/* RxRPC packet transmission
 *
 * 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/net.h>
#include <linux/gfp.h>
#include <linux/skbuff.h>
#include <linux/circ_buf.h>
#include <linux/export.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "ar-internal.h"

/*
 * Time till packet resend (in jiffies).
 */
unsigned int rxrpc_resend_timeout = 4 * HZ;

static int rxrpc_send_data(struct rxrpc_sock *rx,
                           struct rxrpc_call *call,
                           struct msghdr *msg, size_t len);

/*
 * extract control messages from the sendmsg() control buffer
 */
static int rxrpc_sendmsg_cmsg(struct rxrpc_sock *rx, struct msghdr *msg,
                              unsigned long *user_call_ID,
                              enum rxrpc_command *command,
                              u32 *abort_code,
                              bool server)
{
        struct cmsghdr *cmsg;
        int len;

        *command = RXRPC_CMD_SEND_DATA;

        if (msg->msg_controllen == 0)
                return -EINVAL;

        for_each_cmsghdr(cmsg, msg) {
                if (!CMSG_OK(msg, cmsg))
                        return -EINVAL;

                len = cmsg->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr));
                _debug("CMSG %d, %d, %d",
                       cmsg->cmsg_level, cmsg->cmsg_type, len);

                if (cmsg->cmsg_level != SOL_RXRPC)
                        continue;

                switch (cmsg->cmsg_type) {
                case RXRPC_USER_CALL_ID:
                        if (msg->msg_flags & MSG_CMSG_COMPAT) {
                                if (len != sizeof(u32))
                                        return -EINVAL;
                                *user_call_ID = *(u32 *) CMSG_DATA(cmsg);
                        } else {
                                if (len != sizeof(unsigned long))
                                        return -EINVAL;
                                *user_call_ID = *(unsigned long *)
                                        CMSG_DATA(cmsg);
                        }
                        _debug("User Call ID %lx", *user_call_ID);
                        break;

                case RXRPC_ABORT:
                        if (*command != RXRPC_CMD_SEND_DATA)
                                return -EINVAL;
                        *command = RXRPC_CMD_SEND_ABORT;
                        if (len != sizeof(*abort_code))
                                return -EINVAL;
                        *abort_code = *(unsigned int *) CMSG_DATA(cmsg);
                        _debug("Abort %x", *abort_code);
                        if (*abort_code == 0)
                                return -EINVAL;
                        break;

                case RXRPC_ACCEPT:
                        if (*command != RXRPC_CMD_SEND_DATA)
                                return -EINVAL;
                        *command = RXRPC_CMD_ACCEPT;
                        if (len != 0)
                                return -EINVAL;
                        if (!server)
                                return -EISCONN;
                        break;

                default:
                        return -EINVAL;
                }
        }

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

/*
 * abort a call, sending an ABORT packet to the peer
 */
static void rxrpc_send_abort(struct rxrpc_call *call, u32 abort_code)
{
        write_lock_bh(&call->state_lock);

        if (call->state <= RXRPC_CALL_COMPLETE) {
                call->state = RXRPC_CALL_LOCALLY_ABORTED;
                call->local_abort = abort_code;
                set_bit(RXRPC_CALL_EV_ABORT, &call->events);
                del_timer_sync(&call->resend_timer);
                del_timer_sync(&call->ack_timer);
                clear_bit(RXRPC_CALL_EV_RESEND_TIMER, &call->events);
                clear_bit(RXRPC_CALL_EV_ACK, &call->events);
                clear_bit(RXRPC_CALL_RUN_RTIMER, &call->flags);
                rxrpc_queue_call(call);
        }

        write_unlock_bh(&call->state_lock);
}

/*
 * send a message forming part of a client call through an RxRPC socket
 * - caller holds the socket locked
 * - the socket may be either a client socket or a server socket
 */
int rxrpc_client_sendmsg(struct rxrpc_sock *rx, struct rxrpc_transport *trans,
                         struct msghdr *msg, size_t len)
{
        struct rxrpc_conn_bundle *bundle;
        enum rxrpc_command cmd;
        struct rxrpc_call *call;
        unsigned long user_call_ID = 0;
        struct key *key;
        u16 service_id;
        u32 abort_code = 0;
        int ret;

        _enter("");

        ASSERT(trans != NULL);

        ret = rxrpc_sendmsg_cmsg(rx, msg, &user_call_ID, &cmd, &abort_code,
                                 false);
        if (ret < 0)
                return ret;

        bundle = NULL;
        if (trans) {
                service_id = rx->srx.srx_service;
                if (msg->msg_name) {
                        DECLARE_SOCKADDR(struct sockaddr_rxrpc *, srx,
                                         msg->msg_name);
                        service_id = srx->srx_service;
                }
                key = rx->key;
                if (key && !rx->key->payload.data[0])
                        key = NULL;
                bundle = rxrpc_get_bundle(rx, trans, key, service_id,
                                          GFP_KERNEL);
                if (IS_ERR(bundle))
                        return PTR_ERR(bundle);
        }

        call = rxrpc_get_client_call(rx, trans, bundle, user_call_ID,
                                     abort_code == 0, GFP_KERNEL);
        if (trans)
                rxrpc_put_bundle(trans, bundle);
        if (IS_ERR(call)) {
                _leave(" = %ld", PTR_ERR(call));
                return PTR_ERR(call);
        }

        _debug("CALL %d USR %lx ST %d on CONN %p",
               call->debug_id, call->user_call_ID, call->state, call->conn);

        if (call->state >= RXRPC_CALL_COMPLETE) {
                /* it's too late for this call */
                ret = -ESHUTDOWN;
        } else if (cmd == RXRPC_CMD_SEND_ABORT) {
                rxrpc_send_abort(call, abort_code);
        } else if (cmd != RXRPC_CMD_SEND_DATA) {
                ret = -EINVAL;
        } else if (call->state != RXRPC_CALL_CLIENT_SEND_REQUEST) {
                /* request phase complete for this client call */
                ret = -EPROTO;
        } else {
                ret = rxrpc_send_data(rx, call, msg, len);
        }

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

/**
 * rxrpc_kernel_send_data - Allow a kernel service to send data on a call
 * @call: The call to send data through
 * @msg: The data to send
 * @len: The amount of data to send
 *
 * Allow a kernel service to send data on a call.  The call must be in an state
 * appropriate to sending data.  No control data should be supplied in @msg,
 * nor should an address be supplied.  MSG_MORE should be flagged if there's
 * more data to come, otherwise this data will end the transmission phase.
 */
int rxrpc_kernel_send_data(struct rxrpc_call *call, struct msghdr *msg,
                           size_t len)
{
        int ret;

        _enter("{%d,%s},", call->debug_id, rxrpc_call_states[call->state]);

        ASSERTCMP(msg->msg_name, ==, NULL);
        ASSERTCMP(msg->msg_control, ==, NULL);

        lock_sock(&call->socket->sk);

        _debug("CALL %d USR %lx ST %d on CONN %p",
               call->debug_id, call->user_call_ID, call->state, call->conn);

        if (call->state >= RXRPC_CALL_COMPLETE) {
                ret = -ESHUTDOWN; /* it's too late for this call */
        } else if (call->state != RXRPC_CALL_CLIENT_SEND_REQUEST &&
                   call->state != RXRPC_CALL_SERVER_ACK_REQUEST &&
                   call->state != RXRPC_CALL_SERVER_SEND_REPLY) {
                ret = -EPROTO; /* request phase complete for this client call */
        } else {
                ret = rxrpc_send_data(call->socket, call, msg, len);
        }

        release_sock(&call->socket->sk);
        _leave(" = %d", ret);
        return ret;
}

EXPORT_SYMBOL(rxrpc_kernel_send_data);

/**
 * rxrpc_kernel_abort_call - Allow a kernel service to abort a call
 * @call: The call to be aborted
 * @abort_code: The abort code to stick into the ABORT packet
 *
 * Allow a kernel service to abort a call, if it's still in an abortable state.
 */
void rxrpc_kernel_abort_call(struct rxrpc_call *call, u32 abort_code)
{
        _enter("{%d},%d", call->debug_id, abort_code);

        lock_sock(&call->socket->sk);

        _debug("CALL %d USR %lx ST %d on CONN %p",
               call->debug_id, call->user_call_ID, call->state, call->conn);

        if (call->state < RXRPC_CALL_COMPLETE)
                rxrpc_send_abort(call, abort_code);

        release_sock(&call->socket->sk);
        _leave("");
}

EXPORT_SYMBOL(rxrpc_kernel_abort_call);

/*
 * send a message through a server socket
 * - caller holds the socket locked
 */
int rxrpc_server_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg, size_t len)
{
        enum rxrpc_command cmd;
        struct rxrpc_call *call;
        unsigned long user_call_ID = 0;
        u32 abort_code = 0;
        int ret;

        _enter("");

        ret = rxrpc_sendmsg_cmsg(rx, msg, &user_call_ID, &cmd, &abort_code,
                                 true);
        if (ret < 0)
                return ret;

        if (cmd == RXRPC_CMD_ACCEPT) {
                call = rxrpc_accept_call(rx, user_call_ID);
                if (IS_ERR(call))
                        return PTR_ERR(call);
                rxrpc_put_call(call);
                return 0;
        }

        call = rxrpc_find_server_call(rx, user_call_ID);
        if (!call)
                return -EBADSLT;
        if (call->state >= RXRPC_CALL_COMPLETE) {
                ret = -ESHUTDOWN;
                goto out;
        }

        switch (cmd) {
        case RXRPC_CMD_SEND_DATA:
                if (call->state != RXRPC_CALL_CLIENT_SEND_REQUEST &&
                    call->state != RXRPC_CALL_SERVER_ACK_REQUEST &&
                    call->state != RXRPC_CALL_SERVER_SEND_REPLY) {
                        /* Tx phase not yet begun for this call */
                        ret = -EPROTO;
                        break;
                }

                ret = rxrpc_send_data(rx, call, msg, len);
                break;

        case RXRPC_CMD_SEND_ABORT:
                rxrpc_send_abort(call, abort_code);
                break;
        default:
                BUG();
        }

        out:
        rxrpc_put_call(call);
        _leave(" = %d", ret);
        return ret;
}

/*
 * send a packet through the transport endpoint
 */
int rxrpc_send_packet(struct rxrpc_transport *trans, struct sk_buff *skb)
{
        struct kvec iov[1];
        struct msghdr msg;
        int ret, opt;

        _enter(",{%d}", skb->len);

        iov[0].iov_base = skb->head;
        iov[0].iov_len = skb->len;

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

        /* send the packet with the don't fragment bit set if we currently
         * think it's small enough */
        if (skb->len - sizeof(struct rxrpc_wire_header) < trans->peer->maxdata) {
                down_read(&trans->local->defrag_sem);
                /* send the packet by UDP
                 * - returns -EMSGSIZE if UDP would have to fragment the packet
                 *   to go out of the interface
                 *   - in which case, we'll have processed the ICMP error
                 *     message and update the peer record
                 */
                ret = kernel_sendmsg(trans->local->socket, &msg, iov, 1,
                                     iov[0].iov_len);

                up_read(&trans->local->defrag_sem);
                if (ret == -EMSGSIZE)
                        goto send_fragmentable;

                _leave(" = %d [%u]", ret, trans->peer->maxdata);
                return ret;
        }

send_fragmentable:
        /* attempt to send this message with fragmentation enabled */
        _debug("send fragment");

        down_write(&trans->local->defrag_sem);
        opt = IP_PMTUDISC_DONT;
        ret = kernel_setsockopt(trans->local->socket, SOL_IP, IP_MTU_DISCOVER,
                                (char *) &opt, sizeof(opt));
        if (ret == 0) {
                ret = kernel_sendmsg(trans->local->socket, &msg, iov, 1,
                                     iov[0].iov_len);

                opt = IP_PMTUDISC_DO;
                kernel_setsockopt(trans->local->socket, SOL_IP,
                                  IP_MTU_DISCOVER, (char *) &opt, sizeof(opt));
        }

        up_write(&trans->local->defrag_sem);
        _leave(" = %d [frag %u]", ret, trans->peer->maxdata);
        return ret;
}

/*
 * wait for space to appear in the transmit/ACK window
 * - caller holds the socket locked
 */
static int rxrpc_wait_for_tx_window(struct rxrpc_sock *rx,
                                    struct rxrpc_call *call,
                                    long *timeo)
{
        DECLARE_WAITQUEUE(myself, current);
        int ret;

        _enter(",{%d},%ld",
               CIRC_SPACE(call->acks_head, ACCESS_ONCE(call->acks_tail),
                          call->acks_winsz),
               *timeo);

        add_wait_queue(&call->tx_waitq, &myself);

        for (;;) {
                set_current_state(TASK_INTERRUPTIBLE);
                ret = 0;
                if (CIRC_SPACE(call->acks_head, ACCESS_ONCE(call->acks_tail),
                               call->acks_winsz) > 0)
                        break;
                if (signal_pending(current)) {
                        ret = sock_intr_errno(*timeo);
                        break;
                }

                release_sock(&rx->sk);
                *timeo = schedule_timeout(*timeo);
                lock_sock(&rx->sk);
        }

        remove_wait_queue(&call->tx_waitq, &myself);
        set_current_state(TASK_RUNNING);
        _leave(" = %d", ret);
        return ret;
}

/*
 * attempt to schedule an instant Tx resend
 */
static inline void rxrpc_instant_resend(struct rxrpc_call *call)
{
        read_lock_bh(&call->state_lock);
        if (try_to_del_timer_sync(&call->resend_timer) >= 0) {
                clear_bit(RXRPC_CALL_RUN_RTIMER, &call->flags);
                if (call->state < RXRPC_CALL_COMPLETE &&
                    !test_and_set_bit(RXRPC_CALL_EV_RESEND_TIMER, &call->events))
                        rxrpc_queue_call(call);
        }
        read_unlock_bh(&call->state_lock);
}

/*
 * queue a packet for transmission, set the resend timer and attempt
 * to send the packet immediately
 */
static void rxrpc_queue_packet(struct rxrpc_call *call, struct sk_buff *skb,
                               bool last)
{
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
        int ret;

        _net("queue skb %p [%d]", skb, call->acks_head);

        ASSERT(call->acks_window != NULL);
        call->acks_window[call->acks_head] = (unsigned long) skb;
        smp_wmb();
        call->acks_head = (call->acks_head + 1) & (call->acks_winsz - 1);

        if (last || call->state == RXRPC_CALL_SERVER_ACK_REQUEST) {
                _debug("________awaiting reply/ACK__________");
                write_lock_bh(&call->state_lock);
                switch (call->state) {
                case RXRPC_CALL_CLIENT_SEND_REQUEST:
                        call->state = RXRPC_CALL_CLIENT_AWAIT_REPLY;
                        break;
                case RXRPC_CALL_SERVER_ACK_REQUEST:
                        call->state = RXRPC_CALL_SERVER_SEND_REPLY;
                        if (!last)
                                break;
                case RXRPC_CALL_SERVER_SEND_REPLY:
                        call->state = RXRPC_CALL_SERVER_AWAIT_ACK;
                        break;
                default:
                        break;
                }
                write_unlock_bh(&call->state_lock);
        }

        _proto("Tx DATA %%%u { #%u }", sp->hdr.serial, sp->hdr.seq);

        sp->need_resend = false;
        sp->resend_at = jiffies + rxrpc_resend_timeout;
        if (!test_and_set_bit(RXRPC_CALL_RUN_RTIMER, &call->flags)) {
                _debug("run timer");
                call->resend_timer.expires = sp->resend_at;
                add_timer(&call->resend_timer);
        }

        /* attempt to cancel the rx-ACK timer, deferring reply transmission if
         * we're ACK'ing the request phase of an incoming call */
        ret = -EAGAIN;
        if (try_to_del_timer_sync(&call->ack_timer) >= 0) {
                /* the packet may be freed by rxrpc_process_call() before this
                 * returns */
                ret = rxrpc_send_packet(call->conn->trans, skb);
                _net("sent skb %p", skb);
        } else {
                _debug("failed to delete ACK timer");
        }

        if (ret < 0) {
                _debug("need instant resend %d", ret);
                sp->need_resend = true;
                rxrpc_instant_resend(call);
        }

        _leave("");
}

/*
 * Convert a host-endian header into a network-endian header.
 */
static void rxrpc_insert_header(struct sk_buff *skb)
{
        struct rxrpc_wire_header whdr;
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);

        whdr.epoch      = htonl(sp->hdr.epoch);
        whdr.cid        = htonl(sp->hdr.cid);
        whdr.callNumber = htonl(sp->hdr.callNumber);
        whdr.seq        = htonl(sp->hdr.seq);
        whdr.serial     = htonl(sp->hdr.serial);
        whdr.type       = sp->hdr.type;
        whdr.flags      = sp->hdr.flags;
        whdr.userStatus = sp->hdr.userStatus;
        whdr.securityIndex = sp->hdr.securityIndex;
        whdr._rsvd      = htons(sp->hdr._rsvd);
        whdr.serviceId  = htons(sp->hdr.serviceId);

        memcpy(skb->head, &whdr, sizeof(whdr));
}

/*
 * send data through a socket
 * - must be called in process context
 * - caller holds the socket locked
 */
static int rxrpc_send_data(struct rxrpc_sock *rx,
                           struct rxrpc_call *call,
                           struct msghdr *msg, size_t len)
{
        struct rxrpc_skb_priv *sp;
        struct sk_buff *skb;
        struct sock *sk = &rx->sk;
        long timeo;
        bool more;
        int ret, copied;

        timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);

        /* this should be in poll */
        sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);

        if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
                return -EPIPE;

        more = msg->msg_flags & MSG_MORE;

        skb = call->tx_pending;
        call->tx_pending = NULL;

        copied = 0;
        do {
                if (!skb) {
                        size_t size, chunk, max, space;

                        _debug("alloc");

                        if (CIRC_SPACE(call->acks_head,
                                       ACCESS_ONCE(call->acks_tail),
                                       call->acks_winsz) <= 0) {
                                ret = -EAGAIN;
                                if (msg->msg_flags & MSG_DONTWAIT)
                                        goto maybe_error;
                                ret = rxrpc_wait_for_tx_window(rx, call,
                                                               &timeo);
                                if (ret < 0)
                                        goto maybe_error;
                        }

                        max = call->conn->trans->peer->maxdata;
                        max -= call->conn->security_size;
                        max &= ~(call->conn->size_align - 1UL);

                        chunk = max;
                        if (chunk > msg_data_left(msg) && !more)
                                chunk = msg_data_left(msg);

                        space = chunk + call->conn->size_align;
                        space &= ~(call->conn->size_align - 1UL);

                        size = space + call->conn->header_size;

                        _debug("SIZE: %zu/%zu/%zu", chunk, space, size);

                        /* create a buffer that we can retain until it's ACK'd */
                        skb = sock_alloc_send_skb(
                                sk, size, msg->msg_flags & MSG_DONTWAIT, &ret);
                        if (!skb)
                                goto maybe_error;

                        rxrpc_new_skb(skb);

                        _debug("ALLOC SEND %p", skb);

                        ASSERTCMP(skb->mark, ==, 0);

                        _debug("HS: %u", call->conn->header_size);
                        skb_reserve(skb, call->conn->header_size);
                        skb->len += call->conn->header_size;

                        sp = rxrpc_skb(skb);
                        sp->remain = chunk;
                        if (sp->remain > skb_tailroom(skb))
                                sp->remain = skb_tailroom(skb);

                        _net("skb: hr %d, tr %d, hl %d, rm %d",
                               skb_headroom(skb),
                               skb_tailroom(skb),
                               skb_headlen(skb),
                               sp->remain);

                        skb->ip_summed = CHECKSUM_UNNECESSARY;
                }

                _debug("append");
                sp = rxrpc_skb(skb);

                /* append next segment of data to the current buffer */
                if (msg_data_left(msg) > 0) {
                        int copy = skb_tailroom(skb);
                        ASSERTCMP(copy, >, 0);
                        if (copy > msg_data_left(msg))
                                copy = msg_data_left(msg);
                        if (copy > sp->remain)
                                copy = sp->remain;

                        _debug("add");
                        ret = skb_add_data(skb, &msg->msg_iter, copy);
                        _debug("added");
                        if (ret < 0)
                                goto efault;
                        sp->remain -= copy;
                        skb->mark += copy;
                        copied += copy;
                }

                /* check for the far side aborting the call or a network error
                 * occurring */
                if (call->state > RXRPC_CALL_COMPLETE)
                        goto call_aborted;

                /* add the packet to the send queue if it's now full */
                if (sp->remain <= 0 ||
                    (msg_data_left(msg) == 0 && !more)) {
                        struct rxrpc_connection *conn = call->conn;
                        uint32_t seq;
                        size_t pad;

                        /* pad out if we're using security */
                        if (conn->security_ix) {
                                pad = conn->security_size + skb->mark;
                                pad = conn->size_align - pad;
                                pad &= conn->size_align - 1;
                                _debug("pad %zu", pad);
                                if (pad)
                                        memset(skb_put(skb, pad), 0, pad);
                        }

                        seq = atomic_inc_return(&call->sequence);

                        sp->hdr.epoch   = conn->epoch;
                        sp->hdr.cid     = call->cid;
                        sp->hdr.callNumber = call->call_id;
                        sp->hdr.seq     = seq;
                        sp->hdr.serial  = atomic_inc_return(&conn->serial);
                        sp->hdr.type    = RXRPC_PACKET_TYPE_DATA;
                        sp->hdr.userStatus = 0;
                        sp->hdr.securityIndex = conn->security_ix;
                        sp->hdr._rsvd   = 0;
                        sp->hdr.serviceId = call->service_id;

                        sp->hdr.flags = conn->out_clientflag;
                        if (msg_data_left(msg) == 0 && !more)
                                sp->hdr.flags |= RXRPC_LAST_PACKET;
                        else if (CIRC_SPACE(call->acks_head,
                                            ACCESS_ONCE(call->acks_tail),
                                            call->acks_winsz) > 1)
                                sp->hdr.flags |= RXRPC_MORE_PACKETS;
                        if (more && seq & 1)
                                sp->hdr.flags |= RXRPC_REQUEST_ACK;

                        ret = conn->security->secure_packet(
                                call, skb, skb->mark,
                                skb->head + sizeof(struct rxrpc_wire_header));
                        if (ret < 0)
                                goto out;

                        rxrpc_insert_header(skb);
                        rxrpc_queue_packet(call, skb, !msg_data_left(msg) && !more);
                        skb = NULL;
                }
        } while (msg_data_left(msg) > 0);

success:
        ret = copied;
out:
        call->tx_pending = skb;
        _leave(" = %d", ret);
        return ret;

call_aborted:
        rxrpc_free_skb(skb);
        if (call->state == RXRPC_CALL_NETWORK_ERROR)
                ret = call->conn->trans->peer->net_error;
        else
                ret = -ECONNABORTED;
        _leave(" = %d", ret);
        return ret;

maybe_error:
        if (copied)
                goto success;
        goto out;

efault:
        ret = -EFAULT;
        goto out;
}