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

#include <linux/slab.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <rxrpc/packet.h>
#include "internal.h"
#include "afs_cm.h"

struct socket *afs_socket; /* my RxRPC socket */
static struct workqueue_struct *afs_async_calls;
static struct afs_call *afs_spare_incoming_call;
static atomic_t afs_outstanding_calls;

static void afs_free_call(struct afs_call *);
static void afs_wake_up_call_waiter(struct sock *, struct rxrpc_call *, unsigned long);
static int afs_wait_for_call_to_complete(struct afs_call *);
static void afs_wake_up_async_call(struct sock *, struct rxrpc_call *, unsigned long);
static int afs_dont_wait_for_call_to_complete(struct afs_call *);
static void afs_process_async_call(struct work_struct *);
static void afs_rx_new_call(struct sock *, struct rxrpc_call *, unsigned long);
static void afs_rx_discard_new_call(struct rxrpc_call *, unsigned long);
static int afs_deliver_cm_op_id(struct afs_call *);

/* synchronous call management */
const struct afs_wait_mode afs_sync_call = {
        .notify_rx      = afs_wake_up_call_waiter,
        .wait           = afs_wait_for_call_to_complete,
};

/* asynchronous call management */
const struct afs_wait_mode afs_async_call = {
        .notify_rx      = afs_wake_up_async_call,
        .wait           = afs_dont_wait_for_call_to_complete,
};

/* asynchronous incoming call management */
static const struct afs_wait_mode afs_async_incoming_call = {
        .notify_rx      = afs_wake_up_async_call,
};

/* asynchronous incoming call initial processing */
static const struct afs_call_type afs_RXCMxxxx = {
        .name           = "CB.xxxx",
        .deliver        = afs_deliver_cm_op_id,
        .abort_to_error = afs_abort_to_error,
};

static void afs_charge_preallocation(struct work_struct *);

static DECLARE_WORK(afs_charge_preallocation_work, afs_charge_preallocation);

static int afs_wait_atomic_t(atomic_t *p)
{
        schedule();
        return 0;
}

/*
 * open an RxRPC socket and bind it to be a server for callback notifications
 * - the socket is left in blocking mode and non-blocking ops use MSG_DONTWAIT
 */
int afs_open_socket(void)
{
        struct sockaddr_rxrpc srx;
        struct socket *socket;
        int ret;

        _enter("");

        ret = -ENOMEM;
        afs_async_calls = alloc_workqueue("kafsd", WQ_MEM_RECLAIM, 0);
        if (!afs_async_calls)
                goto error_0;

        ret = sock_create_kern(&init_net, AF_RXRPC, SOCK_DGRAM, PF_INET, &socket);
        if (ret < 0)
                goto error_1;

        socket->sk->sk_allocation = GFP_NOFS;

        /* bind the callback manager's address to make this a server socket */
        srx.srx_family                  = AF_RXRPC;
        srx.srx_service                 = CM_SERVICE;
        srx.transport_type              = SOCK_DGRAM;
        srx.transport_len               = sizeof(srx.transport.sin);
        srx.transport.sin.sin_family    = AF_INET;
        srx.transport.sin.sin_port      = htons(AFS_CM_PORT);
        memset(&srx.transport.sin.sin_addr, 0,
               sizeof(srx.transport.sin.sin_addr));

        ret = kernel_bind(socket, (struct sockaddr *) &srx, sizeof(srx));
        if (ret < 0)
                goto error_2;

        rxrpc_kernel_new_call_notification(socket, afs_rx_new_call,
                                           afs_rx_discard_new_call);

        ret = kernel_listen(socket, INT_MAX);
        if (ret < 0)
                goto error_2;

        afs_socket = socket;
        afs_charge_preallocation(NULL);
        _leave(" = 0");
        return 0;

error_2:
        sock_release(socket);
error_1:
        destroy_workqueue(afs_async_calls);
error_0:
        _leave(" = %d", ret);
        return ret;
}

/*
 * close the RxRPC socket AFS was using
 */
void afs_close_socket(void)
{
        _enter("");

        if (afs_spare_incoming_call) {
                atomic_inc(&afs_outstanding_calls);
                afs_free_call(afs_spare_incoming_call);
                afs_spare_incoming_call = NULL;
        }

        _debug("outstanding %u", atomic_read(&afs_outstanding_calls));
        wait_on_atomic_t(&afs_outstanding_calls, afs_wait_atomic_t,
                         TASK_UNINTERRUPTIBLE);
        _debug("no outstanding calls");

        flush_workqueue(afs_async_calls);
        kernel_sock_shutdown(afs_socket, SHUT_RDWR);
        flush_workqueue(afs_async_calls);
        sock_release(afs_socket);

        _debug("dework");
        destroy_workqueue(afs_async_calls);
        _leave("");
}

/*
 * free a call
 */
static void afs_free_call(struct afs_call *call)
{
        _debug("DONE %p{%s} [%d]",
               call, call->type->name, atomic_read(&afs_outstanding_calls));

        ASSERTCMP(call->rxcall, ==, NULL);
        ASSERT(!work_pending(&call->async_work));
        ASSERT(call->type->name != NULL);

        kfree(call->request);
        kfree(call);

        if (atomic_dec_and_test(&afs_outstanding_calls))
                wake_up_atomic_t(&afs_outstanding_calls);
}

/*
 * End a call but do not free it
 */
static void afs_end_call_nofree(struct afs_call *call)
{
        if (call->rxcall) {
                rxrpc_kernel_end_call(afs_socket, call->rxcall);
                call->rxcall = NULL;
        }
        if (call->type->destructor)
                call->type->destructor(call);
}

/*
 * End a call and free it
 */
static void afs_end_call(struct afs_call *call)
{
        afs_end_call_nofree(call);
        afs_free_call(call);
}

/*
 * allocate a call with flat request and reply buffers
 */
struct afs_call *afs_alloc_flat_call(const struct afs_call_type *type,
                                     size_t request_size, size_t reply_max)
{
        struct afs_call *call;

        call = kzalloc(sizeof(*call), GFP_NOFS);
        if (!call)
                goto nomem_call;

        _debug("CALL %p{%s} [%d]",
               call, type->name, atomic_read(&afs_outstanding_calls));
        atomic_inc(&afs_outstanding_calls);

        call->type = type;
        call->request_size = request_size;
        call->reply_max = reply_max;

        if (request_size) {
                call->request = kmalloc(request_size, GFP_NOFS);
                if (!call->request)
                        goto nomem_free;
        }

        if (reply_max) {
                call->buffer = kmalloc(reply_max, GFP_NOFS);
                if (!call->buffer)
                        goto nomem_free;
        }

        init_waitqueue_head(&call->waitq);
        return call;

nomem_free:
        afs_free_call(call);
nomem_call:
        return NULL;
}

/*
 * clean up a call with flat buffer
 */
void afs_flat_call_destructor(struct afs_call *call)
{
        _enter("");

        kfree(call->request);
        call->request = NULL;
        kfree(call->buffer);
        call->buffer = NULL;
}

/*
 * attach the data from a bunch of pages on an inode to a call
 */
static int afs_send_pages(struct afs_call *call, struct msghdr *msg,
                          struct kvec *iov)
{
        struct page *pages[8];
        unsigned count, n, loop, offset, to;
        pgoff_t first = call->first, last = call->last;
        int ret;

        _enter("");

        offset = call->first_offset;
        call->first_offset = 0;

        do {
                _debug("attach %lx-%lx", first, last);

                count = last - first + 1;
                if (count > ARRAY_SIZE(pages))
                        count = ARRAY_SIZE(pages);
                n = find_get_pages_contig(call->mapping, first, count, pages);
                ASSERTCMP(n, ==, count);

                loop = 0;
                do {
                        msg->msg_flags = 0;
                        to = PAGE_SIZE;
                        if (first + loop >= last)
                                to = call->last_to;
                        else
                                msg->msg_flags = MSG_MORE;
                        iov->iov_base = kmap(pages[loop]) + offset;
                        iov->iov_len = to - offset;
                        offset = 0;

                        _debug("- range %u-%u%s",
                               offset, to, msg->msg_flags ? " [more]" : "");
                        iov_iter_kvec(&msg->msg_iter, WRITE | ITER_KVEC,
                                      iov, 1, to - offset);

                        /* have to change the state *before* sending the last
                         * packet as RxRPC might give us the reply before it
                         * returns from sending the request */
                        if (first + loop >= last)
                                call->state = AFS_CALL_AWAIT_REPLY;
                        ret = rxrpc_kernel_send_data(afs_socket, call->rxcall,
                                                     msg, to - offset);
                        kunmap(pages[loop]);
                        if (ret < 0)
                                break;
                } while (++loop < count);
                first += count;

                for (loop = 0; loop < count; loop++)
                        put_page(pages[loop]);
                if (ret < 0)
                        break;
        } while (first <= last);

        _leave(" = %d", ret);
        return ret;
}

/*
 * initiate a call
 */
int afs_make_call(struct in_addr *addr, struct afs_call *call, gfp_t gfp,
                  const struct afs_wait_mode *wait_mode)
{
        struct sockaddr_rxrpc srx;
        struct rxrpc_call *rxcall;
        struct msghdr msg;
        struct kvec iov[1];
        int ret;

        _enter("%x,{%d},", addr->s_addr, ntohs(call->port));

        ASSERT(call->type != NULL);
        ASSERT(call->type->name != NULL);

        _debug("____MAKE %p{%s,%x} [%d]____",
               call, call->type->name, key_serial(call->key),
               atomic_read(&afs_outstanding_calls));

        call->wait_mode = wait_mode;
        INIT_WORK(&call->async_work, afs_process_async_call);

        memset(&srx, 0, sizeof(srx));
        srx.srx_family = AF_RXRPC;
        srx.srx_service = call->service_id;
        srx.transport_type = SOCK_DGRAM;
        srx.transport_len = sizeof(srx.transport.sin);
        srx.transport.sin.sin_family = AF_INET;
        srx.transport.sin.sin_port = call->port;
        memcpy(&srx.transport.sin.sin_addr, addr, 4);

        /* create a call */
        rxcall = rxrpc_kernel_begin_call(afs_socket, &srx, call->key,
                                         (unsigned long) call, gfp,
                                         wait_mode->notify_rx);
        call->key = NULL;
        if (IS_ERR(rxcall)) {
                ret = PTR_ERR(rxcall);
                goto error_kill_call;
        }

        call->rxcall = rxcall;

        /* send the request */
        iov[0].iov_base = call->request;
        iov[0].iov_len  = call->request_size;

        msg.msg_name            = NULL;
        msg.msg_namelen         = 0;
        iov_iter_kvec(&msg.msg_iter, WRITE | ITER_KVEC, iov, 1,
                      call->request_size);
        msg.msg_control         = NULL;
        msg.msg_controllen      = 0;
        msg.msg_flags           = (call->send_pages ? MSG_MORE : 0);

        /* have to change the state *before* sending the last packet as RxRPC
         * might give us the reply before it returns from sending the
         * request */
        if (!call->send_pages)
                call->state = AFS_CALL_AWAIT_REPLY;
        ret = rxrpc_kernel_send_data(afs_socket, rxcall,
                                     &msg, call->request_size);
        if (ret < 0)
                goto error_do_abort;

        if (call->send_pages) {
                ret = afs_send_pages(call, &msg, iov);
                if (ret < 0)
                        goto error_do_abort;
        }

        /* at this point, an async call may no longer exist as it may have
         * already completed */
        return wait_mode->wait(call);

error_do_abort:
        rxrpc_kernel_abort_call(afs_socket, rxcall, RX_USER_ABORT, -ret, "KSD");
error_kill_call:
        afs_end_call(call);
        _leave(" = %d", ret);
        return ret;
}

/*
 * deliver messages to a call
 */
static void afs_deliver_to_call(struct afs_call *call)
{
        u32 abort_code;
        int ret;

        _enter("%s", call->type->name);

        while (call->state == AFS_CALL_AWAIT_REPLY ||
               call->state == AFS_CALL_AWAIT_OP_ID ||
               call->state == AFS_CALL_AWAIT_REQUEST ||
               call->state == AFS_CALL_AWAIT_ACK
               ) {
                if (call->state == AFS_CALL_AWAIT_ACK) {
                        size_t offset = 0;
                        ret = rxrpc_kernel_recv_data(afs_socket, call->rxcall,
                                                     NULL, 0, &offset, false,
                                                     &call->abort_code);
                        if (ret == -EINPROGRESS || ret == -EAGAIN)
                                return;
                        if (ret == 1 || ret < 0) {
                                call->state = AFS_CALL_COMPLETE;
                                goto done;
                        }
                        return;
                }

                ret = call->type->deliver(call);
                switch (ret) {
                case 0:
                        if (call->state == AFS_CALL_AWAIT_REPLY)
                                call->state = AFS_CALL_COMPLETE;
                        goto done;
                case -EINPROGRESS:
                case -EAGAIN:
                        goto out;
                case -ENOTCONN:
                        abort_code = RX_CALL_DEAD;
                        rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                                abort_code, -ret, "KNC");
                        goto do_abort;
                case -ENOTSUPP:
                        abort_code = RX_INVALID_OPERATION;
                        rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                                abort_code, -ret, "KIV");
                        goto do_abort;
                case -ENODATA:
                case -EBADMSG:
                case -EMSGSIZE:
                default:
                        abort_code = RXGEN_CC_UNMARSHAL;
                        if (call->state != AFS_CALL_AWAIT_REPLY)
                                abort_code = RXGEN_SS_UNMARSHAL;
                        rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                                abort_code, EBADMSG, "KUM");
                        goto do_abort;
                }
        }

done:
        if (call->state == AFS_CALL_COMPLETE && call->incoming)
                afs_end_call(call);
out:
        _leave("");
        return;

do_abort:
        call->error = ret;
        call->state = AFS_CALL_COMPLETE;
        goto done;
}

/*
 * wait synchronously for a call to complete
 */
static int afs_wait_for_call_to_complete(struct afs_call *call)
{
        const char *abort_why;
        int ret;

        DECLARE_WAITQUEUE(myself, current);

        _enter("");

        add_wait_queue(&call->waitq, &myself);
        for (;;) {
                set_current_state(TASK_INTERRUPTIBLE);

                /* deliver any messages that are in the queue */
                if (call->state < AFS_CALL_COMPLETE && call->need_attention) {
                        call->need_attention = false;
                        __set_current_state(TASK_RUNNING);
                        afs_deliver_to_call(call);
                        continue;
                }

                abort_why = "KWC";
                ret = call->error;
                if (call->state == AFS_CALL_COMPLETE)
                        break;
                abort_why = "KWI";
                ret = -EINTR;
                if (signal_pending(current))
                        break;
                schedule();
        }

        remove_wait_queue(&call->waitq, &myself);
        __set_current_state(TASK_RUNNING);

        /* kill the call */
        if (call->state < AFS_CALL_COMPLETE) {
                _debug("call incomplete");
                rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                        RX_CALL_DEAD, -ret, abort_why);
        }

        _debug("call complete");
        afs_end_call(call);
        _leave(" = %d", ret);
        return ret;
}

/*
 * wake up a waiting call
 */
static void afs_wake_up_call_waiter(struct sock *sk, struct rxrpc_call *rxcall,
                                    unsigned long call_user_ID)
{
        struct afs_call *call = (struct afs_call *)call_user_ID;

        call->need_attention = true;
        wake_up(&call->waitq);
}

/*
 * wake up an asynchronous call
 */
static void afs_wake_up_async_call(struct sock *sk, struct rxrpc_call *rxcall,
                                   unsigned long call_user_ID)
{
        struct afs_call *call = (struct afs_call *)call_user_ID;

        call->need_attention = true;
        queue_work(afs_async_calls, &call->async_work);
}

/*
 * put a call into asynchronous mode
 * - mustn't touch the call descriptor as the call my have completed by the
 *   time we get here
 */
static int afs_dont_wait_for_call_to_complete(struct afs_call *call)
{
        _enter("");
        return -EINPROGRESS;
}

/*
 * delete an asynchronous call
 */
static void afs_delete_async_call(struct work_struct *work)
{
        struct afs_call *call = container_of(work, struct afs_call, async_work);

        _enter("");

        afs_free_call(call);

        _leave("");
}

/*
 * perform processing on an asynchronous call
 */
static void afs_process_async_call(struct work_struct *work)
{
        struct afs_call *call = container_of(work, struct afs_call, async_work);

        _enter("");

        if (call->state < AFS_CALL_COMPLETE && call->need_attention) {
                call->need_attention = false;
                afs_deliver_to_call(call);
        }

        if (call->state == AFS_CALL_COMPLETE && call->wait_mode) {
                if (call->wait_mode->async_complete)
                        call->wait_mode->async_complete(call->reply,
                                                        call->error);
                call->reply = NULL;

                /* kill the call */
                afs_end_call_nofree(call);

                /* we can't just delete the call because the work item may be
                 * queued */
                call->async_work.func = afs_delete_async_call;
                queue_work(afs_async_calls, &call->async_work);
        }

        _leave("");
}

static void afs_rx_attach(struct rxrpc_call *rxcall, unsigned long user_call_ID)
{
        struct afs_call *call = (struct afs_call *)user_call_ID;

        call->rxcall = rxcall;
}

/*
 * Charge the incoming call preallocation.
 */
static void afs_charge_preallocation(struct work_struct *work)
{
        struct afs_call *call = afs_spare_incoming_call;

        for (;;) {
                if (!call) {
                        call = kzalloc(sizeof(struct afs_call), GFP_KERNEL);
                        if (!call)
                                break;

                        INIT_WORK(&call->async_work, afs_process_async_call);
                        call->wait_mode = &afs_async_incoming_call;
                        call->type = &afs_RXCMxxxx;
                        init_waitqueue_head(&call->waitq);
                        call->state = AFS_CALL_AWAIT_OP_ID;
                }

                if (rxrpc_kernel_charge_accept(afs_socket,
                                               afs_wake_up_async_call,
                                               afs_rx_attach,
                                               (unsigned long)call,
                                               GFP_KERNEL) < 0)
                        break;
                call = NULL;
        }
        afs_spare_incoming_call = call;
}

/*
 * Discard a preallocated call when a socket is shut down.
 */
static void afs_rx_discard_new_call(struct rxrpc_call *rxcall,
                                    unsigned long user_call_ID)
{
        struct afs_call *call = (struct afs_call *)user_call_ID;

        atomic_inc(&afs_outstanding_calls);
        call->rxcall = NULL;
        afs_free_call(call);
}

/*
 * Notification of an incoming call.
 */
static void afs_rx_new_call(struct sock *sk, struct rxrpc_call *rxcall,
                            unsigned long user_call_ID)
{
        atomic_inc(&afs_outstanding_calls);
        queue_work(afs_wq, &afs_charge_preallocation_work);
}

/*
 * Grab the operation ID from an incoming cache manager call.  The socket
 * buffer is discarded on error or if we don't yet have sufficient data.
 */
static int afs_deliver_cm_op_id(struct afs_call *call)
{
        int ret;

        _enter("{%zu}", call->offset);

        ASSERTCMP(call->offset, <, 4);

        /* the operation ID forms the first four bytes of the request data */
        ret = afs_extract_data(call, &call->tmp, 4, true);
        if (ret < 0)
                return ret;

        call->operation_ID = ntohl(call->tmp);
        call->state = AFS_CALL_AWAIT_REQUEST;
        call->offset = 0;

        /* ask the cache manager to route the call (it'll change the call type
         * if successful) */
        if (!afs_cm_incoming_call(call))
                return -ENOTSUPP;

        /* pass responsibility for the remainer of this message off to the
         * cache manager op */
        return call->type->deliver(call);
}

/*
 * send an empty reply
 */
void afs_send_empty_reply(struct afs_call *call)
{
        struct msghdr msg;

        _enter("");

        msg.msg_name            = NULL;
        msg.msg_namelen         = 0;
        iov_iter_kvec(&msg.msg_iter, WRITE | ITER_KVEC, NULL, 0, 0);
        msg.msg_control         = NULL;
        msg.msg_controllen      = 0;
        msg.msg_flags           = 0;

        call->state = AFS_CALL_AWAIT_ACK;
        switch (rxrpc_kernel_send_data(afs_socket, call->rxcall, &msg, 0)) {
        case 0:
                _leave(" [replied]");
                return;

        case -ENOMEM:
                _debug("oom");
                rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                        RX_USER_ABORT, ENOMEM, "KOO");
        default:
                afs_end_call(call);
                _leave(" [error]");
                return;
        }
}

/*
 * send a simple reply
 */
void afs_send_simple_reply(struct afs_call *call, const void *buf, size_t len)
{
        struct msghdr msg;
        struct kvec iov[1];
        int n;

        _enter("");

        iov[0].iov_base         = (void *) buf;
        iov[0].iov_len          = len;
        msg.msg_name            = NULL;
        msg.msg_namelen         = 0;
        iov_iter_kvec(&msg.msg_iter, WRITE | ITER_KVEC, iov, 1, len);
        msg.msg_control         = NULL;
        msg.msg_controllen      = 0;
        msg.msg_flags           = 0;

        call->state = AFS_CALL_AWAIT_ACK;
        n = rxrpc_kernel_send_data(afs_socket, call->rxcall, &msg, len);
        if (n >= 0) {
                /* Success */
                _leave(" [replied]");
                return;
        }

        if (n == -ENOMEM) {
                _debug("oom");
                rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                        RX_USER_ABORT, ENOMEM, "KOO");
        }
        afs_end_call(call);
        _leave(" [error]");
}

/*
 * Extract a piece of data from the received data socket buffers.
 */
int afs_extract_data(struct afs_call *call, void *buf, size_t count,
                     bool want_more)
{
        int ret;

        _enter("{%s,%zu},,%zu,%d",
               call->type->name, call->offset, count, want_more);

        ASSERTCMP(call->offset, <=, count);

        ret = rxrpc_kernel_recv_data(afs_socket, call->rxcall,
                                     buf, count, &call->offset,
                                     want_more, &call->abort_code);
        if (ret == 0 || ret == -EAGAIN)
                return ret;

        if (ret == 1) {
                switch (call->state) {
                case AFS_CALL_AWAIT_REPLY:
                        call->state = AFS_CALL_COMPLETE;
                        break;
                case AFS_CALL_AWAIT_REQUEST:
                        call->state = AFS_CALL_REPLYING;
                        break;
                default:
                        break;
                }
                return 0;
        }

        if (ret == -ECONNABORTED)
                call->error = call->type->abort_to_error(call->abort_code);
        else
                call->error = ret;
        call->state = AFS_CALL_COMPLETE;
        return ret;
}