linux/net/rds/loop.c
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   1/*
   2 * Copyright (c) 2006 Oracle.  All rights reserved.
   3 *
   4 * This software is available to you under a choice of one of two
   5 * licenses.  You may choose to be licensed under the terms of the GNU
   6 * General Public License (GPL) Version 2, available from the file
   7 * COPYING in the main directory of this source tree, or the
   8 * OpenIB.org BSD license below:
   9 *
  10 *     Redistribution and use in source and binary forms, with or
  11 *     without modification, are permitted provided that the following
  12 *     conditions are met:
  13 *
  14 *      - Redistributions of source code must retain the above
  15 *        copyright notice, this list of conditions and the following
  16 *        disclaimer.
  17 *
  18 *      - Redistributions in binary form must reproduce the above
  19 *        copyright notice, this list of conditions and the following
  20 *        disclaimer in the documentation and/or other materials
  21 *        provided with the distribution.
  22 *
  23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  27 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  28 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  29 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  30 * SOFTWARE.
  31 *
  32 */
  33#include <linux/kernel.h>
  34#include <linux/slab.h>
  35#include <linux/in.h>
  36
  37#include "rds.h"
  38#include "loop.h"
  39
  40static DEFINE_SPINLOCK(loop_conns_lock);
  41static LIST_HEAD(loop_conns);
  42
  43/*
  44 * This 'loopback' transport is a special case for flows that originate
  45 * and terminate on the same machine.
  46 *
  47 * Connection build-up notices if the destination address is thought of
  48 * as a local address by a transport.  At that time it decides to use the
  49 * loopback transport instead of the bound transport of the sending socket.
  50 *
  51 * The loopback transport's sending path just hands the sent rds_message
  52 * straight to the receiving path via an embedded rds_incoming.
  53 */
  54
  55/*
  56 * Usually a message transits both the sender and receiver's conns as it
  57 * flows to the receiver.  In the loopback case, though, the receive path
  58 * is handed the sending conn so the sense of the addresses is reversed.
  59 */
  60static int rds_loop_xmit(struct rds_connection *conn, struct rds_message *rm,
  61                         unsigned int hdr_off, unsigned int sg,
  62                         unsigned int off)
  63{
  64        struct scatterlist *sgp = &rm->data.op_sg[sg];
  65        int ret = sizeof(struct rds_header) +
  66                        be32_to_cpu(rm->m_inc.i_hdr.h_len);
  67
  68        /* Do not send cong updates to loopback */
  69        if (rm->m_inc.i_hdr.h_flags & RDS_FLAG_CONG_BITMAP) {
  70                rds_cong_map_updated(conn->c_fcong, ~(u64) 0);
  71                ret = min_t(int, ret, sgp->length - conn->c_xmit_data_off);
  72                goto out;
  73        }
  74
  75        BUG_ON(hdr_off || sg || off);
  76
  77        rds_inc_init(&rm->m_inc, conn, conn->c_laddr);
  78        /* For the embedded inc. Matching put is in loop_inc_free() */
  79        rds_message_addref(rm);
  80
  81        rds_recv_incoming(conn, conn->c_laddr, conn->c_faddr, &rm->m_inc,
  82                          GFP_KERNEL);
  83
  84        rds_send_drop_acked(conn, be64_to_cpu(rm->m_inc.i_hdr.h_sequence),
  85                            NULL);
  86
  87        rds_inc_put(&rm->m_inc);
  88out:
  89        return ret;
  90}
  91
  92/*
  93 * See rds_loop_xmit(). Since our inc is embedded in the rm, we
  94 * make sure the rm lives at least until the inc is done.
  95 */
  96static void rds_loop_inc_free(struct rds_incoming *inc)
  97{
  98        struct rds_message *rm = container_of(inc, struct rds_message, m_inc);
  99        rds_message_put(rm);
 100}
 101
 102/* we need to at least give the thread something to succeed */
 103static int rds_loop_recv(struct rds_connection *conn)
 104{
 105        return 0;
 106}
 107
 108struct rds_loop_connection {
 109        struct list_head loop_node;
 110        struct rds_connection *conn;
 111};
 112
 113/*
 114 * Even the loopback transport needs to keep track of its connections,
 115 * so it can call rds_conn_destroy() on them on exit. N.B. there are
 116 * 1+ loopback addresses (127.*.*.*) so it's not a bug to have
 117 * multiple loopback conns allocated, although rather useless.
 118 */
 119static int rds_loop_conn_alloc(struct rds_connection *conn, gfp_t gfp)
 120{
 121        struct rds_loop_connection *lc;
 122        unsigned long flags;
 123
 124        lc = kzalloc(sizeof(struct rds_loop_connection), gfp);
 125        if (!lc)
 126                return -ENOMEM;
 127
 128        INIT_LIST_HEAD(&lc->loop_node);
 129        lc->conn = conn;
 130        conn->c_transport_data = lc;
 131
 132        spin_lock_irqsave(&loop_conns_lock, flags);
 133        list_add_tail(&lc->loop_node, &loop_conns);
 134        spin_unlock_irqrestore(&loop_conns_lock, flags);
 135
 136        return 0;
 137}
 138
 139static void rds_loop_conn_free(void *arg)
 140{
 141        struct rds_loop_connection *lc = arg;
 142        unsigned long flags;
 143
 144        rdsdebug("lc %p\n", lc);
 145        spin_lock_irqsave(&loop_conns_lock, flags);
 146        list_del(&lc->loop_node);
 147        spin_unlock_irqrestore(&loop_conns_lock, flags);
 148        kfree(lc);
 149}
 150
 151static int rds_loop_conn_connect(struct rds_connection *conn)
 152{
 153        rds_connect_complete(conn);
 154        return 0;
 155}
 156
 157static void rds_loop_conn_shutdown(struct rds_connection *conn)
 158{
 159}
 160
 161void rds_loop_exit(void)
 162{
 163        struct rds_loop_connection *lc, *_lc;
 164        LIST_HEAD(tmp_list);
 165
 166        /* avoid calling conn_destroy with irqs off */
 167        spin_lock_irq(&loop_conns_lock);
 168        list_splice(&loop_conns, &tmp_list);
 169        INIT_LIST_HEAD(&loop_conns);
 170        spin_unlock_irq(&loop_conns_lock);
 171
 172        list_for_each_entry_safe(lc, _lc, &tmp_list, loop_node) {
 173                WARN_ON(lc->conn->c_passive);
 174                rds_conn_destroy(lc->conn);
 175        }
 176}
 177
 178/*
 179 * This is missing .xmit_* because loop doesn't go through generic
 180 * rds_send_xmit() and doesn't call rds_recv_incoming().  .listen_stop and
 181 * .laddr_check are missing because transport.c doesn't iterate over
 182 * rds_loop_transport.
 183 */
 184struct rds_transport rds_loop_transport = {
 185        .xmit                   = rds_loop_xmit,
 186        .recv                   = rds_loop_recv,
 187        .conn_alloc             = rds_loop_conn_alloc,
 188        .conn_free              = rds_loop_conn_free,
 189        .conn_connect           = rds_loop_conn_connect,
 190        .conn_shutdown          = rds_loop_conn_shutdown,
 191        .inc_copy_to_user       = rds_message_inc_copy_to_user,
 192        .inc_free               = rds_loop_inc_free,
 193        .t_name                 = "loopback",
 194};
 195
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