// SPDX-License-Identifier: GPL-2.0
#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/nsproxy.h>
#include <linux/sched/mm.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/string.h>
#ifdef  CONFIG_BLOCK
#include <linux/bio.h>
#endif  /* CONFIG_BLOCK */
#include <linux/dns_resolver.h>
#include <net/tcp.h>
#include <trace/events/sock.h>

#include <linux/ceph/ceph_features.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 */

static bool con_flag_valid(unsigned long con_flag)
{
        switch (con_flag) {
        case CEPH_CON_F_LOSSYTX:
        case CEPH_CON_F_KEEPALIVE_PENDING:
        case CEPH_CON_F_WRITE_PENDING:
        case CEPH_CON_F_SOCK_CLOSED:
        case CEPH_CON_F_BACKOFF:
                return true;
        default:
                return false;
        }
}

void ceph_con_flag_clear(struct ceph_connection *con, unsigned long con_flag)
{
        BUG_ON(!con_flag_valid(con_flag));

        clear_bit(con_flag, &con->flags);
}

void ceph_con_flag_set(struct ceph_connection *con, unsigned long con_flag)
{
        BUG_ON(!con_flag_valid(con_flag));

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

bool ceph_con_flag_test(struct ceph_connection *con, unsigned long con_flag)
{
        BUG_ON(!con_flag_valid(con_flag));

        return test_bit(con_flag, &con->flags);
}

bool ceph_con_flag_test_and_clear(struct ceph_connection *con,
                                  unsigned long con_flag)
{
        BUG_ON(!con_flag_valid(con_flag));

        return test_and_clear_bit(con_flag, &con->flags);
}

bool ceph_con_flag_test_and_set(struct ceph_connection *con,
                                unsigned long con_flag)
{
        BUG_ON(!con_flag_valid(con_flag));

        return test_and_set_bit(con_flag, &con->flags);
}

/* Slab caches for frequently-allocated structures */

static struct kmem_cache        *ceph_msg_cache;

#ifdef CONFIG_LOCKDEP
static struct lock_class_key socket_class;
#endif

static void queue_con(struct ceph_connection *con);
static void cancel_con(struct ceph_connection *con);
static void ceph_con_workfn(struct work_struct *);
static void con_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);

struct page *ceph_zero_page;            /* used in certain error cases */

const char *ceph_pr_addr(const struct ceph_entity_addr *addr)
{
        int i;
        char *s;
        struct sockaddr_storage ss = addr->in_addr; /* align */
        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, "(%d)%pI4:%hu",
                         le32_to_cpu(addr->type), &in4->sin_addr,
                         ntohs(in4->sin_port));
                break;

        case AF_INET6:
                snprintf(s, MAX_ADDR_STR_LEN, "(%d)[%pI6c]:%hu",
                         le32_to_cpu(addr->type), &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);

void ceph_encode_my_addr(struct ceph_messenger *msgr)
{
        if (!ceph_msgr2(from_msgr(msgr))) {
                memcpy(&msgr->my_enc_addr, &msgr->inst.addr,
                       sizeof(msgr->my_enc_addr));
                ceph_encode_banner_addr(&msgr->my_enc_addr);
        }
}

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

static int ceph_msgr_slab_init(void)
{
        BUG_ON(ceph_msg_cache);
        ceph_msg_cache = KMEM_CACHE(ceph_msg, 0);
        if (!ceph_msg_cache)
                return -ENOMEM;

        return 0;
}

static void ceph_msgr_slab_exit(void)
{
        BUG_ON(!ceph_msg_cache);
        kmem_cache_destroy(ceph_msg_cache);
        ceph_msg_cache = NULL;
}

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

        BUG_ON(!ceph_zero_page);
        put_page(ceph_zero_page);
        ceph_zero_page = NULL;

        ceph_msgr_slab_exit();
}

int __init ceph_msgr_init(void)
{
        if (ceph_msgr_slab_init())
                return -ENOMEM;

        BUG_ON(ceph_zero_page);
        ceph_zero_page = ZERO_PAGE(0);
        get_page(ceph_zero_page);

        /*
         * The number of active work items is limited by the number of
         * connections, so leave @max_active at default.
         */
        ceph_msgr_wq = alloc_workqueue("ceph-msgr",
                                       WQ_MEM_RECLAIM | WQ_PERCPU, 0);
        if (ceph_msgr_wq)
                return 0;

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

        return -ENOMEM;
}

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

        _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)
{
        struct ceph_connection *con = sk->sk_user_data;

        trace_sk_data_ready(sk);

        if (atomic_read(&con->msgr->stopping)) {
                return;
        }

        if (sk->sk_state != TCP_CLOSE_WAIT) {
                dout("%s %p state = %d, 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 (ceph_con_flag_test(con, CEPH_CON_F_WRITE_PENDING)) {
                if (sk_stream_is_writeable(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 = %d sk_state = %u\n", __func__,
             con, con->state, sk->sk_state);

        switch (sk->sk_state) {
        case TCP_CLOSE:
                dout("%s TCP_CLOSE\n", __func__);
                fallthrough;
        case TCP_CLOSE_WAIT:
                dout("%s TCP_CLOSE_WAIT\n", __func__);
                con_sock_state_closing(con);
                ceph_con_flag_set(con, CEPH_CON_F_SOCK_CLOSED);
                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.
 */
int ceph_tcp_connect(struct ceph_connection *con)
{
        struct sockaddr_storage ss = con->peer_addr.in_addr; /* align */
        struct socket *sock;
        unsigned int noio_flag;
        int ret;

        dout("%s con %p peer_addr %s\n", __func__, con,
             ceph_pr_addr(&con->peer_addr));
        BUG_ON(con->sock);

        /* sock_create_kern() allocates with GFP_KERNEL */
        noio_flag = memalloc_noio_save();
        ret = sock_create_kern(read_pnet(&con->msgr->net), ss.ss_family,
                               SOCK_STREAM, IPPROTO_TCP, &sock);
        memalloc_noio_restore(noio_flag);
        if (ret)
                return ret;
        sock->sk->sk_allocation = GFP_NOFS;
        sock->sk->sk_use_task_frag = false;

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

        set_sock_callbacks(sock, con);

        con_sock_state_connecting(con);
        ret = kernel_connect(sock, (struct sockaddr_unsized *)&ss, sizeof(ss),
                             O_NONBLOCK);
        if (ret == -EINPROGRESS) {
                dout("connect %s EINPROGRESS sk_state = %u\n",
                     ceph_pr_addr(&con->peer_addr),
                     sock->sk->sk_state);
        } else if (ret < 0) {
                pr_err("connect %s error %d\n",
                       ceph_pr_addr(&con->peer_addr), ret);
                sock_release(sock);
                return ret;
        }

        if (ceph_test_opt(from_msgr(con->msgr), TCP_NODELAY))
                tcp_sock_set_nodelay(sock->sk);

        con->sock = sock;
        return 0;
}

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

        dout("%s con %p sock %p\n", __func__, 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.
         */
        ceph_con_flag_clear(con, CEPH_CON_F_SOCK_CLOSED);

        con_sock_state_closed(con);
        return rc;
}

static void ceph_con_reset_protocol(struct ceph_connection *con)
{
        dout("%s con %p\n", __func__, con);

        ceph_con_close_socket(con);
        if (con->in_msg) {
                WARN_ON(con->in_msg->con != con);
                ceph_msg_put(con->in_msg);
                con->in_msg = NULL;
        }
        if (con->out_msg) {
                WARN_ON(con->out_msg->con != con);
                ceph_msg_put(con->out_msg);
                con->out_msg = NULL;
        }
        if (con->bounce_page) {
                __free_page(con->bounce_page);
                con->bounce_page = NULL;
        }

        if (ceph_msgr2(from_msgr(con->msgr)))
                ceph_con_v2_reset_protocol(con);
        else
                ceph_con_v1_reset_protocol(con);
}

/*
 * 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);

        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);
        }
}

void ceph_con_reset_session(struct ceph_connection *con)
{
        dout("%s con %p\n", __func__, con);

        WARN_ON(con->in_msg);
        WARN_ON(con->out_msg);
        ceph_msg_remove_list(&con->out_queue);
        ceph_msg_remove_list(&con->out_sent);
        con->out_seq = 0;
        con->in_seq = 0;
        con->in_seq_acked = 0;

        if (ceph_msgr2(from_msgr(con->msgr)))
                ceph_con_v2_reset_session(con);
        else
                ceph_con_v1_reset_session(con);
}

/*
 * 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));
        con->state = CEPH_CON_S_CLOSED;

        ceph_con_flag_clear(con, CEPH_CON_F_LOSSYTX);  /* so we retry next
                                                          connect */
        ceph_con_flag_clear(con, CEPH_CON_F_KEEPALIVE_PENDING);
        ceph_con_flag_clear(con, CEPH_CON_F_WRITE_PENDING);
        ceph_con_flag_clear(con, CEPH_CON_F_BACKOFF);

        ceph_con_reset_protocol(con);
        ceph_con_reset_session(con);
        cancel_con(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));

        WARN_ON(con->state != CEPH_CON_S_CLOSED);
        con->state = CEPH_CON_S_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)
{
        if (ceph_msgr2(from_msgr(con->msgr)))
                return ceph_con_v2_opened(con);

        return ceph_con_v1_opened(con);
}

/*
 * 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, ceph_con_workfn);

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

/*
 * We maintain a global counter to order connection attempts.  Get
 * a unique seq greater than @gt.
 */
u32 ceph_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;
}

/*
 * Discard messages that have been acked by the server.
 */
void ceph_con_discard_sent(struct ceph_connection *con, u64 ack_seq)
{
        struct ceph_msg *msg;
        u64 seq;

        dout("%s con %p ack_seq %llu\n", __func__, con, ack_seq);
        while (!list_empty(&con->out_sent)) {
                msg = list_first_entry(&con->out_sent, struct ceph_msg,
                                       list_head);
                WARN_ON(msg->needs_out_seq);
                seq = le64_to_cpu(msg->hdr.seq);
                if (seq > ack_seq)
                        break;

                dout("%s con %p discarding msg %p seq %llu\n", __func__, con,
                     msg, seq);
                ceph_msg_remove(msg);
        }
}

/*
 * Discard messages that have been requeued in con_fault(), up to
 * reconnect_seq.  This avoids gratuitously resending messages that
 * the server had received and handled prior to reconnect.
 */
void ceph_con_discard_requeued(struct ceph_connection *con, u64 reconnect_seq)
{
        struct ceph_msg *msg;
        u64 seq;

        dout("%s con %p reconnect_seq %llu\n", __func__, con, reconnect_seq);
        while (!list_empty(&con->out_queue)) {
                msg = list_first_entry(&con->out_queue, struct ceph_msg,
                                       list_head);
                if (msg->needs_out_seq)
                        break;
                seq = le64_to_cpu(msg->hdr.seq);
                if (seq > reconnect_seq)
                        break;

                dout("%s con %p discarding msg %p seq %llu\n", __func__, con,
                     msg, seq);
                ceph_msg_remove(msg);
        }
}

#ifdef CONFIG_BLOCK

/*
 * For a bio data item, a piece is whatever remains of the next
 * entry in the current bio iovec, or the first entry in the next
 * bio in the list.
 */
static void ceph_msg_data_bio_cursor_init(struct ceph_msg_data_cursor *cursor,
                                        size_t length)
{
        struct ceph_msg_data *data = cursor->data;
        struct ceph_bio_iter *it = &cursor->bio_iter;

        cursor->resid = min_t(size_t, length, data->bio_length);
        *it = data->bio_pos;
        if (cursor->resid < it->iter.bi_size)
                it->iter.bi_size = cursor->resid;

        BUG_ON(cursor->resid < bio_iter_len(it->bio, it->iter));
}

static struct page *ceph_msg_data_bio_next(struct ceph_msg_data_cursor *cursor,
                                                size_t *page_offset,
                                                size_t *length)
{
        struct bio_vec bv = bio_iter_iovec(cursor->bio_iter.bio,
                                           cursor->bio_iter.iter);

        *page_offset = bv.bv_offset;
        *length = bv.bv_len;
        return bv.bv_page;
}

static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
                                        size_t bytes)
{
        struct ceph_bio_iter *it = &cursor->bio_iter;
        struct page *page = bio_iter_page(it->bio, it->iter);

        BUG_ON(bytes > cursor->resid);
        BUG_ON(bytes > bio_iter_len(it->bio, it->iter));
        cursor->resid -= bytes;
        bio_advance_iter(it->bio, &it->iter, bytes);

        if (!cursor->resid)
                return false;   /* no more data */

        if (!bytes || (it->iter.bi_size && it->iter.bi_bvec_done &&
                       page == bio_iter_page(it->bio, it->iter)))
                return false;   /* more bytes to process in this segment */

        if (!it->iter.bi_size) {
                it->bio = it->bio->bi_next;
                it->iter = it->bio->bi_iter;
                if (cursor->resid < it->iter.bi_size)
                        it->iter.bi_size = cursor->resid;
        }

        BUG_ON(cursor->resid < bio_iter_len(it->bio, it->iter));
        return true;
}
#endif /* CONFIG_BLOCK */

static void ceph_msg_data_bvecs_cursor_init(struct ceph_msg_data_cursor *cursor,
                                        size_t length)
{
        struct ceph_msg_data *data = cursor->data;
        struct bio_vec *bvecs = data->bvec_pos.bvecs;

        cursor->resid = min_t(size_t, length, data->bvec_pos.iter.bi_size);
        cursor->bvec_iter = data->bvec_pos.iter;
        cursor->bvec_iter.bi_size = cursor->resid;

        BUG_ON(cursor->resid < bvec_iter_len(bvecs, cursor->bvec_iter));
}

static struct page *ceph_msg_data_bvecs_next(struct ceph_msg_data_cursor *cursor,
                                                size_t *page_offset,
                                                size_t *length)
{
        struct bio_vec bv = bvec_iter_bvec(cursor->data->bvec_pos.bvecs,
                                           cursor->bvec_iter);

        *page_offset = bv.bv_offset;
        *length = bv.bv_len;
        return bv.bv_page;
}

static bool ceph_msg_data_bvecs_advance(struct ceph_msg_data_cursor *cursor,
                                        size_t bytes)
{
        struct bio_vec *bvecs = cursor->data->bvec_pos.bvecs;
        struct page *page = bvec_iter_page(bvecs, cursor->bvec_iter);

        BUG_ON(bytes > cursor->resid);
        BUG_ON(bytes > bvec_iter_len(bvecs, cursor->bvec_iter));
        cursor->resid -= bytes;
        bvec_iter_advance(bvecs, &cursor->bvec_iter, bytes);

        if (!cursor->resid)
                return false;   /* no more data */

        if (!bytes || (cursor->bvec_iter.bi_bvec_done &&
                       page == bvec_iter_page(bvecs, cursor->bvec_iter)))
                return false;   /* more bytes to process in this segment */

        BUG_ON(cursor->resid < bvec_iter_len(bvecs, cursor->bvec_iter));
        return true;
}

/*
 * For a page array, a piece comes from the first page in the array
 * that has not already been fully consumed.
 */
static void ceph_msg_data_pages_cursor_init(struct ceph_msg_data_cursor *cursor,
                                        size_t length)
{
        struct ceph_msg_data *data = cursor->data;
        int page_count;

        BUG_ON(data->type != CEPH_MSG_DATA_PAGES);

        BUG_ON(!data->pages);
        BUG_ON(!data->length);

        cursor->resid = min(length, data->length);
        page_count = calc_pages_for(data->alignment, (u64)data->length);
        cursor->page_offset = data->alignment & ~PAGE_MASK;
        cursor->page_index = 0;
        BUG_ON(page_count > (int)USHRT_MAX);
        cursor->page_count = (unsigned short)page_count;
        BUG_ON(length > SIZE_MAX - cursor->page_offset);
}

static struct page *
ceph_msg_data_pages_next(struct ceph_msg_data_cursor *cursor,
                                        size_t *page_offset, size_t *length)
{
        struct ceph_msg_data *data = cursor->data;

        BUG_ON(data->type != CEPH_MSG_DATA_PAGES);

        BUG_ON(cursor->page_index >= cursor->page_count);
        BUG_ON(cursor->page_offset >= PAGE_SIZE);

        *page_offset = cursor->page_offset;
        *length = min_t(size_t, cursor->resid, PAGE_SIZE - *page_offset);
        return data->pages[cursor->page_index];
}

static bool ceph_msg_data_pages_advance(struct ceph_msg_data_cursor *cursor,
                                                size_t bytes)
{
        BUG_ON(cursor->data->type != CEPH_MSG_DATA_PAGES);

        BUG_ON(cursor->page_offset + bytes > PAGE_SIZE);

        /* Advance the cursor page offset */

        cursor->resid -= bytes;
        cursor->page_offset = (cursor->page_offset + bytes) & ~PAGE_MASK;
        if (!bytes || cursor->page_offset)
                return false;   /* more bytes to process in the current page */

        if (!cursor->resid)
                return false;   /* no more data */

        /* Move on to the next page; offset is already at 0 */

        BUG_ON(cursor->page_index >= cursor->page_count);
        cursor->page_index++;
        return true;
}

/*
 * For a pagelist, a piece is whatever remains to be consumed in the
 * first page in the list, or the front of the next page.
 */
static void
ceph_msg_data_pagelist_cursor_init(struct ceph_msg_data_cursor *cursor,
                                        size_t length)
{
        struct ceph_msg_data *data = cursor->data;
        struct ceph_pagelist *pagelist;
        struct page *page;

        BUG_ON(data->type != CEPH_MSG_DATA_PAGELIST);

        pagelist = data->pagelist;
        BUG_ON(!pagelist);

        if (!length)
                return;         /* pagelist can be assigned but empty */

        BUG_ON(list_empty(&pagelist->head));
        page = list_first_entry(&pagelist->head, struct page, lru);

        cursor->resid = min(length, pagelist->length);
        cursor->page = page;
        cursor->offset = 0;
}

static struct page *
ceph_msg_data_pagelist_next(struct ceph_msg_data_cursor *cursor,
                                size_t *page_offset, size_t *length)
{
        struct ceph_msg_data *data = cursor->data;
        struct ceph_pagelist *pagelist;

        BUG_ON(data->type != CEPH_MSG_DATA_PAGELIST);

        pagelist = data->pagelist;
        BUG_ON(!pagelist);

        BUG_ON(!cursor->page);
        BUG_ON(cursor->offset + cursor->resid != pagelist->length);

        /* offset of first page in pagelist is always 0 */
        *page_offset = cursor->offset & ~PAGE_MASK;
        *length = min_t(size_t, cursor->resid, PAGE_SIZE - *page_offset);
        return cursor->page;
}

static bool ceph_msg_data_pagelist_advance(struct ceph_msg_data_cursor *cursor,
                                                size_t bytes)
{
        struct ceph_msg_data *data = cursor->data;
        struct ceph_pagelist *pagelist;

        BUG_ON(data->type != CEPH_MSG_DATA_PAGELIST);

        pagelist = data->pagelist;
        BUG_ON(!pagelist);

        BUG_ON(cursor->offset + cursor->resid != pagelist->length);
        BUG_ON((cursor->offset & ~PAGE_MASK) + bytes > PAGE_SIZE);

        /* Advance the cursor offset */

        cursor->resid -= bytes;
        cursor->offset += bytes;
        /* offset of first page in pagelist is always 0 */
        if (!bytes || cursor->offset & ~PAGE_MASK)
                return false;   /* more bytes to process in the current page */

        if (!cursor->resid)
                return false;   /* no more data */

        /* Move on to the next page */

        BUG_ON(list_is_last(&cursor->page->lru, &pagelist->head));
        cursor->page = list_next_entry(cursor->page, lru);
        return true;
}

static void ceph_msg_data_iter_cursor_init(struct ceph_msg_data_cursor *cursor,
                                           size_t length)
{
        struct ceph_msg_data *data = cursor->data;

        cursor->iov_iter = data->iter;
        cursor->lastlen = 0;
        iov_iter_truncate(&cursor->iov_iter, length);
        cursor->resid = iov_iter_count(&cursor->iov_iter);
}

static struct page *ceph_msg_data_iter_next(struct ceph_msg_data_cursor *cursor,
                                            size_t *page_offset, size_t *length)
{
        struct page *page;
        ssize_t len;

        if (cursor->lastlen)
                iov_iter_revert(&cursor->iov_iter, cursor->lastlen);

        len = iov_iter_get_pages2(&cursor->iov_iter, &page, PAGE_SIZE,
                                  1, page_offset);
        BUG_ON(len < 0);

        cursor->lastlen = len;

        /*
         * FIXME: The assumption is that the pages represented by the iov_iter
         *        are pinned, with the references held by the upper-level
         *        callers, or by virtue of being under writeback. Eventually,
         *        we'll get an iov_iter_get_pages2 variant that doesn't take
         *        page refs. Until then, just put the page ref.
         */
        VM_BUG_ON_PAGE(!PageWriteback(page) && page_count(page) < 2, page);
        put_page(page);

        *length = min_t(size_t, len, cursor->resid);
        return page;
}

static bool ceph_msg_data_iter_advance(struct ceph_msg_data_cursor *cursor,
                                       size_t bytes)
{
        BUG_ON(bytes > cursor->resid);
        cursor->resid -= bytes;

        if (bytes < cursor->lastlen) {
                cursor->lastlen -= bytes;
        } else {
                iov_iter_advance(&cursor->iov_iter, bytes - cursor->lastlen);
                cursor->lastlen = 0;
        }

        return cursor->resid;
}

/*
 * Message data is handled (sent or received) in pieces, where each
 * piece resides on a single page.  The network layer might not
 * consume an entire piece at once.  A data item's cursor keeps
 * track of which piece is next to process and how much remains to
 * be processed in that piece.  It also tracks whether the current
 * piece is the last one in the data item.
 */
static void __ceph_msg_data_cursor_init(struct ceph_msg_data_cursor *cursor)
{
        size_t length = cursor->total_resid;

        switch (cursor->data->type) {
        case CEPH_MSG_DATA_PAGELIST:
                ceph_msg_data_pagelist_cursor_init(cursor, length);
                break;
        case CEPH_MSG_DATA_PAGES:
                ceph_msg_data_pages_cursor_init(cursor, length);
                break;
#ifdef CONFIG_BLOCK
        case CEPH_MSG_DATA_BIO:
                ceph_msg_data_bio_cursor_init(cursor, length);
                break;
#endif /* CONFIG_BLOCK */
        case CEPH_MSG_DATA_BVECS:
                ceph_msg_data_bvecs_cursor_init(cursor, length);
                break;
        case CEPH_MSG_DATA_ITER:
                ceph_msg_data_iter_cursor_init(cursor, length);
                break;
        case CEPH_MSG_DATA_NONE:
        default:
                /* BUG(); */
                break;
        }
        cursor->need_crc = true;
}

void ceph_msg_data_cursor_init(struct ceph_msg_data_cursor *cursor,
                               struct ceph_msg *msg, size_t length)
{
        BUG_ON(!length);
        BUG_ON(length > msg->data_length);
        BUG_ON(!msg->num_data_items);

        cursor->total_resid = length;
        cursor->data = msg->data;
        cursor->sr_resid = 0;

        __ceph_msg_data_cursor_init(cursor);
}

/*
 * Return the page containing the next piece to process for a given
 * data item, and supply the page offset and length of that piece.
 * Indicate whether this is the last piece in this data item.
 */
struct page *ceph_msg_data_next(struct ceph_msg_data_cursor *cursor,
                                size_t *page_offset, size_t *length)
{
        struct page *page;

        switch (cursor->data->type) {
        case CEPH_MSG_DATA_PAGELIST:
                page = ceph_msg_data_pagelist_next(cursor, page_offset, length);
                break;
        case CEPH_MSG_DATA_PAGES:
                page = ceph_msg_data_pages_next(cursor, page_offset, length);
                break;
#ifdef CONFIG_BLOCK
        case CEPH_MSG_DATA_BIO:
                page = ceph_msg_data_bio_next(cursor, page_offset, length);
                break;
#endif /* CONFIG_BLOCK */
        case CEPH_MSG_DATA_BVECS:
                page = ceph_msg_data_bvecs_next(cursor, page_offset, length);
                break;
        case CEPH_MSG_DATA_ITER:
                page = ceph_msg_data_iter_next(cursor, page_offset, length);
                break;
        case CEPH_MSG_DATA_NONE:
        default:
                page = NULL;
                break;
        }

        BUG_ON(!page);
        BUG_ON(*page_offset + *length > PAGE_SIZE);
        BUG_ON(!*length);
        BUG_ON(*length > cursor->resid);

        return page;
}

/*
 * Returns true if the result moves the cursor on to the next piece
 * of the data item.
 */
void ceph_msg_data_advance(struct ceph_msg_data_cursor *cursor, size_t bytes)
{
        bool new_piece;

        BUG_ON(bytes > cursor->resid);
        switch (cursor->data->type) {
        case CEPH_MSG_DATA_PAGELIST:
                new_piece = ceph_msg_data_pagelist_advance(cursor, bytes);
                break;
        case CEPH_MSG_DATA_PAGES:
                new_piece = ceph_msg_data_pages_advance(cursor, bytes);
                break;
#ifdef CONFIG_BLOCK
        case CEPH_MSG_DATA_BIO:
                new_piece = ceph_msg_data_bio_advance(cursor, bytes);
                break;
#endif /* CONFIG_BLOCK */
        case CEPH_MSG_DATA_BVECS:
                new_piece = ceph_msg_data_bvecs_advance(cursor, bytes);
                break;
        case CEPH_MSG_DATA_ITER:
                new_piece = ceph_msg_data_iter_advance(cursor, bytes);
                break;
        case CEPH_MSG_DATA_NONE:
        default:
                BUG();
                break;
        }
        cursor->total_resid -= bytes;

        if (!cursor->resid && cursor->total_resid) {
                cursor->data++;
                __ceph_msg_data_cursor_init(cursor);
                new_piece = true;
        }
        cursor->need_crc = new_piece;
}

u32 ceph_crc32c_page(u32 crc, struct page *page, unsigned int page_offset,
                     unsigned int length)
{
        char *kaddr;

        kaddr = kmap(page);
        BUG_ON(kaddr == NULL);
        crc = crc32c(crc, kaddr + page_offset, length);
        kunmap(page);

        return crc;
}

bool ceph_addr_is_blank(const struct ceph_entity_addr *addr)
{
        struct sockaddr_storage ss = addr->in_addr; /* align */
        struct in_addr *addr4 = &((struct sockaddr_in *)&ss)->sin_addr;
        struct in6_addr *addr6 = &((struct sockaddr_in6 *)&ss)->sin6_addr;

        switch (ss.ss_family) {
        case AF_INET:
                return addr4->s_addr == htonl(INADDR_ANY);
        case AF_INET6:
                return ipv6_addr_any(addr6);
        default:
                return true;
        }
}
EXPORT_SYMBOL(ceph_addr_is_blank);

int ceph_addr_port(const struct ceph_entity_addr *addr)
{
        switch (get_unaligned(&addr->in_addr.ss_family)) {
        case AF_INET:
                return ntohs(get_unaligned(&((struct sockaddr_in *)&addr->in_addr)->sin_port));
        case AF_INET6:
                return ntohs(get_unaligned(&((struct sockaddr_in6 *)&addr->in_addr)->sin6_port));
        }
        return 0;
}

void ceph_addr_set_port(struct ceph_entity_addr *addr, int p)
{
        switch (get_unaligned(&addr->in_addr.ss_family)) {
        case AF_INET:
                put_unaligned(htons(p), &((struct sockaddr_in *)&addr->in_addr)->sin_port);
                break;
        case AF_INET6:
                put_unaligned(htons(p), &((struct sockaddr_in6 *)&addr->in_addr)->sin6_port);
                break;
        }
}

/*
 * Unlike other *_pton function semantics, zero indicates success.
 */
static int ceph_pton(const char *str, size_t len, struct ceph_entity_addr *addr,
                char delim, const char **ipend)
{
        memset(&addr->in_addr, 0, sizeof(addr->in_addr));

        if (in4_pton(str, len, (u8 *)&((struct sockaddr_in *)&addr->in_addr)->sin_addr.s_addr, delim, ipend)) {
                put_unaligned(AF_INET, &addr->in_addr.ss_family);
                return 0;
        }

        if (in6_pton(str, len, (u8 *)&((struct sockaddr_in6 *)&addr->in_addr)->sin6_addr.s6_addr, delim, ipend)) {
                put_unaligned(AF_INET6, &addr->in_addr.ss_family);
                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 ceph_entity_addr *addr, 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 = min(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(current->nsproxy->net_ns,
                           NULL, name, end - name, NULL, &ip_addr, NULL, false);
        if (ip_len > 0)
                ret = ceph_pton(ip_addr, ip_len, addr, -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(addr));

        return ret;
}
#else
static inline int ceph_dns_resolve_name(const char *name, size_t namelen,
                struct ceph_entity_addr *addr, 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 ceph_entity_addr *addr, char delim, const char **ipend)
{
        int ret;

        ret = ceph_pton(name, namelen, addr, delim, ipend);
        if (ret)
                ret = ceph_dns_resolve_name(name, namelen, addr, 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, char delim)
{
        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++) {
                char cur_delim = delim;
                const char *ipend;
                int port;

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

                ret = ceph_parse_server_name(p, end - p, &addr[i], cur_delim,
                                             &ipend);
                if (ret)
                        goto bad;
                ret = -EINVAL;

                p = ipend;

                if (cur_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 == 0)
                                port = CEPH_MON_PORT;
                        else if (port > 65535)
                                goto bad;
                } else {
                        port = CEPH_MON_PORT;
                }

                ceph_addr_set_port(&addr[i], port);
                /*
                 * We want the type to be set according to ms_mode
                 * option, but options are normally parsed after mon
                 * addresses.  Rather than complicating parsing, set
                 * to LEGACY and override in build_initial_monmap()
                 * for mon addresses and ceph_messenger_init() for
                 * ip option.
                 */
                addr[i].type = CEPH_ENTITY_ADDR_TYPE_LEGACY;
                addr[i].nonce = 0;

                dout("%s got %s\n", __func__, ceph_pr_addr(&addr[i]));

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

        if (p != end)
                goto bad;

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

bad:
        return ret;
}

/*
 * 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.
 */
void ceph_con_process_message(struct ceph_connection *con)
{
        struct ceph_msg *msg = con->in_msg;

        BUG_ON(con->in_msg->con != con);
        con->in_msg = NULL;

        /* 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+%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.middle_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);
}

/*
 * Atomically queue work on a connection after the specified delay.
 * Bump @con reference to avoid races with connection teardown.
 * Returns 0 if work was queued, or an error code otherwise.
 */
static int queue_con_delay(struct ceph_connection *con, unsigned long delay)
{
        if (!con->ops->get(con)) {
                dout("%s %p ref count 0\n", __func__, con);
                return -ENOENT;
        }

        if (delay >= HZ)
                delay = round_jiffies_relative(delay);

        dout("%s %p %lu\n", __func__, con, delay);
        if (!queue_delayed_work(ceph_msgr_wq, &con->work, delay)) {
                dout("%s %p - already queued\n", __func__, con);
                con->ops->put(con);
                return -EBUSY;
        }

        return 0;
}

static void queue_con(struct ceph_connection *con)
{
        (void) queue_con_delay(con, 0);
}

static void cancel_con(struct ceph_connection *con)
{
        if (cancel_delayed_work(&con->work)) {
                dout("%s %p\n", __func__, con);
                con->ops->put(con);
        }
}

static bool con_sock_closed(struct ceph_connection *con)
{
        if (!ceph_con_flag_test_and_clear(con, CEPH_CON_F_SOCK_CLOSED))
                return false;

#define CASE(x)                                                         \
        case CEPH_CON_S_ ## x:                                          \
                con->error_msg = "socket closed (con state " #x ")";    \
                break;

        switch (con->state) {
        CASE(CLOSED);
        CASE(PREOPEN);
        CASE(V1_BANNER);
        CASE(V1_CONNECT_MSG);
        CASE(V2_BANNER_PREFIX);
        CASE(V2_BANNER_PAYLOAD);
        CASE(V2_HELLO);
        CASE(V2_AUTH);
        CASE(V2_AUTH_SIGNATURE);
        CASE(V2_SESSION_CONNECT);
        CASE(V2_SESSION_RECONNECT);
        CASE(OPEN);
        CASE(STANDBY);
        default:
                BUG();
        }
#undef CASE

        return true;
}

static bool con_backoff(struct ceph_connection *con)
{
        int ret;

        if (!ceph_con_flag_test_and_clear(con, CEPH_CON_F_BACKOFF))
                return false;

        ret = queue_con_delay(con, con->delay);
        if (ret) {
                dout("%s: con %p FAILED to back off %lu\n", __func__,
                        con, con->delay);
                BUG_ON(ret == -ENOENT);
                ceph_con_flag_set(con, CEPH_CON_F_BACKOFF);
        }

        return true;
}

/* Finish fault handling; con->mutex must *not* be held here */

static void con_fault_finish(struct ceph_connection *con)
{
        dout("%s %p\n", __func__, con);

        /*
         * in case we faulted due to authentication, invalidate our
         * current tickets so that we can get new ones.
         */
        if (!ceph_msgr2(from_msgr(con->msgr)) && con->v1.auth_retry) {
                dout("auth_retry %d, invalidating\n", con->v1.auth_retry);
                if (con->ops->invalidate_authorizer)
                        con->ops->invalidate_authorizer(con);
                con->v1.auth_retry = 0;
        }

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

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

        mutex_lock(&con->mutex);
        while (true) {
                int ret;

                if ((fault = con_sock_closed(con))) {
                        dout("%s: con %p SOCK_CLOSED\n", __func__, con);
                        break;
                }
                if (con_backoff(con)) {
                        dout("%s: con %p BACKOFF\n", __func__, con);
                        break;
                }
                if (con->state == CEPH_CON_S_STANDBY) {
                        dout("%s: con %p STANDBY\n", __func__, con);
                        break;
                }
                if (con->state == CEPH_CON_S_CLOSED) {
                        dout("%s: con %p CLOSED\n", __func__, con);
                        BUG_ON(con->sock);
                        break;
                }
                if (con->state == CEPH_CON_S_PREOPEN) {
                        dout("%s: con %p PREOPEN\n", __func__, con);
                        BUG_ON(con->sock);
                }

                if (ceph_msgr2(from_msgr(con->msgr)))
                        ret = ceph_con_v2_try_read(con);
                else
                        ret = ceph_con_v1_try_read(con);
                if (ret < 0) {
                        if (ret == -EAGAIN)
                                continue;
                        if (!con->error_msg)
                                con->error_msg = "socket error on read";
                        fault = true;
                        break;
                }

                if (ceph_msgr2(from_msgr(con->msgr)))
                        ret = ceph_con_v2_try_write(con);
                else
                        ret = ceph_con_v1_try_write(con);
                if (ret < 0) {
                        if (ret == -EAGAIN)
                                continue;
                        if (!con->error_msg)
                                con->error_msg = "socket error on write";
                        fault = true;
                }

                break;  /* If we make it to here, we're done */
        }
        if (fault)
                con_fault(con);
        mutex_unlock(&con->mutex);

        if (fault)
                con_fault_finish(con);

        con->ops->put(con);
}

/*
 * Generic error/fault handler.  A retry mechanism is used with
 * exponential backoff
 */
static void con_fault(struct ceph_connection *con)
{
        dout("fault %p state %d to peer %s\n",
             con, con->state, ceph_pr_addr(&con->peer_addr));

        pr_warn("%s%lld %s %s\n", ENTITY_NAME(con->peer_name),
                ceph_pr_addr(&con->peer_addr), con->error_msg);
        con->error_msg = NULL;

        WARN_ON(con->state == CEPH_CON_S_STANDBY ||
                con->state == CEPH_CON_S_CLOSED);

        ceph_con_reset_protocol(con);

        if (ceph_con_flag_test(con, CEPH_CON_F_LOSSYTX)) {
                dout("fault on LOSSYTX channel, marking CLOSED\n");
                con->state = CEPH_CON_S_CLOSED;
                return;
        }

        /* 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) &&
            !ceph_con_flag_test(con, CEPH_CON_F_KEEPALIVE_PENDING)) {
                dout("fault %p setting STANDBY clearing WRITE_PENDING\n", con);
                ceph_con_flag_clear(con, CEPH_CON_F_WRITE_PENDING);
                con->state = CEPH_CON_S_STANDBY;
        } else {
                /* retry after a delay. */
                con->state = CEPH_CON_S_PREOPEN;
                if (!con->delay) {
                        con->delay = BASE_DELAY_INTERVAL;
                } else if (con->delay < MAX_DELAY_INTERVAL) {
                        con->delay *= 2;
                        if (con->delay > MAX_DELAY_INTERVAL)
                                con->delay = MAX_DELAY_INTERVAL;
                }
                ceph_con_flag_set(con, CEPH_CON_F_BACKOFF);
                queue_con(con);
        }
}

void ceph_messenger_reset_nonce(struct ceph_messenger *msgr)
{
        u32 nonce = le32_to_cpu(msgr->inst.addr.nonce) + 1000000;
        msgr->inst.addr.nonce = cpu_to_le32(nonce);
        ceph_encode_my_addr(msgr);
}

/*
 * initialize a new messenger instance
 */
void ceph_messenger_init(struct ceph_messenger *msgr,
                         struct ceph_entity_addr *myaddr)
{
        spin_lock_init(&msgr->global_seq_lock);

        if (myaddr) {
                memcpy(&msgr->inst.addr.in_addr, &myaddr->in_addr,
                       sizeof(msgr->inst.addr.in_addr));
                ceph_addr_set_port(&msgr->inst.addr, 0);
        }

        /*
         * Since nautilus, clients are identified using type ANY.
         * For msgr1, ceph_encode_banner_addr() munges it to NONE.
         */
        msgr->inst.addr.type = CEPH_ENTITY_ADDR_TYPE_ANY;

        /* generate a random non-zero nonce */
        do {
                get_random_bytes(&msgr->inst.addr.nonce,
                                 sizeof(msgr->inst.addr.nonce));
        } while (!msgr->inst.addr.nonce);
        ceph_encode_my_addr(msgr);

        atomic_set(&msgr->stopping, 0);
        write_pnet(&msgr->net, get_net(current->nsproxy->net_ns));

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

void ceph_messenger_fini(struct ceph_messenger *msgr)
{
        put_net(read_pnet(&msgr->net));
}

static void msg_con_set(struct ceph_msg *msg, struct ceph_connection *con)
{
        if (msg->con)
                msg->con->ops->put(msg->con);

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

static void clear_standby(struct ceph_connection *con)
{
        /* come back from STANDBY? */
        if (con->state == CEPH_CON_S_STANDBY) {
                dout("clear_standby %p\n", con);
                con->state = CEPH_CON_S_PREOPEN;
                if (!ceph_msgr2(from_msgr(con->msgr)))
                        con->v1.connect_seq++;
                WARN_ON(ceph_con_flag_test(con, CEPH_CON_F_WRITE_PENDING));
                WARN_ON(ceph_con_flag_test(con, CEPH_CON_F_KEEPALIVE_PENDING));
        }
}

/*
 * Queue up an outgoing message on the given connection.
 *
 * Consumes a ref on @msg.
 */
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 == CEPH_CON_S_CLOSED) {
                dout("con_send %p closed, dropping %p\n", con, msg);
                ceph_msg_put(msg);
                mutex_unlock(&con->mutex);
                return;
        }

        msg_con_set(msg, con);

        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 (!ceph_con_flag_test_and_set(con, CEPH_CON_F_WRITE_PENDING))
                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) {
                dout("%s msg %p null con\n", __func__, msg);
                return;         /* Message not in our possession */
        }

        mutex_lock(&con->mutex);
        if (list_empty(&msg->list_head)) {
                WARN_ON(con->out_msg == msg);
                dout("%s con %p msg %p not linked\n", __func__, con, msg);
                mutex_unlock(&con->mutex);
                return;
        }

        dout("%s con %p msg %p was linked\n", __func__, con, msg);
        msg->hdr.seq = 0;
        ceph_msg_remove(msg);

        if (con->out_msg == msg) {
                WARN_ON(con->state != CEPH_CON_S_OPEN);
                dout("%s con %p msg %p was sending\n", __func__, con, msg);
                if (ceph_msgr2(from_msgr(con->msgr)))
                        ceph_con_v2_revoke(con, msg);
                else
                        ceph_con_v1_revoke(con, msg);
                ceph_msg_put(con->out_msg);
                con->out_msg = NULL;
        } else {
                dout("%s con %p msg %p not current, out_msg %p\n", __func__,
                     con, msg, con->out_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 = msg->con;

        if (!con) {
                dout("%s msg %p null con\n", __func__, msg);
                return;         /* Message not in our possession */
        }

        mutex_lock(&con->mutex);
        if (con->in_msg == msg) {
                WARN_ON(con->state != CEPH_CON_S_OPEN);
                dout("%s con %p msg %p was recving\n", __func__, con, msg);
                if (ceph_msgr2(from_msgr(con->msgr)))
                        ceph_con_v2_revoke_incoming(con);
                else
                        ceph_con_v1_revoke_incoming(con);
                ceph_msg_put(con->in_msg);
                con->in_msg = NULL;
        } else {
                dout("%s con %p msg %p not current, in_msg %p\n", __func__,
                     con, msg, con->in_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);
        ceph_con_flag_set(con, CEPH_CON_F_KEEPALIVE_PENDING);
        mutex_unlock(&con->mutex);

        if (!ceph_con_flag_test_and_set(con, CEPH_CON_F_WRITE_PENDING))
                queue_con(con);
}
EXPORT_SYMBOL(ceph_con_keepalive);

bool ceph_con_keepalive_expired(struct ceph_connection *con,
                               unsigned long interval)
{
        if (interval > 0 &&
            (con->peer_features & CEPH_FEATURE_MSGR_KEEPALIVE2)) {
                struct timespec64 now;
                struct timespec64 ts;
                ktime_get_real_ts64(&now);
                jiffies_to_timespec64(interval, &ts);
                ts = timespec64_add(con->last_keepalive_ack, ts);
                return timespec64_compare(&now, &ts) >= 0;
        }
        return false;
}

static struct ceph_msg_data *ceph_msg_data_add(struct ceph_msg *msg)
{
        BUG_ON(msg->num_data_items >= msg->max_data_items);
        return &msg->data[msg->num_data_items++];
}

static void ceph_msg_data_destroy(struct ceph_msg_data *data)
{
        if (data->type == CEPH_MSG_DATA_PAGES && data->own_pages) {
                int num_pages = calc_pages_for(data->alignment, data->length);
                ceph_release_page_vector(data->pages, num_pages);
        } else if (data->type == CEPH_MSG_DATA_PAGELIST) {
                ceph_pagelist_release(data->pagelist);
        }
}

void ceph_msg_data_add_pages(struct ceph_msg *msg, struct page **pages,
                             size_t length, size_t alignment, bool own_pages)
{
        struct ceph_msg_data *data;

        BUG_ON(!pages);
        BUG_ON(!length);

        data = ceph_msg_data_add(msg);
        data->type = CEPH_MSG_DATA_PAGES;
        data->pages = pages;
        data->length = length;
        data->alignment = alignment & ~PAGE_MASK;
        data->own_pages = own_pages;

        msg->data_length += length;
}
EXPORT_SYMBOL(ceph_msg_data_add_pages);

void ceph_msg_data_add_pagelist(struct ceph_msg *msg,
                                struct ceph_pagelist *pagelist)
{
        struct ceph_msg_data *data;

        BUG_ON(!pagelist);
        BUG_ON(!pagelist->length);

        data = ceph_msg_data_add(msg);
        data->type = CEPH_MSG_DATA_PAGELIST;
        refcount_inc(&pagelist->refcnt);
        data->pagelist = pagelist;

        msg->data_length += pagelist->length;
}
EXPORT_SYMBOL(ceph_msg_data_add_pagelist);

#ifdef  CONFIG_BLOCK
void ceph_msg_data_add_bio(struct ceph_msg *msg, struct ceph_bio_iter *bio_pos,
                           u32 length)
{
        struct ceph_msg_data *data;

        data = ceph_msg_data_add(msg);
        data->type = CEPH_MSG_DATA_BIO;
        data->bio_pos = *bio_pos;
        data->bio_length = length;

        msg->data_length += length;
}
EXPORT_SYMBOL(ceph_msg_data_add_bio);
#endif  /* CONFIG_BLOCK */

void ceph_msg_data_add_bvecs(struct ceph_msg *msg,
                             struct ceph_bvec_iter *bvec_pos)
{
        struct ceph_msg_data *data;

        data = ceph_msg_data_add(msg);
        data->type = CEPH_MSG_DATA_BVECS;
        data->bvec_pos = *bvec_pos;

        msg->data_length += bvec_pos->iter.bi_size;
}
EXPORT_SYMBOL(ceph_msg_data_add_bvecs);

void ceph_msg_data_add_iter(struct ceph_msg *msg,
                            struct iov_iter *iter)
{
        struct ceph_msg_data *data;

        data = ceph_msg_data_add(msg);
        data->type = CEPH_MSG_DATA_ITER;
        data->iter = *iter;

        msg->data_length += iov_iter_count(&data->iter);
}

/*
 * construct a new message with given type, size
 * the new msg has a ref count of 1.
 */
struct ceph_msg *ceph_msg_new2(int type, int front_len, int max_data_items,
                               gfp_t flags, bool can_fail)
{
        struct ceph_msg *m;

        m = kmem_cache_zalloc(ceph_msg_cache, flags);
        if (m == NULL)
                goto out;

        m->hdr.type = cpu_to_le16(type);
        m->hdr.priority = cpu_to_le16(CEPH_MSG_PRIO_DEFAULT);
        m->hdr.front_len = cpu_to_le32(front_len);

        INIT_LIST_HEAD(&m->list_head);
        kref_init(&m->kref);

        /* front */
        if (front_len) {
                m->front.iov_base = kvmalloc(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_alloc_len = m->front.iov_len = front_len;

        if (max_data_items) {
                m->data = kmalloc_objs(*m->data, max_data_items, flags);
                if (!m->data)
                        goto out2;

                m->max_data_items = max_data_items;
        }

        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_new2);

struct ceph_msg *ceph_msg_new(int type, int front_len, gfp_t flags,
                              bool can_fail)
{
        return ceph_msg_new2(type, front_len, 0, flags, can_fail);
}
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
 */
int ceph_con_in_msg_alloc(struct ceph_connection *con,
                          struct ceph_msg_header *hdr, int *skip)
{
        int middle_len = le32_to_cpu(hdr->middle_len);
        struct ceph_msg *msg;
        int ret = 0;

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

        mutex_unlock(&con->mutex);
        msg = con->ops->alloc_msg(con, hdr, skip);
        mutex_lock(&con->mutex);
        if (con->state != CEPH_CON_S_OPEN) {
                if (msg)
                        ceph_msg_put(msg);
                return -EAGAIN;
        }
        if (msg) {
                BUG_ON(*skip);
                msg_con_set(msg, con);
                con->in_msg = msg;
        } else {
                /*
                 * Null message pointer means either we should skip
                 * this message or we couldn't allocate memory.  The
                 * former is not an error.
                 */
                if (*skip)
                        return 0;

                con->error_msg = "error allocating memory for incoming message";
                return -ENOMEM;
        }
        memcpy(&con->in_msg->hdr, hdr, sizeof(*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;
}

struct ceph_msg *ceph_con_get_out_msg(struct ceph_connection *con)
{
        struct ceph_msg *msg;

        if (list_empty(&con->out_queue))
                return NULL;

        msg = list_first_entry(&con->out_queue, struct ceph_msg, list_head);
        WARN_ON(msg->con != con);

        /*
         * Put the message on "sent" list using a ref from ceph_con_send().
         * It is put when the message is acked or revoked.
         */
        list_move_tail(&msg->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 (msg->needs_out_seq) {
                msg->hdr.seq = cpu_to_le64(++con->out_seq);
                msg->needs_out_seq = false;

                if (con->ops->reencode_message)
                        con->ops->reencode_message(msg);
        }

        /*
         * Get a ref for out_msg.  It is put when we are done sending the
         * message or in case of a fault.
         */
        WARN_ON(con->out_msg);
        return con->out_msg = ceph_msg_get(msg);
}

/*
 * Free a generically kmalloc'd message.
 */
static void ceph_msg_free(struct ceph_msg *m)
{
        dout("%s %p\n", __func__, m);
        kvfree(m->front.iov_base);
        kfree(m->data);
        kmem_cache_free(ceph_msg_cache, m);
}

static void ceph_msg_release(struct kref *kref)
{
        struct ceph_msg *m = container_of(kref, struct ceph_msg, kref);
        int i;

        dout("%s %p\n", __func__, m);
        WARN_ON(!list_empty(&m->list_head));

        msg_con_set(m, NULL);

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

        for (i = 0; i < m->num_data_items; i++)
                ceph_msg_data_destroy(&m->data[i]);

        if (m->pool)
                ceph_msgpool_put(m->pool, m);
        else
                ceph_msg_free(m);
}

struct ceph_msg *ceph_msg_get(struct ceph_msg *msg)
{
        dout("%s %p (was %d)\n", __func__, msg,
             kref_read(&msg->kref));
        kref_get(&msg->kref);
        return msg;
}
EXPORT_SYMBOL(ceph_msg_get);

void ceph_msg_put(struct ceph_msg *msg)
{
        dout("%s %p (was %d)\n", __func__, msg,
             kref_read(&msg->kref));
        kref_put(&msg->kref, ceph_msg_release);
}
EXPORT_SYMBOL(ceph_msg_put);

void ceph_msg_dump(struct ceph_msg *msg)
{
        pr_debug("msg_dump %p (front_alloc_len %d length %zd)\n", msg,
                 msg->front_alloc_len, msg->data_length);
        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);