1/* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements.  See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License.  You may obtain a copy of the License at
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "apr.h"
18#include "apr_strings.h"
19
20#include "ap_config.h"
21#include "httpd.h"
22#include "http_connection.h"
23#include "http_request.h"
24#include "http_protocol.h"
25#include "ap_mpm.h"
26#include "http_config.h"
27#include "http_core.h"
28#include "http_vhost.h"
29#include "scoreboard.h"
30#include "http_log.h"
31#include "util_filter.h"
32
33APR_HOOK_STRUCT(
34            APR_HOOK_LINK(create_connection)
35            APR_HOOK_LINK(process_connection)
36            APR_HOOK_LINK(pre_connection)
37)
38AP_IMPLEMENT_HOOK_RUN_FIRST(conn_rec *,create_connection,
39                            (apr_pool_t *p, server_rec *server, apr_socket_t *csd, long conn_id, void *sbh, apr_bucket_alloc_t *alloc),
40                            (p, server, csd, conn_id, sbh, alloc), NULL)
41AP_IMPLEMENT_HOOK_RUN_FIRST(int,process_connection,(conn_rec *c),(c),DECLINED)
42AP_IMPLEMENT_HOOK_RUN_ALL(int,pre_connection,(conn_rec *c, void *csd),(c, csd),OK,DECLINED)
43/*
44 * More machine-dependent networking gooo... on some systems,
45 * you've got to be *really* sure that all the packets are acknowledged
46 * before closing the connection, since the client will not be able
47 * to see the last response if their TCP buffer is flushed by a RST
48 * packet from us, which is what the server's TCP stack will send
49 * if it receives any request data after closing the connection.
50 *
51 * In an ideal world, this function would be accomplished by simply
52 * setting the socket option SO_LINGER and handling it within the
53 * server's TCP stack while the process continues on to the next request.
54 * Unfortunately, it seems that most (if not all) operating systems
55 * block the server process on close() when SO_LINGER is used.
56 * For those that don't, see USE_SO_LINGER below.  For the rest,
57 * we have created a home-brew lingering_close.
58 *
59 * Many operating systems tend to block, puke, or otherwise mishandle
60 * calls to shutdown only half of the connection.  You should define
61 * NO_LINGCLOSE in ap_config.h if such is the case for your system.
62 */
63#ifndef MAX_SECS_TO_LINGER
64#define MAX_SECS_TO_LINGER 30
65#endif
66
67AP_CORE_DECLARE(void) ap_flush_conn(conn_rec *c)
68{
69    apr_bucket_brigade *bb;
70    apr_bucket *b;
71
72    bb = apr_brigade_create(c->pool, c->bucket_alloc);
73
74    /* FLUSH bucket */
75    b = apr_bucket_flush_create(c->bucket_alloc);
76    APR_BRIGADE_INSERT_TAIL(bb, b);
77
78    /* End Of Connection bucket */
79    b = ap_bucket_eoc_create(c->bucket_alloc);
80    APR_BRIGADE_INSERT_TAIL(bb, b);
81
82    ap_pass_brigade(c->output_filters, bb);
83}
84
85/* we now proceed to read from the client until we get EOF, or until
86 * MAX_SECS_TO_LINGER has passed.  the reasons for doing this are
87 * documented in a draft:
88 *
89 * http://www.ics.uci.edu/pub/ietf/http/draft-ietf-http-connection-00.txt
90 *
91 * in a nutshell -- if we don't make this effort we risk causing
92 * TCP RST packets to be sent which can tear down a connection before
93 * all the response data has been sent to the client.
94 */
95#define SECONDS_TO_LINGER  2
96
97AP_DECLARE(int) ap_start_lingering_close(conn_rec *c)
98{
99    apr_socket_t *csd = ap_get_conn_socket(c);
100
101    if (!csd) {
102        return 1;
103    }
104
105    if (c->sbh) {
106        ap_update_child_status(c->sbh, SERVER_CLOSING, NULL);
107    }
108
109#ifdef NO_LINGCLOSE
110    ap_flush_conn(c); /* just close it */
111    apr_socket_close(csd);
112    return 1;
113#endif
114
115    /* Close the connection, being careful to send out whatever is still
116     * in our buffers.  If possible, try to avoid a hard close until the
117     * client has ACKed our FIN and/or has stopped sending us data.
118     */
119
120    /* Send any leftover data to the client, but never try to again */
121    ap_flush_conn(c);
122
123    if (c->aborted) {
124        apr_socket_close(csd);
125        return 1;
126    }
127
128    /* Shut down the socket for write, which will send a FIN
129     * to the peer.
130     */
131    if (apr_socket_shutdown(csd, APR_SHUTDOWN_WRITE) != APR_SUCCESS
132        || c->aborted) {
133        apr_socket_close(csd);
134        return 1;
135    }
136
137    return 0;
138}
139
140AP_DECLARE(void) ap_lingering_close(conn_rec *c)
141{
142    char dummybuf[512];
143    apr_size_t nbytes;
144    apr_time_t timeup = 0;
145    apr_socket_t *csd = ap_get_conn_socket(c);
146
147    if (ap_start_lingering_close(c)) {
148        return;
149    }
150
151    /* Read available data from the client whilst it continues sending
152     * it, for a maximum time of MAX_SECS_TO_LINGER.  If the client
153     * does not send any data within 2 seconds (a value pulled from
154     * Apache 1.3 which seems to work well), give up.
155     */
156    apr_socket_timeout_set(csd, apr_time_from_sec(SECONDS_TO_LINGER));
157    apr_socket_opt_set(csd, APR_INCOMPLETE_READ, 1);
158
159    /* The common path here is that the initial apr_socket_recv() call
160     * will return 0 bytes read; so that case must avoid the expensive
161     * apr_time_now() call and time arithmetic. */
162
163    do {
164        nbytes = sizeof(dummybuf);
165        if (apr_socket_recv(csd, dummybuf, &nbytes) || nbytes == 0)
166            break;
167
168        if (timeup == 0) {
169            /*
170             * First time through;
171             * calculate now + 30 seconds (MAX_SECS_TO_LINGER).
172             *
173             * If some module requested a shortened waiting period, only wait for
174             * 2s (SECONDS_TO_LINGER). This is useful for mitigating certain
175             * DoS attacks.
176             */
177            if (apr_table_get(c->notes, "short-lingering-close")) {
178                timeup = apr_time_now() + apr_time_from_sec(SECONDS_TO_LINGER);
179            }
180            else {
181                timeup = apr_time_now() + apr_time_from_sec(MAX_SECS_TO_LINGER);
182            }
183            continue;
184        }
185    } while (apr_time_now() < timeup);
186
187    apr_socket_close(csd);
188    return;
189}
190
191AP_CORE_DECLARE(void) ap_process_connection(conn_rec *c, void *csd)
192{
193    int rc;
194    ap_update_vhost_given_ip(c);
195
196    rc = ap_run_pre_connection(c, csd);
197    if (rc != OK && rc != DONE) {
198        c->aborted = 1;
199    }
200
201    if (!c->aborted) {
202        ap_run_process_connection(c);
203    }
204}
205
206