO-frame failed");
    }
}

static void colo_compare_inconsistency_notify(CompareState *s)
{
    if (s->notify_dev) {
        notify_remote_frame(s);
    } else {
        notifier_list_notify(&colo_compare_notifiers,
                             migrate_get_current());
    }
}

/* Use restricted to colo_insert_packet() */
static gint seq_sorter(Packet *a, Packet *b, gpointer data)
{
    return a->tcp_seq - b->tcp_seq;
}

static void fill_pkt_tcp_info(void *data, uint32_t *max_ack)
{
    Packet *pkt = data;
    struct tcp_hdr *tcphd;

    tcphd = (struct tcp_hdr *)pkt->transport_header;

    pkt->tcp_seq = ntohl(tcphd->th_seq);
    pkt->tcp_ack = ntohl(tcphd->th_ack);
    *max_ack = *max_ack > pkt->tcp_ack ? *max_ack : pkt->tcp_ack;
    pkt->header_size = pkt->transport_header - (uint8_t *)pkt->data
                       + (tcphd->th_off << 2);
    pkt->payload_size = pkt->size - pkt->header_size;
    pkt->seq_end = pkt->tcp_seq + pkt->payload_size;
    pkt->flags = tcphd->th_flags;
}

/*
 * Return 1 on success, if return 0 means the
 * packet will be dropped
 */
static int colo_insert_packet(GQueue *queue, Packet *pkt, uint32_t *max_ack)
{
    if (g_queue_get_length(queue) <= max_queue_size) {
        if (pkt->ip->ip_p == IPPROTO_TCP) {
            fill_pkt_tcp_info(pkt, max_ack);
            g_queue_insert_sorted(queue,
                                  pkt,
                                  (GCompareDataFunc)seq_sorter,
                                  NULL);
        } else {
            g_queue_push_tail(queue, pkt);
        }
        return 1;
    }
    return 0;
}

/*
 * Return 0 on success, if return -1 means the pkt
 * is unsupported(arp and ipv6) and will be sent later
 */
static int packet_enqueue(CompareState *s, int mode, Connection **con)
{
    ConnectionKey key;
    Packet *pkt = NULL;
    Connection *conn;
    int ret;

    if (mode == PRIMARY_IN) {
        pkt = packet_new(s->pri_rs.buf,
                         s->pri_rs.packet_len,
                         s->pri_rs.vnet_hdr_len);
    } else {
        pkt = packet_new(s->sec_rs.buf,
                         s->sec_rs.packet_len,
                         s->sec_rs.vnet_hdr_len);
    }

    if (parse_packet_early(pkt)) {
        packet_destroy(pkt, NULL);
        pkt = NULL;
        return -1;
    }
    fill_connection_key(pkt, &key);

    conn = connection_get(s->connection_track_table,
                          &key,
                          &s->conn_list);

    if (!conn->processing) {
        g_queue_push_tail(&s->conn_list, conn);
        conn->processing = true;
    }

    if (mode == PRIMARY_IN) {
        ret = colo_insert_packet(&conn->primary_list, pkt, &conn->pack);
    } else {
        ret = colo_insert_packet(&conn->secondary_list, pkt, &conn->sack);
    }

    if (!ret) {
        trace_colo_compare_drop_packet(colo_mode[mode],
            "queue size too big, drop packet");
        packet_destroy(pkt, NULL);
        pkt = NULL;
    }

    *con = conn;

    return 0;
}

static inline bool after(uint32_t seq1, uint32_t seq2)
{
        return (int32_t)(seq1 - seq2) > 0;
}

static void colo_release_primary_pkt(CompareState *s, Packet *pkt)
{
    int ret;
    ret = compare_chr_send(s,
                           pkt->data,
                           pkt->size,
                           pkt->vnet_hdr_len,
                           false,
                           true);
    if (ret < 0) {
        error_report("colo send primary packet failed");
    }
    trace_colo_compare_main("packet same and release packet");
    packet_destroy_partial(pkt, NULL);
}

/*
 * The IP packets sent by primary and secondary
 * will be compared in here
 * TODO support ip fragment, Out-Of-Order
 * return:    0  means packet same
 *            > 0 || < 0 means packet different
 */
static int colo_compare_packet_payload(Packet *ppkt,
                                       Packet *spkt,
                                       uint16_t poffset,
                                       uint16_t soffset,
                                       uint16_t len)

{
    if (trace_event_get_state_backends(TRACE_COLO_COMPARE_IP_INFO)) {
        char pri_ip_src[20], pri_ip_dst[20], sec_ip_src[20], sec_ip_dst[20];

        strcpy(pri_ip_src, inet_ntoa(ppkt->ip->ip_src));
        strcpy(pri_ip_dst, inet_ntoa(ppkt->ip->ip_dst));
        strcpy(sec_ip_src, inet_ntoa(spkt->ip->ip_src));
        strcpy(sec_ip_dst, inet_ntoa(spkt->ip->ip_dst));

        trace_colo_compare_ip_info(ppkt->size, pri_ip_src,
                                   pri_ip_dst, spkt->size,
                                   sec_ip_src, sec_ip_dst);
    }

    return memcmp(ppkt->data + poffset, spkt->data + soffset, len);
}

/*
 * return true means that the payload is consist and
 * need to make the next comparison, false means do
 * the checkpoint
*/
static bool colo_mark_tcp_pkt(Packet *ppkt, Packet *spkt,
                              int8_t *mark, uint32_t max_ack)
{
    *mark = 0;

    if (ppkt->tcp_seq == spkt->tcp_seq && ppkt->seq_end == spkt->seq_end) {
        if (!colo_compare_packet_payload(ppkt, spkt,
                                        ppkt->header_size, spkt->header_size,
                                        ppkt->payload_size)) {
            *mark = COLO_COMPARE_FREE_SECONDARY | COLO_COMPARE_FREE_PRIMARY;
            return true;
        }
    }

    /* one part of secondary packet payload still need to be compared */
    if (!after(ppkt->seq_end, spkt->seq_end)) {
        if (!colo_compare_packet_payload(ppkt, spkt,
                                        ppkt->header_size + ppkt->offset,
                                        spkt->header_size + spkt->offset,
                                        ppkt->payload_size - ppkt->offset)) {
            if (!after(ppkt->tcp_ack, max_ack)) {
                *mark = COLO_COMPARE_FREE_PRIMARY;
                spkt->offset += ppkt->payload_size - ppkt->offset;
                return true;
            } else {
                /* secondary guest hasn't ack the data, don't send
                 * out this packet
                 */
                return false;
            }
        }
    } else {
        /* primary packet is longer than secondary packet, compare
         * the same part and mark the primary packet offset
         */
        if (!colo_compare_packet_payload(ppkt, spkt,
                                        ppkt->header_size + ppkt->offset,
                                        spkt->header_size + spkt->offset,
                                        spkt->payload_size - spkt->offset)) {
            *mark = COLO_COMPARE_FREE_SECONDARY;
            ppkt->offset += spkt->payload_size - spkt->offset;
            return true;
        }
    }

    return false;
}

static void colo_compare_tcp(CompareState *s, Connection *conn)
{
    Packet *ppkt = NULL, *spkt = NULL;
    int8_t mark;

    /*
     * If ppkt and spkt have the same payload, but ppkt's ACK
     * is greater than spkt's ACK, in this case we can not
     * send the ppkt because it will cause the secondary guest
     * to miss sending some data in the next. Therefore, we
     * record the maximum ACK in the current queue at both
     * primary side and secondary side. Only when the ack is
     * less than the smaller of the two maximum ack, then we
     * can ensure that the packet's payload is acknowledged by
     * primary and secondary.
    */
    uint32_t min_ack = conn->pack > conn->sack ? conn->sack : conn->pack;

pri:
    if (g_queue_is_empty(&conn->primary_list)) {
        return;
    }
    ppkt = g_queue_pop_head(&conn->primary_list);
sec:
    if (g_queue_is_empty(&conn->secondary_list)) {
        g_queue_push_head(&conn->primary_list, ppkt);
        return;
    }
    spkt = g_queue_pop_head(&conn->secondary_list);

    if (ppkt->tcp_seq == ppkt->seq_end) {
        colo_release_primary_pkt(s, ppkt);
        ppkt = NULL;
    }

    if (ppkt && conn->compare_seq && !after(ppkt->seq_end, conn->compare_seq)) {
        trace_colo_compare_main("pri: this packet has compared");
        colo_release_primary_pkt(s, ppkt);
        ppkt = NULL;
    }

    if (spkt->tcp_seq == spkt->seq_end) {
        packet_destroy(spkt, NULL);
        if (!ppkt) {
            goto pri;
        } else {
            goto sec;
        }
    } else {
        if (conn->compare_seq && !after(spkt->seq_end, conn->compare_seq)) {
            trace_colo_compare_main("sec: this packet has compared");
            packet_destroy(spkt, NULL);
            if (!ppkt) {
                goto pri;
            } else {
                goto sec;
            }
        }
        if (!ppkt) {
            g_queue_push_head(&conn->secondary_list, spkt);
            goto pri;
        }
    }

    if (colo_mark_tcp_pkt(ppkt, spkt, &mark, min_ack)) {
        trace_colo_compare_tcp_info("pri",
                                    ppkt->tcp_seq, ppkt->tcp_ack,
                                    ppkt->header_size, ppkt->payload_size,
                                    ppkt->offset, ppkt->flags);

        trace_colo_compare_tcp_info("sec",
                                    spkt->tcp_seq, spkt->tcp_ack,
                                    spkt->header_size, spkt->payload_size,
                                    spkt->offset, spkt->flags);

        if (mark == COLO_COMPARE_FREE_PRIMARY) {
            conn->compare_seq = ppkt->seq_end;
            colo_release_primary_pkt(s, ppkt);
            g_queue_push_head(&conn->secondary_list, spkt);
            goto pri;
        } else if (mark == COLO_COMPARE_FREE_SECONDARY) {
            conn->compare_seq = spkt->seq_end;
            packet_destroy(spkt, NULL);
            goto sec;
        } else if (mark == (COLO_COMPARE_FREE_PRIMARY | COLO_COMPARE_FREE_SECONDARY)) {
            conn->compare_seq = ppkt->seq_end;
            colo_release_primary_pkt(s, ppkt);
            packet_destroy(spkt, NULL);
            goto pri;
        }
    } else {
        g_queue_push_head(&conn->primary_list, ppkt);
        g_queue_push_head(&conn->secondary_list, spkt);

#ifdef DEBUG_COLO_PACKETS
        qemu_hexdump(stderr, "colo-compare ppkt", ppkt->data, ppkt->size);
        qemu_hexdump(stderr, "colo-compare spkt", spkt->data, spkt->size);
#endif

        colo_compare_inconsistency_notify(s);
    }
}


/*
 * Called from the compare thread on the primary
 * for compare udp packet
 */
static int colo_packet_compare_udp(Packet *spkt, Packet *ppkt)
{
    uint16_t network_header_length = ppkt->ip->ip_hl << 2;
    uint16_t offset = network_header_length + ETH_HLEN + ppkt->vnet_hdr_len;

    trace_colo_compare_main("compare udp");

    /*
     * Because of ppkt and spkt are both in the same connection,
     * The ppkt's src ip, dst ip, src port, dst port, ip_proto all are
     * same with spkt. In addition, IP header's Identification is a random
     * field, we can handle it in IP fragmentation function later.
     * COLO just concern the response net packet payload from primary guest
     * and secondary guest are same or not, So we ignored all IP header include
     * other field like TOS,TTL,IP Checksum. we only need to compare
     * the ip payload here.
     */
    if (ppkt->size != spkt->size) {
        trace_colo_compare_main("UDP: payload size of packets are different");
        return -1;
    }
    if (colo_compare_packet_payload(ppkt, spkt, offset, offset,
                                    ppkt->size - offset)) {
        trace_colo_compare_udp_miscompare("primary pkt size", ppkt->size);
        trace_colo_compare_udp_miscompare("Secondary pkt size", spkt->size);
#ifdef DEBUG_COLO_PACKETS
        qemu_hexdump(stderr, "colo-compare pri pkt", ppkt->data, ppkt->size);
        qemu_hexdump(stderr, "colo-compare sec pkt", spkt->data, spkt->size);
#endif
        return -1;
    } else {
        return 0;
    }
}

/*
 * Called from the compare thread on the primary
 * for compare icmp packet
 */
static int colo_packet_compare_icmp(Packet *spkt, Packet *ppkt)
{
    uint16_t network_header_length = ppkt->ip->ip_hl << 2;
    uint16_t offset = network_header_length + ETH_HLEN + ppkt->vnet_hdr_len;

    trace_colo_compare_main("compare icmp");

    /*
     * Because of ppkt and spkt are both in the same connection,
     * The ppkt's src ip, dst ip, src port, dst port, ip_proto all are
     * same with spkt. In addition, IP header's Identification is a random
     * field, we can handle it in IP fragmentation function later.
     * COLO just concern the response net packet payload from primary guest
     * and secondary guest are same or not, So we ignored all IP header include
     * other field like TOS,TTL,IP Checksum. we only need to compare
     * the ip payload here.
     */
    if (ppkt->size != spkt->size) {
        trace_colo_compare_main("ICMP: payload size of packets are different");
        return -1;
    }
    if (colo_compare_packet_payload(ppkt, spkt, offset, offset,
                                    ppkt->size - offset)) {
        trace_colo_compare_icmp_miscompare("primary pkt size",
                                           ppkt->size);
        trace_colo_compare_icmp_miscompare("Secondary pkt size",
                                           spkt->size);
#ifdef DEBUG_COLO_PACKETS
        qemu_hexdump(stderr, "colo-compare pri pkt", ppkt->data, ppkt->size);
        qemu_hexdump(stderr, "colo-compare sec pkt", spkt->data, spkt->size);
#endif
        return -1;
    } else {
        return 0;
    }
}

/*
 * Called from the compare thread on the primary
 * for compare other packet
 */
static int colo_packet_compare_other(Packet *spkt, Packet *ppkt)
{
    uint16_t offset = ppkt->vnet_hdr_len;

    trace_colo_compare_main("compare other");
    if (ppkt->size != spkt->size) {
        trace_colo_compare_main("Other: payload size of packets are different");
        return -1;
    }
    return colo_compare_packet_payload(ppkt, spkt, offset, offset,
                                       ppkt->size - offset);
}

static int colo_old_packet_check_one(Packet *pkt, int64_t *check_time)
{
    int64_t now = qemu_clock_get_ms(QEMU_CLOCK_HOST);

    if ((now - pkt->creation_ms) > (*check_time)) {
        trace_colo_old_packet_check_found(pkt->creation_ms);
        return 0;
    } else {
        return 1;
    }
}

void colo_compare_register_notifier(Notifier *notify)
{
    notifier_list_add(&colo_compare_notifiers, notify);
}

void colo_compare_unregister_notifier(Notifier *notify)
{
    notifier_remove(notify);
}

static int colo_old_packet_check_one_conn(Connection *conn,
                                          CompareState *s)
{
    if (!g_queue_is_empty(&conn->primary_list)) {
        if (g_queue_find_custom(&conn->primary_list,
                                &s->compare_timeout,
                                (GCompareFunc)colo_old_packet_check_one))
            goto out;
    }

    if (!g_queue_is_empty(&conn->secondary_list)) {
        if (g_queue_find_custom(&conn->secondary_list,
                                &s->compare_timeout,
                                (GCompareFunc)colo_old_packet_check_one))
            goto out;
    }

    return 1;

out:
    /* Do checkpoint will flush old packet */
    colo_compare_inconsistency_notify(s);
    return 0;
}

/*
 * Look for old packets that the secondary hasn't matched,
 * if we have some then we have to checkpoint to wake
 * the secondary up.
 */
static void colo_old_packet_check(void *opaque)
{
    CompareState *s = opaque;

    /*
     * If we find one old packet, stop finding job and notify
     * COLO frame do checkpoint.
     */
    g_queue_find_custom(&s->conn_list, s,
                        (GCompareFunc)colo_old_packet_check_one_conn);
}

static void colo_compare_packet(CompareState *s, Connection *conn,
                                int (*HandlePacket)(Packet *spkt,
                                Packet *ppkt))
{
    Packet *pkt = NULL;
    GList *result = NULL;

    while (!g_queue_is_empty(&conn->primary_list) &&
           !g_queue_is_empty(&conn->secondary_list)) {
        pkt = g_queue_pop_head(&conn->primary_list);
        result = g_queue_find_custom(&conn->secondary_list,
                 pkt, (GCompareFunc)HandlePacket);

        if (result) {
            colo_release_primary_pkt(s, pkt);
            packet_destroy(result->data, NULL);
            g_queue_delete_link(&conn->secondary_list, result);
        } else {
            /*
             * If one packet arrive late, the secondary_list or
             * primary_list will be empty, so we can't compare it
             * until next comparison. If the packets in the list are
             * timeout, it will trigger a checkpoint request.
             */
            trace_colo_compare_main("packet different");
            g_queue_push_head(&conn->primary_list, pkt);

            colo_compare_inconsistency_notify(s);
            break;
        }
    }
}

/*
 * Called from the compare thread on the primary
 * for compare packet with secondary list of the
 * specified connection when a new packet was
 * queued to it.
 */
static void colo_compare_connection(void *opaque, void *user_data)
{
    CompareState *s = user_data;
    Connection *conn = opaque;

    switch (conn->ip_proto) {
    case IPPROTO_TCP:
        colo_compare_tcp(s, conn);
        break;
    case IPPROTO_UDP:
        colo_compare_packet(s, conn, colo_packet_compare_udp);
        break;
    case IPPROTO_ICMP:
        colo_compare_packet(s, conn, colo_packet_compare_icmp);
        break;
    default:
        colo_compare_packet(s, conn, colo_packet_compare_other);
        break;
    }
}

static void coroutine_fn _compare_chr_send(void *opaque)
{
    SendCo *sendco = opaque;
    CompareState *s = sendco->s;
    int ret = 0;

    while (!g_queue_is_empty(&sendco->send_list)) {
        SendEntry *entry = g_queue_pop_tail(&sendco->send_list);
        uint32_t len = htonl(entry->size);

        ret = qemu_chr_fe_write_all(sendco->chr, (uint8_t *)&len, sizeof(len));

        if (ret != sizeof(len)) {
            g_free(entry->buf);
            g_slice_free(SendEntry, entry);
            goto err;
        }

        if (!sendco->notify_remote_frame && s->vnet_hdr) {
            /*
             * We send vnet header len make other module(like filter-redirector)
             * know how to parse net packet correctly.
             */
            len = htonl(entry->vnet_hdr_len);

            ret = qemu_chr_fe_write_all(sendco->chr,
                                        (uint8_t *)&len,
                                        sizeof(len));

            if (ret != sizeof(len)) {
                g_free(entry->buf);
                g_slice_free(SendEntry, entry);
                goto err;
            }
        }

        ret = qemu_chr_fe_write_all(sendco->chr,
                                    (uint8_t *)entry->buf,
                                    entry->size);

        if (ret != entry->size) {
            g_free(entry->buf);
            g_slice_free(SendEntry, entry);
            goto err;
        }

        g_free(entry->buf);
        g_slice_free(SendEntry, entry);
    }

    sendco->ret = 0;
    goto out;

err:
    while (!g_queue_is_empty(&sendco->send_list)) {
        SendEntry *entry = g_queue_pop_tail(&sendco->send_list);
        g_free(entry->buf);
        g_slice_free(SendEntry, entry);
    }
    sendco->ret = ret < 0 ? ret : -EIO;
out:
    sendco->co = NULL;
    sendco->done = true;
    aio_wait_kick();
}

static int compare_chr_send(CompareState *s,
                            uint8_t *buf,
                            uint32_t size,
                            uint32_t vnet_hdr_len,
                            bool notify_remote_frame,
                            bool zero_copy)
{
    SendCo *sendco;
    SendEntry *entry;

    if (notify_remote_frame) {
        sendco = &s->notify_sendco;
    } else {
        sendco = &s->out_sendco;
    }

    if (!size) {
        return 0;
    }

    entry = g_slice_new(SendEntry);
    entry->size = size;
    entry->vnet_hdr_len = vnet_hdr_len;
    if (zero_copy) {
        entry->buf = buf;
    } else {
        entry->buf = g_malloc(size);
        memcpy(entry->buf, buf, size);
    }
    g_queue_push_head(&sendco->send_list, entry);

    if (sendco->done) {
        sendco->co = qemu_coroutine_create(_compare_chr_send, sendco);
        sendco->done = false;
        qemu_coroutine_enter(sendco->co);
        if (sendco->done) {
            /* report early errors */
            return sendco->ret;
        }
    }

    /* assume success */
    return 0;
}

static int compare_chr_can_read(void *opaque)
{
    return COMPARE_READ_LEN_MAX;
}

/*
 * Called from the main thread on the primary for packets
 * arriving over the socket from the primary.
 */
static void compare_pri_chr_in(void *opaque, const uint8_t *buf, int size)
{
    CompareState *s = COLO_COMPARE(opaque);
    int ret;

    ret = net_fill_rstate(&s->pri_rs, buf, size);
    if (ret == -1) {
        qemu_chr_fe_set_handlers(&s->chr_pri_in, NULL, NULL, NULL, NULL,
                                 NULL, NULL, true);
        error_report("colo-compare primary_in error");
    }
}

/*
 * Called from the main thread on the primary for packets
 * arriving over the socket from the secondary.
 */
static void compare_sec_chr_in(void *opaque, const uint8_t *buf, int size)
{
    CompareState *s = COLO_COMPARE(opaque);
    int ret;

    ret = net_fill_rstate(&s->sec_rs, buf, size);
    if (ret == -1) {
        qemu_chr_fe_set_handlers(&s->chr_sec_in, NULL, NULL, NULL, NULL,
                                 NULL, NULL, true);
        error_report("colo-compare secondary_in error");
    }
}

static void compare_notify_chr(void *opaque, const uint8_t *buf, int size)
{
    CompareState *s = COLO_COMPARE(opaque);
    int ret;

    ret = net_fill_rstate(&s->notify_rs, buf, size);
    if (ret == -1) {
        qemu_chr_fe_set_handlers(&s->chr_notify_dev, NULL, NULL, NULL, NULL,
                                 NULL, NULL, true);
        error_report("colo-compare notify_dev error");
    }
}

/*
 * Check old packet regularly so it can watch for any packets
 * that the secondary hasn't produced equivalents of.
 */
static void check_old_packet_regular(void *opaque)
{
    CompareState *s = opaque;

    /* if have old packet we will notify checkpoint */
    colo_old_packet_check(s);
    timer_mod(s->packet_check_timer, qemu_clock_get_ms(QEMU_CLOCK_HOST) +
              s->expired_scan_cycle);
}

/* Public API, Used for COLO frame to notify compare event */
void colo_notify_compares_event(void *opaque, int event, Error **errp)
{
    CompareState *s;
    qemu_mutex_lock(&colo_compare_mutex);

    if (!colo_compare_active) {
        qemu_mutex_unlock(&colo_compare_mutex);
        return;
    }

    qemu_mutex_lock(&event_mtx);
    QTAILQ_FOREACH(s, &net_compares, next) {
        s->event = event;
        qemu_bh_schedule(s->event_bh);
        event_unhandled_count++;
    }
    /* Wait all compare threads to finish handling this event */
    while (event_unhandled_count > 0) {
        qemu_cond_wait(&event_complete_cond, &event_mtx);
    }

    qemu_mutex_unlock(&event_mtx);
    qemu_mutex_unlock(&colo_compare_mutex);
}

static void colo_compare_timer_init(CompareState *s)
{
    AioContext *ctx = iothread_get_aio_context(s->iothread);

    s->packet_check_timer = aio_timer_new(ctx, QEMU_CLOCK_HOST,
                                SCALE_MS, check_old_packet_regular,
                                s);
    timer_mod(s->packet_check_timer, qemu_clock_get_ms(QEMU_CLOCK_HOST) +
              s->expired_scan_cycle);
}

static void colo_compare_timer_del(CompareState *s)
{
    if (s->packet_check_timer) {
        timer_free(s->packet_check_timer);
        s->packet_check_timer = NULL;
    }
 }

static void colo_flush_packets(void *opaque, void *user_data);

static void colo_compare_handle_event(void *opaque)
{
    CompareState *s = opaque;

    switch (s->event) {
    case COLO_EVENT_CHECKPOINT:
        g_queue_foreach(&s->conn_list, colo_flush_packets, s);
        break;
    case COLO_EVENT_FAILOVER:
        break;
    default:
        break;
    }

    qemu_mutex_lock(&event_mtx);
    assert(event_unhandled_count > 0);
    event_unhandled_count--;
    qemu_cond_broadcast(&event_complete_cond);
    qemu_mutex_unlock(&event_mtx);
}

static void colo_compare_iothread(CompareState *s)
{
    AioContext *ctx = iothread_get_aio_context(s->iothread);
    object_ref(OBJECT(s->iothread));
    s->worker_context = iothread_get_g_main_context(s->iothread);

    qemu_chr_fe_set_handlers(&s->chr_pri_in, compare_chr_can_read,
                             compare_pri_chr_in, NULL, NULL,
                             s, s->worker_context, true);
    qemu_chr_fe_set_handlers(&s->chr_sec_in, compare_chr_can_read,
                             compare_sec_chr_in, NULL, NULL,
                             s, s->worker_context, true);
    if (s->notify_dev) {
        qemu_chr_fe_set_handlers(&s->chr_notify_dev, compare_chr_can_read,
                                 compare_notify_chr, NULL, NULL,
                                 s, s->worker_context, true);
    }

    colo_compare_timer_init(s);
    s->event_bh = aio_bh_new(ctx, colo_compare_handle_event, s);
}

static char *compare_get_pri_indev(Object *obj, Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    return g_strdup(s->pri_indev);
}

static void compare_set_pri_indev(Object *obj, const char *value, Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    g_free(s->pri_indev);
    s->pri_indev = g_strdup(value);
}

static char *compare_get_sec_indev(Object *obj, Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    return g_strdup(s->sec_indev);
}

static void compare_set_sec_indev(Object *obj, const char *value, Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    g_free(s->sec_indev);
    s->sec_indev = g_strdup(value);
}

static char *compare_get_outdev(Object *obj, Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    return g_strdup(s->outdev);
}

static void compare_set_outdev(Object *obj, const char *value, Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    g_free(s->outdev);
    s->outdev = g_strdup(value);
}

static bool compare_get_vnet_hdr(Object *obj, Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    return s->vnet_hdr;
}

static void compare_set_vnet_hdr(Object *obj,
                                 bool value,
                                 Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    s->vnet_hdr = value;
}

static char *compare_get_notify_dev(Object *obj, Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    return g_strdup(s->notify_dev);
}

static void compare_set_notify_dev(Object *obj, const char *value, Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);

    g_free(s->notify_dev);
    s->notify_dev = g_strdup(value);
}

static void compare_get_timeout(Object *obj, Visitor *v,
                                const char *name, void *opaque,
                                Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);
    uint64_t value = s->compare_timeout;

    visit_type_uint64(v, name, &value, errp);
}

static void compare_set_timeout(Object *obj, Visitor *v,
                                const char *name, void *opaque,
                                Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);
    uint32_t value;

    if (!visit_type_uint32(v, name, &value, errp)) {
        return;
    }
    if (!value) {
        error_setg(errp, "Property '%s.%s' requires a positive value",
                   object_get_typename(obj), name);
        return;
    }
    s->compare_timeout = value;
}

static void compare_get_expired_scan_cycle(Object *obj, Visitor *v,
                                           const char *name, void *opaque,
                                           Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);
    uint32_t value = s->expired_scan_cycle;

    visit_type_uint32(v, name, &value, errp);
}

static void compare_set_expired_scan_cycle(Object *obj, Visitor *v,
                                           const char *name, void *opaque,
                                           Error **errp)
{
    CompareState *s = COLO_COMPARE(obj);
    uint32_t value;

    if (!visit_type_uint32(v, name, &value, errp)) {
        return;
    }
    if (!value) {
        error_setg(errp, "Property '%s.%s' requires a positive value",
                   object_get_typename(obj), name);
        return;
    }
    s->expired_scan_cycle = value;
}

static void get_max_queue_size(Object *obj, Visitor *v,
                               const char *name, void *opaque,
                               Error **errp)
{
    uint32_t value = max_queue_size;

    visit_type_uint32(v, name, &value, errp);
}

static void set_max_queue_size(Object *obj, Visitor *v,
                               const char *name, void *opaque,
                               Error **errp)
{
    Error *local_err = NULL;
    uint64_t value;

    visit_type_uint64(v, name, &value, &local_err);
    if (local_err) {
        goto out;
    }
    if (!value) {
        error_setg(&local_err, "Property '%s.%s' requires a positive value",
                   object_get_typename(obj), name);
        goto out;
    }
    max_queue_size = value;

out:
    error_propagate(errp, local_err);
}

static void compare_pri_rs_finalize(SocketReadState *pri_rs)
{
    CompareState *s = container_of(pri_rs, CompareState, pri_rs);
    Connection *conn = NULL;

    if (packet_enqueue(s, PRIMARY_IN, &conn)) {
        trace_colo_compare_main("primary: unsupported packet in");
        compare_chr_send(s,
                         pri_rs->buf,
                         pri_rs->packet_len,
                         pri_rs->vnet_hdr_len,
                         false,
                         false);
    } else {
        /* compare packet in the specified connection */
        colo_compare_connection(conn, s);
    }
}

static void compare_sec_rs_finalize(SocketReadState *sec_rs)
{
    CompareState *s = container_of(sec_rs, CompareState, sec_rs);
    Connection *conn = NULL;

    if (packet_enqueue(s, SECONDARY_IN, &conn)) {
        trace_colo_compare_main("secondary: unsupported packet in");
    } else {
        /* compare packet in the specified connection */
        colo_compare_connection(conn, s);
    }
}

static void compare_notify_rs_finalize(SocketReadState *notify_rs)
{
    CompareState *s = container_of(notify_rs, CompareState, notify_rs);

    const char msg[] = "COLO_COMPARE_GET_XEN_INIT";
    int ret;

    if (packet_matches_str("COLO_USERSPACE_PROXY_INIT",
                           notify_rs->buf,
                           notify_rs->packet_len)) {
        ret = compare_chr_send(s, (uint8_t *)msg, strlen(msg), 0, true, false);
        if (ret < 0) {
            error_report("Notify Xen COLO-frame INIT failed");
        }
    } else if (packet_matches_str("COLO_CHECKPOINT",
                                  notify_rs->buf,
                                  notify_rs->packet_len)) {
        /* colo-compare do checkpoint, flush pri packet and remove sec packet */
        g_queue_foreach(&s->conn_list, colo_flush_packets, s);
    } else {
        error_report("COLO compare got unsupported instruction");
    }
}

/*
 * Return 0 is success.
 * Return 1 is failed.
 */
static int find_and_check_chardev(Chardev **chr,
                                  char *chr_name,
                                  Error **errp)
{
    *chr = qemu_chr_find(chr_name);
    if (*chr == NULL) {
        error_setg(errp, "Device '%s' not found",
                   chr_name);
        return 1;
    }

    if (!qemu_chr_has_feature(*chr, QEMU_CHAR_FEATURE_RECONNECTABLE)) {
        error_setg(errp, "chardev \"%s\" is not reconnectable",
                   chr_name);
        return 1;
    }

    if (!qemu_chr_has_feature(*chr, QEMU_CHAR_FEATURE_GCONTEXT)) {
        error_setg(errp, "chardev \"%s\" cannot switch context",
                   chr_name);
        return 1;
    }

    return 0;
}

/*
 * Called from the main thread on the primary
 * to setup colo-compare.
 */
static void colo_compare_complete(UserCreatable *uc, Error **errp)
{
    CompareState *s = COLO_COMPARE(uc);
    Chardev *chr;

    if (!s->pri_indev || !s->sec_indev || !s->outdev || !s->iothread) {
        error_setg(errp, "colo compare needs 'primary_in' ,"
                   "'secondary_in','outdev','iothread' property set");
        return;
    } else if (!strcmp(s->pri_indev, s->outdev) ||
               !strcmp(s->sec_indev, s->outdev) ||
               !strcmp(s->pri_indev, s->sec_indev)) {
        error_setg(errp, "'indev' and 'outdev' could not be same "
                   "for compare module");
        return;
    }

    if (!s->compare_timeout) {
        /* Set default value to 3000 MS */
        s->compare_timeout = DEFAULT_TIME_OUT_MS;
    }

    if (!s->expired_scan_cycle) {
        /* Set default value to 3000 MS */
        s->expired_scan_cycle = REGULAR_PACKET_CHECK_MS;
    }

    if (!max_queue_size) {
        /* Set default queue size to 1024 */
        max_queue_size = MAX_QUEUE_SIZE;
    }

    if (find_and_check_chardev(&chr, s->pri_indev, errp) ||
        !qemu_chr_fe_init(&s->chr_pri_in, chr, errp)) {
        return;
    }

    if (find_and_check_chardev(&chr, s->sec_indev, errp) ||
        !qemu_chr_fe_init(&s->chr_sec_in, chr, errp)) {
        return;
    }

    if (find_and_check_chardev(&chr, s->outdev, errp) ||
        !qemu_chr_fe_init(&s->chr_out, chr, errp)) {
        return;
    }

    net_socket_rs_init(&s->pri_rs, compare_pri_rs_finalize, s->vnet_hdr);
    net_socket_rs_init(&s->sec_rs, compare_sec_rs_finalize, s->vnet_hdr);

    /* Try to enable remote notify chardev, currently just for Xen COLO */
    if (s->notify_dev) {
        if (find_and_check_chardev(&chr, s->notify_dev, errp) ||
            !qemu_chr_fe_init(&s->chr_notify_dev, chr, errp)) {
            return;
        }

        net_socket_rs_init(&s->notify_rs, compare_notify_rs_finalize,
                           s->vnet_hdr);
    }

    s->out_sendco.s = s;
    s->out_sendco.chr = &s->chr_out;
    s->out_sendco.notify_remote_frame = false;
    s->out_sendco.done = true;
    g_queue_init(&s->out_sendco.send_list);

    if (s->notify_dev) {
        s->notify_sendco.s = s;
        s->notify_sendco.chr = &s->chr_notify_dev;
        s->notify_sendco.notify_remote_frame = true;
        s->notify_sendco.done = true;
        g_queue_init(&s->notify_sendco.send_list);
    }

    g_queue_init(&s->conn_list);

    s->connection_track_table = g_hash_table_new_full(connection_key_hash,
                                                      connection_key_equal,
                                                      g_free,
                                                      connection_destroy);

    colo_compare_iothread(s);

    qemu_mutex_lock(&colo_compare_mutex);
    if (!colo_compare_active) {
        qemu_mutex_init(&event_mtx);
        qemu_cond_init(&event_complete_cond);
        colo_compare_active = true;
    }
    QTAILQ_INSERT_TAIL(&net_compares, s, next);
    qemu_mutex_unlock(&colo_compare_mutex);

    return;
}

static void colo_flush_packets(void *opaque, void *user_data)
{
    CompareState *s = user_data;
    Connection *conn = opaque;
    Packet *pkt = NULL;

    while (!g_queue_is_empty(&conn->primary_list)) {
        pkt = g_queue_pop_head(&conn->primary_list);
        compare_chr_send(s,
                         pkt->data,
                         pkt->size,
                         pkt->vnet_hdr_len,
                         false,
                         true);
        packet_destroy_partial(pkt, NULL);
    }
    while (!g_queue_is_empty(&conn->secondary_list)) {
        pkt = g_queue_pop_head(&conn->secondary_list);
        packet_destroy(pkt, NULL);
    }
}

static void colo_compare_class_init(ObjectClass *oc, void *data)
{
    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);

    ucc->complete = colo_compare_complete;
}

static void colo_compare_init(Object *obj)
{
    CompareState *s = COLO_COMPARE(obj);

    object_property_add_str(obj, "primary_in",
                            compare_get_pri_indev, compare_set_pri_indev);
    object_property_add_str(obj, "secondary_in",
                            compare_get_sec_indev, compare_set_sec_indev);
    object_property_add_str(obj, "outdev",
                            compare_get_outdev, compare_set_outdev);
    object_property_add_link(obj, "iothread", TYPE_IOTHREAD,
                            (Object **)&s->iothread,
                            object_property_allow_set_link,
                            OBJ_PROP_LINK_STRONG);
    /* This parameter just for Xen COLO */
    object_property_add_str(obj, "notify_dev",
                            compare_get_notify_dev, compare_set_notify_dev);

    object_property_add(obj, "compare_timeout", "uint64",
                        compare_get_timeout,
                        compare_set_timeout, NULL, NULL);

    object_property_add(obj, "expired_scan_cycle", "uint32",
                        compare_get_expired_scan_cycle,
                        compare_set_expired_scan_cycle, NULL, NULL);

    object_property_add(obj, "max_queue_size", "uint32",
                        get_max_queue_size,
                        set_max_queue_size, NULL, NULL);

    s->vnet_hdr = false;
    object_property_add_bool(obj, "vnet_hdr_support", compare_get_vnet_hdr,
                             compare_set_vnet_hdr);
}

void colo_compare_cleanup(void)
{
    CompareState *tmp = NULL;
    CompareState *n = NULL;

    QTAILQ_FOREACH_SAFE(tmp, &net_compares, next, n) {
        object_unparent(OBJECT(tmp));
    }
}

static void colo_compare_finalize(Object *obj)
{
    CompareState *s = COLO_COMPARE(obj);
    CompareState *tmp = NULL;

    qemu_mutex_lock(&colo_compare_mutex);
    QTAILQ_FOREACH(tmp, &net_compares, next) {
        if (tmp == s) {
            QTAILQ_REMOVE(&net_compares, s, next);
            break;
        }
    }
    if (QTAILQ_EMPTY(&net_compares)) {
        colo_compare_active = false;
        qemu_mutex_destroy(&event_mtx);
        qemu_cond_destroy(&event_complete_cond);
    }
    qemu_mutex_unlock(&colo_compare_mutex);

    qemu_chr_fe_deinit(&s->chr_pri_in, false);
    qemu_chr_fe_deinit(&s->chr_sec_in, false);
    qemu_chr_fe_deinit(&s->chr_out, false);
    if (s->notify_dev) {
        qemu_chr_fe_deinit(&s->chr_notify_dev, false);
    }

    colo_compare_timer_del(s);

    qemu_bh_delete(s->event_bh);

    AioContext *ctx = iothread_get_aio_context(s->iothread);
    aio_context_acquire(ctx);
    AIO_WAIT_WHILE(ctx, !s->out_sendco.done);
    if (s->notify_dev) {
        AIO_WAIT_WHILE(ctx, !s->notify_sendco.done);
    }
    aio_context_release(ctx);

    /* Release all unhandled packets after compare thead exited */
    g_queue_foreach(&s->conn_list, colo_flush_packets, s);
    AIO_WAIT_WHILE(NULL, !s->out_sendco.done);

    g_queue_clear(&s->conn_list);
    g_queue_clear(&s->out_sendco.send_list);
    if (s->notify_dev) {
        g_queue_clear(&s->notify_sendco.send_list);
    }

    if (s->connection_track_table) {
        g_hash_table_destroy(s->connection_track_table);
    }

    object_unref(OBJECT(s->iothread));

    g_free(s->pri_indev);
    g_free(s->sec_indev);
    g_free(s->outdev);
    g_free(s->notify_dev);
}

static void __attribute__((__constructor__)) colo_compare_init_globals(void)
{
    colo_compare_active = false;
    qemu_mutex_init(&colo_compare_mutex);
}

static const TypeInfo colo_compare_info = {
    .name = TYPE_COLO_COMPARE,
    .parent = TYPE_OBJECT,
    .instance_size = sizeof(CompareState),
    .instance_init = colo_compare_init,
    .instance_finalize = colo_compare_finalize,
    .class_size = sizeof(CompareClass),
    .class_init = colo_compare_class_init,
    .interfaces = (InterfaceInfo[]) {
        { TYPE_USER_CREATABLE },
        { }
    }
};

static void register_types(void)
{
    type_register_static(&colo_compare_info);
}

type_init(register_types);