printf: Remove unused 'bprintf'

[drm/drm-misc.git] / net / rxrpc / output.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* RxRPC packet transmission
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#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 <net/udp.h>
#include "ar-internal.h"

extern int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len);

static ssize_t do_udp_sendmsg(struct socket *socket, struct msghdr *msg, size_t len)
{
        struct sockaddr *sa = msg->msg_name;
        struct sock *sk = socket->sk;

        if (IS_ENABLED(CONFIG_AF_RXRPC_IPV6)) {
                if (sa->sa_family == AF_INET6) {
                        if (sk->sk_family != AF_INET6) {
                                pr_warn("AF_INET6 address on AF_INET socket\n");
                                return -ENOPROTOOPT;
                        }
                        return udpv6_sendmsg(sk, msg, len);
                }
        }
        return udp_sendmsg(sk, msg, len);
}

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

static const char rxrpc_keepalive_string[] = "";

/*
 * Increase Tx backoff on transmission failure and clear it on success.
 */
static void rxrpc_tx_backoff(struct rxrpc_call *call, int ret)
{
        if (ret < 0) {
                if (call->tx_backoff < 1000)
                        call->tx_backoff += 100;
        } else {
                call->tx_backoff = 0;
        }
}

/*
 * Arrange for a keepalive ping a certain time after we last transmitted.  This
 * lets the far side know we're still interested in this call and helps keep
 * the route through any intervening firewall open.
 *
 * Receiving a response to the ping will prevent the ->expect_rx_by timer from
 * expiring.
 */
static void rxrpc_set_keepalive(struct rxrpc_call *call, ktime_t now)
{
        ktime_t delay = ms_to_ktime(READ_ONCE(call->next_rx_timo) / 6);

        call->keepalive_at = ktime_add(ktime_get_real(), delay);
        trace_rxrpc_timer_set(call, delay, rxrpc_timer_trace_keepalive);
}

/*
 * Fill out an ACK packet.
 */
static void rxrpc_fill_out_ack(struct rxrpc_call *call,
                               struct rxrpc_txbuf *txb,
                               u8 ack_reason,
                               rxrpc_serial_t serial)
{
        struct rxrpc_wire_header *whdr = txb->kvec[0].iov_base;
        struct rxrpc_acktrailer *trailer = txb->kvec[2].iov_base + 3;
        struct rxrpc_ackpacket *ack = (struct rxrpc_ackpacket *)(whdr + 1);
        unsigned int qsize, sack, wrap, to;
        rxrpc_seq_t window, wtop;
        int rsize;
        u32 mtu, jmax;
        u8 *filler = txb->kvec[2].iov_base;
        u8 *sackp = txb->kvec[1].iov_base;

        rxrpc_inc_stat(call->rxnet, stat_tx_ack_fill);

        window = call->ackr_window;
        wtop   = call->ackr_wtop;
        sack   = call->ackr_sack_base % RXRPC_SACK_SIZE;

        whdr->seq               = 0;
        whdr->type              = RXRPC_PACKET_TYPE_ACK;
        txb->flags              |= RXRPC_SLOW_START_OK;
        ack->bufferSpace        = 0;
        ack->maxSkew            = 0;
        ack->firstPacket        = htonl(window);
        ack->previousPacket     = htonl(call->rx_highest_seq);
        ack->serial             = htonl(serial);
        ack->reason             = ack_reason;
        ack->nAcks              = wtop - window;
        filler[0]               = 0;
        filler[1]               = 0;
        filler[2]               = 0;

        if (ack_reason == RXRPC_ACK_PING)
                txb->flags |= RXRPC_REQUEST_ACK;

        if (after(wtop, window)) {
                txb->len += ack->nAcks;
                txb->kvec[1].iov_base = sackp;
                txb->kvec[1].iov_len = ack->nAcks;

                wrap = RXRPC_SACK_SIZE - sack;
                to = min_t(unsigned int, ack->nAcks, RXRPC_SACK_SIZE);

                if (sack + ack->nAcks <= RXRPC_SACK_SIZE) {
                        memcpy(sackp, call->ackr_sack_table + sack, ack->nAcks);
                } else {
                        memcpy(sackp, call->ackr_sack_table + sack, wrap);
                        memcpy(sackp + wrap, call->ackr_sack_table, to - wrap);
                }
        } else if (before(wtop, window)) {
                pr_warn("ack window backward %x %x", window, wtop);
        } else if (ack->reason == RXRPC_ACK_DELAY) {
                ack->reason = RXRPC_ACK_IDLE;
        }

        mtu = call->peer->if_mtu;
        mtu -= call->peer->hdrsize;
        jmax = rxrpc_rx_jumbo_max;
        qsize = (window - 1) - call->rx_consumed;
        rsize = max_t(int, call->rx_winsize - qsize, 0);
        txb->ack_rwind = rsize;
        trailer->maxMTU         = htonl(rxrpc_rx_mtu);
        trailer->ifMTU          = htonl(mtu);
        trailer->rwind          = htonl(rsize);
        trailer->jumbo_max      = htonl(jmax);
}

/*
 * Record the beginning of an RTT probe.
 */
static void rxrpc_begin_rtt_probe(struct rxrpc_call *call, rxrpc_serial_t serial,
                                  ktime_t now, enum rxrpc_rtt_tx_trace why)
{
        unsigned long avail = call->rtt_avail;
        int rtt_slot = 9;

        if (!(avail & RXRPC_CALL_RTT_AVAIL_MASK))
                goto no_slot;

        rtt_slot = __ffs(avail & RXRPC_CALL_RTT_AVAIL_MASK);
        if (!test_and_clear_bit(rtt_slot, &call->rtt_avail))
                goto no_slot;

        call->rtt_serial[rtt_slot] = serial;
        call->rtt_sent_at[rtt_slot] = now;
        smp_wmb(); /* Write data before avail bit */
        set_bit(rtt_slot + RXRPC_CALL_RTT_PEND_SHIFT, &call->rtt_avail);

        trace_rxrpc_rtt_tx(call, why, rtt_slot, serial);
        return;

no_slot:
        trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_no_slot, rtt_slot, serial);
}

/*
 * Transmit an ACK packet.
 */
static void rxrpc_send_ack_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
{
        struct rxrpc_wire_header *whdr = txb->kvec[0].iov_base;
        struct rxrpc_connection *conn;
        struct rxrpc_ackpacket *ack = (struct rxrpc_ackpacket *)(whdr + 1);
        struct msghdr msg;
        ktime_t now;
        int ret;

        if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
                return;

        conn = call->conn;

        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   = MSG_SPLICE_PAGES;

        whdr->flags = txb->flags & RXRPC_TXBUF_WIRE_FLAGS;

        txb->serial = rxrpc_get_next_serial(conn);
        whdr->serial = htonl(txb->serial);
        trace_rxrpc_tx_ack(call->debug_id, txb->serial,
                           ntohl(ack->firstPacket),
                           ntohl(ack->serial), ack->reason, ack->nAcks,
                           txb->ack_rwind);

        rxrpc_inc_stat(call->rxnet, stat_tx_ack_send);

        iov_iter_kvec(&msg.msg_iter, WRITE, txb->kvec, txb->nr_kvec, txb->len);
        rxrpc_local_dont_fragment(conn->local, false);
        ret = do_udp_sendmsg(conn->local->socket, &msg, txb->len);
        call->peer->last_tx_at = ktime_get_seconds();
        if (ret < 0) {
                trace_rxrpc_tx_fail(call->debug_id, txb->serial, ret,
                                    rxrpc_tx_point_call_ack);
        } else {
                trace_rxrpc_tx_packet(call->debug_id, whdr,
                                      rxrpc_tx_point_call_ack);
                now = ktime_get_real();
                if (ack->reason == RXRPC_ACK_PING)
                        rxrpc_begin_rtt_probe(call, txb->serial, now, rxrpc_rtt_tx_ping);
                if (txb->flags & RXRPC_REQUEST_ACK)
                        call->peer->rtt_last_req = now;
                rxrpc_set_keepalive(call, now);
        }
        rxrpc_tx_backoff(call, ret);
}

/*
 * Queue an ACK for immediate transmission.
 */
void rxrpc_send_ACK(struct rxrpc_call *call, u8 ack_reason,
                    rxrpc_serial_t serial, enum rxrpc_propose_ack_trace why)
{
        struct rxrpc_txbuf *txb;

        if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
                return;

        rxrpc_inc_stat(call->rxnet, stat_tx_acks[ack_reason]);

        txb = rxrpc_alloc_ack_txbuf(call, call->ackr_wtop - call->ackr_window);
        if (!txb) {
                kleave(" = -ENOMEM");
                return;
        }

        txb->ack_why = why;

        rxrpc_fill_out_ack(call, txb, ack_reason, serial);
        call->ackr_nr_unacked = 0;
        atomic_set(&call->ackr_nr_consumed, 0);
        clear_bit(RXRPC_CALL_RX_IS_IDLE, &call->flags);

        trace_rxrpc_send_ack(call, why, ack_reason, serial);
        rxrpc_send_ack_packet(call, txb);
        rxrpc_put_txbuf(txb, rxrpc_txbuf_put_ack_tx);
}

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

        /* Don't bother sending aborts for a client call once the server has
         * hard-ACK'd all of its request data.  After that point, we're not
         * going to stop the operation proceeding, and whilst we might limit
         * the reply, it's not worth it if we can send a new call on the same
         * channel instead, thereby closing off this call.
         */
        if (rxrpc_is_client_call(call) &&
            test_bit(RXRPC_CALL_TX_ALL_ACKED, &call->flags))
                return 0;

        if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
                return -ECONNRESET;

        conn = call->conn;

        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->dest_srx.srx_service);
        pkt.abort_code          = htonl(call->abort_code);

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

        serial = rxrpc_get_next_serial(conn);
        pkt.whdr.serial = htonl(serial);

        iov_iter_kvec(&msg.msg_iter, WRITE, iov, 1, sizeof(pkt));
        ret = do_udp_sendmsg(conn->local->socket, &msg, sizeof(pkt));
        conn->peer->last_tx_at = ktime_get_seconds();
        if (ret < 0)
                trace_rxrpc_tx_fail(call->debug_id, serial, ret,
                                    rxrpc_tx_point_call_abort);
        else
                trace_rxrpc_tx_packet(call->debug_id, &pkt.whdr,
                                      rxrpc_tx_point_call_abort);
        rxrpc_tx_backoff(call, ret);
        return ret;
}

/*
 * Prepare a (sub)packet for transmission.
 */
static void rxrpc_prepare_data_subpacket(struct rxrpc_call *call, struct rxrpc_txbuf *txb,
                                         rxrpc_serial_t serial)
{
        struct rxrpc_wire_header *whdr = txb->kvec[0].iov_base;
        enum rxrpc_req_ack_trace why;
        struct rxrpc_connection *conn = call->conn;

        _enter("%x,{%d}", txb->seq, txb->len);

        txb->serial = serial;

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

        /* If our RTT cache needs working on, request an ACK.  Also request
         * ACKs if a DATA packet appears to have been lost.
         *
         * However, we mustn't request an ACK on the last reply packet of a
         * service call, lest OpenAFS incorrectly send us an ACK with some
         * soft-ACKs in it and then never follow up with a proper hard ACK.
         */
        if (txb->flags & RXRPC_REQUEST_ACK)
                why = rxrpc_reqack_already_on;
        else if ((txb->flags & RXRPC_LAST_PACKET) && rxrpc_sending_to_client(txb))
                why = rxrpc_reqack_no_srv_last;
        else if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events))
                why = rxrpc_reqack_ack_lost;
        else if (txb->flags & RXRPC_TXBUF_RESENT)
                why = rxrpc_reqack_retrans;
        else if (call->cong_mode == RXRPC_CALL_SLOW_START && call->cong_cwnd <= 2)
                why = rxrpc_reqack_slow_start;
        else if (call->tx_winsize <= 2)
                why = rxrpc_reqack_small_txwin;
        else if (call->peer->rtt_count < 3 && txb->seq & 1)
                why = rxrpc_reqack_more_rtt;
        else if (ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000), ktime_get_real()))
                why = rxrpc_reqack_old_rtt;
        else
                goto dont_set_request_ack;

        rxrpc_inc_stat(call->rxnet, stat_why_req_ack[why]);
        trace_rxrpc_req_ack(call->debug_id, txb->seq, why);
        if (why != rxrpc_reqack_no_srv_last)
                txb->flags |= RXRPC_REQUEST_ACK;
dont_set_request_ack:

        whdr->flags = txb->flags & RXRPC_TXBUF_WIRE_FLAGS;
        whdr->serial    = htonl(txb->serial);
        whdr->cksum     = txb->cksum;

        trace_rxrpc_tx_data(call, txb->seq, txb->serial, txb->flags, false);
}

/*
 * Prepare a packet for transmission.
 */
static size_t rxrpc_prepare_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
{
        rxrpc_serial_t serial;

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

        rxrpc_prepare_data_subpacket(call, txb, serial);

        return txb->len;
}

/*
 * Set timeouts after transmitting a packet.
 */
static void rxrpc_tstamp_data_packets(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
{
        ktime_t now = ktime_get_real();
        bool ack_requested = txb->flags & RXRPC_REQUEST_ACK;

        call->tx_last_sent = now;
        txb->last_sent = now;

        if (ack_requested) {
                rxrpc_begin_rtt_probe(call, txb->serial, now, rxrpc_rtt_tx_data);

                call->peer->rtt_last_req = now;
                if (call->peer->rtt_count > 1) {
                        ktime_t delay = rxrpc_get_rto_backoff(call->peer, false);

                        call->ack_lost_at = ktime_add(now, delay);
                        trace_rxrpc_timer_set(call, delay, rxrpc_timer_trace_lost_ack);
                }
        }

        if (!test_and_set_bit(RXRPC_CALL_BEGAN_RX_TIMER, &call->flags)) {
                ktime_t delay = ms_to_ktime(READ_ONCE(call->next_rx_timo));

                call->expect_rx_by = ktime_add(now, delay);
                trace_rxrpc_timer_set(call, delay, rxrpc_timer_trace_expect_rx);
        }

        rxrpc_set_keepalive(call, now);
}

/*
 * send a packet through the transport endpoint
 */
static int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
{
        struct rxrpc_wire_header *whdr = txb->kvec[0].iov_base;
        struct rxrpc_connection *conn = call->conn;
        enum rxrpc_tx_point frag;
        struct msghdr msg;
        size_t len;
        int ret;

        _enter("%x,{%d}", txb->seq, txb->len);

        len = rxrpc_prepare_data_packet(call, txb);

        if (IS_ENABLED(CONFIG_AF_RXRPC_INJECT_LOSS)) {
                static int lose;
                if ((lose++ & 7) == 7) {
                        ret = 0;
                        trace_rxrpc_tx_data(call, txb->seq, txb->serial,
                                            txb->flags, true);
                        goto done;
                }
        }

        iov_iter_kvec(&msg.msg_iter, WRITE, txb->kvec, txb->nr_kvec, 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   = MSG_SPLICE_PAGES;

        /* Track what we've attempted to transmit at least once so that the
         * retransmission algorithm doesn't try to resend what we haven't sent
         * yet.
         */
        if (txb->seq == call->tx_transmitted + 1)
                call->tx_transmitted = txb->seq;

        /* send the packet with the don't fragment bit set if we currently
         * think it's small enough */
        if (txb->len >= call->peer->maxdata) {
                rxrpc_local_dont_fragment(conn->local, false);
                frag = rxrpc_tx_point_call_data_frag;
        } else {
                rxrpc_local_dont_fragment(conn->local, true);
                frag = rxrpc_tx_point_call_data_nofrag;
        }

retry:
        /* 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
         */
        rxrpc_inc_stat(call->rxnet, stat_tx_data_send);
        ret = do_udp_sendmsg(conn->local->socket, &msg, len);
        conn->peer->last_tx_at = ktime_get_seconds();

        if (ret < 0) {
                rxrpc_inc_stat(call->rxnet, stat_tx_data_send_fail);
                trace_rxrpc_tx_fail(call->debug_id, txb->serial, ret, frag);
        } else {
                trace_rxrpc_tx_packet(call->debug_id, whdr, frag);
        }

        rxrpc_tx_backoff(call, ret);
        if (ret == -EMSGSIZE && frag == rxrpc_tx_point_call_data_frag) {
                rxrpc_local_dont_fragment(conn->local, false);
                frag = rxrpc_tx_point_call_data_frag;
                goto retry;
        }

done:
        if (ret >= 0) {
                rxrpc_tstamp_data_packets(call, txb);
        } else {
                /* Cancel the call if the initial transmission fails,
                 * particularly if that's due to network routing issues that
                 * aren't going away anytime soon.  The layer above can arrange
                 * the retransmission.
                 */
                if (!test_and_set_bit(RXRPC_CALL_BEGAN_RX_TIMER, &call->flags))
                        rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
                                                  RX_USER_ABORT, ret);
        }

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

/*
 * Transmit a connection-level abort.
 */
void rxrpc_send_conn_abort(struct rxrpc_connection *conn)
{
        struct rxrpc_wire_header whdr;
        struct msghdr msg;
        struct kvec iov[2];
        __be32 word;
        size_t len;
        u32 serial;
        int ret;

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

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

        word            = htonl(conn->abort_code);

        iov[0].iov_base = &whdr;
        iov[0].iov_len  = sizeof(whdr);
        iov[1].iov_base = &word;
        iov[1].iov_len  = sizeof(word);

        len = iov[0].iov_len + iov[1].iov_len;

        serial = rxrpc_get_next_serial(conn);
        whdr.serial = htonl(serial);

        iov_iter_kvec(&msg.msg_iter, WRITE, iov, 2, len);
        ret = do_udp_sendmsg(conn->local->socket, &msg, len);
        if (ret < 0) {
                trace_rxrpc_tx_fail(conn->debug_id, serial, ret,
                                    rxrpc_tx_point_conn_abort);
                _debug("sendmsg failed: %d", ret);
                return;
        }

        trace_rxrpc_tx_packet(conn->debug_id, &whdr, rxrpc_tx_point_conn_abort);

        conn->peer->last_tx_at = ktime_get_seconds();
}

/*
 * Reject a packet through the local endpoint.
 */
void rxrpc_reject_packet(struct rxrpc_local *local, struct sk_buff *skb)
{
        struct rxrpc_wire_header whdr;
        struct sockaddr_rxrpc srx;
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
        struct msghdr msg;
        struct kvec iov[2];
        size_t size;
        __be32 code;
        int ret, ioc;

        rxrpc_see_skb(skb, rxrpc_skb_see_reject);

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

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

        memset(&whdr, 0, sizeof(whdr));

        switch (skb->mark) {
        case RXRPC_SKB_MARK_REJECT_BUSY:
                whdr.type = RXRPC_PACKET_TYPE_BUSY;
                size = sizeof(whdr);
                ioc = 1;
                break;
        case RXRPC_SKB_MARK_REJECT_ABORT:
                whdr.type = RXRPC_PACKET_TYPE_ABORT;
                code = htonl(skb->priority);
                size = sizeof(whdr) + sizeof(code);
                ioc = 2;
                break;
        default:
                return;
        }

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

                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;

                iov_iter_kvec(&msg.msg_iter, WRITE, iov, ioc, size);
                ret = do_udp_sendmsg(local->socket, &msg, size);
                if (ret < 0)
                        trace_rxrpc_tx_fail(local->debug_id, 0, ret,
                                            rxrpc_tx_point_reject);
                else
                        trace_rxrpc_tx_packet(local->debug_id, &whdr,
                                              rxrpc_tx_point_reject);
        }
}

/*
 * Send a VERSION reply to a peer as a keepalive.
 */
void rxrpc_send_keepalive(struct rxrpc_peer *peer)
{
        struct rxrpc_wire_header whdr;
        struct msghdr msg;
        struct kvec iov[2];
        size_t len;
        int ret;

        _enter("");

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

        whdr.epoch      = htonl(peer->local->rxnet->epoch);
        whdr.cid        = 0;
        whdr.callNumber = 0;
        whdr.seq        = 0;
        whdr.serial     = 0;
        whdr.type       = RXRPC_PACKET_TYPE_VERSION; /* Not client-initiated */
        whdr.flags      = RXRPC_LAST_PACKET;
        whdr.userStatus = 0;
        whdr.securityIndex = 0;
        whdr._rsvd      = 0;
        whdr.serviceId  = 0;

        iov[0].iov_base = &whdr;
        iov[0].iov_len  = sizeof(whdr);
        iov[1].iov_base = (char *)rxrpc_keepalive_string;
        iov[1].iov_len  = sizeof(rxrpc_keepalive_string);

        len = iov[0].iov_len + iov[1].iov_len;

        iov_iter_kvec(&msg.msg_iter, WRITE, iov, 2, len);
        ret = do_udp_sendmsg(peer->local->socket, &msg, len);
        if (ret < 0)
                trace_rxrpc_tx_fail(peer->debug_id, 0, ret,
                                    rxrpc_tx_point_version_keepalive);
        else
                trace_rxrpc_tx_packet(peer->debug_id, &whdr,
                                      rxrpc_tx_point_version_keepalive);

        peer->last_tx_at = ktime_get_seconds();
        _leave("");
}

/*
 * Schedule an instant Tx resend.
 */
static inline void rxrpc_instant_resend(struct rxrpc_call *call,
                                        struct rxrpc_txbuf *txb)
{
        if (!__rxrpc_call_is_complete(call))
                kdebug("resend");
}

/*
 * Transmit one packet.
 */
void rxrpc_transmit_one(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
{
        int ret;

        ret = rxrpc_send_data_packet(call, txb);
        if (ret < 0) {
                switch (ret) {
                case -ENETUNREACH:
                case -EHOSTUNREACH:
                case -ECONNREFUSED:
                        rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
                                                  0, ret);
                        break;
                default:
                        _debug("need instant resend %d", ret);
                        rxrpc_instant_resend(call, txb);
                }
        } else {
                ktime_t delay = ns_to_ktime(call->peer->rto_us * NSEC_PER_USEC);

                call->resend_at = ktime_add(ktime_get_real(), delay);
                trace_rxrpc_timer_set(call, delay, rxrpc_timer_trace_resend_tx);
        }
}