/* Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License.
*/
/* * More machine-dependent networking gooo... on some systems, * you've got to be *really* sure that all the packets are acknowledged * before closing the connection, since the client will not be able * to see the last response if their TCP buffer is flushed by a RST * packet from us, which is what the server's TCP stack will send * if it receives any request data after closing the connection. * * In an ideal world, this function would be accomplished by simply * setting the socket option SO_LINGER and handling it within the * server's TCP stack while the process continues on to the next request. * Unfortunately, it seems that most (if not all) operating systems * block the server process on close() when SO_LINGER is used. * For those that don't, see USE_SO_LINGER below. For the rest, * we have created a home-brew lingering_close. * * Many operating systems tend to block, puke, or otherwise mishandle * calls to shutdown only half of the connection. You should define * NO_LINGCLOSE in ap_config.h if such is the case for your system.
*/ #ifndef MAX_SECS_TO_LINGER #define MAX_SECS_TO_LINGER 30 #endif
AP_DECLARE(int) ap_prep_lingering_close(conn_rec *c)
{ /* Give protocol handlers one last chance to raise their voice */
ap_run_pre_close_connection(c);
if (c->sbh) {
ap_update_child_status(c->sbh, SERVER_CLOSING, NULL);
} return 0;
}
/* we now proceed to read from the client until we get EOF, or until * MAX_SECS_TO_LINGER has passed. The reasons for doing this are * documented in a draft: * * http://tools.ietf.org/html/draft-ietf-http-connection-00.txt * * in a nutshell -- if we don't make this effort we risk causing * TCP RST packets to be sent which can tear down a connection before * all the response data has been sent to the client.
*/ #define SECONDS_TO_LINGER 2
/* Close the connection, being careful to send out whatever is still * in our buffers. If possible, try to avoid a hard close until the * client has ACKed our FIN and/or has stopped sending us data.
*/
/* Send any leftover data to the client, but never try to again */
ap_flush_conn(c);
#ifdef NO_LINGCLOSE return 1; #else /* Shut down the socket for write, which will send a FIN * to the peer.
*/ return (c->aborted || apr_socket_shutdown(csd, APR_SHUTDOWN_WRITE)); #endif
}
if (!csd) { /* Be safe with third-party modules that: * ap_set_core_module_config(c->conn_config, NULL) * to no-op ap_lingering_close().
*/
c->aborted = 1; return;
}
if (ap_start_lingering_close(c)) {
apr_socket_close(csd); return;
}
/* Read available data from the client whilst it continues sending * it, for a maximum time of MAX_SECS_TO_LINGER. If the client * does not send any data within 2 seconds (a value pulled from * Apache 1.3 which seems to work well), give up.
*/
apr_socket_timeout_set(csd, apr_time_from_sec(SECONDS_TO_LINGER));
apr_socket_opt_set(csd, APR_INCOMPLETE_READ, 1);
/* The common path here is that the initial apr_socket_recv() call * will return 0 bytes read; so that case must avoid the expensive
* apr_time_now() call and time arithmetic. */
do {
nbytes = sizeof(dummybuf); if (apr_socket_recv(csd, dummybuf, &nbytes) || nbytes == 0) break;
now = apr_time_now(); if (timeup == 0) { /* * First time through; * calculate now + 30 seconds (MAX_SECS_TO_LINGER). * * If some module requested a shortened waiting period, only wait for * 2s (SECONDS_TO_LINGER). This is useful for mitigating certain * DoS attacks.
*/ if (apr_table_get(c->notes, "short-lingering-close")) {
timeup = now + apr_time_from_sec(SECONDS_TO_LINGER);
} else {
timeup = now + apr_time_from_sec(MAX_SECS_TO_LINGER);
} continue;
}
} while (now < timeup);
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