3 * $Id: bres.c,v 1.1 1999/07/01 08:56:23 mdw Exp $
5 * Background reverse name resolution
7 * (c) 1999 Mark Wooding
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of the `fw' port forwarder.
14 * `fw' is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU General Public License as published by
16 * the Free Software Foundation; either version 2 of the License, or
17 * (at your option) any later version.
19 * `fw' is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU General Public License for more details.
24 * You should have received a copy of the GNU General Public License
25 * along with `fw'; if not, write to the Free Software Foundation,
26 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
29 /*----- Revision history --------------------------------------------------*
32 * Revision 1.1 1999/07/01 08:56:23 mdw
37 /*----- Header files ------------------------------------------------------*/
45 #include <sys/types.h>
50 #include <sys/socket.h>
51 #include <netinet/in.h>
52 #include <arpa/inet.h>
55 #include <mLib/report.h>
57 #include <mLib/selbuf.h>
61 /*----- Magic numbers -----------------------------------------------------*/
63 #define BRES_MAX 5 /* Maximum number of resolvers */
64 #define BRES_IDLE 60 /* Lifetime of an idle resolver */
66 /*----- Static variables --------------------------------------------------*/
68 static bres_server servers
[BRES_MAX
]; /* Statically allocated servers */
70 #define FREE ((bres_server *)&freelist)
71 static struct { bres_server
*next
, *prev
; } freelist
= { FREE
, FREE
};
73 #define QUEUE ((bres_client *)&queue)
74 static struct { bres_client
*next
, *prev
; } queue
= { QUEUE
, QUEUE
};
76 static sel_state
*sel
;
78 /*----- Main code ---------------------------------------------------------*/
82 * Arguments: @bres_server *rs@ = pointer to server block
86 * Use: Kills a server process, reaps the losing child and makes
87 * things generally clean again.
90 static void zap(bres_server
*rs
)
92 /* --- Close the pipes, kill the child, and reap it --- */
95 selbuf_disable(&rs
->b
);
97 close(rs
->b
.reader
.fd
);
98 kill(rs
->kid
, SIGTERM
);
99 waitpid(rs
->kid
, 0, 0);
103 /* --- Move the server to the back of the list --- */
105 rs
->next
->prev
= rs
->prev
;
106 rs
->prev
->next
= rs
->next
;
108 rs
->prev
= FREE
->prev
;
109 FREE
->prev
->next
= rs
;
113 /* --- @bres_abort@ --- *
115 * Arguments: @bres_client *rc@ = pointer to client block
119 * Use: Removes a queued job.
122 void bres_abort(bres_client
*rc
)
128 rc
->next
->prev
= rc
->prev
;
129 rc
->prev
->next
= rc
->next
;
135 * Arguments: @int rfd@ = output file descriptor for resolved hostnames
136 * @int cfd@ = input file descriptor for raw addresses
140 * Use: Asynchronous name resolving process.
143 static void child(int rfd
, int cfd
)
146 FILE *fp
= fdopen(rfd
, "w");
150 int maxfd
= sysconf(_SC_OPEN_MAX
);
152 for (i
= 0; i
< maxfd
; i
++) {
153 if (i
!= rfd
&& i
!= cfd
)
159 int r
= read(cfd
, &addr
, sizeof(addr
));
165 else if (r
!= sizeof(addr
))
168 h
= gethostbyaddr((char *)&addr
, sizeof(addr
), AF_INET
);
173 fprintf(fp
, "%s\n", p
);
181 * Arguments: @struct timeval *tv@ = pointer to the current time
182 * @void *vp@ = pointer to a server block
186 * Use: Kills off a child which has been idle for too long.
189 static void idle(struct timeval
*tv
, void *vp
)
191 bres_server
*rs
= vp
;
195 /* --- @answer@ --- *
197 * Arguments: @char *p@ = pointer to string read
198 * @void *vp@ = pointer to server block
202 * Use: Retrieves an answer from a name resolver process.
205 static void attach(bres_client */
*rc*/
);
207 static void answer(char *p
, void *vp
)
209 bres_server
*rs
= vp
;
210 bres_client
*rc
= rs
->rc
;
212 /* --- Report the result to my client --- */
221 /* --- Wrap up the various structures --- */
225 rs
->next
= FREE
->next
;
227 FREE
->next
->prev
= rs
;
230 /* --- Tie a timer onto the server block --- */
235 gettimeofday(&tv
, 0);
236 tv
.tv_sec
+= BRES_IDLE
;
237 sel_addtimer(sel
, &rs
->t
, &tv
, idle
, rs
);
240 /* --- If there are any clients waiting, attach one --- */
242 if (QUEUE
->next
!= QUEUE
) {
244 QUEUE
->next
= rc
->next
;
245 rc
->next
->prev
= QUEUE
;
252 * Arguments: @bres_server *rs@ = pointer to a server block
254 * Returns: Zero if OK, nonzero if something failed.
256 * Use: Starts up a child resolver process.
259 static int start(bres_server
*rs
)
264 /* --- Make the pipes --- */
271 /* --- Start up the child process --- */
273 if ((kid
= fork()) < 0)
278 child(rfd
[1], cfd
[0]);
282 /* --- Fix up everything in the server block --- */
287 selbuf_init(&rs
->b
, sel
, rfd
[0], answer
, rs
);
291 /* --- Fix up after errors --- */
303 /* --- @attach@ --- *
305 * Arguments: @bres_client *rc@ = pointer to a client block
309 * Use: Attaches a client to a spare server (which is assumed to
313 static void attach(bres_client
*rc
)
318 /* --- Fix up the server ready for the job --- *
320 * If the server has a process, remove its timer. Otherwise, fork off a
321 * new resolver process. This is also where I go if I find that the child
322 * resolver process has lost while I wasn't looking. Only one attempt at
323 * forking is performed.
331 if (lose
|| start(rs
))
336 /* --- Submit the job to the resolver --- */
339 struct sigaction sa
, osa
;
342 /* --- Ignore @SIGPIPE@ for now --- *
344 * This way I can trap @EPIPE@ and reap a losing child, if there was one.
347 sa
.sa_handler
= SIG_IGN
;
349 sigemptyset(&sa
.sa_mask
);
350 sigaction(SIGPIPE
, &sa
, &osa
);
352 /* --- Write the new job to the child --- */
355 if (write(rs
->fd
, &rc
->addr
, sizeof(rc
->addr
)) < 0)
357 sigaction(SIGPIPE
, &osa
, 0);
359 /* --- Sort out various errors --- */
368 /* --- Fiddle with lists so that everything's OK --- */
370 rs
->next
->prev
= FREE
;
371 FREE
->next
= rs
->next
;
372 rs
->next
= rs
->prev
= rs
;
381 /* --- @bres_resolve@ --- *
383 * Arguments: @bres_client *rc@ = pointer to client block
384 * @struct in_addr addr@ = address to resolve
385 * @void (*func)(const char *host, void *p)@ = handler function
386 * @void *p@ = argument for handler function
390 * Use: Adds a resolver job to the queue. The job will be processed
391 * when there's a spare resolver process to deal with it.
394 void bres_resolve(bres_client
*rc
, struct in_addr addr
,
395 void (*func
)(const char */
*host*/
, void */
*p*/
), void *p
)
397 /* --- Fill in the structure --- */
404 /* --- If there's a free server, plug it in --- */
406 if (FREE
->next
== FREE
) {
408 rc
->prev
= QUEUE
->prev
;
409 QUEUE
->prev
->next
= rc
;
415 /* --- @bres_init@ --- *
417 * Arguments: @sel_state *s@ = pointer to select multiplexor
421 * Use: Initializes the background resolver for use.
424 void bres_init(sel_state
*s
)
429 for (i
= 0; i
< BRES_MAX
; i
++) {
430 servers
[i
].next
= FREE
;
431 servers
[i
].prev
= FREE
->prev
;
434 FREE
->prev
->next
= &servers
[i
];
435 FREE
->prev
= &servers
[i
];
439 /*----- That's all, folks -------------------------------------------------*/