/* 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/net.h>
#include <linux/gfp.h>
#include <linux/skbuff.h>
#include <linux/export.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "ar-internal.h"

struct rxrpc_ack_buffer {
        struct rxrpc_wire_header whdr;
        struct rxrpc_ackpacket ack;
        u8 acks[255];
        u8 pad[3];
        struct rxrpc_ackinfo ackinfo;
};

struct rxrpc_abort_buffer {
        struct rxrpc_wire_header whdr;
        __be32 abort_code;
};

/*
 * Fill out an ACK packet.
 */
static size_t rxrpc_fill_out_ack(struct rxrpc_call *call,
                                 struct rxrpc_ack_buffer *pkt,
                                 rxrpc_seq_t *_hard_ack,
                                 rxrpc_seq_t *_top,
                                 u8 reason)
{
        rxrpc_serial_t serial;
        rxrpc_seq_t hard_ack, top, seq;
        int ix;
        u32 mtu, jmax;
        u8 *ackp = pkt->acks;

        /* Barrier against rxrpc_input_data(). */
        serial = call->ackr_serial;
        hard_ack = READ_ONCE(call->rx_hard_ack);
        top = smp_load_acquire(&call->rx_top);
        *_hard_ack = hard_ack;
        *_top = top;

        pkt->ack.bufferSpace    = htons(8);
        pkt->ack.maxSkew        = htons(call->ackr_skew);
        pkt->ack.firstPacket    = htonl(hard_ack + 1);
        pkt->ack.previousPacket = htonl(call->ackr_prev_seq);
        pkt->ack.serial         = htonl(serial);
        pkt->ack.reason         = reason;
        pkt->ack.nAcks          = top - hard_ack;

        if (reason == RXRPC_ACK_PING)
                pkt->whdr.flags |= RXRPC_REQUEST_ACK;

        if (after(top, hard_ack)) {
                seq = hard_ack + 1;
                do {
                        ix = seq & RXRPC_RXTX_BUFF_MASK;
                        if (call->rxtx_buffer[ix])
                                *ackp++ = RXRPC_ACK_TYPE_ACK;
                        else
                                *ackp++ = RXRPC_ACK_TYPE_NACK;
                        seq++;
                } while (before_eq(seq, top));
        }

        mtu = call->conn->params.peer->if_mtu;
        mtu -= call->conn->params.peer->hdrsize;
        jmax = (call->nr_jumbo_bad > 3) ? 1 : rxrpc_rx_jumbo_max;
        pkt->ackinfo.rxMTU      = htonl(rxrpc_rx_mtu);
        pkt->ackinfo.maxMTU     = htonl(mtu);
        pkt->ackinfo.rwind      = htonl(call->rx_winsize);
        pkt->ackinfo.jumbo_max  = htonl(jmax);

        *ackp++ = 0;
        *ackp++ = 0;
        *ackp++ = 0;
        return top - hard_ack + 3;
}

/*
 * Send an ACK call packet.
 */
int rxrpc_send_ack_packet(struct rxrpc_call *call, bool ping)
{
        struct rxrpc_connection *conn = NULL;
        struct rxrpc_ack_buffer *pkt;
        struct msghdr msg;
        struct kvec iov[2];
        rxrpc_serial_t serial;
        rxrpc_seq_t hard_ack, top;
        size_t len, n;
        int ret;
        u8 reason;

        spin_lock_bh(&call->lock);
        if (call->conn)
                conn = rxrpc_get_connection_maybe(call->conn);
        spin_unlock_bh(&call->lock);
        if (!conn)
                return -ECONNRESET;

        pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
        if (!pkt) {
                rxrpc_put_connection(conn);
                return -ENOMEM;
        }

        msg.msg_name    = &call->peer->srx.transport;
        msg.msg_namelen = call->peer->srx.transport_len;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags   = 0;

        pkt->whdr.epoch         = htonl(conn->proto.epoch);
        pkt->whdr.cid           = htonl(call->cid);
        pkt->whdr.callNumber    = htonl(call->call_id);
        pkt->whdr.seq           = 0;
        pkt->whdr.type          = RXRPC_PACKET_TYPE_ACK;
        pkt->whdr.flags         = RXRPC_SLOW_START_OK | conn->out_clientflag;
        pkt->whdr.userStatus    = 0;
        pkt->whdr.securityIndex = call->security_ix;
        pkt->whdr._rsvd         = 0;
        pkt->whdr.serviceId     = htons(call->service_id);

        spin_lock_bh(&call->lock);
        if (ping) {
                reason = RXRPC_ACK_PING;
        } else {
                reason = call->ackr_reason;
                if (!call->ackr_reason) {
                        spin_unlock_bh(&call->lock);
                        ret = 0;
                        goto out;
                }
                call->ackr_reason = 0;
        }
        n = rxrpc_fill_out_ack(call, pkt, &hard_ack, &top, reason);

        spin_unlock_bh(&call->lock);

        iov[0].iov_base = pkt;
        iov[0].iov_len  = sizeof(pkt->whdr) + sizeof(pkt->ack) + n;
        iov[1].iov_base = &pkt->ackinfo;
        iov[1].iov_len  = sizeof(pkt->ackinfo);
        len = iov[0].iov_len + iov[1].iov_len;

        serial = atomic_inc_return(&conn->serial);
        pkt->whdr.serial = htonl(serial);
        trace_rxrpc_tx_ack(call, serial,
                           ntohl(pkt->ack.firstPacket),
                           ntohl(pkt->ack.serial),
                           pkt->ack.reason, pkt->ack.nAcks);

        if (ping) {
                call->ping_serial = serial;
                smp_wmb();
                /* We need to stick a time in before we send the packet in case
                 * the reply gets back before kernel_sendmsg() completes - but
                 * asking UDP to send the packet can take a relatively long
                 * time, so we update the time after, on the assumption that
                 * the packet transmission is more likely to happen towards the
                 * end of the kernel_sendmsg() call.
                 */
                call->ping_time = ktime_get_real();
                set_bit(RXRPC_CALL_PINGING, &call->flags);
                trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_ping, serial);
        }

        ret = kernel_sendmsg(conn->params.local->socket, &msg, iov, 2, len);
        if (ping)
                call->ping_time = ktime_get_real();

        if (call->state < RXRPC_CALL_COMPLETE) {
                if (ret < 0) {
                        if (ping)
                                clear_bit(RXRPC_CALL_PINGING, &call->flags);
                        rxrpc_propose_ACK(call, pkt->ack.reason,
                                          ntohs(pkt->ack.maxSkew),
                                          ntohl(pkt->ack.serial),
                                          true, true,
                                          rxrpc_propose_ack_retry_tx);
                } else {
                        spin_lock_bh(&call->lock);
                        if (after(hard_ack, call->ackr_consumed))
                                call->ackr_consumed = hard_ack;
                        if (after(top, call->ackr_seen))
                                call->ackr_seen = top;
                        spin_unlock_bh(&call->lock);
                }
        }

out:
        rxrpc_put_connection(conn);
        kfree(pkt);
        return ret;
}

/*
 * Send an ABORT call packet.
 */
int rxrpc_send_abort_packet(struct rxrpc_call *call)
{
        struct rxrpc_connection *conn = NULL;
        struct rxrpc_abort_buffer pkt;
        struct msghdr msg;
        struct kvec iov[1];
        rxrpc_serial_t serial;
        int ret;

        spin_lock_bh(&call->lock);
        if (call->conn)
                conn = rxrpc_get_connection_maybe(call->conn);
        spin_unlock_bh(&call->lock);
        if (!conn)
                return -ECONNRESET;

        msg.msg_name    = &call->peer->srx.transport;
        msg.msg_namelen = call->peer->srx.transport_len;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags   = 0;

        pkt.whdr.epoch          = htonl(conn->proto.epoch);
        pkt.whdr.cid            = htonl(call->cid);
        pkt.whdr.callNumber     = htonl(call->call_id);
        pkt.whdr.seq            = 0;
        pkt.whdr.type           = RXRPC_PACKET_TYPE_ABORT;
        pkt.whdr.flags          = conn->out_clientflag;
        pkt.whdr.userStatus     = 0;
        pkt.whdr.securityIndex  = call->security_ix;
        pkt.whdr._rsvd          = 0;
        pkt.whdr.serviceId      = htons(call->service_id);
        pkt.abort_code          = htonl(call->abort_code);

        iov[0].iov_base = &pkt;
        iov[0].iov_len  = sizeof(pkt);

        serial = atomic_inc_return(&conn->serial);
        pkt.whdr.serial = htonl(serial);

        ret = kernel_sendmsg(conn->params.local->socket,
                             &msg, iov, 1, sizeof(pkt));

        rxrpc_put_connection(conn);
        return ret;
}

/*
 * send a packet through the transport endpoint
 */
int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
                           bool retrans)
{
        struct rxrpc_connection *conn = call->conn;
        struct rxrpc_wire_header whdr;
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
        struct msghdr msg;
        struct kvec iov[2];
        rxrpc_serial_t serial;
        size_t len;
        bool lost = false;
        int ret, opt;

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

        /* Each transmission of a Tx packet needs a new serial number */
        serial = atomic_inc_return(&conn->serial);

        whdr.epoch      = htonl(conn->proto.epoch);
        whdr.cid        = htonl(call->cid);
        whdr.callNumber = htonl(call->call_id);
        whdr.seq        = htonl(sp->hdr.seq);
        whdr.serial     = htonl(serial);
        whdr.type       = RXRPC_PACKET_TYPE_DATA;
        whdr.flags      = sp->hdr.flags;
        whdr.userStatus = 0;
        whdr.securityIndex = call->security_ix;
        whdr._rsvd      = htons(sp->hdr._rsvd);
        whdr.serviceId  = htons(call->service_id);

        if (test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags) &&
            sp->hdr.seq == 1)
                whdr.userStatus = RXRPC_USERSTATUS_SERVICE_UPGRADE;

        iov[0].iov_base = &whdr;
        iov[0].iov_len = sizeof(whdr);
        iov[1].iov_base = skb->head;
        iov[1].iov_len = skb->len;
        len = iov[0].iov_len + iov[1].iov_len;

        msg.msg_name = &call->peer->srx.transport;
        msg.msg_namelen = call->peer->srx.transport_len;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags = 0;

        /* If our RTT cache needs working on, request an ACK.  Also request
         * ACKs if a DATA packet appears to have been lost.
         */
        if (!(sp->hdr.flags & RXRPC_LAST_PACKET) &&
            (retrans ||
             call->cong_mode == RXRPC_CALL_SLOW_START ||
             (call->peer->rtt_usage < 3 && sp->hdr.seq & 1) ||
             ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000),
                          ktime_get_real())))
                whdr.flags |= RXRPC_REQUEST_ACK;

        if (IS_ENABLED(CONFIG_AF_RXRPC_INJECT_LOSS)) {
                static int lose;
                if ((lose++ & 7) == 7) {
                        ret = 0;
                        lost = true;
                        goto done;
                }
        }

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

        /* send the packet with the don't fragment bit set if we currently
         * think it's small enough */
        if (iov[1].iov_len >= call->peer->maxdata)
                goto send_fragmentable;

        down_read(&conn->params.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(conn->params.local->socket, &msg, iov, 2, len);

        up_read(&conn->params.local->defrag_sem);
        if (ret == -EMSGSIZE)
                goto send_fragmentable;

done:
        trace_rxrpc_tx_data(call, sp->hdr.seq, serial, whdr.flags,
                            retrans, lost);
        if (ret >= 0) {
                ktime_t now = ktime_get_real();
                skb->tstamp = now;
                smp_wmb();
                sp->hdr.serial = serial;
                if (whdr.flags & RXRPC_REQUEST_ACK) {
                        call->peer->rtt_last_req = now;
                        trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_data, serial);
                }
        }
        _leave(" = %d [%u]", ret, call->peer->maxdata);
        return ret;

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

        down_write(&conn->params.local->defrag_sem);

        switch (conn->params.local->srx.transport.family) {
        case AF_INET:
                opt = IP_PMTUDISC_DONT;
                ret = kernel_setsockopt(conn->params.local->socket,
                                        SOL_IP, IP_MTU_DISCOVER,
                                        (char *)&opt, sizeof(opt));
                if (ret == 0) {
                        ret = kernel_sendmsg(conn->params.local->socket, &msg,
                                             iov, 2, len);

                        opt = IP_PMTUDISC_DO;
                        kernel_setsockopt(conn->params.local->socket, SOL_IP,
                                          IP_MTU_DISCOVER,
                                          (char *)&opt, sizeof(opt));
                }
                break;

#ifdef CONFIG_AF_RXRPC_IPV6
        case AF_INET6:
                opt = IPV6_PMTUDISC_DONT;
                ret = kernel_setsockopt(conn->params.local->socket,
                                        SOL_IPV6, IPV6_MTU_DISCOVER,
                                        (char *)&opt, sizeof(opt));
                if (ret == 0) {
                        ret = kernel_sendmsg(conn->params.local->socket, &msg,
                                             iov, 1, iov[0].iov_len);

                        opt = IPV6_PMTUDISC_DO;
                        kernel_setsockopt(conn->params.local->socket,
                                          SOL_IPV6, IPV6_MTU_DISCOVER,
                                          (char *)&opt, sizeof(opt));
                }
                break;
#endif
        }

        up_write(&conn->params.local->defrag_sem);
        goto done;
}

/*
 * reject packets through the local endpoint
 */
void rxrpc_reject_packets(struct rxrpc_local *local)
{
        struct sockaddr_rxrpc srx;
        struct rxrpc_skb_priv *sp;
        struct rxrpc_wire_header whdr;
        struct sk_buff *skb;
        struct msghdr msg;
        struct kvec iov[2];
        size_t size;
        __be32 code;

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

        iov[0].iov_base = &whdr;
        iov[0].iov_len = sizeof(whdr);
        iov[1].iov_base = &code;
        iov[1].iov_len = sizeof(code);
        size = sizeof(whdr) + sizeof(code);

        msg.msg_name = &srx.transport;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags = 0;

        memset(&whdr, 0, sizeof(whdr));
        whdr.type = RXRPC_PACKET_TYPE_ABORT;

        while ((skb = skb_dequeue(&local->reject_queue))) {
                rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
                sp = rxrpc_skb(skb);

                if (rxrpc_extract_addr_from_skb(local, &srx, skb) == 0) {
                        msg.msg_namelen = srx.transport_len;

                        code = htonl(skb->priority);

                        whdr.epoch      = htonl(sp->hdr.epoch);
                        whdr.cid        = htonl(sp->hdr.cid);
                        whdr.callNumber = htonl(sp->hdr.callNumber);
                        whdr.serviceId  = htons(sp->hdr.serviceId);
                        whdr.flags      = sp->hdr.flags;
                        whdr.flags      ^= RXRPC_CLIENT_INITIATED;
                        whdr.flags      &= RXRPC_CLIENT_INITIATED;

                        kernel_sendmsg(local->socket, &msg, iov, 2, size);
                }

                rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
        }

        _leave("");
}