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33 #include <linux/kernel.h>
34 #include <linux/slab.h>
40 static DEFINE_SPINLOCK(loop_conns_lock);
41 static LIST_HEAD(loop_conns);
44 * This 'loopback' transport is a special case for flows that originate
45 * and terminate on the same machine.
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.
51 * The loopback transport's sending path just hands the sent rds_message
52 * straight to the receiving path via an embedded rds_incoming.
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.
60 static int rds_loop_xmit(struct rds_connection *conn, struct rds_message *rm,
61 unsigned int hdr_off, unsigned int sg,
64 /* Do not send cong updates to loopback */
65 if (rm->m_inc.i_hdr.h_flags & RDS_FLAG_CONG_BITMAP) {
66 rds_cong_map_updated(conn->c_fcong, ~(u64) 0);
67 return sizeof(struct rds_header) + RDS_CONG_MAP_BYTES;
70 BUG_ON(hdr_off || sg || off);
72 rds_inc_init(&rm->m_inc, conn, conn->c_laddr);
73 /* For the embedded inc. Matching put is in loop_inc_free() */
74 rds_message_addref(rm);
76 rds_recv_incoming(conn, conn->c_laddr, conn->c_faddr, &rm->m_inc,
77 GFP_KERNEL, KM_USER0);
79 rds_send_drop_acked(conn, be64_to_cpu(rm->m_inc.i_hdr.h_sequence),
82 rds_inc_put(&rm->m_inc);
84 return sizeof(struct rds_header) + be32_to_cpu(rm->m_inc.i_hdr.h_len);
88 * See rds_loop_xmit(). Since our inc is embedded in the rm, we
89 * make sure the rm lives at least until the inc is done.
91 static void rds_loop_inc_free(struct rds_incoming *inc)
93 struct rds_message *rm = container_of(inc, struct rds_message, m_inc);
97 /* we need to at least give the thread something to succeed */
98 static int rds_loop_recv(struct rds_connection *conn)
103 struct rds_loop_connection {
104 struct list_head loop_node;
105 struct rds_connection *conn;
109 * Even the loopback transport needs to keep track of its connections,
110 * so it can call rds_conn_destroy() on them on exit. N.B. there are
111 * 1+ loopback addresses (127.*.*.*) so it's not a bug to have
112 * multiple loopback conns allocated, although rather useless.
114 static int rds_loop_conn_alloc(struct rds_connection *conn, gfp_t gfp)
116 struct rds_loop_connection *lc;
119 lc = kzalloc(sizeof(struct rds_loop_connection), GFP_KERNEL);
123 INIT_LIST_HEAD(&lc->loop_node);
125 conn->c_transport_data = lc;
127 spin_lock_irqsave(&loop_conns_lock, flags);
128 list_add_tail(&lc->loop_node, &loop_conns);
129 spin_unlock_irqrestore(&loop_conns_lock, flags);
134 static void rds_loop_conn_free(void *arg)
136 struct rds_loop_connection *lc = arg;
137 rdsdebug("lc %p\n", lc);
138 list_del(&lc->loop_node);
142 static int rds_loop_conn_connect(struct rds_connection *conn)
144 rds_connect_complete(conn);
148 static void rds_loop_conn_shutdown(struct rds_connection *conn)
152 void rds_loop_exit(void)
154 struct rds_loop_connection *lc, *_lc;
157 /* avoid calling conn_destroy with irqs off */
158 spin_lock_irq(&loop_conns_lock);
159 list_splice(&loop_conns, &tmp_list);
160 INIT_LIST_HEAD(&loop_conns);
161 spin_unlock_irq(&loop_conns_lock);
163 list_for_each_entry_safe(lc, _lc, &tmp_list, loop_node) {
164 WARN_ON(lc->conn->c_passive);
165 rds_conn_destroy(lc->conn);
170 * This is missing .xmit_* because loop doesn't go through generic
171 * rds_send_xmit() and doesn't call rds_recv_incoming(). .listen_stop and
172 * .laddr_check are missing because transport.c doesn't iterate over
173 * rds_loop_transport.
175 struct rds_transport rds_loop_transport = {
176 .xmit = rds_loop_xmit,
177 .recv = rds_loop_recv,
178 .conn_alloc = rds_loop_conn_alloc,
179 .conn_free = rds_loop_conn_free,
180 .conn_connect = rds_loop_conn_connect,
181 .conn_shutdown = rds_loop_conn_shutdown,
182 .inc_copy_to_user = rds_message_inc_copy_to_user,
183 .inc_free = rds_loop_inc_free,
184 .t_name = "loopback",