/* RxRPC individual remote procedure call handling
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

const char *const rxrpc_call_states[NR__RXRPC_CALL_STATES] = {
        [RXRPC_CALL_UNINITIALISED]              = "Uninit  ",
        [RXRPC_CALL_CLIENT_AWAIT_CONN]          = "ClWtConn",
        [RXRPC_CALL_CLIENT_SEND_REQUEST]        = "ClSndReq",
        [RXRPC_CALL_CLIENT_AWAIT_REPLY]         = "ClAwtRpl",
        [RXRPC_CALL_CLIENT_RECV_REPLY]          = "ClRcvRpl",
        [RXRPC_CALL_SERVER_PREALLOC]            = "SvPrealc",
        [RXRPC_CALL_SERVER_SECURING]            = "SvSecure",
        [RXRPC_CALL_SERVER_ACCEPTING]           = "SvAccept",
        [RXRPC_CALL_SERVER_RECV_REQUEST]        = "SvRcvReq",
        [RXRPC_CALL_SERVER_ACK_REQUEST]         = "SvAckReq",
        [RXRPC_CALL_SERVER_SEND_REPLY]          = "SvSndRpl",
        [RXRPC_CALL_SERVER_AWAIT_ACK]           = "SvAwtACK",
        [RXRPC_CALL_COMPLETE]                   = "Complete",
};

const char *const rxrpc_call_completions[NR__RXRPC_CALL_COMPLETIONS] = {
        [RXRPC_CALL_SUCCEEDED]                  = "Complete",
        [RXRPC_CALL_REMOTELY_ABORTED]           = "RmtAbort",
        [RXRPC_CALL_LOCALLY_ABORTED]            = "LocAbort",
        [RXRPC_CALL_LOCAL_ERROR]                = "LocError",
        [RXRPC_CALL_NETWORK_ERROR]              = "NetError",
};

struct kmem_cache *rxrpc_call_jar;

static void rxrpc_call_timer_expired(unsigned long _call)
{
        struct rxrpc_call *call = (struct rxrpc_call *)_call;

        _enter("%d", call->debug_id);

        if (call->state < RXRPC_CALL_COMPLETE)
                rxrpc_set_timer(call, rxrpc_timer_expired, ktime_get_real());
}

/*
 * find an extant server call
 * - called in process context with IRQs enabled
 */
struct rxrpc_call *rxrpc_find_call_by_user_ID(struct rxrpc_sock *rx,
                                              unsigned long user_call_ID)
{
        struct rxrpc_call *call;
        struct rb_node *p;

        _enter("%p,%lx", rx, user_call_ID);

        read_lock(&rx->call_lock);

        p = rx->calls.rb_node;
        while (p) {
                call = rb_entry(p, struct rxrpc_call, sock_node);

                if (user_call_ID < call->user_call_ID)
                        p = p->rb_left;
                else if (user_call_ID > call->user_call_ID)
                        p = p->rb_right;
                else
                        goto found_extant_call;
        }

        read_unlock(&rx->call_lock);
        _leave(" = NULL");
        return NULL;

found_extant_call:
        rxrpc_get_call(call, rxrpc_call_got);
        read_unlock(&rx->call_lock);
        _leave(" = %p [%d]", call, atomic_read(&call->usage));
        return call;
}

/*
 * allocate a new call
 */
struct rxrpc_call *rxrpc_alloc_call(gfp_t gfp)
{
        struct rxrpc_call *call;

        call = kmem_cache_zalloc(rxrpc_call_jar, gfp);
        if (!call)
                return NULL;

        call->rxtx_buffer = kcalloc(RXRPC_RXTX_BUFF_SIZE,
                                    sizeof(struct sk_buff *),
                                    gfp);
        if (!call->rxtx_buffer)
                goto nomem;

        call->rxtx_annotations = kcalloc(RXRPC_RXTX_BUFF_SIZE, sizeof(u8), gfp);
        if (!call->rxtx_annotations)
                goto nomem_2;

        mutex_init(&call->user_mutex);
        setup_timer(&call->timer, rxrpc_call_timer_expired,
                    (unsigned long)call);
        INIT_WORK(&call->processor, &rxrpc_process_call);
        INIT_LIST_HEAD(&call->link);
        INIT_LIST_HEAD(&call->chan_wait_link);
        INIT_LIST_HEAD(&call->accept_link);
        INIT_LIST_HEAD(&call->recvmsg_link);
        INIT_LIST_HEAD(&call->sock_link);
        init_waitqueue_head(&call->waitq);
        spin_lock_init(&call->lock);
        rwlock_init(&call->state_lock);
        atomic_set(&call->usage, 1);
        call->debug_id = atomic_inc_return(&rxrpc_debug_id);
        call->tx_total_len = -1;

        memset(&call->sock_node, 0xed, sizeof(call->sock_node));

        /* Leave space in the ring to handle a maxed-out jumbo packet */
        call->rx_winsize = rxrpc_rx_window_size;
        call->tx_winsize = 16;
        call->rx_expect_next = 1;

        call->cong_cwnd = 2;
        call->cong_ssthresh = RXRPC_RXTX_BUFF_SIZE - 1;
        return call;

nomem_2:
        kfree(call->rxtx_buffer);
nomem:
        kmem_cache_free(rxrpc_call_jar, call);
        return NULL;
}

/*
 * Allocate a new client call.
 */
static struct rxrpc_call *rxrpc_alloc_client_call(struct sockaddr_rxrpc *srx,
                                                  gfp_t gfp)
{
        struct rxrpc_call *call;
        ktime_t now;

        _enter("");

        call = rxrpc_alloc_call(gfp);
        if (!call)
                return ERR_PTR(-ENOMEM);
        call->state = RXRPC_CALL_CLIENT_AWAIT_CONN;
        call->service_id = srx->srx_service;
        call->tx_phase = true;
        now = ktime_get_real();
        call->acks_latest_ts = now;
        call->cong_tstamp = now;

        _leave(" = %p", call);
        return call;
}

/*
 * Initiate the call ack/resend/expiry timer.
 */
static void rxrpc_start_call_timer(struct rxrpc_call *call)
{
        ktime_t now = ktime_get_real(), expire_at;

        expire_at = ktime_add_ms(now, rxrpc_max_call_lifetime);
        call->expire_at = expire_at;
        call->ack_at = expire_at;
        call->ping_at = expire_at;
        call->resend_at = expire_at;
        call->timer.expires = jiffies + LONG_MAX / 2;
        rxrpc_set_timer(call, rxrpc_timer_begin, now);
}

/*
 * Set up a call for the given parameters.
 * - Called with the socket lock held, which it must release.
 * - If it returns a call, the call's lock will need releasing by the caller.
 */
struct rxrpc_call *rxrpc_new_client_call(struct rxrpc_sock *rx,
                                         struct rxrpc_conn_parameters *cp,
                                         struct sockaddr_rxrpc *srx,
                                         unsigned long user_call_ID,
                                         s64 tx_total_len,
                                         gfp_t gfp)
        __releases(&rx->sk.sk_lock.slock)
{
        struct rxrpc_call *call, *xcall;
        struct rxrpc_net *rxnet = rxrpc_net(sock_net(&rx->sk));
        struct rb_node *parent, **pp;
        const void *here = __builtin_return_address(0);
        int ret;

        _enter("%p,%lx", rx, user_call_ID);

        call = rxrpc_alloc_client_call(srx, gfp);
        if (IS_ERR(call)) {
                release_sock(&rx->sk);
                _leave(" = %ld", PTR_ERR(call));
                return call;
        }

        call->tx_total_len = tx_total_len;
        trace_rxrpc_call(call, rxrpc_call_new_client, atomic_read(&call->usage),
                         here, (const void *)user_call_ID);

        /* We need to protect a partially set up call against the user as we
         * will be acting outside the socket lock.
         */
        mutex_lock(&call->user_mutex);

        /* Publish the call, even though it is incompletely set up as yet */
        write_lock(&rx->call_lock);

        pp = &rx->calls.rb_node;
        parent = NULL;
        while (*pp) {
                parent = *pp;
                xcall = rb_entry(parent, struct rxrpc_call, sock_node);

                if (user_call_ID < xcall->user_call_ID)
                        pp = &(*pp)->rb_left;
                else if (user_call_ID > xcall->user_call_ID)
                        pp = &(*pp)->rb_right;
                else
                        goto error_dup_user_ID;
        }

        rcu_assign_pointer(call->socket, rx);
        call->user_call_ID = user_call_ID;
        __set_bit(RXRPC_CALL_HAS_USERID, &call->flags);
        rxrpc_get_call(call, rxrpc_call_got_userid);
        rb_link_node(&call->sock_node, parent, pp);
        rb_insert_color(&call->sock_node, &rx->calls);
        list_add(&call->sock_link, &rx->sock_calls);

        write_unlock(&rx->call_lock);

        write_lock(&rxnet->call_lock);
        list_add_tail(&call->link, &rxnet->calls);
        write_unlock(&rxnet->call_lock);

        /* From this point on, the call is protected by its own lock. */
        release_sock(&rx->sk);

        /* Set up or get a connection record and set the protocol parameters,
         * including channel number and call ID.
         */
        ret = rxrpc_connect_call(call, cp, srx, gfp);
        if (ret < 0)
                goto error;

        trace_rxrpc_call(call, rxrpc_call_connected, atomic_read(&call->usage),
                         here, NULL);

        rxrpc_start_call_timer(call);

        _net("CALL new %d on CONN %d", call->debug_id, call->conn->debug_id);

        _leave(" = %p [new]", call);
        return call;

        /* We unexpectedly found the user ID in the list after taking
         * the call_lock.  This shouldn't happen unless the user races
         * with itself and tries to add the same user ID twice at the
         * same time in different threads.
         */
error_dup_user_ID:
        write_unlock(&rx->call_lock);
        release_sock(&rx->sk);
        ret = -EEXIST;

error:
        __rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
                                    RX_CALL_DEAD, ret);
        trace_rxrpc_call(call, rxrpc_call_error, atomic_read(&call->usage),
                         here, ERR_PTR(ret));
        rxrpc_release_call(rx, call);
        mutex_unlock(&call->user_mutex);
        rxrpc_put_call(call, rxrpc_call_put);
        _leave(" = %d", ret);
        return ERR_PTR(ret);
}

/*
 * Retry a call to a new address.  It is expected that the Tx queue of the call
 * will contain data previously packaged for an old call.
 */
int rxrpc_retry_client_call(struct rxrpc_sock *rx,
                            struct rxrpc_call *call,
                            struct rxrpc_conn_parameters *cp,
                            struct sockaddr_rxrpc *srx,
                            gfp_t gfp)
{
        const void *here = __builtin_return_address(0);
        int ret;

        /* Set up or get a connection record and set the protocol parameters,
         * including channel number and call ID.
         */
        ret = rxrpc_connect_call(call, cp, srx, gfp);
        if (ret < 0)
                goto error;

        trace_rxrpc_call(call, rxrpc_call_connected, atomic_read(&call->usage),
                         here, NULL);

        rxrpc_start_call_timer(call);

        _net("CALL new %d on CONN %d", call->debug_id, call->conn->debug_id);

        if (!test_and_set_bit(RXRPC_CALL_EV_RESEND, &call->events))
                rxrpc_queue_call(call);

        _leave(" = 0");
        return 0;

error:
        rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
                                  RX_CALL_DEAD, ret);
        trace_rxrpc_call(call, rxrpc_call_error, atomic_read(&call->usage),
                         here, ERR_PTR(ret));
        _leave(" = %d", ret);
        return ret;
}

/*
 * Set up an incoming call.  call->conn points to the connection.
 * This is called in BH context and isn't allowed to fail.
 */
void rxrpc_incoming_call(struct rxrpc_sock *rx,
                         struct rxrpc_call *call,
                         struct sk_buff *skb)
{
        struct rxrpc_connection *conn = call->conn;
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
        u32 chan;

        _enter(",%d", call->conn->debug_id);

        rcu_assign_pointer(call->socket, rx);
        call->call_id           = sp->hdr.callNumber;
        call->service_id        = sp->hdr.serviceId;
        call->cid               = sp->hdr.cid;
        call->state             = RXRPC_CALL_SERVER_ACCEPTING;
        if (sp->hdr.securityIndex > 0)
                call->state     = RXRPC_CALL_SERVER_SECURING;
        call->cong_tstamp       = skb->tstamp;

        /* Set the channel for this call.  We don't get channel_lock as we're
         * only defending against the data_ready handler (which we're called
         * from) and the RESPONSE packet parser (which is only really
         * interested in call_counter and can cope with a disagreement with the
         * call pointer).
         */
        chan = sp->hdr.cid & RXRPC_CHANNELMASK;
        conn->channels[chan].call_counter = call->call_id;
        conn->channels[chan].call_id = call->call_id;
        rcu_assign_pointer(conn->channels[chan].call, call);

        spin_lock(&conn->params.peer->lock);
        hlist_add_head(&call->error_link, &conn->params.peer->error_targets);
        spin_unlock(&conn->params.peer->lock);

        _net("CALL incoming %d on CONN %d", call->debug_id, call->conn->debug_id);

        rxrpc_start_call_timer(call);
        _leave("");
}

/*
 * Queue a call's work processor, getting a ref to pass to the work queue.
 */
bool rxrpc_queue_call(struct rxrpc_call *call)
{
        const void *here = __builtin_return_address(0);
        int n = __atomic_add_unless(&call->usage, 1, 0);
        if (n == 0)
                return false;
        if (rxrpc_queue_work(&call->processor))
                trace_rxrpc_call(call, rxrpc_call_queued, n + 1, here, NULL);
        else
                rxrpc_put_call(call, rxrpc_call_put_noqueue);
        return true;
}

/*
 * Queue a call's work processor, passing the callers ref to the work queue.
 */
bool __rxrpc_queue_call(struct rxrpc_call *call)
{
        const void *here = __builtin_return_address(0);
        int n = atomic_read(&call->usage);
        ASSERTCMP(n, >=, 1);
        if (rxrpc_queue_work(&call->processor))
                trace_rxrpc_call(call, rxrpc_call_queued_ref, n, here, NULL);
        else
                rxrpc_put_call(call, rxrpc_call_put_noqueue);
        return true;
}

/*
 * Note the re-emergence of a call.
 */
void rxrpc_see_call(struct rxrpc_call *call)
{
        const void *here = __builtin_return_address(0);
        if (call) {
                int n = atomic_read(&call->usage);

                trace_rxrpc_call(call, rxrpc_call_seen, n, here, NULL);
        }
}

/*
 * Note the addition of a ref on a call.
 */
void rxrpc_get_call(struct rxrpc_call *call, enum rxrpc_call_trace op)
{
        const void *here = __builtin_return_address(0);
        int n = atomic_inc_return(&call->usage);

        trace_rxrpc_call(call, op, n, here, NULL);
}

/*
 * Detach a call from its owning socket.
 */
void rxrpc_release_call(struct rxrpc_sock *rx, struct rxrpc_call *call)
{
        const void *here = __builtin_return_address(0);
        struct rxrpc_connection *conn = call->conn;
        bool put = false;
        int i;

        _enter("{%d,%d}", call->debug_id, atomic_read(&call->usage));

        trace_rxrpc_call(call, rxrpc_call_release, atomic_read(&call->usage),
                         here, (const void *)call->flags);

        ASSERTCMP(call->state, ==, RXRPC_CALL_COMPLETE);

        spin_lock_bh(&call->lock);
        if (test_and_set_bit(RXRPC_CALL_RELEASED, &call->flags))
                BUG();
        spin_unlock_bh(&call->lock);

        del_timer_sync(&call->timer);

        /* Make sure we don't get any more notifications */
        write_lock_bh(&rx->recvmsg_lock);

        if (!list_empty(&call->recvmsg_link)) {
                _debug("unlinking once-pending call %p { e=%lx f=%lx }",
                       call, call->events, call->flags);
                list_del(&call->recvmsg_link);
                put = true;
        }

        /* list_empty() must return false in rxrpc_notify_socket() */
        call->recvmsg_link.next = NULL;
        call->recvmsg_link.prev = NULL;

        write_unlock_bh(&rx->recvmsg_lock);
        if (put)
                rxrpc_put_call(call, rxrpc_call_put);

        write_lock(&rx->call_lock);

        if (test_and_clear_bit(RXRPC_CALL_HAS_USERID, &call->flags)) {
                rb_erase(&call->sock_node, &rx->calls);
                memset(&call->sock_node, 0xdd, sizeof(call->sock_node));
                rxrpc_put_call(call, rxrpc_call_put_userid);
        }

        list_del(&call->sock_link);
        write_unlock(&rx->call_lock);

        _debug("RELEASE CALL %p (%d CONN %p)", call, call->debug_id, conn);

        if (conn)
                rxrpc_disconnect_call(call);

        for (i = 0; i < RXRPC_RXTX_BUFF_SIZE; i++) {
                rxrpc_free_skb(call->rxtx_buffer[i],
                               (call->tx_phase ? rxrpc_skb_tx_cleaned :
                                rxrpc_skb_rx_cleaned));
                call->rxtx_buffer[i] = NULL;
        }

        _leave("");
}

/*
 * Prepare a kernel service call for retry.
 */
int rxrpc_prepare_call_for_retry(struct rxrpc_sock *rx, struct rxrpc_call *call)
{
        const void *here = __builtin_return_address(0);
        int i;
        u8 last = 0;

        _enter("{%d,%d}", call->debug_id, atomic_read(&call->usage));

        trace_rxrpc_call(call, rxrpc_call_release, atomic_read(&call->usage),
                         here, (const void *)call->flags);

        ASSERTCMP(call->state, ==, RXRPC_CALL_COMPLETE);
        ASSERTCMP(call->completion, !=, RXRPC_CALL_REMOTELY_ABORTED);
        ASSERTCMP(call->completion, !=, RXRPC_CALL_LOCALLY_ABORTED);
        ASSERT(list_empty(&call->recvmsg_link));

        del_timer_sync(&call->timer);

        _debug("RELEASE CALL %p (%d CONN %p)", call, call->debug_id, call->conn);

        if (call->conn)
                rxrpc_disconnect_call(call);

        if (rxrpc_is_service_call(call) ||
            !call->tx_phase ||
            call->tx_hard_ack != 0 ||
            call->rx_hard_ack != 0 ||
            call->rx_top != 0)
                return -EINVAL;

        call->state = RXRPC_CALL_UNINITIALISED;
        call->completion = RXRPC_CALL_SUCCEEDED;
        call->call_id = 0;
        call->cid = 0;
        call->cong_cwnd = 0;
        call->cong_extra = 0;
        call->cong_ssthresh = 0;
        call->cong_mode = 0;
        call->cong_dup_acks = 0;
        call->cong_cumul_acks = 0;
        call->acks_lowest_nak = 0;

        for (i = 0; i < RXRPC_RXTX_BUFF_SIZE; i++) {
                last |= call->rxtx_annotations[i];
                call->rxtx_annotations[i] &= RXRPC_TX_ANNO_LAST;
                call->rxtx_annotations[i] |= RXRPC_TX_ANNO_RETRANS;
        }

        _leave(" = 0");
        return 0;
}

/*
 * release all the calls associated with a socket
 */
void rxrpc_release_calls_on_socket(struct rxrpc_sock *rx)
{
        struct rxrpc_call *call;

        _enter("%p", rx);

        while (!list_empty(&rx->to_be_accepted)) {
                call = list_entry(rx->to_be_accepted.next,
                                  struct rxrpc_call, accept_link);
                list_del(&call->accept_link);
                rxrpc_abort_call("SKR", call, 0, RX_CALL_DEAD, -ECONNRESET);
                rxrpc_put_call(call, rxrpc_call_put);
        }

        while (!list_empty(&rx->sock_calls)) {
                call = list_entry(rx->sock_calls.next,
                                  struct rxrpc_call, sock_link);
                rxrpc_get_call(call, rxrpc_call_got);
                rxrpc_abort_call("SKT", call, 0, RX_CALL_DEAD, -ECONNRESET);
                rxrpc_send_abort_packet(call);
                rxrpc_release_call(rx, call);
                rxrpc_put_call(call, rxrpc_call_put);
        }

        _leave("");
}

/*
 * release a call
 */
void rxrpc_put_call(struct rxrpc_call *call, enum rxrpc_call_trace op)
{
        struct rxrpc_net *rxnet;
        const void *here = __builtin_return_address(0);
        int n;

        ASSERT(call != NULL);

        n = atomic_dec_return(&call->usage);
        trace_rxrpc_call(call, op, n, here, NULL);
        ASSERTCMP(n, >=, 0);
        if (n == 0) {
                _debug("call %d dead", call->debug_id);
                ASSERTCMP(call->state, ==, RXRPC_CALL_COMPLETE);

                if (!list_empty(&call->link)) {
                        rxnet = rxrpc_net(sock_net(&call->socket->sk));
                        write_lock(&rxnet->call_lock);
                        list_del_init(&call->link);
                        write_unlock(&rxnet->call_lock);
                }

                rxrpc_cleanup_call(call);
        }
}

/*
 * Final call destruction under RCU.
 */
static void rxrpc_rcu_destroy_call(struct rcu_head *rcu)
{
        struct rxrpc_call *call = container_of(rcu, struct rxrpc_call, rcu);

        rxrpc_put_peer(call->peer);
        kfree(call->rxtx_buffer);
        kfree(call->rxtx_annotations);
        kmem_cache_free(rxrpc_call_jar, call);
}

/*
 * clean up a call
 */
void rxrpc_cleanup_call(struct rxrpc_call *call)
{
        int i;

        _net("DESTROY CALL %d", call->debug_id);

        memset(&call->sock_node, 0xcd, sizeof(call->sock_node));

        del_timer_sync(&call->timer);

        ASSERTCMP(call->state, ==, RXRPC_CALL_COMPLETE);
        ASSERT(test_bit(RXRPC_CALL_RELEASED, &call->flags));
        ASSERTCMP(call->conn, ==, NULL);

        /* Clean up the Rx/Tx buffer */
        for (i = 0; i < RXRPC_RXTX_BUFF_SIZE; i++)
                rxrpc_free_skb(call->rxtx_buffer[i],
                               (call->tx_phase ? rxrpc_skb_tx_cleaned :
                                rxrpc_skb_rx_cleaned));

        rxrpc_free_skb(call->tx_pending, rxrpc_skb_tx_cleaned);

        call_rcu(&call->rcu, rxrpc_rcu_destroy_call);
}

/*
 * Make sure that all calls are gone from a network namespace.  To reach this
 * point, any open UDP sockets in that namespace must have been closed, so any
 * outstanding calls cannot be doing I/O.
 */
void rxrpc_destroy_all_calls(struct rxrpc_net *rxnet)
{
        struct rxrpc_call *call;

        _enter("");

        if (list_empty(&rxnet->calls))
                return;

        write_lock(&rxnet->call_lock);

        while (!list_empty(&rxnet->calls)) {
                call = list_entry(rxnet->calls.next, struct rxrpc_call, link);
                _debug("Zapping call %p", call);

                rxrpc_see_call(call);
                list_del_init(&call->link);

                pr_err("Call %p still in use (%d,%s,%lx,%lx)!\n",
                       call, atomic_read(&call->usage),
                       rxrpc_call_states[call->state],
                       call->flags, call->events);

                write_unlock(&rxnet->call_lock);
                cond_resched();
                write_lock(&rxnet->call_lock);
        }

        write_unlock(&rxnet->call_lock);
}