/* rds_tcp_accept_one_path(): if accepting on cp_index > 0, make sure the
* client's ipaddr < server's ipaddr. Otherwise, close the accepted
* socket and force a reconneect from smaller -> larger ip addr. The reason
* we special case cp_index 0 is to allow the rds probe ping itself to itself
* get through efficiently.
* Since reconnects are only initiated from the node with the numerically
* smaller ip address, we recycle conns in RDS_CONN_ERROR on the passive side
* by moving them to CONNECTING in this function.
*/
static
struct rds_tcp_connection *rds_tcp_accept_one_path(struct rds_connection *conn)
{
int i;
bool peer_is_smaller = (conn->c_faddr < conn->c_laddr);
int npaths = max_t(int, 1, conn->c_npaths);
/* for mprds, all paths MUST be initiated by the peer
* with the smaller address.
*/
if (!peer_is_smaller) {
/* Make sure we initiate at least one path if this
* has not already been done; rds_start_mprds() will
* take care of additional paths, if necessary.
*/
if (npaths == 1)
rds_conn_path_connect_if_down(&conn->c_path[0]);
return NULL;
}
for (i = 0; i < npaths; i++) {
struct rds_conn_path *cp = &conn->c_path[i];
if (rds_conn_path_transition(cp, RDS_CONN_DOWN,
RDS_CONN_CONNECTING) ||
rds_conn_path_transition(cp, RDS_CONN_ERROR,
RDS_CONN_CONNECTING)) {
return cp->cp_transport_data;
}
}
return NULL;
}
/* rds_start_mprds() will synchronously start multiple paths when appropriate.
* The scheme is based on the following rules:
*
* 1. rds_sendmsg on first connect attempt sends the probe ping, with the
* sender's npaths (s_npaths)
* 2. rcvr of probe-ping knows the mprds_paths = min(s_npaths, r_npaths). It
* sends back a probe-pong with r_npaths. After that, if rcvr is the
* smaller ip addr, it starts rds_conn_path_connect_if_down on all
* mprds_paths.
* 3. sender gets woken up, and can move to rds_conn_path_connect_if_down.
* If it is the smaller ipaddr, rds_conn_path_connect_if_down can be
* called after reception of the probe-pong on all mprds_paths.
* Otherwise (sender of probe-ping is not the smaller ip addr): just call
* rds_conn_path_connect_if_down on the hashed path. (see rule 4)
* 4. when cp_index > 0, rds_connect_worker must only trigger
* a connection if laddr < faddr.
* 5. sender may end up queuing the packet on the cp. will get sent out later.
* when connection is completed.
*/
static void rds_start_mprds(struct rds_connection *conn)
{
int i;
struct rds_conn_path *cp;
if (conn->c_npaths > 1 && conn->c_laddr < conn->c_faddr) {
for (i = 1; i < conn->c_npaths; i++) {
cp = &conn->c_path[i];
rds_conn_path_connect_if_down(cp);
}
}
}
