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Tree: 2705426f630f6e62f738ff35da68c91824fe6bbd

Files: 2705426f630f6e62f738ff35da68c91824fe6bbd / sslh-select.c

11703 bytesRaw
1/*
2   sslh-select: mono-processus server
3
4# Copyright (C) 2007-2010  Yves Rutschle
5# 
6# This program is free software; you can redistribute it
7# and/or modify it under the terms of the GNU General Public
8# License as published by the Free Software Foundation; either
9# version 2 of the License, or (at your option) any later
10# version.
11# 
12# This program is distributed in the hope that it will be
13# useful, but WITHOUT ANY WARRANTY; without even the implied
14# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
15# PURPOSE.  See the GNU General Public License for more
16# details.
17# 
18# The full text for the General Public License is here:
19# http://www.gnu.org/licenses/gpl.html
20
21*/
22
23#define __LINUX__
24
25#include "common.h"
26#include "probe.h"
27
28const char* server_type = "sslh-select";
29
30/* cnx_num_alloc is the number of connection to allocate at once (at start-up,
31 * and then every time we get too many simultaneous connections: e.g. start
32 * with 100 slots, then if we get more than 100 connections allocate another
33 * 100 slots, and so on). We never free up connection structures. We try to
34 * allocate as many structures at once as will fit in one page (which is 102
35 * in sslh 1.9 on Linux on x86)
36 */
37static long cnx_num_alloc;
38
39/* Make the file descriptor non-block  */
40int set_nonblock(int fd)
41{
42    int flags;
43
44    flags = fcntl(fd, F_GETFL);
45    CHECK_RES_RETURN(flags, "fcntl");
46
47    flags |= O_NONBLOCK;
48
49    flags = fcntl(fd, F_SETFL, flags);
50    CHECK_RES_RETURN(flags, "fcntl");
51
52    return flags;
53}
54
55int tidy_connection(struct connection *cnx, fd_set *fds, fd_set *fds2)
56{
57    int i;
58
59    for (i = 0; i < 2; i++) {
60        if (cnx->q[i].fd != -1) {
61            if (verbose)
62                fprintf(stderr, "closing fd %d\n", cnx->q[i].fd);
63
64            close(cnx->q[i].fd);
65            FD_CLR(cnx->q[i].fd, fds);
66            FD_CLR(cnx->q[i].fd, fds2);
67            if (cnx->q[i].deferred_data)
68                free(cnx->q[i].deferred_data);
69        }
70    }
71    init_cnx(cnx);
72    return 0;
73}
74
75/* if fd becomes higher than FD_SETSIZE, things won't work so well with FD_SET
76 * and FD_CLR. Need to drop connections if we go above that limit */
77int fd_is_in_range(int fd) {
78    if (fd >= FD_SETSIZE) {
79        log_message(LOG_ERR, "too many open file descriptor to monitor them all -- dropping connection\n");
80        return 0;
81    }
82    return 1;
83}
84
85/* Accepts a connection from the main socket and assigns it to an empty slot.
86 * If no slots are available, allocate another few. If that fails, drop the
87 * connexion */
88int accept_new_connection(int listen_socket, struct connection *cnx[], int* cnx_size) 
89{
90    int in_socket, free, i, res;
91    struct connection *new;
92
93    in_socket = accept(listen_socket, 0, 0);
94    CHECK_RES_RETURN(in_socket, "accept");
95
96    if (!fd_is_in_range(in_socket))
97        return -1;
98
99    res = set_nonblock(in_socket);
100    if (res == -1) return -1;
101
102    /* Find an empty slot */
103    for (free = 0; (free < *cnx_size) && ((*cnx)[free].q[0].fd != -1); free++) {
104        /* nothing */
105    }
106    if (free >= *cnx_size)  {
107        if (verbose)
108            fprintf(stderr, "buying more slots from the slot machine.\n");
109        new = realloc(*cnx, (*cnx_size + cnx_num_alloc) * sizeof((*cnx)[0]));
110        if (!new) {
111            log_message(LOG_ERR, "unable to realloc -- dropping connection\n");
112            return -1;
113        }
114        *cnx = new;
115        *cnx_size += cnx_num_alloc;
116        for (i = free; i < *cnx_size; i++) {
117            init_cnx(&(*cnx)[i]); 
118        }
119    }
120    (*cnx)[free].q[0].fd = in_socket;
121    (*cnx)[free].state = ST_PROBING;
122    (*cnx)[free].probe_timeout = time(NULL) + probing_timeout;
123
124    if (verbose) 
125        fprintf(stderr, "accepted fd %d on slot %d\n", in_socket, free);
126
127    return in_socket;
128}
129
130
131/* Connect queue 1 of connection to SSL; returns new file descriptor */
132int connect_queue(struct connection *cnx, fd_set *fds_r, fd_set *fds_w)
133{
134    struct queue *q = &cnx->q[1];
135
136    q->fd = connect_addr(cnx, cnx->q[0].fd);
137    if ((q->fd != -1) && fd_is_in_range(q->fd)) {
138        log_connection(cnx);
139        set_nonblock(q->fd);
140        flush_deferred(q);
141        if (q->deferred_data) {
142            FD_SET(q->fd, fds_w);
143        } else {
144            FD_SET(q->fd, fds_r);
145        }
146        return q->fd;
147    } else {
148        tidy_connection(cnx, fds_r, fds_w);
149        return -1;
150    }
151}
152
153/* shovels data from active fd to the other
154   returns after one socket closed or operation would block
155 */
156void shovel(struct connection *cnx, int active_fd, 
157            fd_set *fds_r, fd_set *fds_w)
158{
159    struct queue *read_q, *write_q;
160
161    read_q = &cnx->q[active_fd];
162    write_q = &cnx->q[1-active_fd];
163
164    if (verbose)
165        fprintf(stderr, "activity on fd%d\n", read_q->fd);
166
167    switch(fd2fd(write_q, read_q)) {
168    case -1:
169    case FD_CNXCLOSED:
170        tidy_connection(cnx, fds_r, fds_w);
171        break;
172
173    case FD_STALLED:
174        FD_SET(write_q->fd, fds_w);
175        FD_CLR(read_q->fd, fds_r);
176        break;
177
178    default: /* Nothing */
179        break;
180    }
181}
182
183/* returns true if specified fd is initialised and present in fd_set */
184int is_fd_active(int fd, fd_set* set)
185{
186    if (fd == -1) return 0;
187    return FD_ISSET(fd, set);
188}
189
190/* Main loop: the idea is as follow:
191 * - fds_r and fds_w contain the file descriptors to monitor in read and write
192 * - When a file descriptor goes off, process it: read from it, write the data
193 * to its corresponding pair.
194 * - When a file descriptor blocks when writing, remove the read fd from fds_r,
195 * move the data to a deferred buffer, and add the write fd to fds_w. Defered
196 * buffer is allocated dynamically.
197 * - When we can write to a file descriptor that has deferred data, we try to
198 * write as much as we can. Once all data is written, remove the fd from fds_w
199 * and add its corresponding pair to fds_r, free the buffer.
200 *
201 * That way, each pair of file descriptor (read from one, write to the other)
202 * is monitored either for read or for write, but never for both.
203 */
204void main_loop(int listen_sockets[], int num_addr_listen)
205{
206    fd_set fds_r, fds_w;  /* reference fd sets (used to init the next 2) */
207    fd_set readfds, writefds; /* working read and write fd sets */
208    struct timeval tv;
209    int max_fd, in_socket, i, j, res;
210    struct connection *cnx;
211    int num_cnx;  /* Number of connections in *cnx */
212    int num_probing = 0; /* Number of connections currently probing 
213                          * We use this to know if we need to time out of
214                          * select() */
215
216    FD_ZERO(&fds_r);
217    FD_ZERO(&fds_w);
218
219    for (i = 0; i < num_addr_listen; i++) {
220        FD_SET(listen_sockets[i], &fds_r); 
221        set_nonblock(listen_sockets[i]);
222    }
223    max_fd = listen_sockets[num_addr_listen-1] + 1;
224
225    cnx_num_alloc = getpagesize() / sizeof(struct connection);
226
227    num_cnx = cnx_num_alloc; /* Start with a set pool of slots */
228    cnx = malloc(num_cnx * sizeof(struct connection));
229    for (i = 0; i < num_cnx; i++)
230        init_cnx(&cnx[i]);
231
232    while (1)
233    {
234        memset(&tv, 0, sizeof(tv));
235        tv.tv_sec = probing_timeout;
236
237        memcpy(&readfds, &fds_r, sizeof(readfds));
238        memcpy(&writefds, &fds_w, sizeof(writefds));
239
240        if (verbose)
241            fprintf(stderr, "selecting... max_fd=%d num_probing=%d\n", max_fd, num_probing);
242        res = select(max_fd, &readfds, &writefds, NULL, num_probing ? &tv : NULL);
243        if (res < 0)
244            perror("select");
245
246
247        /* Check main socket for new connections */
248        for (i = 0; i < num_addr_listen; i++) {
249            if (FD_ISSET(listen_sockets[i], &readfds)) {
250                in_socket = accept_new_connection(listen_sockets[i], &cnx, &num_cnx);
251                if (in_socket != -1)
252                    num_probing++;
253
254                if (in_socket > 0) {
255                    FD_SET(in_socket, &fds_r);
256                    if (in_socket >= max_fd)
257                        max_fd = in_socket + 1;;
258                }
259                FD_CLR(listen_sockets[i], &readfds);
260            }
261        }
262
263        /* Check all sockets for write activity */
264        for (i = 0; i < num_cnx; i++) {
265            if (cnx[i].q[0].fd != -1) {
266                for (j = 0; j < 2; j++) {
267                    if (is_fd_active(cnx[i].q[j].fd, &writefds)) {
268                        res = flush_deferred(&cnx[i].q[j]);
269                        if ((res == -1) && ((errno == EPIPE) || (errno == ECONNRESET))) {
270                            if (cnx[i].state == ST_PROBING) num_probing--;
271                            tidy_connection(&cnx[i], &fds_r, &fds_w);
272                            if (verbose)
273                                fprintf(stderr, "closed slot %d\n", i);
274                        } else {
275                            /* If no deferred data is left, stop monitoring the fd 
276                             * for write, and restart monitoring the other one for reads*/
277                            if (!cnx[i].q[j].deferred_data_size) {
278                                FD_CLR(cnx[i].q[j].fd, &fds_w);
279                                FD_SET(cnx[i].q[1-j].fd, &fds_r);
280                            }
281                        }
282                    }
283                }
284            }
285        }
286
287        /* Check all sockets for read activity */
288        for (i = 0; i < num_cnx; i++) {
289            for (j = 0; j < 2; j++) {
290                if (is_fd_active(cnx[i].q[j].fd, &readfds) || 
291                    ((cnx[i].state == ST_PROBING) && (cnx[i].probe_timeout < time(NULL)))) {
292                    if (verbose)
293                        fprintf(stderr, "processing fd%d slot %d\n", j, i);
294
295                    switch (cnx[i].state) {
296
297                    case ST_PROBING:
298                        if (j == 1) {
299                            fprintf(stderr, "Activity on fd2 while probing, impossible\n");
300                            dump_connection(&cnx[i]);
301                            exit(1);
302                        }
303
304                        /* If timed out it's SSH, otherwise the client sent
305                         * data so probe the protocol */
306                        if ((cnx[i].probe_timeout < time(NULL))) {
307                            cnx[i].proto = timeout_protocol();
308                        } else {
309                            res = probe_client_protocol(&cnx[i]);
310                            if (res == PROBE_AGAIN)
311                                continue;
312                        }
313
314                        num_probing--;
315                        cnx[i].state = ST_SHOVELING;
316
317                        /* libwrap check if required for this protocol */
318                        if (cnx[i].proto->service &&
319                            check_access_rights(in_socket, cnx[i].proto->service)) {
320                            tidy_connection(&cnx[i], &fds_r, &fds_w);
321                            res = -1;
322                        } else {
323                            res = connect_queue(&cnx[i], &fds_r, &fds_w);
324                        }
325
326                        if (res >= max_fd)
327                            max_fd = res + 1;;
328                        break;
329
330                    case ST_SHOVELING:
331                        shovel(&cnx[i], j, &fds_r, &fds_w);
332                        break;
333
334                    default: /* illegal */
335                        log_message(LOG_ERR, "Illegal connection state %d\n", cnx[i].state);
336                        exit(1);
337                    }
338                }
339            }
340        }
341    }
342}
343
344
345void start_shoveler(int listen_socket) {
346    fprintf(stderr, "inetd mode is not supported in select mode\n");
347    exit(1);
348}
349
350
351/* The actual main is in common.c: it's the same for both version of
352 * the server
353 */
354
355
356

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