messenger.c

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#include <linux/ceph/ceph_debug.h>

#include <linux/crc32c.h>
#include <linux/ctype.h>
#include <linux/highmem.h>
#include <linux/inet.h>
#include <linux/kthread.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/string.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/dns_resolver.h>
#include <net/tcp.h>

#include <linux/ceph/libceph.h>
#include <linux/ceph/messenger.h>
#include <linux/ceph/decode.h>
#include <linux/ceph/pagelist.h>
#include <linux/export.h>

/*
 * Ceph uses the messenger to exchange ceph_msg messages with other
 * hosts in the system.  The messenger provides ordered and reliable
 * delivery.  We tolerate TCP disconnects by reconnecting (with
 * exponential backoff) in the case of a fault (disconnection, bad
 * crc, protocol error).  Acks allow sent messages to be discarded by
 * the sender.
 */

/*
 * We track the state of the socket on a given connection using
 * values defined below.  The transition to a new socket state is
 * handled by a function which verifies we aren't coming from an
 * unexpected state.
 *
 *      --------
 *      | NEW* |  transient initial state
 *      --------
 *          | con_sock_state_init()
 *          v
 *      ----------
 *      | CLOSED |  initialized, but no socket (and no
 *      ----------  TCP connection)
 *       ^      \
 *       |       \ con_sock_state_connecting()
 *       |        ----------------------
 *       |                              \
 *       + con_sock_state_closed()       \
 *       |+---------------------------    \
 *       | \                          \    \
 *       |  -----------                \    \
 *       |  | CLOSING |  socket event;  \    \
 *       |  -----------  await close     \    \
 *       |       ^                        \   |
 *       |       |                         \  |
 *       |       + con_sock_state_closing() \ |
 *       |      / \                         | |
 *       |     /   ---------------          | |
 *       |    /                   \         v v
 *       |   /                    --------------
 *       |  /    -----------------| CONNECTING |  socket created, TCP
 *       |  |   /                 --------------  connect initiated
 *       |  |   | con_sock_state_connected()
 *       |  |   v
 *      -------------
 *      | CONNECTED |  TCP connection established
 *      -------------
 *
 * State values for ceph_connection->sock_state; NEW is assumed to be 0.
 */

#define CON_SOCK_STATE_NEW      0   /* -> CLOSED */
#define CON_SOCK_STATE_CLOSED       1   /* -> CONNECTING */
#define CON_SOCK_STATE_CONNECTING   2   /* -> CONNECTED or -> CLOSING */
#define CON_SOCK_STATE_CONNECTED    3   /* -> CLOSING or -> CLOSED */
#define CON_SOCK_STATE_CLOSING      4   /* -> CLOSED */

/*
 * connection states
 */
#define CON_STATE_CLOSED        1  /* -> PREOPEN */
#define CON_STATE_PREOPEN       2  /* -> CONNECTING, CLOSED */
#define CON_STATE_CONNECTING    3  /* -> NEGOTIATING, CLOSED */
#define CON_STATE_NEGOTIATING   4  /* -> OPEN, CLOSED */
#define CON_STATE_OPEN          5  /* -> STANDBY, CLOSED */
#define CON_STATE_STANDBY       6  /* -> PREOPEN, CLOSED */

/*
 * ceph_connection flag bits
 */
#define CON_FLAG_LOSSYTX           0  /* we can close channel or drop
                       * messages on errors */
#define CON_FLAG_KEEPALIVE_PENDING 1  /* we need to send a keepalive */
#define CON_FLAG_WRITE_PENDING     2  /* we have data ready to send */
#define CON_FLAG_SOCK_CLOSED       3  /* socket state changed to closed */
#define CON_FLAG_BACKOFF           4  /* need to retry queuing delayed work */

/* static tag bytes (protocol control messages) */
static char tag_msg = CEPH_MSGR_TAG_MSG;
static char tag_ack = CEPH_MSGR_TAG_ACK;
static char tag_keepalive = CEPH_MSGR_TAG_KEEPALIVE;

#ifdef CONFIG_LOCKDEP
static struct lock_class_key socket_class;
#endif

/*
 * When skipping (ignoring) a block of input we read it into a "skip
 * buffer," which is this many bytes in size.
 */
#define SKIP_BUF_SIZE   1024

static void queue_con(struct ceph_connection *con);
static void con_work(struct work_struct *);
static void ceph_fault(struct ceph_connection *con);

/*
 * Nicely render a sockaddr as a string.  An array of formatted
 * strings is used, to approximate reentrancy.
 */
#define ADDR_STR_COUNT_LOG  5   /* log2(# address strings in array) */
#define ADDR_STR_COUNT      (1 << ADDR_STR_COUNT_LOG)
#define ADDR_STR_COUNT_MASK (ADDR_STR_COUNT - 1)
#define MAX_ADDR_STR_LEN    64  /* 54 is enough */

static char addr_str[ADDR_STR_COUNT][MAX_ADDR_STR_LEN];
static atomic_t addr_str_seq = ATOMIC_INIT(0);

static struct page *zero_page;      /* used in certain error cases */

const char *ceph_pr_addr(const struct sockaddr_storage *ss)
{
    int i;
    char *s;
    struct sockaddr_in *in4 = (struct sockaddr_in *) ss;
    struct sockaddr_in6 *in6 = (struct sockaddr_in6 *) ss;

    i = atomic_inc_return(&addr_str_seq) & ADDR_STR_COUNT_MASK;
    s = addr_str[i];

    switch (ss->ss_family) {
    case AF_INET:
        snprintf(s, MAX_ADDR_STR_LEN, "%pI4:%hu", &in4->sin_addr,
             ntohs(in4->sin_port));
        break;

    case AF_INET6:
        snprintf(s, MAX_ADDR_STR_LEN, "[%pI6c]:%hu", &in6->sin6_addr,
             ntohs(in6->sin6_port));
        break;

    default:
        snprintf(s, MAX_ADDR_STR_LEN, "(unknown sockaddr family %hu)",
             ss->ss_family);
    }

    return s;
}
EXPORT_SYMBOL(ceph_pr_addr);

static void encode_my_addr(struct ceph_messenger *msgr)
{
    memcpy(&msgr->my_enc_addr, &msgr->inst.addr, sizeof(msgr->my_enc_addr));
    ceph_encode_addr(&msgr->my_enc_addr);
}

/*
 * work queue for all reading and writing to/from the socket.
 */
static struct workqueue_struct *ceph_msgr_wq;

void _ceph_msgr_exit(void)
{
    if (ceph_msgr_wq) {
        destroy_workqueue(ceph_msgr_wq);
        ceph_msgr_wq = NULL;
    }

    BUG_ON(zero_page == NULL);
    kunmap(zero_page);
    page_cache_release(zero_page);
    zero_page = NULL;
}

int ceph_msgr_init(void)
{
    BUG_ON(zero_page != NULL);
    zero_page = ZERO_PAGE(0);
    page_cache_get(zero_page);

    ceph_msgr_wq = alloc_workqueue("ceph-msgr", WQ_NON_REENTRANT, 0);
    if (ceph_msgr_wq)
        return 0;

    pr_err("msgr_init failed to create workqueue\n");
    _ceph_msgr_exit();

    return -ENOMEM;
}
EXPORT_SYMBOL(ceph_msgr_init);

void ceph_msgr_exit(void)
{
    BUG_ON(ceph_msgr_wq == NULL);

    _ceph_msgr_exit();
}
EXPORT_SYMBOL(ceph_msgr_exit);

void ceph_msgr_flush(void)
{
    flush_workqueue(ceph_msgr_wq);
}
EXPORT_SYMBOL(ceph_msgr_flush);

/* Connection socket state transition functions */

static void con_sock_state_init(struct ceph_connection *con)
{
    int old_state;

    old_state = atomic_xchg(&con->sock_state, CON_SOCK_STATE_CLOSED);
    if (WARN_ON(old_state != CON_SOCK_STATE_NEW))
        printk("%s: unexpected old state %d\n", __func__, old_state);
    dout("%s con %p sock %d -> %d\n", __func__, con, old_state,
         CON_SOCK_STATE_CLOSED);
}

static void con_sock_state_connecting(struct ceph_connection *con)
{
    int old_state;

    old_state = atomic_xchg(&con->sock_state, CON_SOCK_STATE_CONNECTING);
    if (WARN_ON(old_state != CON_SOCK_STATE_CLOSED))
        printk("%s: unexpected old state %d\n", __func__, old_state);
    dout("%s con %p sock %d -> %d\n", __func__, con, old_state,
         CON_SOCK_STATE_CONNECTING);
}

static void con_sock_state_connected(struct ceph_connection *con)
{
    int old_state;

    old_state = atomic_xchg(&con->sock_state, CON_SOCK_STATE_CONNECTED);
    if (WARN_ON(old_state != CON_SOCK_STATE_CONNECTING))
        printk("%s: unexpected old state %d\n", __func__, old_state);
    dout("%s con %p sock %d -> %d\n", __func__, con, old_state,
         CON_SOCK_STATE_CONNECTED);
}

static void con_sock_state_closing(struct ceph_connection *con)
{
    int old_state;

    old_state = atomic_xchg(&con->sock_state, CON_SOCK_STATE_CLOSING);
    if (WARN_ON(old_state != CON_SOCK_STATE_CONNECTING &&
            old_state != CON_SOCK_STATE_CONNECTED &&
            old_state != CON_SOCK_STATE_CLOSING))
        printk("%s: unexpected old state %d\n", __func__, old_state);
    dout("%s con %p sock %d -> %d\n", __func__, con, old_state,
         CON_SOCK_STATE_CLOSING);
}

static void con_sock_state_closed(struct ceph_connection *con)
{
    int old_state;

    old_state = atomic_xchg(&con->sock_state, CON_SOCK_STATE_CLOSED);
    if (WARN_ON(old_state != CON_SOCK_STATE_CONNECTED &&
            old_state != CON_SOCK_STATE_CLOSING &&
            old_state != CON_SOCK_STATE_CONNECTING &&
            old_state != CON_SOCK_STATE_CLOSED))
        printk("%s: unexpected old state %d\n", __func__, old_state);
    dout("%s con %p sock %d -> %d\n", __func__, con, old_state,
         CON_SOCK_STATE_CLOSED);
}

/*
 * socket callback functions
 */

/* data available on socket, or listen socket received a connect */
static void ceph_sock_data_ready(struct sock *sk, int count_unused)
{
    struct ceph_connection *con = sk->sk_user_data;
    if (atomic_read(&con->msgr->stopping)) {
        return;
    }

    if (sk->sk_state != TCP_CLOSE_WAIT) {
        dout("%s on %p state = %lu, queueing work\n", __func__,
             con, con->state);
        queue_con(con);
    }
}

/* socket has buffer space for writing */
static void ceph_sock_write_space(struct sock *sk)
{
    struct ceph_connection *con = sk->sk_user_data;

    /* only queue to workqueue if there is data we want to write,
     * and there is sufficient space in the socket buffer to accept
     * more data.  clear SOCK_NOSPACE so that ceph_sock_write_space()
     * doesn't get called again until try_write() fills the socket
     * buffer. See net/ipv4/tcp_input.c:tcp_check_space()
     * and net/core/stream.c:sk_stream_write_space().
     */
    if (test_bit(CON_FLAG_WRITE_PENDING, &con->flags)) {
        if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) {
            dout("%s %p queueing write work\n", __func__, con);
            clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
            queue_con(con);
        }
    } else {
        dout("%s %p nothing to write\n", __func__, con);
    }
}

/* socket's state has changed */
static void ceph_sock_state_change(struct sock *sk)
{
    struct ceph_connection *con = sk->sk_user_data;

    dout("%s %p state = %lu sk_state = %u\n", __func__,
         con, con->state, sk->sk_state);

    switch (sk->sk_state) {
    case TCP_CLOSE:
        dout("%s TCP_CLOSE\n", __func__);
    case TCP_CLOSE_WAIT:
        dout("%s TCP_CLOSE_WAIT\n", __func__);
        con_sock_state_closing(con);
        set_bit(CON_FLAG_SOCK_CLOSED, &con->flags);
        queue_con(con);
        break;
    case TCP_ESTABLISHED:
        dout("%s TCP_ESTABLISHED\n", __func__);
        con_sock_state_connected(con);
        queue_con(con);
        break;
    default:    /* Everything else is uninteresting */
        break;
    }
}

/*
 * set up socket callbacks
 */
static void set_sock_callbacks(struct socket *sock,
                   struct ceph_connection *con)
{
    struct sock *sk = sock->sk;
    sk->sk_user_data = con;
    sk->sk_data_ready = ceph_sock_data_ready;
    sk->sk_write_space = ceph_sock_write_space;
    sk->sk_state_change = ceph_sock_state_change;
}


/*
 * socket helpers
 */

/*
 * initiate connection to a remote socket.
 */
static int ceph_tcp_connect(struct ceph_connection *con)
{
    struct sockaddr_storage *paddr = &con->peer_addr.in_addr;
    struct socket *sock;
    int ret;

    BUG_ON(con->sock);
    ret = sock_create_kern(con->peer_addr.in_addr.ss_family, SOCK_STREAM,
                   IPPROTO_TCP, &sock);
    if (ret)
        return ret;
    sock->sk->sk_allocation = GFP_NOFS;

#ifdef CONFIG_LOCKDEP
    lockdep_set_class(&sock->sk->sk_lock, &socket_class);
#endif

    set_sock_callbacks(sock, con);

    dout("connect %s\n", ceph_pr_addr(&con->peer_addr.in_addr));

    con_sock_state_connecting(con);
    ret = sock->ops->connect(sock, (struct sockaddr *)paddr, sizeof(*paddr),
                 O_NONBLOCK);
    if (ret == -EINPROGRESS) {
        dout("connect %s EINPROGRESS sk_state = %u\n",
             ceph_pr_addr(&con->peer_addr.in_addr),
             sock->sk->sk_state);
    } else if (ret < 0) {
        pr_err("connect %s error %d\n",
               ceph_pr_addr(&con->peer_addr.in_addr), ret);
        sock_release(sock);
        con->error_msg = "connect error";

        return ret;
    }
    con->sock = sock;
    return 0;
}

static int ceph_tcp_recvmsg(struct socket *sock, void *buf, size_t len)
{
    struct kvec iov = {buf, len};
    struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL };
    int r;

    r = kernel_recvmsg(sock, &msg, &iov, 1, len, msg.msg_flags);
    if (r == -EAGAIN)
        r = 0;
    return r;
}

/*
 * write something.  @more is true if caller will be sending more data
 * shortly.
 */
static int ceph_tcp_sendmsg(struct socket *sock, struct kvec *iov,
             size_t kvlen, size_t len, int more)
{
    struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL };
    int r;

    if (more)
        msg.msg_flags |= MSG_MORE;
    else
        msg.msg_flags |= MSG_EOR;  /* superfluous, but what the hell */

    r = kernel_sendmsg(sock, &msg, iov, kvlen, len);
    if (r == -EAGAIN)
        r = 0;
    return r;
}

static int ceph_tcp_sendpage(struct socket *sock, struct page *page,
             int offset, size_t size, int more)
{
    int flags = MSG_DONTWAIT | MSG_NOSIGNAL | (more ? MSG_MORE : MSG_EOR);
    int ret;

    ret = kernel_sendpage(sock, page, offset, size, flags);
    if (ret == -EAGAIN)
        ret = 0;

    return ret;
}


/*
 * Shutdown/close the socket for the given connection.
 */
static int con_close_socket(struct ceph_connection *con)
{
    int rc = 0;

    dout("con_close_socket on %p sock %p\n", con, con->sock);
    if (con->sock) {
        rc = con->sock->ops->shutdown(con->sock, SHUT_RDWR);
        sock_release(con->sock);
        con->sock = NULL;
    }

    /*
     * Forcibly clear the SOCK_CLOSED flag.  It gets set
     * independent of the connection mutex, and we could have
     * received a socket close event before we had the chance to
     * shut the socket down.
     */
    clear_bit(CON_FLAG_SOCK_CLOSED, &con->flags);

    con_sock_state_closed(con);
    return rc;
}

/*
 * Reset a connection.  Discard all incoming and outgoing messages
 * and clear *_seq state.
 */
static void ceph_msg_remove(struct ceph_msg *msg)
{
    list_del_init(&msg->list_head);
    BUG_ON(msg->con == NULL);
    msg->con->ops->put(msg->con);
    msg->con = NULL;

    ceph_msg_put(msg);
}
static void ceph_msg_remove_list(struct list_head *head)
{
    while (!list_empty(head)) {
        struct ceph_msg *msg = list_first_entry(head, struct ceph_msg,
                            list_head);
        ceph_msg_remove(msg);
    }
}

static void reset_connection(struct ceph_connection *con)
{
    /* reset connection, out_queue, msg_ and connect_seq */
    /* discard existing out_queue and msg_seq */
    ceph_msg_remove_list(&con->out_queue);
    ceph_msg_remove_list(&con->out_sent);

    if (con->in_msg) {
        BUG_ON(con->in_msg->con != con);
        con->in_msg->con = NULL;
        ceph_msg_put(con->in_msg);
        con->in_msg = NULL;
        con->ops->put(con);
    }

    con->connect_seq = 0;
    con->out_seq = 0;
    if (con->out_msg) {
        ceph_msg_put(con->out_msg);
        con->out_msg = NULL;
    }
    con->in_seq = 0;
    con->in_seq_acked = 0;
}

/*
 * mark a peer down.  drop any open connections.
 */
void ceph_con_close(struct ceph_connection *con)
{
    mutex_lock(&con->mutex);
    dout("con_close %p peer %s\n", con,
         ceph_pr_addr(&con->peer_addr.in_addr));
    con->state = CON_STATE_CLOSED;

    clear_bit(CON_FLAG_LOSSYTX, &con->flags); /* so we retry next connect */
    clear_bit(CON_FLAG_KEEPALIVE_PENDING, &con->flags);
    clear_bit(CON_FLAG_WRITE_PENDING, &con->flags);
    clear_bit(CON_FLAG_KEEPALIVE_PENDING, &con->flags);
    clear_bit(CON_FLAG_BACKOFF, &con->flags);

    reset_connection(con);
    con->peer_global_seq = 0;
    cancel_delayed_work(&con->work);
    con_close_socket(con);
    mutex_unlock(&con->mutex);
}
EXPORT_SYMBOL(ceph_con_close);

/*
 * Reopen a closed connection, with a new peer address.
 */
void ceph_con_open(struct ceph_connection *con,
           __u8 entity_type, __u64 entity_num,
           struct ceph_entity_addr *addr)
{
    mutex_lock(&con->mutex);
    dout("con_open %p %s\n", con, ceph_pr_addr(&addr->in_addr));

    BUG_ON(con->state != CON_STATE_CLOSED);
    con->state = CON_STATE_PREOPEN;

    con->peer_name.type = (__u8) entity_type;
    con->peer_name.num = cpu_to_le64(entity_num);

    memcpy(&con->peer_addr, addr, sizeof(*addr));
    con->delay = 0;      /* reset backoff memory */
    mutex_unlock(&con->mutex);
    queue_con(con);
}
EXPORT_SYMBOL(ceph_con_open);

/*
 * return true if this connection ever successfully opened
 */
bool ceph_con_opened(struct ceph_connection *con)
{
    return con->connect_seq > 0;
}

/*
 * initialize a new connection.
 */
void ceph_con_init(struct ceph_connection *con, void *private,
    const struct ceph_connection_operations *ops,
    struct ceph_messenger *msgr)
{
    dout("con_init %p\n", con);
    memset(con, 0, sizeof(*con));
    con->private = private;
    con->ops = ops;
    con->msgr = msgr;

    con_sock_state_init(con);

    mutex_init(&con->mutex);
    INIT_LIST_HEAD(&con->out_queue);
    INIT_LIST_HEAD(&con->out_sent);
    INIT_DELAYED_WORK(&con->work, con_work);

    con->state = CON_STATE_CLOSED;
}
EXPORT_SYMBOL(ceph_con_init);


/*
 * We maintain a global counter to order connection attempts.  Get
 * a unique seq greater than @gt.
 */
static u32 get_global_seq(struct ceph_messenger *msgr, u32 gt)
{
    u32 ret;

    spin_lock(&msgr->global_seq_lock);
    if (msgr->global_seq < gt)
        msgr->global_seq = gt;
    ret = ++msgr->global_seq;
    spin_unlock(&msgr->global_seq_lock);
    return ret;
}

static void con_out_kvec_reset(struct ceph_connection *con)
{
    con->out_kvec_left = 0;
    con->out_kvec_bytes = 0;
    con->out_kvec_cur = &con->out_kvec[0];
}

static void con_out_kvec_add(struct ceph_connection *con,
                size_t size, void *data)
{
    int index;

    index = con->out_kvec_left;
    BUG_ON(index >= ARRAY_SIZE(con->out_kvec));

    con->out_kvec[index].iov_len = size;
    con->out_kvec[index].iov_base = data;
    con->out_kvec_left++;
    con->out_kvec_bytes += size;
}

#ifdef CONFIG_BLOCK
static void init_bio_iter(struct bio *bio, struct bio **iter, int *seg)
{
    if (!bio) {
        *iter = NULL;
        *seg = 0;
        return;
    }
    *iter = bio;
    *seg = bio->bi_idx;
}

static void iter_bio_next(struct bio **bio_iter, int *seg)
{
    if (*bio_iter == NULL)
        return;

    BUG_ON(*seg >= (*bio_iter)->bi_vcnt);

    (*seg)++;
    if (*seg == (*bio_iter)->bi_vcnt)
        init_bio_iter((*bio_iter)->bi_next, bio_iter, seg);
}
#endif

static void prepare_write_message_data(struct ceph_connection *con)
{
    struct ceph_msg *msg = con->out_msg;

    BUG_ON(!msg);
    BUG_ON(!msg->hdr.data_len);

    /* initialize page iterator */
    con->out_msg_pos.page = 0;
    if (msg->pages)
        con->out_msg_pos.page_pos = msg->page_alignment;
    else
        con->out_msg_pos.page_pos = 0;
#ifdef CONFIG_BLOCK
    if (msg->bio)
        init_bio_iter(msg->bio, &msg->bio_iter, &msg->bio_seg);
#endif
    con->out_msg_pos.data_pos = 0;
    con->out_msg_pos.did_page_crc = false;
    con->out_more = 1;  /* data + footer will follow */
}

/*
 * Prepare footer for currently outgoing message, and finish things
 * off.  Assumes out_kvec* are already valid.. we just add on to the end.
 */
static void prepare_write_message_footer(struct ceph_connection *con)
{
    struct ceph_msg *m = con->out_msg;
    int v = con->out_kvec_left;

    m->footer.flags |= CEPH_MSG_FOOTER_COMPLETE;

    dout("prepare_write_message_footer %p\n", con);
    con->out_kvec_is_msg = true;
    con->out_kvec[v].iov_base = &m->footer;
    con->out_kvec[v].iov_len = sizeof(m->footer);
    con->out_kvec_bytes += sizeof(m->footer);
    con->out_kvec_left++;
    con->out_more = m->more_to_follow;
    con->out_msg_done = true;
}

/*
 * Prepare headers for the next outgoing message.
 */
static void prepare_write_message(struct ceph_connection *con)
{
    struct ceph_msg *m;
    u32 crc;

    con_out_kvec_reset(con);
    con->out_kvec_is_msg = true;
    con->out_msg_done = false;

    /* Sneak an ack in there first?  If we can get it into the same
     * TCP packet that's a good thing. */
    if (con->in_seq > con->in_seq_acked) {
        con->in_seq_acked = con->in_seq;
        con_out_kvec_add(con, sizeof (tag_ack), &tag_ack);
        con->out_temp_ack = cpu_to_le64(con->in_seq_acked);
        con_out_kvec_add(con, sizeof (con->out_temp_ack),
            &con->out_temp_ack);
    }

    BUG_ON(list_empty(&con->out_queue));
    m = list_first_entry(&con->out_queue, struct ceph_msg, list_head);
    con->out_msg = m;
    BUG_ON(m->con != con);

    /* put message on sent list */
    ceph_msg_get(m);
    list_move_tail(&m->list_head, &con->out_sent);

    /*
     * only assign outgoing seq # if we haven't sent this message
     * yet.  if it is requeued, resend with it's original seq.
     */
    if (m->needs_out_seq) {
        m->hdr.seq = cpu_to_le64(++con->out_seq);
        m->needs_out_seq = false;
    }
#ifdef CONFIG_BLOCK
    else
        m->bio_iter = NULL;
#endif

    dout("prepare_write_message %p seq %lld type %d len %d+%d+%d %d pgs\n",
         m, con->out_seq, le16_to_cpu(m->hdr.type),
         le32_to_cpu(m->hdr.front_len), le32_to_cpu(m->hdr.middle_len),
         le32_to_cpu(m->hdr.data_len),
         m->nr_pages);
    BUG_ON(le32_to_cpu(m->hdr.front_len) != m->front.iov_len);

    /* tag + hdr + front + middle */
    con_out_kvec_add(con, sizeof (tag_msg), &tag_msg);
    con_out_kvec_add(con, sizeof (m->hdr), &m->hdr);
    con_out_kvec_add(con, m->front.iov_len, m->front.iov_base);

    if (m->middle)
        con_out_kvec_add(con, m->middle->vec.iov_len,
            m->middle->vec.iov_base);

    /* fill in crc (except data pages), footer */
    crc = crc32c(0, &m->hdr, offsetof(struct ceph_msg_header, crc));
    con->out_msg->hdr.crc = cpu_to_le32(crc);
    con->out_msg->footer.flags = 0;

    crc = crc32c(0, m->front.iov_base, m->front.iov_len);
    con->out_msg->footer.front_crc = cpu_to_le32(crc);
    if (m->middle) {
        crc = crc32c(0, m->middle->vec.iov_base,
                m->middle->vec.iov_len);
        con->out_msg->footer.middle_crc = cpu_to_le32(crc);
    } else
        con->out_msg->footer.middle_crc = 0;
    dout("%s front_crc %u middle_crc %u\n", __func__,
         le32_to_cpu(con->out_msg->footer.front_crc),
         le32_to_cpu(con->out_msg->footer.middle_crc));

    /* is there a data payload? */
    con->out_msg->footer.data_crc = 0;
    if (m->hdr.data_len)
        prepare_write_message_data(con);
    else
        /* no, queue up footer too and be done */
        prepare_write_message_footer(con);

    set_bit(CON_FLAG_WRITE_PENDING, &con->flags);
}

/*
 * Prepare an ack.
 */
static void prepare_write_ack(struct ceph_connection *con)
{
    dout("prepare_write_ack %p %llu -> %llu\n", con,
         con->in_seq_acked, con->in_seq);
    con->in_seq_acked = con->in_seq;

    con_out_kvec_reset(con);

    con_out_kvec_add(con, sizeof (tag_ack), &tag_ack);

    con->out_temp_ack = cpu_to_le64(con->in_seq_acked);
    con_out_kvec_add(con, sizeof (con->out_temp_ack),
                &con->out_temp_ack);

    con->out_more = 1;  /* more will follow.. eventually.. */
    set_bit(CON_FLAG_WRITE_PENDING, &con->flags);
}

/*
 * Prepare to write keepalive byte.
 */
static void prepare_write_keepalive(struct ceph_connection *con)
{
    dout("prepare_write_keepalive %p\n", con);
    con_out_kvec_reset(con);
    con_out_kvec_add(con, sizeof (tag_keepalive), &tag_keepalive);
    set_bit(CON_FLAG_WRITE_PENDING, &con->flags);
}

/*
 * Connection negotiation.
 */

static struct ceph_auth_handshake *get_connect_authorizer(struct ceph_connection *con,
                        int *auth_proto)
{
    struct ceph_auth_handshake *auth;

    if (!con->ops->get_authorizer) {
        con->out_connect.authorizer_protocol = CEPH_AUTH_UNKNOWN;
        con->out_connect.authorizer_len = 0;
        return NULL;
    }

    /* Can't hold the mutex while getting authorizer */
    mutex_unlock(&con->mutex);
    auth = con->ops->get_authorizer(con, auth_proto, con->auth_retry);
    mutex_lock(&con->mutex);

    if (IS_ERR(auth))
        return auth;
    if (con->state != CON_STATE_NEGOTIATING)
        return ERR_PTR(-EAGAIN);

    con->auth_reply_buf = auth->authorizer_reply_buf;
    con->auth_reply_buf_len = auth->authorizer_reply_buf_len;
    return auth;
}

/*
 * We connected to a peer and are saying hello.
 */
static void prepare_write_banner(struct ceph_connection *con)
{
    con_out_kvec_add(con, strlen(CEPH_BANNER), CEPH_BANNER);
    con_out_kvec_add(con, sizeof (con->msgr->my_enc_addr),
                    &con->msgr->my_enc_addr);

    con->out_more = 0;
    set_bit(CON_FLAG_WRITE_PENDING, &con->flags);
}

static int prepare_write_connect(struct ceph_connection *con)
{
    unsigned int global_seq = get_global_seq(con->msgr, 0);
    int proto;
    int auth_proto;
    struct ceph_auth_handshake *auth;

    switch (con->peer_name.type) {
    case CEPH_ENTITY_TYPE_MON:
        proto = CEPH_MONC_PROTOCOL;
        break;
    case CEPH_ENTITY_TYPE_OSD:
        proto = CEPH_OSDC_PROTOCOL;
        break;
    case CEPH_ENTITY_TYPE_MDS:
        proto = CEPH_MDSC_PROTOCOL;
        break;
    default:
        BUG();
    }

    dout("prepare_write_connect %p cseq=%d gseq=%d proto=%d\n", con,
         con->connect_seq, global_seq, proto);

    con->out_connect.features = cpu_to_le64(con->msgr->supported_features);
    con->out_connect.host_type = cpu_to_le32(CEPH_ENTITY_TYPE_CLIENT);
    con->out_connect.connect_seq = cpu_to_le32(con->connect_seq);
    con->out_connect.global_seq = cpu_to_le32(global_seq);
    con->out_connect.protocol_version = cpu_to_le32(proto);
    con->out_connect.flags = 0;

    auth_proto = CEPH_AUTH_UNKNOWN;
    auth = get_connect_authorizer(con, &auth_proto);
    if (IS_ERR(auth))
        return PTR_ERR(auth);

    con->out_connect.authorizer_protocol = cpu_to_le32(auth_proto);
    con->out_connect.authorizer_len = auth ?
        cpu_to_le32(auth->authorizer_buf_len) : 0;

    con_out_kvec_add(con, sizeof (con->out_connect),
                    &con->out_connect);
    if (auth && auth->authorizer_buf_len)
        con_out_kvec_add(con, auth->authorizer_buf_len,
                    auth->authorizer_buf);

    con->out_more = 0;
    set_bit(CON_FLAG_WRITE_PENDING, &con->flags);

    return 0;
}

/*
 * write as much of pending kvecs to the socket as we can.
 *  1 -> done
 *  0 -> socket full, but more to do
 * <0 -> error
 */
static int write_partial_kvec(struct ceph_connection *con)
{
    int ret;

    dout("write_partial_kvec %p %d left\n", con, con->out_kvec_bytes);
    while (con->out_kvec_bytes > 0) {
        ret = ceph_tcp_sendmsg(con->sock, con->out_kvec_cur,
                       con->out_kvec_left, con->out_kvec_bytes,
                       con->out_more);
        if (ret <= 0)
            goto out;
        con->out_kvec_bytes -= ret;
        if (con->out_kvec_bytes == 0)
            break;            /* done */

        /* account for full iov entries consumed */
        while (ret >= con->out_kvec_cur->iov_len) {
            BUG_ON(!con->out_kvec_left);
            ret -= con->out_kvec_cur->iov_len;
            con->out_kvec_cur++;
            con->out_kvec_left--;
        }
        /* and for a partially-consumed entry */
        if (ret) {
            con->out_kvec_cur->iov_len -= ret;
            con->out_kvec_cur->iov_base += ret;
        }
    }
    con->out_kvec_left = 0;
    con->out_kvec_is_msg = false;
    ret = 1;
out:
    dout("write_partial_kvec %p %d left in %d kvecs ret = %d\n", con,
         con->out_kvec_bytes, con->out_kvec_left, ret);
    return ret;  /* done! */
}

static void out_msg_pos_next(struct ceph_connection *con, struct page *page,
            size_t len, size_t sent, bool in_trail)
{
    struct ceph_msg *msg = con->out_msg;

    BUG_ON(!msg);
    BUG_ON(!sent);

    con->out_msg_pos.data_pos += sent;
    con->out_msg_pos.page_pos += sent;
    if (sent < len)
        return;

    BUG_ON(sent != len);
    con->out_msg_pos.page_pos = 0;
    con->out_msg_pos.page++;
    con->out_msg_pos.did_page_crc = false;
    if (in_trail)
        list_move_tail(&page->lru,
                   &msg->trail->head);
    else if (msg->pagelist)
        list_move_tail(&page->lru,
                   &msg->pagelist->head);
#ifdef CONFIG_BLOCK
    else if (msg->bio)
        iter_bio_next(&msg->bio_iter, &msg->bio_seg);
#endif
}

/*
 * Write as much message data payload as we can.  If we finish, queue
 * up the footer.
 *  1 -> done, footer is now queued in out_kvec[].
 *  0 -> socket full, but more to do
 * <0 -> error
 */
static int write_partial_msg_pages(struct ceph_connection *con)
{
    struct ceph_msg *msg = con->out_msg;
    unsigned int data_len = le32_to_cpu(msg->hdr.data_len);
    size_t len;
    bool do_datacrc = !con->msgr->nocrc;
    int ret;
    int total_max_write;
    bool in_trail = false;
    const size_t trail_len = (msg->trail ? msg->trail->length : 0);
    const size_t trail_off = data_len - trail_len;

    dout("write_partial_msg_pages %p msg %p page %d/%d offset %d\n",
         con, msg, con->out_msg_pos.page, msg->nr_pages,
         con->out_msg_pos.page_pos);

    /*
     * Iterate through each page that contains data to be
     * written, and send as much as possible for each.
     *
     * If we are calculating the data crc (the default), we will
     * need to map the page.  If we have no pages, they have
     * been revoked, so use the zero page.
     */
    while (data_len > con->out_msg_pos.data_pos) {
        struct page *page = NULL;
        int max_write = PAGE_SIZE;
        int bio_offset = 0;

        in_trail = in_trail || con->out_msg_pos.data_pos >= trail_off;
        if (!in_trail)
            total_max_write = trail_off - con->out_msg_pos.data_pos;

        if (in_trail) {
            total_max_write = data_len - con->out_msg_pos.data_pos;

            page = list_first_entry(&msg->trail->head,
                        struct page, lru);
        } else if (msg->pages) {
            page = msg->pages[con->out_msg_pos.page];
        } else if (msg->pagelist) {
            page = list_first_entry(&msg->pagelist->head,
                        struct page, lru);
#ifdef CONFIG_BLOCK
        } else if (msg->bio) {
            struct bio_vec *bv;

            bv = bio_iovec_idx(msg->bio_iter, msg->bio_seg);
            page = bv->bv_page;
            bio_offset = bv->bv_offset;
            max_write = bv->bv_len;
#endif
        } else {
            page = zero_page;
        }
        len = min_t(int, max_write - con->out_msg_pos.page_pos,
                total_max_write);

        if (do_datacrc && !con->out_msg_pos.did_page_crc) {
            void *base;
            u32 crc = le32_to_cpu(msg->footer.data_crc);
            char *kaddr;

            kaddr = kmap(page);
            BUG_ON(kaddr == NULL);
            base = kaddr + con->out_msg_pos.page_pos + bio_offset;
            crc = crc32c(crc, base, len);
            kunmap(page);
            msg->footer.data_crc = cpu_to_le32(crc);
            con->out_msg_pos.did_page_crc = true;
        }
        ret = ceph_tcp_sendpage(con->sock, page,
                      con->out_msg_pos.page_pos + bio_offset,
                      len, 1);
        if (ret <= 0)
            goto out;

        out_msg_pos_next(con, page, len, (size_t) ret, in_trail);
    }

    dout("write_partial_msg_pages %p msg %p done\n", con, msg);

    /* prepare and queue up footer, too */
    if (!do_datacrc)
        msg->footer.flags |= CEPH_MSG_FOOTER_NOCRC;
    con_out_kvec_reset(con);
    prepare_write_message_footer(con);
    ret = 1;
out:
    return ret;
}

/*
 * write some zeros
 */
static int write_partial_skip(struct ceph_connection *con)
{
    int ret;

    while (con->out_skip > 0) {
        size_t size = min(con->out_skip, (int) PAGE_CACHE_SIZE);

        ret = ceph_tcp_sendpage(con->sock, zero_page, 0, size, 1);
        if (ret <= 0)
            goto out;
        con->out_skip -= ret;
    }
    ret = 1;
out:
    return ret;
}

/*
 * Prepare to read connection handshake, or an ack.
 */
static void prepare_read_banner(struct ceph_connection *con)
{
    dout("prepare_read_banner %p\n", con);
    con->in_base_pos = 0;
}

static void prepare_read_connect(struct ceph_connection *con)
{
    dout("prepare_read_connect %p\n", con);
    con->in_base_pos = 0;
}

static void prepare_read_ack(struct ceph_connection *con)
{
    dout("prepare_read_ack %p\n", con);
    con->in_base_pos = 0;
}

static void prepare_read_tag(struct ceph_connection *con)
{
    dout("prepare_read_tag %p\n", con);
    con->in_base_pos = 0;
    con->in_tag = CEPH_MSGR_TAG_READY;
}

/*
 * Prepare to read a message.
 */
static int prepare_read_message(struct ceph_connection *con)
{
    dout("prepare_read_message %p\n", con);
    BUG_ON(con->in_msg != NULL);
    con->in_base_pos = 0;
    con->in_front_crc = con->in_middle_crc = con->in_data_crc = 0;
    return 0;
}


static int read_partial(struct ceph_connection *con,
            int end, int size, void *object)
{
    while (con->in_base_pos < end) {
        int left = end - con->in_base_pos;
        int have = size - left;
        int ret = ceph_tcp_recvmsg(con->sock, object + have, left);
        if (ret <= 0)
            return ret;
        con->in_base_pos += ret;
    }
    return 1;
}


/*
 * Read all or part of the connect-side handshake on a new connection
 */
static int read_partial_banner(struct ceph_connection *con)
{
    int size;
    int end;
    int ret;

    dout("read_partial_banner %p at %d\n", con, con->in_base_pos);

    /* peer's banner */
    size = strlen(CEPH_BANNER);
    end = size;
    ret = read_partial(con, end, size, con->in_banner);
    if (ret <= 0)
        goto out;

    size = sizeof (con->actual_peer_addr);
    end += size;
    ret = read_partial(con, end, size, &con->actual_peer_addr);
    if (ret <= 0)
        goto out;

    size = sizeof (con->peer_addr_for_me);
    end += size;
    ret = read_partial(con, end, size, &con->peer_addr_for_me);
    if (ret <= 0)
        goto out;

out:
    return ret;
}

static int read_partial_connect(struct ceph_connection *con)
{
    int size;
    int end;
    int ret;

    dout("read_partial_connect %p at %d\n", con, con->in_base_pos);

    size = sizeof (con->in_reply);
    end = size;
    ret = read_partial(con, end, size, &con->in_reply);
    if (ret <= 0)
        goto out;

    size = le32_to_cpu(con->in_reply.authorizer_len);
    end += size;
    ret = read_partial(con, end, size, con->auth_reply_buf);
    if (ret <= 0)
        goto out;

    dout("read_partial_connect %p tag %d, con_seq = %u, g_seq = %u\n",
         con, (int)con->in_reply.tag,
         le32_to_cpu(con->in_reply.connect_seq),
         le32_to_cpu(con->in_reply.global_seq));
out:
    return ret;

}

/*
 * Verify the hello banner looks okay.
 */
static int verify_hello(struct ceph_connection *con)
{
    if (memcmp(con->in_banner, CEPH_BANNER, strlen(CEPH_BANNER))) {
        pr_err("connect to %s got bad banner\n",
               ceph_pr_addr(&con->peer_addr.in_addr));
        con->error_msg = "protocol error, bad banner";
        return -1;
    }
    return 0;
}

static bool addr_is_blank(struct sockaddr_storage *ss)
{
    switch (ss->ss_family) {
    case AF_INET:
        return ((struct sockaddr_in *)ss)->sin_addr.s_addr == 0;
    case AF_INET6:
        return
             ((struct sockaddr_in6 *)ss)->sin6_addr.s6_addr32[0] == 0 &&
             ((struct sockaddr_in6 *)ss)->sin6_addr.s6_addr32[1] == 0 &&
             ((struct sockaddr_in6 *)ss)->sin6_addr.s6_addr32[2] == 0 &&
             ((struct sockaddr_in6 *)ss)->sin6_addr.s6_addr32[3] == 0;
    }
    return false;
}

static int addr_port(struct sockaddr_storage *ss)
{
    switch (ss->ss_family) {
    case AF_INET:
        return ntohs(((struct sockaddr_in *)ss)->sin_port);
    case AF_INET6:
        return ntohs(((struct sockaddr_in6 *)ss)->sin6_port);
    }
    return 0;
}

static void addr_set_port(struct sockaddr_storage *ss, int p)
{
    switch (ss->ss_family) {
    case AF_INET:
        ((struct sockaddr_in *)ss)->sin_port = htons(p);
        break;
    case AF_INET6:
        ((struct sockaddr_in6 *)ss)->sin6_port = htons(p);
        break;
    }
}

/*
 * Unlike other *_pton function semantics, zero indicates success.
 */
static int ceph_pton(const char *str, size_t len, struct sockaddr_storage *ss,
        char delim, const char **ipend)
{
    struct sockaddr_in *in4 = (struct sockaddr_in *) ss;
    struct sockaddr_in6 *in6 = (struct sockaddr_in6 *) ss;

    memset(ss, 0, sizeof(*ss));

    if (in4_pton(str, len, (u8 *)&in4->sin_addr.s_addr, delim, ipend)) {
        ss->ss_family = AF_INET;
        return 0;
    }

    if (in6_pton(str, len, (u8 *)&in6->sin6_addr.s6_addr, delim, ipend)) {
        ss->ss_family = AF_INET6;
        return 0;
    }

    return -EINVAL;
}

/*
 * Extract hostname string and resolve using kernel DNS facility.
 */
#ifdef CONFIG_CEPH_LIB_USE_DNS_RESOLVER
static int ceph_dns_resolve_name(const char *name, size_t namelen,
        struct sockaddr_storage *ss, char delim, const char **ipend)
{
    const char *end, *delim_p;
    char *colon_p, *ip_addr = NULL;
    int ip_len, ret;

    /*
     * The end of the hostname occurs immediately preceding the delimiter or
     * the port marker (':') where the delimiter takes precedence.
     */
    delim_p = memchr(name, delim, namelen);
    colon_p = memchr(name, ':', namelen);

    if (delim_p && colon_p)
        end = delim_p < colon_p ? delim_p : colon_p;
    else if (!delim_p && colon_p)
        end = colon_p;
    else {
        end = delim_p;
        if (!end) /* case: hostname:/ */
            end = name + namelen;
    }

    if (end <= name)
        return -EINVAL;

    /* do dns_resolve upcall */
    ip_len = dns_query(NULL, name, end - name, NULL, &ip_addr, NULL);
    if (ip_len > 0)
        ret = ceph_pton(ip_addr, ip_len, ss, -1, NULL);
    else
        ret = -ESRCH;

    kfree(ip_addr);

    *ipend = end;

    pr_info("resolve '%.*s' (ret=%d): %s\n", (int)(end - name), name,
            ret, ret ? "failed" : ceph_pr_addr(ss));

    return ret;
}
#else
static inline int ceph_dns_resolve_name(const char *name, size_t namelen,
        struct sockaddr_storage *ss, char delim, const char **ipend)
{
    return -EINVAL;
}
#endif

/*
 * Parse a server name (IP or hostname). If a valid IP address is not found
 * then try to extract a hostname to resolve using userspace DNS upcall.
 */
static int ceph_parse_server_name(const char *name, size_t namelen,
            struct sockaddr_storage *ss, char delim, const char **ipend)
{
    int ret;

    ret = ceph_pton(name, namelen, ss, delim, ipend);
    if (ret)
        ret = ceph_dns_resolve_name(name, namelen, ss, delim, ipend);

    return ret;
}

/*
 * Parse an ip[:port] list into an addr array.  Use the default
 * monitor port if a port isn't specified.
 */
int ceph_parse_ips(const char *c, const char *end,
           struct ceph_entity_addr *addr,
           int max_count, int *count)
{
    int i, ret = -EINVAL;
    const char *p = c;

    dout("parse_ips on '%.*s'\n", (int)(end-c), c);
    for (i = 0; i < max_count; i++) {
        const char *ipend;
        struct sockaddr_storage *ss = &addr[i].in_addr;
        int port;
        char delim = ',';

        if (*p == '[') {
            delim = ']';
            p++;
        }

        ret = ceph_parse_server_name(p, end - p, ss, delim, &ipend);
        if (ret)
            goto bad;
        ret = -EINVAL;

        p = ipend;

        if (delim == ']') {
            if (*p != ']') {
                dout("missing matching ']'\n");
                goto bad;
            }
            p++;
        }

        /* port? */
        if (p < end && *p == ':') {
            port = 0;
            p++;
            while (p < end && *p >= '0' && *p <= '9') {
                port = (port * 10) + (*p - '0');
                p++;
            }
            if (port > 65535 || port == 0)
                goto bad;
        } else {
            port = CEPH_MON_PORT;
        }

        addr_set_port(ss, port);

        dout("parse_ips got %s\n", ceph_pr_addr(ss));

        if (p == end)
            break;
        if (*p != ',')
            goto bad;
        p++;
    }

    if (p != end)
        goto bad;

    if (count)
        *count = i + 1;
    return 0;

bad:
    pr_err("parse_ips bad ip '%.*s'\n", (int)(end - c), c);
    return ret;
}
EXPORT_SYMBOL(ceph_parse_ips);

static int process_banner(struct ceph_connection *con)
{
    dout("process_banner on %p\n", con);

    if (verify_hello(con) < 0)
        return -1;

    ceph_decode_addr(&con->actual_peer_addr);
    ceph_decode_addr(&con->peer_addr_for_me);

    /*
     * Make sure the other end is who we wanted.  note that the other
     * end may not yet know their ip address, so if it's 0.0.0.0, give
     * them the benefit of the doubt.
     */
    if (memcmp(&con->peer_addr, &con->actual_peer_addr,
           sizeof(con->peer_addr)) != 0 &&
        !(addr_is_blank(&con->actual_peer_addr.in_addr) &&
          con->actual_peer_addr.nonce == con->peer_addr.nonce)) {
        pr_warning("wrong peer, want %s/%d, got %s/%d\n",
               ceph_pr_addr(&con->peer_addr.in_addr),
               (int)le32_to_cpu(con->peer_addr.nonce),
               ceph_pr_addr(&con->actual_peer_addr.in_addr),
               (int)le32_to_cpu(con->actual_peer_addr.nonce));
        con->error_msg = "wrong peer at address";
        return -1;
    }

    /*
     * did we learn our address?
     */
    if (addr_is_blank(&con->msgr->inst.addr.in_addr)) {
        int port = addr_port(&con->msgr->inst.addr.in_addr);

        memcpy(&con->msgr->inst.addr.in_addr,
               &con->peer_addr_for_me.in_addr,
               sizeof(con->peer_addr_for_me.in_addr));
        addr_set_port(&con->msgr->inst.addr.in_addr, port);
        encode_my_addr(con->msgr);
        dout("process_banner learned my addr is %s\n",
             ceph_pr_addr(&con->msgr->inst.addr.in_addr));
    }

    return 0;
}

static void fail_protocol(struct ceph_connection *con)
{
    reset_connection(con);
    BUG_ON(con->state != CON_STATE_NEGOTIATING);
    con->state = CON_STATE_CLOSED;
}

static int process_connect(struct ceph_connection *con)
{
    u64 sup_feat = con->msgr->supported_features;
    u64 req_feat = con->msgr->required_features;
    u64 server_feat = le64_to_cpu(con->in_reply.features);
    int ret;

    dout("process_connect on %p tag %d\n", con, (int)con->in_tag);

    switch (con->in_reply.tag) {
    case CEPH_MSGR_TAG_FEATURES:
        pr_err("%s%lld %s feature set mismatch,"
               " my %llx < server's %llx, missing %llx\n",
               ENTITY_NAME(con->peer_name),
               ceph_pr_addr(&con->peer_addr.in_addr),
               sup_feat, server_feat, server_feat & ~sup_feat);
        con->error_msg = "missing required protocol features";
        fail_protocol(con);
        return -1;

    case CEPH_MSGR_TAG_BADPROTOVER:
        pr_err("%s%lld %s protocol version mismatch,"
               " my %d != server's %d\n",
               ENTITY_NAME(con->peer_name),
               ceph_pr_addr(&con->peer_addr.in_addr),
               le32_to_cpu(con->out_connect.protocol_version),
               le32_to_cpu(con->in_reply.protocol_version));
        con->error_msg = "protocol version mismatch";
        fail_protocol(con);
        return -1;

    case CEPH_MSGR_TAG_BADAUTHORIZER:
        con->auth_retry++;
        dout("process_connect %p got BADAUTHORIZER attempt %d\n", con,
             con->auth_retry);
        if (con->auth_retry == 2) {
            con->error_msg = "connect authorization failure";
            return -1;
        }
        con->auth_retry = 1;
        con_out_kvec_reset(con);
        ret = prepare_write_connect(con);
        if (ret < 0)
            return ret;
        prepare_read_connect(con);
        break;

    case CEPH_MSGR_TAG_RESETSESSION:
        /*
         * If we connected with a large connect_seq but the peer
         * has no record of a session with us (no connection, or
         * connect_seq == 0), they will send RESETSESION to indicate
         * that they must have reset their session, and may have
         * dropped messages.
         */
        dout("process_connect got RESET peer seq %u\n",
             le32_to_cpu(con->in_reply.connect_seq));
        pr_err("%s%lld %s connection reset\n",
               ENTITY_NAME(con->peer_name),
               ceph_pr_addr(&con->peer_addr.in_addr));
        reset_connection(con);
        con_out_kvec_reset(con);
        ret = prepare_write_connect(con);
        if (ret < 0)
            return ret;
        prepare_read_connect(con);

        /* Tell ceph about it. */
        mutex_unlock(&con->mutex);
        pr_info("reset on %s%lld\n", ENTITY_NAME(con->peer_name));
        if (con->ops->peer_reset)
            con->ops->peer_reset(con);
        mutex_lock(&con->mutex);
        if (con->state != CON_STATE_NEGOTIATING)
            return -EAGAIN;
        break;

    case CEPH_MSGR_TAG_RETRY_SESSION:
        /*
         * If we sent a smaller connect_seq than the peer has, try
         * again with a larger value.
         */
        dout("process_connect got RETRY_SESSION my seq %u, peer %u\n",
             le32_to_cpu(con->out_connect.connect_seq),
             le32_to_cpu(con->in_reply.connect_seq));
        con->connect_seq = le32_to_cpu(con->in_reply.connect_seq);
        con_out_kvec_reset(con);
        ret = prepare_write_connect(con);
        if (ret < 0)
            return ret;
        prepare_read_connect(con);
        break;

    case CEPH_MSGR_TAG_RETRY_GLOBAL:
        /*
         * If we sent a smaller global_seq than the peer has, try
         * again with a larger value.
         */
        dout("process_connect got RETRY_GLOBAL my %u peer_gseq %u\n",
             con->peer_global_seq,
             le32_to_cpu(con->in_reply.global_seq));
        get_global_seq(con->msgr,
                   le32_to_cpu(con->in_reply.global_seq));
        con_out_kvec_reset(con);
        ret = prepare_write_connect(con);
        if (ret < 0)
            return ret;
        prepare_read_connect(con);
        break;

    case CEPH_MSGR_TAG_READY:
        if (req_feat & ~server_feat) {
            pr_err("%s%lld %s protocol feature mismatch,"
                   " my required %llx > server's %llx, need %llx\n",
                   ENTITY_NAME(con->peer_name),
                   ceph_pr_addr(&con->peer_addr.in_addr),
                   req_feat, server_feat, req_feat & ~server_feat);
            con->error_msg = "missing required protocol features";
            fail_protocol(con);
            return -1;
        }

        BUG_ON(con->state != CON_STATE_NEGOTIATING);
        con->state = CON_STATE_OPEN;

        con->peer_global_seq = le32_to_cpu(con->in_reply.global_seq);
        con->connect_seq++;
        con->peer_features = server_feat;
        dout("process_connect got READY gseq %d cseq %d (%d)\n",
             con->peer_global_seq,
             le32_to_cpu(con->in_reply.connect_seq),
             con->connect_seq);
        WARN_ON(con->connect_seq !=
            le32_to_cpu(con->in_reply.connect_seq));

        if (con->in_reply.flags & CEPH_MSG_CONNECT_LOSSY)
            set_bit(CON_FLAG_LOSSYTX, &con->flags);

        con->delay = 0;      /* reset backoff memory */

        prepare_read_tag(con);
        break;

    case CEPH_MSGR_TAG_WAIT:
        /*
         * If there is a connection race (we are opening
         * connections to each other), one of us may just have
         * to WAIT.  This shouldn't happen if we are the
         * client.
         */
        pr_err("process_connect got WAIT as client\n");
        con->error_msg = "protocol error, got WAIT as client";
        return -1;

    default:
        pr_err("connect protocol error, will retry\n");
        con->error_msg = "protocol error, garbage tag during connect";
        return -1;
    }
    return 0;
}


/*
 * read (part of) an ack
 */
static int read_partial_ack(struct ceph_connection *con)
{
    int size = sizeof (con->in_temp_ack);
    int end = size;

    return read_partial(con, end, size, &con->in_temp_ack);
}


/*
 * We can finally discard anything that's been acked.
 */
static void process_ack(struct ceph_connection *con)
{
    struct ceph_msg *m;
    u64 ack = le64_to_cpu(con->in_temp_ack);
    u64 seq;

    while (!list_empty(&con->out_sent)) {
        m = list_first_entry(&con->out_sent, struct ceph_msg,
                     list_head);
        seq = le64_to_cpu(m->hdr.seq);
        if (seq > ack)
            break;
        dout("got ack for seq %llu type %d at %p\n", seq,
             le16_to_cpu(m->hdr.type), m);
        m->ack_stamp = jiffies;
        ceph_msg_remove(m);
    }
    prepare_read_tag(con);
}




static int read_partial_message_section(struct ceph_connection *con,
                    struct kvec *section,
                    unsigned int sec_len, u32 *crc)
{
    int ret, left;

    BUG_ON(!section);

    while (section->iov_len < sec_len) {
        BUG_ON(section->iov_base == NULL);
        left = sec_len - section->iov_len;
        ret = ceph_tcp_recvmsg(con->sock, (char *)section->iov_base +
                       section->iov_len, left);
        if (ret <= 0)
            return ret;
        section->iov_len += ret;
    }
    if (section->iov_len == sec_len)
        *crc = crc32c(0, section->iov_base, section->iov_len);

    return 1;
}

static int ceph_con_in_msg_alloc(struct ceph_connection *con, int *skip);

static int read_partial_message_pages(struct ceph_connection *con,
                      struct page **pages,
                      unsigned int data_len, bool do_datacrc)
{
    void *p;
    int ret;
    int left;

    left = min((int)(data_len - con->in_msg_pos.data_pos),
           (int)(PAGE_SIZE - con->in_msg_pos.page_pos));
    /* (page) data */
    BUG_ON(pages == NULL);
    p = kmap(pages[con->in_msg_pos.page]);
    ret = ceph_tcp_recvmsg(con->sock, p + con->in_msg_pos.page_pos,
                   left);
    if (ret > 0 && do_datacrc)
        con->in_data_crc =
            crc32c(con->in_data_crc,
                  p + con->in_msg_pos.page_pos, ret);
    kunmap(pages[con->in_msg_pos.page]);
    if (ret <= 0)
        return ret;
    con->in_msg_pos.data_pos += ret;
    con->in_msg_pos.page_pos += ret;
    if (con->in_msg_pos.page_pos == PAGE_SIZE) {
        con->in_msg_pos.page_pos = 0;
        con->in_msg_pos.page++;
    }

    return ret;
}

#ifdef CONFIG_BLOCK
static int read_partial_message_bio(struct ceph_connection *con,
                    struct bio **bio_iter, int *bio_seg,
                    unsigned int data_len, bool do_datacrc)
{
    struct bio_vec *bv = bio_iovec_idx(*bio_iter, *bio_seg);
    void *p;
    int ret, left;

    left = min((int)(data_len - con->in_msg_pos.data_pos),
           (int)(bv->bv_len - con->in_msg_pos.page_pos));

    p = kmap(bv->bv_page) + bv->bv_offset;

    ret = ceph_tcp_recvmsg(con->sock, p + con->in_msg_pos.page_pos,
                   left);
    if (ret > 0 && do_datacrc)
        con->in_data_crc =
            crc32c(con->in_data_crc,
                  p + con->in_msg_pos.page_pos, ret);
    kunmap(bv->bv_page);
    if (ret <= 0)
        return ret;
    con->in_msg_pos.data_pos += ret;
    con->in_msg_pos.page_pos += ret;
    if (con->in_msg_pos.page_pos == bv->bv_len) {
        con->in_msg_pos.page_pos = 0;
        iter_bio_next(bio_iter, bio_seg);
    }

    return ret;
}
#endif

/*
 * read (part of) a message.
 */
static int read_partial_message(struct ceph_connection *con)
{
    struct ceph_msg *m = con->in_msg;
    int size;
    int end;
    int ret;
    unsigned int front_len, middle_len, data_len;
    bool do_datacrc = !con->msgr->nocrc;
    u64 seq;
    u32 crc;

    dout("read_partial_message con %p msg %p\n", con, m);

    /* header */
    size = sizeof (con->in_hdr);
    end = size;
    ret = read_partial(con, end, size, &con->in_hdr);
    if (ret <= 0)
        return ret;

    crc = crc32c(0, &con->in_hdr, offsetof(struct ceph_msg_header, crc));
    if (cpu_to_le32(crc) != con->in_hdr.crc) {
        pr_err("read_partial_message bad hdr "
               " crc %u != expected %u\n",
               crc, con->in_hdr.crc);
        return -EBADMSG;
    }

    front_len = le32_to_cpu(con->in_hdr.front_len);
    if (front_len > CEPH_MSG_MAX_FRONT_LEN)
        return -EIO;
    middle_len = le32_to_cpu(con->in_hdr.middle_len);
    if (middle_len > CEPH_MSG_MAX_DATA_LEN)
        return -EIO;
    data_len = le32_to_cpu(con->in_hdr.data_len);
    if (data_len > CEPH_MSG_MAX_DATA_LEN)
        return -EIO;

    /* verify seq# */
    seq = le64_to_cpu(con->in_hdr.seq);
    if ((s64)seq - (s64)con->in_seq < 1) {
        pr_info("skipping %s%lld %s seq %lld expected %lld\n",
            ENTITY_NAME(con->peer_name),
            ceph_pr_addr(&con->peer_addr.in_addr),
            seq, con->in_seq + 1);
        con->in_base_pos = -front_len - middle_len - data_len -
            sizeof(m->footer);
        con->in_tag = CEPH_MSGR_TAG_READY;
        return 0;
    } else if ((s64)seq - (s64)con->in_seq > 1) {
        pr_err("read_partial_message bad seq %lld expected %lld\n",
               seq, con->in_seq + 1);
        con->error_msg = "bad message sequence # for incoming message";
        return -EBADMSG;
    }

    /* allocate message? */
    if (!con->in_msg) {
        int skip = 0;

        dout("got hdr type %d front %d data %d\n", con->in_hdr.type,
             con->in_hdr.front_len, con->in_hdr.data_len);
        ret = ceph_con_in_msg_alloc(con, &skip);
        if (ret < 0)
            return ret;
        if (skip) {
            /* skip this message */
            dout("alloc_msg said skip message\n");
            BUG_ON(con->in_msg);
            con->in_base_pos = -front_len - middle_len - data_len -
                sizeof(m->footer);
            con->in_tag = CEPH_MSGR_TAG_READY;
            con->in_seq++;
            return 0;
        }

        BUG_ON(!con->in_msg);
        BUG_ON(con->in_msg->con != con);
        m = con->in_msg;
        m->front.iov_len = 0;    /* haven't read it yet */
        if (m->middle)
            m->middle->vec.iov_len = 0;

        con->in_msg_pos.page = 0;
        if (m->pages)
            con->in_msg_pos.page_pos = m->page_alignment;
        else
            con->in_msg_pos.page_pos = 0;
        con->in_msg_pos.data_pos = 0;

#ifdef CONFIG_BLOCK
        if (m->bio)
            init_bio_iter(m->bio, &m->bio_iter, &m->bio_seg);
#endif
    }

    /* front */
    ret = read_partial_message_section(con, &m->front, front_len,
                       &con->in_front_crc);
    if (ret <= 0)
        return ret;

    /* middle */
    if (m->middle) {
        ret = read_partial_message_section(con, &m->middle->vec,
                           middle_len,
                           &con->in_middle_crc);
        if (ret <= 0)
            return ret;
    }

    /* (page) data */
    while (con->in_msg_pos.data_pos < data_len) {
        if (m->pages) {
            ret = read_partial_message_pages(con, m->pages,
                         data_len, do_datacrc);
            if (ret <= 0)
                return ret;
#ifdef CONFIG_BLOCK
        } else if (m->bio) {
            BUG_ON(!m->bio_iter);
            ret = read_partial_message_bio(con,
                         &m->bio_iter, &m->bio_seg,
                         data_len, do_datacrc);
            if (ret <= 0)
                return ret;
#endif
        } else {
            BUG_ON(1);
        }
    }

    /* footer */
    size = sizeof (m->footer);
    end += size;
    ret = read_partial(con, end, size, &m->footer);
    if (ret <= 0)
        return ret;

    dout("read_partial_message got msg %p %d (%u) + %d (%u) + %d (%u)\n",
         m, front_len, m->footer.front_crc, middle_len,
         m->footer.middle_crc, data_len, m->footer.data_crc);

    /* crc ok? */
    if (con->in_front_crc != le32_to_cpu(m->footer.front_crc)) {
        pr_err("read_partial_message %p front crc %u != exp. %u\n",
               m, con->in_front_crc, m->footer.front_crc);
        return -EBADMSG;
    }
    if (con->in_middle_crc != le32_to_cpu(m->footer.middle_crc)) {
        pr_err("read_partial_message %p middle crc %u != exp %u\n",
               m, con->in_middle_crc, m->footer.middle_crc);
        return -EBADMSG;
    }
    if (do_datacrc &&
        (m->footer.flags & CEPH_MSG_FOOTER_NOCRC) == 0 &&
        con->in_data_crc != le32_to_cpu(m->footer.data_crc)) {
        pr_err("read_partial_message %p data crc %u != exp. %u\n", m,
               con->in_data_crc, le32_to_cpu(m->footer.data_crc));
        return -EBADMSG;
    }

    return 1; /* done! */
}

/*
 * Process message.  This happens in the worker thread.  The callback should
 * be careful not to do anything that waits on other incoming messages or it
 * may deadlock.
 */
static void process_message(struct ceph_connection *con)
{
    struct ceph_msg *msg;

    BUG_ON(con->in_msg->con != con);
    con->in_msg->con = NULL;
    msg = con->in_msg;
    con->in_msg = NULL;
    con->ops->put(con);

    /* if first message, set peer_name */
    if (con->peer_name.type == 0)
        con->peer_name = msg->hdr.src;

    con->in_seq++;
    mutex_unlock(&con->mutex);

    dout("===== %p %llu from %s%lld %d=%s len %d+%d (%u %u %u) =====\n",
         msg, le64_to_cpu(msg->hdr.seq),
         ENTITY_NAME(msg->hdr.src),
         le16_to_cpu(msg->hdr.type),
         ceph_msg_type_name(le16_to_cpu(msg->hdr.type)),
         le32_to_cpu(msg->hdr.front_len),
         le32_to_cpu(msg->hdr.data_len),
         con->in_front_crc, con->in_middle_crc, con->in_data_crc);
    con->ops->dispatch(con, msg);

    mutex_lock(&con->mutex);
}


/*
 * Write something to the socket.  Called in a worker thread when the
 * socket appears to be writeable and we have something ready to send.
 */
static int try_write(struct ceph_connection *con)
{
    int ret = 1;

    dout("try_write start %p state %lu\n", con, con->state);

more:
    dout("try_write out_kvec_bytes %d\n", con->out_kvec_bytes);

    /* open the socket first? */
    if (con->state == CON_STATE_PREOPEN) {
        BUG_ON(con->sock);
        con->state = CON_STATE_CONNECTING;

        con_out_kvec_reset(con);
        prepare_write_banner(con);
        prepare_read_banner(con);

        BUG_ON(con->in_msg);
        con->in_tag = CEPH_MSGR_TAG_READY;
        dout("try_write initiating connect on %p new state %lu\n",
             con, con->state);
        ret = ceph_tcp_connect(con);
        if (ret < 0) {
            con->error_msg = "connect error";
            goto out;
        }
    }

more_kvec:
    /* kvec data queued? */
    if (con->out_skip) {
        ret = write_partial_skip(con);
        if (ret <= 0)
            goto out;
    }
    if (con->out_kvec_left) {
        ret = write_partial_kvec(con);
        if (ret <= 0)
            goto out;
    }

    /* msg pages? */
    if (con->out_msg) {
        if (con->out_msg_done) {
            ceph_msg_put(con->out_msg);
            con->out_msg = NULL;   /* we're done with this one */
            goto do_next;
        }

        ret = write_partial_msg_pages(con);
        if (ret == 1)
            goto more_kvec;  /* we need to send the footer, too! */
        if (ret == 0)
            goto out;
        if (ret < 0) {
            dout("try_write write_partial_msg_pages err %d\n",
                 ret);
            goto out;
        }
    }

do_next:
    if (con->state == CON_STATE_OPEN) {
        /* is anything else pending? */
        if (!list_empty(&con->out_queue)) {
            prepare_write_message(con);
            goto more;
        }
        if (con->in_seq > con->in_seq_acked) {
            prepare_write_ack(con);
            goto more;
        }
        if (test_and_clear_bit(CON_FLAG_KEEPALIVE_PENDING,
                       &con->flags)) {
            prepare_write_keepalive(con);
            goto more;
        }
    }

    /* Nothing to do! */
    clear_bit(CON_FLAG_WRITE_PENDING, &con->flags);
    dout("try_write nothing else to write.\n");
    ret = 0;
out:
    dout("try_write done on %p ret %d\n", con, ret);
    return ret;
}



/*
 * Read what we can from the socket.
 */
static int try_read(struct ceph_connection *con)
{
    int ret = -1;

more:
    dout("try_read start on %p state %lu\n", con, con->state);
    if (con->state != CON_STATE_CONNECTING &&
        con->state != CON_STATE_NEGOTIATING &&
        con->state != CON_STATE_OPEN)
        return 0;

    BUG_ON(!con->sock);

    dout("try_read tag %d in_base_pos %d\n", (int)con->in_tag,
         con->in_base_pos);

    if (con->state == CON_STATE_CONNECTING) {
        dout("try_read connecting\n");
        ret = read_partial_banner(con);
        if (ret <= 0)
            goto out;
        ret = process_banner(con);
        if (ret < 0)
            goto out;

        BUG_ON(con->state != CON_STATE_CONNECTING);
        con->state = CON_STATE_NEGOTIATING;

        /*
         * Received banner is good, exchange connection info.
         * Do not reset out_kvec, as sending our banner raced
         * with receiving peer banner after connect completed.
         */
        ret = prepare_write_connect(con);
        if (ret < 0)
            goto out;
        prepare_read_connect(con);

        /* Send connection info before awaiting response */
        goto out;
    }

    if (con->state == CON_STATE_NEGOTIATING) {
        dout("try_read negotiating\n");
        ret = read_partial_connect(con);
        if (ret <= 0)
            goto out;
        ret = process_connect(con);
        if (ret < 0)
            goto out;
        goto more;
    }

    BUG_ON(con->state != CON_STATE_OPEN);

    if (con->in_base_pos < 0) {
        /*
         * skipping + discarding content.
         *
         * FIXME: there must be a better way to do this!
         */
        static char buf[SKIP_BUF_SIZE];
        int skip = min((int) sizeof (buf), -con->in_base_pos);

        dout("skipping %d / %d bytes\n", skip, -con->in_base_pos);
        ret = ceph_tcp_recvmsg(con->sock, buf, skip);
        if (ret <= 0)
            goto out;
        con->in_base_pos += ret;
        if (con->in_base_pos)
            goto more;
    }
    if (con->in_tag == CEPH_MSGR_TAG_READY) {
        /*
         * what's next?
         */
        ret = ceph_tcp_recvmsg(con->sock, &con->in_tag, 1);
        if (ret <= 0)
            goto out;
        dout("try_read got tag %d\n", (int)con->in_tag);
        switch (con->in_tag) {
        case CEPH_MSGR_TAG_MSG:
            prepare_read_message(con);
            break;
        case CEPH_MSGR_TAG_ACK:
            prepare_read_ack(con);
            break;
        case CEPH_MSGR_TAG_CLOSE:
            con_close_socket(con);
            con->state = CON_STATE_CLOSED;
            goto out;
        default:
            goto bad_tag;
        }
    }
    if (con->in_tag == CEPH_MSGR_TAG_MSG) {
        ret = read_partial_message(con);
        if (ret <= 0) {
            switch (ret) {
            case -EBADMSG:
                con->error_msg = "bad crc";
                ret = -EIO;
                break;
            case -EIO:
                con->error_msg = "io error";
                break;
            }
            goto out;
        }
        if (con->in_tag == CEPH_MSGR_TAG_READY)
            goto more;
        process_message(con);
        if (con->state == CON_STATE_OPEN)
            prepare_read_tag(con);
        goto more;
    }
    if (con->in_tag == CEPH_MSGR_TAG_ACK) {
        ret = read_partial_ack(con);
        if (ret <= 0)
            goto out;
        process_ack(con);
        goto more;
    }

out:
    dout("try_read done on %p ret %d\n", con, ret);
    return ret;

bad_tag:
    pr_err("try_read bad con->in_tag = %d\n", (int)con->in_tag);
    con->error_msg = "protocol error, garbage tag";
    ret = -1;
    goto out;
}


/*
 * Atomically queue work on a connection.  Bump @con reference to
 * avoid races with connection teardown.
 */
static void queue_con(struct ceph_connection *con)
{
    if (!con->ops->get(con)) {
        dout("queue_con %p ref count 0\n", con);
        return;
    }

    if (!queue_delayed_work(ceph_msgr_wq, &con->work, 0)) {
        dout("queue_con %p - already queued\n", con);
        con->ops->put(con);
    } else {
        dout("queue_con %p\n", con);
    }
}

/*
 * Do some work on a connection.  Drop a connection ref when we're done.
 */
static void con_work(struct work_struct *work)
{
    struct ceph_connection *con = container_of(work, struct ceph_connection,
                           work.work);
    int ret;

    mutex_lock(&con->mutex);
restart:
    if (test_and_clear_bit(CON_FLAG_SOCK_CLOSED, &con->flags)) {
        switch (con->state) {
        case CON_STATE_CONNECTING:
            con->error_msg = "connection failed";
            break;
        case CON_STATE_NEGOTIATING:
            con->error_msg = "negotiation failed";
            break;
        case CON_STATE_OPEN:
            con->error_msg = "socket closed";
            break;
        default:
            dout("unrecognized con state %d\n", (int)con->state);
            con->error_msg = "unrecognized con state";
            BUG();
        }
        goto fault;
    }

    if (test_and_clear_bit(CON_FLAG_BACKOFF, &con->flags)) {
        dout("con_work %p backing off\n", con);
        if (queue_delayed_work(ceph_msgr_wq, &con->work,
                       round_jiffies_relative(con->delay))) {
            dout("con_work %p backoff %lu\n", con, con->delay);
            mutex_unlock(&con->mutex);
            return;
        } else {
            dout("con_work %p FAILED to back off %lu\n", con,
                 con->delay);
            set_bit(CON_FLAG_BACKOFF, &con->flags);
        }
        goto done;
    }

    if (con->state == CON_STATE_STANDBY) {
        dout("con_work %p STANDBY\n", con);
        goto done;
    }
    if (con->state == CON_STATE_CLOSED) {
        dout("con_work %p CLOSED\n", con);
        BUG_ON(con->sock);
        goto done;
    }
    if (con->state == CON_STATE_PREOPEN) {
        dout("con_work OPENING\n");
        BUG_ON(con->sock);
    }

    ret = try_read(con);
    if (ret == -EAGAIN)
        goto restart;
    if (ret < 0) {
        con->error_msg = "socket error on read";
        goto fault;
    }

    ret = try_write(con);
    if (ret == -EAGAIN)
        goto restart;
    if (ret < 0) {
        con->error_msg = "socket error on write";
        goto fault;
    }

done:
    mutex_unlock(&con->mutex);
done_unlocked:
    con->ops->put(con);
    return;

fault:
    ceph_fault(con);     /* error/fault path */
    goto done_unlocked;
}


/*
 * Generic error/fault handler.  A retry mechanism is used with
 * exponential backoff
 */
static void ceph_fault(struct ceph_connection *con)
    __releases(con->mutex)
{
    pr_err("%s%lld %s %s\n", ENTITY_NAME(con->peer_name),
           ceph_pr_addr(&con->peer_addr.in_addr), con->error_msg);
    dout("fault %p state %lu to peer %s\n",
         con, con->state, ceph_pr_addr(&con->peer_addr.in_addr));

    BUG_ON(con->state != CON_STATE_CONNECTING &&
           con->state != CON_STATE_NEGOTIATING &&
           con->state != CON_STATE_OPEN);

    con_close_socket(con);

    if (test_bit(CON_FLAG_LOSSYTX, &con->flags)) {
        dout("fault on LOSSYTX channel, marking CLOSED\n");
        con->state = CON_STATE_CLOSED;
        goto out_unlock;
    }

    if (con->in_msg) {
        BUG_ON(con->in_msg->con != con);
        con->in_msg->con = NULL;
        ceph_msg_put(con->in_msg);
        con->in_msg = NULL;
        con->ops->put(con);
    }

    /* Requeue anything that hasn't been acked */
    list_splice_init(&con->out_sent, &con->out_queue);

    /* If there are no messages queued or keepalive pending, place
     * the connection in a STANDBY state */
    if (list_empty(&con->out_queue) &&
        !test_bit(CON_FLAG_KEEPALIVE_PENDING, &con->flags)) {
        dout("fault %p setting STANDBY clearing WRITE_PENDING\n", con);
        clear_bit(CON_FLAG_WRITE_PENDING, &con->flags);
        con->state = CON_STATE_STANDBY;
    } else {
        /* retry after a delay. */
        con->state = CON_STATE_PREOPEN;
        if (con->delay == 0)
            con->delay = BASE_DELAY_INTERVAL;
        else if (con->delay < MAX_DELAY_INTERVAL)
            con->delay *= 2;
        con->ops->get(con);
        if (queue_delayed_work(ceph_msgr_wq, &con->work,
                       round_jiffies_relative(con->delay))) {
            dout("fault queued %p delay %lu\n", con, con->delay);
        } else {
            con->ops->put(con);
            dout("fault failed to queue %p delay %lu, backoff\n",
                 con, con->delay);
            /*
             * In many cases we see a socket state change
             * while con_work is running and end up
             * queuing (non-delayed) work, such that we
             * can't backoff with a delay.  Set a flag so
             * that when con_work restarts we schedule the
             * delay then.
             */
            set_bit(CON_FLAG_BACKOFF, &con->flags);
        }
    }

out_unlock:
    mutex_unlock(&con->mutex);
    /*
     * in case we faulted due to authentication, invalidate our
     * current tickets so that we can get new ones.
     */
    if (con->auth_retry && con->ops->invalidate_authorizer) {
        dout("calling invalidate_authorizer()\n");
        con->ops->invalidate_authorizer(con);
    }

    if (con->ops->fault)
        con->ops->fault(con);
}



/*
 * initialize a new messenger instance
 */
void ceph_messenger_init(struct ceph_messenger *msgr,
            struct ceph_entity_addr *myaddr,
            u32 supported_features,
            u32 required_features,
            bool nocrc)
{
    msgr->supported_features = supported_features;
    msgr->required_features = required_features;

    spin_lock_init(&msgr->global_seq_lock);

    if (myaddr)
        msgr->inst.addr = *myaddr;

    /* select a random nonce */
    msgr->inst.addr.type = 0;
    get_random_bytes(&msgr->inst.addr.nonce, sizeof(msgr->inst.addr.nonce));
    encode_my_addr(msgr);
    msgr->nocrc = nocrc;

    atomic_set(&msgr->stopping, 0);

    dout("%s %p\n", __func__, msgr);
}
EXPORT_SYMBOL(ceph_messenger_init);

static void clear_standby(struct ceph_connection *con)
{
    /* come back from STANDBY? */
    if (con->state == CON_STATE_STANDBY) {
        dout("clear_standby %p and ++connect_seq\n", con);
        con->state = CON_STATE_PREOPEN;
        con->connect_seq++;
        WARN_ON(test_bit(CON_FLAG_WRITE_PENDING, &con->flags));
        WARN_ON(test_bit(CON_FLAG_KEEPALIVE_PENDING, &con->flags));
    }
}

/*
 * Queue up an outgoing message on the given connection.
 */
void ceph_con_send(struct ceph_connection *con, struct ceph_msg *msg)
{
    /* set src+dst */
    msg->hdr.src = con->msgr->inst.name;
    BUG_ON(msg->front.iov_len != le32_to_cpu(msg->hdr.front_len));
    msg->needs_out_seq = true;

    mutex_lock(&con->mutex);

    if (con->state == CON_STATE_CLOSED) {
        dout("con_send %p closed, dropping %p\n", con, msg);
        ceph_msg_put(msg);
        mutex_unlock(&con->mutex);
        return;
    }

    BUG_ON(msg->con != NULL);
    msg->con = con->ops->get(con);
    BUG_ON(msg->con == NULL);

    BUG_ON(!list_empty(&msg->list_head));
    list_add_tail(&msg->list_head, &con->out_queue);
    dout("----- %p to %s%lld %d=%s len %d+%d+%d -----\n", msg,
         ENTITY_NAME(con->peer_name), le16_to_cpu(msg->hdr.type),
         ceph_msg_type_name(le16_to_cpu(msg->hdr.type)),
         le32_to_cpu(msg->hdr.front_len),
         le32_to_cpu(msg->hdr.middle_len),
         le32_to_cpu(msg->hdr.data_len));

    clear_standby(con);
    mutex_unlock(&con->mutex);

    /* if there wasn't anything waiting to send before, queue
     * new work */
    if (test_and_set_bit(CON_FLAG_WRITE_PENDING, &con->flags) == 0)
        queue_con(con);
}
EXPORT_SYMBOL(ceph_con_send);

/*
 * Revoke a message that was previously queued for send
 */
void ceph_msg_revoke(struct ceph_msg *msg)
{
    struct ceph_connection *con = msg->con;

    if (!con)
        return;     /* Message not in our possession */

    mutex_lock(&con->mutex);
    if (!list_empty(&msg->list_head)) {
        dout("%s %p msg %p - was on queue\n", __func__, con, msg);
        list_del_init(&msg->list_head);
        BUG_ON(msg->con == NULL);
        msg->con->ops->put(msg->con);
        msg->con = NULL;
        msg->hdr.seq = 0;

        ceph_msg_put(msg);
    }
    if (con->out_msg == msg) {
        dout("%s %p msg %p - was sending\n", __func__, con, msg);
        con->out_msg = NULL;
        if (con->out_kvec_is_msg) {
            con->out_skip = con->out_kvec_bytes;
            con->out_kvec_is_msg = false;
        }
        msg->hdr.seq = 0;

        ceph_msg_put(msg);
    }
    mutex_unlock(&con->mutex);
}

/*
 * Revoke a message that we may be reading data into
 */
void ceph_msg_revoke_incoming(struct ceph_msg *msg)
{
    struct ceph_connection *con;

    BUG_ON(msg == NULL);
    if (!msg->con) {
        dout("%s msg %p null con\n", __func__, msg);

        return;     /* Message not in our possession */
    }

    con = msg->con;
    mutex_lock(&con->mutex);
    if (con->in_msg == msg) {
        unsigned int front_len = le32_to_cpu(con->in_hdr.front_len);
        unsigned int middle_len = le32_to_cpu(con->in_hdr.middle_len);
        unsigned int data_len = le32_to_cpu(con->in_hdr.data_len);

        /* skip rest of message */
        dout("%s %p msg %p revoked\n", __func__, con, msg);
        con->in_base_pos = con->in_base_pos -
                sizeof(struct ceph_msg_header) -
                front_len -
                middle_len -
                data_len -
                sizeof(struct ceph_msg_footer);
        ceph_msg_put(con->in_msg);
        con->in_msg = NULL;
        con->in_tag = CEPH_MSGR_TAG_READY;
        con->in_seq++;
    } else {
        dout("%s %p in_msg %p msg %p no-op\n",
             __func__, con, con->in_msg, msg);
    }
    mutex_unlock(&con->mutex);
}

/*
 * Queue a keepalive byte to ensure the tcp connection is alive.
 */
void ceph_con_keepalive(struct ceph_connection *con)
{
    dout("con_keepalive %p\n", con);
    mutex_lock(&con->mutex);
    clear_standby(con);
    mutex_unlock(&con->mutex);
    if (test_and_set_bit(CON_FLAG_KEEPALIVE_PENDING, &con->flags) == 0 &&
        test_and_set_bit(CON_FLAG_WRITE_PENDING, &con->flags) == 0)
        queue_con(con);
}
EXPORT_SYMBOL(ceph_con_keepalive);


/*
 * construct a new message with given type, size
 * the new msg has a ref count of 1.
 */
struct ceph_msg *ceph_msg_new(int type, int front_len, gfp_t flags,
                  bool can_fail)
{
    struct ceph_msg *m;

    m = kmalloc(sizeof(*m), flags);
    if (m == NULL)
        goto out;
    kref_init(&m->kref);

    m->con = NULL;
    INIT_LIST_HEAD(&m->list_head);

    m->hdr.tid = 0;
    m->hdr.type = cpu_to_le16(type);
    m->hdr.priority = cpu_to_le16(CEPH_MSG_PRIO_DEFAULT);
    m->hdr.version = 0;
    m->hdr.front_len = cpu_to_le32(front_len);
    m->hdr.middle_len = 0;
    m->hdr.data_len = 0;
    m->hdr.data_off = 0;
    m->hdr.reserved = 0;
    m->footer.front_crc = 0;
    m->footer.middle_crc = 0;
    m->footer.data_crc = 0;
    m->footer.flags = 0;
    m->front_max = front_len;
    m->front_is_vmalloc = false;
    m->more_to_follow = false;
    m->ack_stamp = 0;
    m->pool = NULL;

    /* middle */
    m->middle = NULL;

    /* data */
    m->nr_pages = 0;
    m->page_alignment = 0;
    m->pages = NULL;
    m->pagelist = NULL;
    m->bio = NULL;
    m->bio_iter = NULL;
    m->bio_seg = 0;
    m->trail = NULL;

    /* front */
    if (front_len) {
        if (front_len > PAGE_CACHE_SIZE) {
            m->front.iov_base = __vmalloc(front_len, flags,
                              PAGE_KERNEL);
            m->front_is_vmalloc = true;
        } else {
            m->front.iov_base = kmalloc(front_len, flags);
        }
        if (m->front.iov_base == NULL) {
            dout("ceph_msg_new can't allocate %d bytes\n",
                 front_len);
            goto out2;
        }
    } else {
        m->front.iov_base = NULL;
    }
    m->front.iov_len = front_len;

    dout("ceph_msg_new %p front %d\n", m, front_len);
    return m;

out2:
    ceph_msg_put(m);
out:
    if (!can_fail) {
        pr_err("msg_new can't create type %d front %d\n", type,
               front_len);
        WARN_ON(1);
    } else {
        dout("msg_new can't create type %d front %d\n", type,
             front_len);
    }
    return NULL;
}
EXPORT_SYMBOL(ceph_msg_new);

/*
 * Allocate "middle" portion of a message, if it is needed and wasn't
 * allocated by alloc_msg.  This allows us to read a small fixed-size
 * per-type header in the front and then gracefully fail (i.e.,
 * propagate the error to the caller based on info in the front) when
 * the middle is too large.
 */
static int ceph_alloc_middle(struct ceph_connection *con, struct ceph_msg *msg)
{
    int type = le16_to_cpu(msg->hdr.type);
    int middle_len = le32_to_cpu(msg->hdr.middle_len);

    dout("alloc_middle %p type %d %s middle_len %d\n", msg, type,
         ceph_msg_type_name(type), middle_len);
    BUG_ON(!middle_len);
    BUG_ON(msg->middle);

    msg->middle = ceph_buffer_new(middle_len, GFP_NOFS);
    if (!msg->middle)
        return -ENOMEM;
    return 0;
}

/*
 * Allocate a message for receiving an incoming message on a
 * connection, and save the result in con->in_msg.  Uses the
 * connection's private alloc_msg op if available.
 *
 * Returns 0 on success, or a negative error code.
 *
 * On success, if we set *skip = 1:
 *  - the next message should be skipped and ignored.
 *  - con->in_msg == NULL
 * or if we set *skip = 0:
 *  - con->in_msg is non-null.
 * On error (ENOMEM, EAGAIN, ...),
 *  - con->in_msg == NULL
 */
static int ceph_con_in_msg_alloc(struct ceph_connection *con, int *skip)
{
    struct ceph_msg_header *hdr = &con->in_hdr;
    int type = le16_to_cpu(hdr->type);
    int front_len = le32_to_cpu(hdr->front_len);
    int middle_len = le32_to_cpu(hdr->middle_len);
    int ret = 0;

    BUG_ON(con->in_msg != NULL);

    if (con->ops->alloc_msg) {
        struct ceph_msg *msg;

        mutex_unlock(&con->mutex);
        msg = con->ops->alloc_msg(con, hdr, skip);
        mutex_lock(&con->mutex);
        if (con->state != CON_STATE_OPEN) {
            if (msg)
                ceph_msg_put(msg);
            return -EAGAIN;
        }
        con->in_msg = msg;
        if (con->in_msg) {
            con->in_msg->con = con->ops->get(con);
            BUG_ON(con->in_msg->con == NULL);
        }
        if (*skip) {
            con->in_msg = NULL;
            return 0;
        }
        if (!con->in_msg) {
            con->error_msg =
                "error allocating memory for incoming message";
            return -ENOMEM;
        }
    }
    if (!con->in_msg) {
        con->in_msg = ceph_msg_new(type, front_len, GFP_NOFS, false);
        if (!con->in_msg) {
            pr_err("unable to allocate msg type %d len %d\n",
                   type, front_len);
            return -ENOMEM;
        }
        con->in_msg->con = con->ops->get(con);
        BUG_ON(con->in_msg->con == NULL);
        con->in_msg->page_alignment = le16_to_cpu(hdr->data_off);
    }
    memcpy(&con->in_msg->hdr, &con->in_hdr, sizeof(con->in_hdr));

    if (middle_len && !con->in_msg->middle) {
        ret = ceph_alloc_middle(con, con->in_msg);
        if (ret < 0) {
            ceph_msg_put(con->in_msg);
            con->in_msg = NULL;
        }
    }

    return ret;
}


/*
 * Free a generically kmalloc'd message.
 */
void ceph_msg_kfree(struct ceph_msg *m)
{
    dout("msg_kfree %p\n", m);
    if (m->front_is_vmalloc)
        vfree(m->front.iov_base);
    else
        kfree(m->front.iov_base);
    kfree(m);
}

/*
 * Drop a msg ref.  Destroy as needed.
 */
void ceph_msg_last_put(struct kref *kref)
{
    struct ceph_msg *m = container_of(kref, struct ceph_msg, kref);

    dout("ceph_msg_put last one on %p\n", m);
    WARN_ON(!list_empty(&m->list_head));

    /* drop middle, data, if any */
    if (m->middle) {
        ceph_buffer_put(m->middle);
        m->middle = NULL;
    }
    m->nr_pages = 0;
    m->pages = NULL;

    if (m->pagelist) {
        ceph_pagelist_release(m->pagelist);
        kfree(m->pagelist);
        m->pagelist = NULL;
    }

    m->trail = NULL;

    if (m->pool)
        ceph_msgpool_put(m->pool, m);
    else
        ceph_msg_kfree(m);
}
EXPORT_SYMBOL(ceph_msg_last_put);

void ceph_msg_dump(struct ceph_msg *msg)
{
    pr_debug("msg_dump %p (front_max %d nr_pages %d)\n", msg,
         msg->front_max, msg->nr_pages);
    print_hex_dump(KERN_DEBUG, "header: ",
               DUMP_PREFIX_OFFSET, 16, 1,
               &msg->hdr, sizeof(msg->hdr), true);
    print_hex_dump(KERN_DEBUG, " front: ",
               DUMP_PREFIX_OFFSET, 16, 1,
               msg->front.iov_base, msg->front.iov_len, true);
    if (msg->middle)
        print_hex_dump(KERN_DEBUG, "middle: ",
                   DUMP_PREFIX_OFFSET, 16, 1,
                   msg->middle->vec.iov_base,
                   msg->middle->vec.iov_len, true);
    print_hex_dump(KERN_DEBUG, "footer: ",
               DUMP_PREFIX_OFFSET, 16, 1,
               &msg->footer, sizeof(msg->footer), true);
}
EXPORT_SYMBOL(ceph_msg_dump);