/* incoming 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.
 */

#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/errqueue.h>
#include <linux/udp.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/icmp.h>
#include <linux/gfp.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <net/ip.h>
#include "ar-internal.h"

/*
 * generate a connection-level abort
 */
static int rxrpc_busy(struct rxrpc_local *local, struct sockaddr_rxrpc *srx,
                      struct rxrpc_header *hdr)
{
        struct msghdr msg;
        struct kvec iov[1];
        size_t len;
        int ret;

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

        msg.msg_name    = &srx->transport.sin;
        msg.msg_namelen = sizeof(srx->transport.sin);
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags   = 0;

        hdr->seq        = 0;
        hdr->type       = RXRPC_PACKET_TYPE_BUSY;
        hdr->flags      = 0;
        hdr->userStatus = 0;
        hdr->_rsvd      = 0;

        iov[0].iov_base = hdr;
        iov[0].iov_len  = sizeof(*hdr);

        len = iov[0].iov_len;

        hdr->serial = htonl(1);
        _proto("Tx BUSY %%%u", ntohl(hdr->serial));

        ret = kernel_sendmsg(local->socket, &msg, iov, 1, len);
        if (ret < 0) {
                _leave(" = -EAGAIN [sendmsg failed: %d]", ret);
                return -EAGAIN;
        }

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

/*
 * accept an incoming call that needs peer, transport and/or connection setting
 * up
 */
static int rxrpc_accept_incoming_call(struct rxrpc_local *local,
                                      struct rxrpc_sock *rx,
                                      struct sk_buff *skb,
                                      struct sockaddr_rxrpc *srx)
{
        struct rxrpc_connection *conn;
        struct rxrpc_transport *trans;
        struct rxrpc_skb_priv *sp, *nsp;
        struct rxrpc_peer *peer;
        struct rxrpc_call *call;
        struct sk_buff *notification;
        int ret;

        _enter("");

        sp = rxrpc_skb(skb);

        /* get a notification message to send to the server app */
        notification = alloc_skb(0, GFP_NOFS);
        if (!notification) {
                _debug("no memory");
                ret = -ENOMEM;
                goto error_nofree;
        }
        rxrpc_new_skb(notification);
        notification->mark = RXRPC_SKB_MARK_NEW_CALL;

        peer = rxrpc_get_peer(srx, GFP_NOIO);
        if (IS_ERR(peer)) {
                _debug("no peer");
                ret = -EBUSY;
                goto error;
        }

        trans = rxrpc_get_transport(local, peer, GFP_NOIO);
        rxrpc_put_peer(peer);
        if (IS_ERR(trans)) {
                _debug("no trans");
                ret = -EBUSY;
                goto error;
        }

        conn = rxrpc_incoming_connection(trans, &sp->hdr, GFP_NOIO);
        rxrpc_put_transport(trans);
        if (IS_ERR(conn)) {
                _debug("no conn");
                ret = PTR_ERR(conn);
                goto error;
        }

        call = rxrpc_incoming_call(rx, conn, &sp->hdr, GFP_NOIO);
        rxrpc_put_connection(conn);
        if (IS_ERR(call)) {
                _debug("no call");
                ret = PTR_ERR(call);
                goto error;
        }

        /* attach the call to the socket */
        read_lock_bh(&local->services_lock);
        if (rx->sk.sk_state == RXRPC_CLOSE)
                goto invalid_service;

        write_lock(&rx->call_lock);
        if (!test_and_set_bit(RXRPC_CALL_INIT_ACCEPT, &call->flags)) {
                rxrpc_get_call(call);

                spin_lock(&call->conn->state_lock);
                if (sp->hdr.securityIndex > 0 &&
                    call->conn->state == RXRPC_CONN_SERVER_UNSECURED) {
                        _debug("await conn sec");
                        list_add_tail(&call->accept_link, &rx->secureq);
                        call->conn->state = RXRPC_CONN_SERVER_CHALLENGING;
                        atomic_inc(&call->conn->usage);
                        set_bit(RXRPC_CONN_CHALLENGE, &call->conn->events);
                        rxrpc_queue_conn(call->conn);
                } else {
                        _debug("conn ready");
                        call->state = RXRPC_CALL_SERVER_ACCEPTING;
                        list_add_tail(&call->accept_link, &rx->acceptq);
                        rxrpc_get_call(call);
                        nsp = rxrpc_skb(notification);
                        nsp->call = call;

                        ASSERTCMP(atomic_read(&call->usage), >=, 3);

                        _debug("notify");
                        spin_lock(&call->lock);
                        ret = rxrpc_queue_rcv_skb(call, notification, true,
                                                  false);
                        spin_unlock(&call->lock);
                        notification = NULL;
                        BUG_ON(ret < 0);
                }
                spin_unlock(&call->conn->state_lock);

                _debug("queued");
        }
        write_unlock(&rx->call_lock);

        _debug("process");
        rxrpc_fast_process_packet(call, skb);

        _debug("done");
        read_unlock_bh(&local->services_lock);
        rxrpc_free_skb(notification);
        rxrpc_put_call(call);
        _leave(" = 0");
        return 0;

invalid_service:
        _debug("invalid");
        read_unlock_bh(&local->services_lock);

        read_lock_bh(&call->state_lock);
        if (!test_bit(RXRPC_CALL_RELEASE, &call->flags) &&
            !test_and_set_bit(RXRPC_CALL_RELEASE, &call->events)) {
                rxrpc_get_call(call);
                rxrpc_queue_call(call);
        }
        read_unlock_bh(&call->state_lock);
        rxrpc_put_call(call);
        ret = -ECONNREFUSED;
error:
        rxrpc_free_skb(notification);
error_nofree:
        _leave(" = %d", ret);
        return ret;
}

/*
 * accept incoming calls that need peer, transport and/or connection setting up
 * - the packets we get are all incoming client DATA packets that have seq == 1
 */
void rxrpc_accept_incoming_calls(struct work_struct *work)
{
        struct rxrpc_local *local =
                container_of(work, struct rxrpc_local, acceptor);
        struct rxrpc_skb_priv *sp;
        struct sockaddr_rxrpc srx;
        struct rxrpc_sock *rx;
        struct sk_buff *skb;
        __be16 service_id;
        int ret;

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

        read_lock_bh(&rxrpc_local_lock);
        if (atomic_read(&local->usage) > 0)
                rxrpc_get_local(local);
        else
                local = NULL;
        read_unlock_bh(&rxrpc_local_lock);
        if (!local) {
                _leave(" [local dead]");
                return;
        }

process_next_packet:
        skb = skb_dequeue(&local->accept_queue);
        if (!skb) {
                rxrpc_put_local(local);
                _leave("\n");
                return;
        }

        _net("incoming call skb %p", skb);

        sp = rxrpc_skb(skb);

        /* determine the remote address */
        memset(&srx, 0, sizeof(srx));
        srx.srx_family = AF_RXRPC;
        srx.transport.family = local->srx.transport.family;
        srx.transport_type = local->srx.transport_type;
        switch (srx.transport.family) {
        case AF_INET:
                srx.transport_len = sizeof(struct sockaddr_in);
                srx.transport.sin.sin_port = udp_hdr(skb)->source;
                srx.transport.sin.sin_addr.s_addr = ip_hdr(skb)->saddr;
                break;
        default:
                goto busy;
        }

        /* get the socket providing the service */
        service_id = sp->hdr.serviceId;
        read_lock_bh(&local->services_lock);
        list_for_each_entry(rx, &local->services, listen_link) {
                if (rx->service_id == service_id &&
                    rx->sk.sk_state != RXRPC_CLOSE)
                        goto found_service;
        }
        read_unlock_bh(&local->services_lock);
        goto invalid_service;

found_service:
        _debug("found service %hd", ntohs(rx->service_id));
        if (sk_acceptq_is_full(&rx->sk))
                goto backlog_full;
        sk_acceptq_added(&rx->sk);
        sock_hold(&rx->sk);
        read_unlock_bh(&local->services_lock);

        ret = rxrpc_accept_incoming_call(local, rx, skb, &srx);
        if (ret < 0)
                sk_acceptq_removed(&rx->sk);
        sock_put(&rx->sk);
        switch (ret) {
        case -ECONNRESET: /* old calls are ignored */
        case -ECONNABORTED: /* aborted calls are reaborted or ignored */
        case 0:
                goto process_next_packet;
        case -ECONNREFUSED:
                goto invalid_service;
        case -EBUSY:
                goto busy;
        case -EKEYREJECTED:
                goto security_mismatch;
        default:
                BUG();
        }

backlog_full:
        read_unlock_bh(&local->services_lock);
busy:
        rxrpc_busy(local, &srx, &sp->hdr);
        rxrpc_free_skb(skb);
        goto process_next_packet;

invalid_service:
        skb->priority = RX_INVALID_OPERATION;
        rxrpc_reject_packet(local, skb);
        goto process_next_packet;

        /* can't change connection security type mid-flow */
security_mismatch:
        skb->priority = RX_PROTOCOL_ERROR;
        rxrpc_reject_packet(local, skb);
        goto process_next_packet;
}

/*
 * handle acceptance of a call by userspace
 * - assign the user call ID to the call at the front of the queue
 */
struct rxrpc_call *rxrpc_accept_call(struct rxrpc_sock *rx,
                                     unsigned long user_call_ID)
{
        struct rxrpc_call *call;
        struct rb_node *parent, **pp;
        int ret;

        _enter(",%lx", user_call_ID);

        ASSERT(!irqs_disabled());

        write_lock(&rx->call_lock);

        ret = -ENODATA;
        if (list_empty(&rx->acceptq))
                goto out;

        /* check the user ID isn't already in use */
        ret = -EBADSLT;
        pp = &rx->calls.rb_node;
        parent = NULL;
        while (*pp) {
                parent = *pp;
                call = rb_entry(parent, struct rxrpc_call, sock_node);

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

        /* dequeue the first call and check it's still valid */
        call = list_entry(rx->acceptq.next, struct rxrpc_call, accept_link);
        list_del_init(&call->accept_link);
        sk_acceptq_removed(&rx->sk);

        write_lock_bh(&call->state_lock);
        switch (call->state) {
        case RXRPC_CALL_SERVER_ACCEPTING:
                call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
                break;
        case RXRPC_CALL_REMOTELY_ABORTED:
        case RXRPC_CALL_LOCALLY_ABORTED:
                ret = -ECONNABORTED;
                goto out_release;
        case RXRPC_CALL_NETWORK_ERROR:
                ret = call->conn->error;
                goto out_release;
        case RXRPC_CALL_DEAD:
                ret = -ETIME;
                goto out_discard;
        default:
                BUG();
        }

        /* formalise the acceptance */
        call->user_call_ID = user_call_ID;
        rb_link_node(&call->sock_node, parent, pp);
        rb_insert_color(&call->sock_node, &rx->calls);
        if (test_and_set_bit(RXRPC_CALL_HAS_USERID, &call->flags))
                BUG();
        if (test_and_set_bit(RXRPC_CALL_ACCEPTED, &call->events))
                BUG();
        rxrpc_queue_call(call);

        rxrpc_get_call(call);
        write_unlock_bh(&call->state_lock);
        write_unlock(&rx->call_lock);
        _leave(" = %p{%d}", call, call->debug_id);
        return call;

        /* if the call is already dying or dead, then we leave the socket's ref
         * on it to be released by rxrpc_dead_call_expired() as induced by
         * rxrpc_release_call() */
out_release:
        _debug("release %p", call);
        if (!test_bit(RXRPC_CALL_RELEASED, &call->flags) &&
            !test_and_set_bit(RXRPC_CALL_RELEASE, &call->events))
                rxrpc_queue_call(call);
out_discard:
        write_unlock_bh(&call->state_lock);
        _debug("discard %p", call);
out:
        write_unlock(&rx->call_lock);
        _leave(" = %d", ret);
        return ERR_PTR(ret);
}

/*
 * handle rejectance of a call by userspace
 * - reject the call at the front of the queue
 */
int rxrpc_reject_call(struct rxrpc_sock *rx)
{
        struct rxrpc_call *call;
        int ret;

        _enter("");

        ASSERT(!irqs_disabled());

        write_lock(&rx->call_lock);

        ret = -ENODATA;
        if (list_empty(&rx->acceptq))
                goto out;

        /* dequeue the first call and check it's still valid */
        call = list_entry(rx->acceptq.next, struct rxrpc_call, accept_link);
        list_del_init(&call->accept_link);
        sk_acceptq_removed(&rx->sk);

        write_lock_bh(&call->state_lock);
        switch (call->state) {
        case RXRPC_CALL_SERVER_ACCEPTING:
                call->state = RXRPC_CALL_SERVER_BUSY;
                if (test_and_set_bit(RXRPC_CALL_REJECT_BUSY, &call->events))
                        rxrpc_queue_call(call);
                ret = 0;
                goto out_release;
        case RXRPC_CALL_REMOTELY_ABORTED:
        case RXRPC_CALL_LOCALLY_ABORTED:
                ret = -ECONNABORTED;
                goto out_release;
        case RXRPC_CALL_NETWORK_ERROR:
                ret = call->conn->error;
                goto out_release;
        case RXRPC_CALL_DEAD:
                ret = -ETIME;
                goto out_discard;
        default:
                BUG();
        }

        /* if the call is already dying or dead, then we leave the socket's ref
         * on it to be released by rxrpc_dead_call_expired() as induced by
         * rxrpc_release_call() */
out_release:
        _debug("release %p", call);
        if (!test_bit(RXRPC_CALL_RELEASED, &call->flags) &&
            !test_and_set_bit(RXRPC_CALL_RELEASE, &call->events))
                rxrpc_queue_call(call);
out_discard:
        write_unlock_bh(&call->state_lock);
        _debug("discard %p", call);
out:
        write_unlock(&rx->call_lock);
        _leave(" = %d", ret);
        return ret;
}

/**
 * rxrpc_kernel_accept_call - Allow a kernel service to accept an incoming call
 * @sock: The socket on which the impending call is waiting
 * @user_call_ID: The tag to attach to the call
 *
 * Allow a kernel service to accept an incoming call, assuming the incoming
 * call is still valid.
 */
struct rxrpc_call *rxrpc_kernel_accept_call(struct socket *sock,
                                            unsigned long user_call_ID)
{
        struct rxrpc_call *call;

        _enter(",%lx", user_call_ID);
        call = rxrpc_accept_call(rxrpc_sk(sock->sk), user_call_ID);
        _leave(" = %p", call);
        return call;
}

EXPORT_SYMBOL(rxrpc_kernel_accept_call);

/**
 * rxrpc_kernel_reject_call - Allow a kernel service to reject an incoming call
 * @sock: The socket on which the impending call is waiting
 *
 * Allow a kernel service to reject an incoming call with a BUSY message,
 * assuming the incoming call is still valid.
 */
int rxrpc_kernel_reject_call(struct socket *sock)
{
        int ret;

        _enter("");
        ret = rxrpc_reject_call(rxrpc_sk(sock->sk));
        _leave(" = %d", ret);
        return ret;
}

EXPORT_SYMBOL(rxrpc_kernel_reject_call);