2006-04-28 10:51:19 +00:00
parent 51c3484a9f
commit 1029d84d23
514 changed files with 2 additions and 2 deletions
@@ -0,0 +1,615 @@
+/* Pluto Asynchronous DNS Helper Program -- for internal use only!
+ * Copyright (C) 2002  D. Hugh Redelmeier.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ *
+ * RCSID $Id: adns.c,v 1.1 2004/03/15 20:35:28 as Exp $
+ */
+
+#ifndef USE_LWRES	/* whole file! */
+
+/* This program executes as multiple processes.  The Master process
+ * receives queries (struct adns_query messages) from Pluto and distributes
+ * them amongst Worker processes.  These Worker processes are created
+ * by the Master whenever a query arrives and no existing Worker is free.
+ * At most MAX_WORKERS will be created; after that, the Master will queue
+ * queries until a Worker becomes free.  When a Worker has an answer from
+ * the resolver, it sends the answer as a struct adns_answer message to the
+ * Master.  The Master then forwards the answer to Pluto, noting that
+ * the Worker is free to accept another query.
+ *
+ * The protocol is simple: Pluto sends a sequence of queries and receives
+ * a sequence of answers.  select(2) is used by Pluto and by the Master
+ * process to decide when to read, but writes are done without checking
+ * for readiness.  Communications is via pipes.  Since only one process
+ * can write to each pipe, messages will not be interleaved.  Fixed length
+ * records are used for simplicity.
+ *
+ * Pluto needs a way to indicate to the Master when to shut down
+ * and the Master needs to indicate this to each worker.  EOF on the pipe
+ * signifies this.
+ *
+ * The interfaces between these components are considered private to
+ * Pluto.  This allows us to get away with less checking.  This is a
+ * reason to use pipes instead of TCP/IP.
+ *
+ * Although the code uses plain old UNIX processes, it could be modified
+ * to use threads.  That might reduce resource requirements.  It would
+ * preclude running on systems without thread-safe resolvers.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <syslog.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+#include <netdb.h>	/* ??? for h_errno */
+
+#include <freeswan.h>
+
+/* GCC magic! */
+#ifdef GCC_LINT
+# define UNUSED __attribute__ ((unused))
+#else
+# define UNUSED /* ignore */
+#endif
+
+#include "constants.h"
+#include "adns.h"	/* needs <resolv.h> */
+
+/* shared by all processes */
+
+static const char *name;	/* program name, for messages */
+
+static bool debug = FALSE;
+
+/* Read a variable-length record from a pipe (and no more!).
+ * First bytes must be a size_t containing the length.
+ * HES_CONTINUE if record read
+ * HES_OK if EOF
+ * HES_IO_ERROR_IN if errno tells the tale.
+ * Others are errors.
+ */
+static enum helper_exit_status
+read_pipe(int fd, unsigned char *stuff, size_t minlen, size_t maxlen)
+{
+    size_t n = 0;
+    size_t goal = minlen;
+
+    do {
+	ssize_t m = read(fd, stuff + n, goal - n);
+
+	if (m == -1)
+	{
+	    if (errno != EINTR)
+	    {
+		syslog(LOG_ERR, "Input error on pipe: %s", strerror(errno));
+		return HES_IO_ERROR_IN;
+	    }
+	}
+	else if (m == 0)
+	{
+	    return HES_OK;	/* treat empty message as EOF */
+	}
+	else
+	{
+	    n += m;
+	    if (n >= sizeof(size_t))
+	    {
+		goal = *(size_t *)(void *)stuff;
+		if (goal < minlen || maxlen < goal)
+		{
+		    if (debug)
+			fprintf(stderr, "%lu : [%lu, %lu]\n"
+			    , (unsigned long)goal
+			    , (unsigned long)minlen, (unsigned long)maxlen);
+		    return HES_BAD_LEN;
+		}
+	    }
+	}
+    } while (n < goal);
+
+    return HES_CONTINUE;
+}
+
+/* Write a variable-length record to a pipe.
+ * First bytes must be a size_t containing the length.
+ * HES_CONTINUE if record written
+ * Others are errors.
+ */
+static enum helper_exit_status
+write_pipe(int fd, const unsigned char *stuff)
+{
+    size_t len = *(const size_t *)(const void *)stuff;
+    size_t n = 0;
+
+    do {
+	ssize_t m = write(fd, stuff + n, len - n);
+
+	if (m == -1)
+	{
+	    /* error, but ignore and retry if EINTR */
+	    if (errno != EINTR)
+	    {
+		syslog(LOG_ERR, "Output error from master: %s", strerror(errno));
+		return HES_IO_ERROR_OUT;
+	    }
+	}
+	else
+	{
+	    n += m;
+	}
+    } while (n != len);
+    return HES_CONTINUE;
+}
+
+/**************** worker process ****************/
+
+/* The interface in RHL6.x and BIND distribution 8.2.2 are different,
+ * so we build some of our own :-(
+ */
+
+/* Support deprecated interface to allow for older releases of the resolver.
+ * Fake new interface!
+ * See resolver(3) bind distribution (should be in RHL6.1, but isn't).
+ * __RES was 19960801 in RHL6.2, an old resolver.
+ */
+
+#if (__RES) <= 19960801
+# define OLD_RESOLVER	1
+#endif
+
+#ifdef OLD_RESOLVER
+
+# define res_ninit(statp) res_init()
+# define res_nquery(statp, dname, class, type, answer, anslen) \
+    res_query(dname, class, type, answer, anslen)
+# define res_nclose(statp) res_close()
+
+static struct __res_state *statp = &_res;
+
+#else /* !OLD_RESOLVER */
+
+static struct __res_state my_res_state /* = { 0 } */;
+static res_state statp = &my_res_state;
+
+#endif /* !OLD_RESOLVER */
+
+static int
+worker(int qfd, int afd)
+{
+    {
+	int r = res_ninit(statp);
+
+	if (r != 0)
+	{
+	    syslog(LOG_ERR, "cannot initialize resolver");
+	    return HES_RES_INIT;
+	}
+#ifndef OLD_RESOLVER
+	statp->options |= RES_ROTATE;
+#endif
+	statp->options |= RES_DEBUG;
+    }
+
+    for (;;)
+    {
+	struct adns_query q;
+	struct adns_answer a;
+
+	enum helper_exit_status r = read_pipe(qfd, (unsigned char *)&q
+	    , sizeof(q), sizeof(q));
+
+	if (r != HES_CONTINUE)
+	    return r;	/* some kind of exit */
+
+	if (q.qmagic != ADNS_Q_MAGIC)
+	{
+	    syslog(LOG_ERR, "error in input from master: bad magic");
+	    return HES_BAD_MAGIC;
+	}
+
+	a.amagic = ADNS_A_MAGIC;
+	a.serial = q.serial;
+
+	a.result = res_nquery(statp, q.name_buf, C_IN, q.type, a.ans, sizeof(a.ans));
+	a.h_errno_val = h_errno;
+
+	a.len = offsetof(struct adns_answer, ans) + (a.result < 0? 0 : a.result);
+
+#ifdef DEBUG
+	if (((q.debugging & IMPAIR_DELAY_ADNS_KEY_ANSWER) && q.type == T_KEY)
+	|| ((q.debugging & IMPAIR_DELAY_ADNS_TXT_ANSWER) && q.type == T_TXT))
+	    sleep(30);	/* delay the answer */
+#endif
+
+	/* write answer, possibly a bit at a time */
+	r = write_pipe(afd, (const unsigned char *)&a);
+
+	if (r != HES_CONTINUE)
+	    return r;	/* some kind of exit */
+    }
+}
+
+/**************** master process ****************/
+
+bool eof_from_pluto = FALSE;
+#define PLUTO_QFD	0	/* queries come on stdin */
+#define PLUTO_AFD	1	/* answers go out on stdout */
+
+#ifndef MAX_WORKERS
+# define MAX_WORKERS 10	/* number of in-flight queries */
+#endif
+
+struct worker_info {
+    int qfd;	/* query pipe's file descriptor */
+    int afd;	/* answer pipe's file descriptor */
+    pid_t pid;
+    bool busy;
+    void *continuation;	/* of outstanding request */
+};
+
+static struct worker_info wi[MAX_WORKERS];
+static struct worker_info *wi_roof = wi;
+
+/* request FIFO */
+
+struct query_list {
+    struct query_list *next;
+    struct adns_query aq;
+};
+
+static struct query_list *oldest_query = NULL;
+static struct query_list *newest_query;	/* undefined when oldest == NULL */
+static struct query_list *free_queries = NULL;
+
+static bool
+spawn_worker(void)
+{
+    int qfds[2];
+    int afds[2];
+    pid_t p;
+
+    if (pipe(qfds) != 0 || pipe(afds) != 0)
+    {
+	syslog(LOG_ERR, "pipe(2) failed: %s", strerror(errno));
+	exit(HES_PIPE);
+    }
+
+    wi_roof->qfd = qfds[1];	/* write end of query pipe */
+    wi_roof->afd = afds[0];	/* read end of answer pipe */
+
+    p = fork();
+    if (p == -1)
+    {
+	/* fork failed: ignore if at least one worker exists */
+	if (wi_roof == wi)
+	{
+	    syslog(LOG_ERR, "fork(2) error creating first worker: %s", strerror(errno));
+	    exit(HES_FORK);
+	}
+	close(qfds[0]);
+	close(qfds[1]);
+	close(afds[0]);
+	close(afds[1]);
+	return FALSE;
+    }
+    else if (p == 0)
+    {
+	/* child */
+	struct worker_info *w;
+
+	close(PLUTO_QFD);
+	close(PLUTO_AFD);
+	/* close all master pipes, including ours */
+	for (w = wi; w <= wi_roof; w++)
+	{
+	    close(w->qfd);
+	    close(w->afd);
+	}
+	exit(worker(qfds[0], afds[1]));
+    }
+    else
+    {
+	/* parent */
+	struct worker_info *w = wi_roof++;
+
+	w->pid = p;
+	w->busy = FALSE;
+	close(qfds[0]);
+	close(afds[1]);
+	return TRUE;
+    }
+}
+
+static void
+send_eof(struct worker_info *w)
+{
+    pid_t p;
+    int status;
+
+    close(w->qfd);
+    w->qfd = NULL_FD;
+
+    close(w->afd);
+    w->afd = NULL_FD;
+
+    /* reap child */
+    p = waitpid(w->pid, &status, 0);
+    /* ignore result -- what could we do with it? */
+}
+
+static void
+forward_query(struct worker_info *w)
+{
+    struct query_list *q = oldest_query;
+
+    if (q == NULL)
+    {
+	if (eof_from_pluto)
+	    send_eof(w);
+    }
+    else
+    {
+	enum helper_exit_status r
+	    = write_pipe(w->qfd, (const unsigned char *) &q->aq);
+
+	if (r != HES_CONTINUE)
+	    exit(r);
+
+	w->busy = TRUE;
+
+	oldest_query = q->next;
+	q->next = free_queries;
+	free_queries = q;
+    }
+}
+
+static void
+query(void)
+{
+    struct query_list *q = free_queries;
+    enum helper_exit_status r;
+
+    /* find an unused queue entry */
+    if (q == NULL)
+    {
+	q = malloc(sizeof(*q));
+	if (q == NULL)
+	{
+	    syslog(LOG_ERR, "malloc(3) failed");
+	    exit(HES_MALLOC);
+	}
+    }
+    else
+    {
+	free_queries = q->next;
+    }
+
+    r = read_pipe(PLUTO_QFD, (unsigned char *)&q->aq
+	, sizeof(q->aq), sizeof(q->aq));
+
+    if (r == HES_OK)
+    {
+	/* EOF: we're done, except for unanswered queries */
+	struct worker_info *w;
+
+	eof_from_pluto = TRUE;
+	q->next = free_queries;
+	free_queries = q;
+
+	/* Send bye-bye to unbusy processes.
+	 * Note that if there are queued queries, there won't be
+	 * any non-busy workers.
+	 */
+	for (w = wi; w != wi_roof; w++)
+	    if (!w->busy)
+		send_eof(w);
+    }
+    else if (r != HES_CONTINUE)
+    {
+	exit(r);
+    }
+    else if (q->aq.qmagic != ADNS_Q_MAGIC)
+    {
+	syslog(LOG_ERR, "error in query from Pluto: bad magic");
+	exit(HES_BAD_MAGIC);
+    }
+    else
+    {
+	struct worker_info *w;
+
+	/* got a query */
+
+	/* add it to FIFO */
+	q->next = NULL;
+	if (oldest_query == NULL)
+	    oldest_query = q;
+	else
+	    newest_query->next = q;
+	newest_query = q;
+
+	/* See if any worker available */
+	for (w = wi; ; w++)
+	{
+	    if (w == wi_roof)
+	    {
+		/* no free worker */
+		if (w == wi + MAX_WORKERS)
+		    break;	/* no more to be created */
+		/* make a new one */
+		if (!spawn_worker())
+		    break;	/* cannot create one at this time */
+	    }
+	    if (!w->busy)
+	    {
+		/* assign first to free worker */
+		forward_query(w);
+		break;
+	    }
+	}
+    }
+    return;
+}
+
+static void
+answer(struct worker_info *w)
+{
+    struct adns_answer a;
+    enum helper_exit_status r = read_pipe(w->afd, (unsigned char *)&a
+	, offsetof(struct adns_answer, ans), sizeof(a));
+
+    if (r == HES_OK)
+    {
+	/* unexpected EOF */
+	syslog(LOG_ERR, "unexpected EOF from worker");
+	exit(HES_IO_ERROR_IN);
+    }
+    else if (r != HES_CONTINUE)
+    {
+	exit(r);
+    }
+    else if (a.amagic != ADNS_A_MAGIC)
+    {
+	syslog(LOG_ERR, "Input from worker error: bad magic");
+	exit(HES_BAD_MAGIC);
+    }
+    else if (a.continuation != w->continuation)
+    {
+	/* answer doesn't match query */
+	syslog(LOG_ERR, "Input from worker error: continuation mismatch");
+	exit(HES_SYNC);
+    }
+    else
+    {
+	/* pass the answer on to Pluto */
+	enum helper_exit_status r
+	    = write_pipe(PLUTO_AFD, (const unsigned char *) &a);
+
+	if (r != HES_CONTINUE)
+	    exit(r);
+	w->busy = FALSE;
+	forward_query(w);
+    }
+}
+
+/* assumption: input limited; accept blocking on output */
+static int
+master(void)
+{
+    for (;;)
+    {
+	fd_set readfds;
+	int maxfd = PLUTO_QFD;		/* approximate lower bound */
+	int ndes = 0;
+	struct worker_info *w;
+
+	FD_ZERO(&readfds);
+	if (!eof_from_pluto)
+	{
+	    FD_SET(PLUTO_QFD, &readfds);
+	    ndes++;
+	}
+	for (w = wi; w != wi_roof; w++)
+	{
+	    if (w->busy)
+	    {
+		FD_SET(w->afd, &readfds);
+		ndes++;
+		if (maxfd < w->afd)
+		    maxfd = w->afd;
+	    }
+	}
+
+	if (ndes == 0)
+	    return HES_OK;	/* done! */
+
+	do {
+	    ndes = select(maxfd + 1, &readfds, NULL, NULL, NULL);
+	} while (ndes == -1 && errno == EINTR);
+	if (ndes == -1)
+	{
+	    syslog(LOG_ERR, "select(2) error: %s", strerror(errno));
+	    exit(HES_IO_ERROR_SELECT);
+	}
+	else if (ndes > 0)
+	{
+	    if (FD_ISSET(PLUTO_QFD, &readfds))
+	    {
+		query();
+		ndes--;
+	    }
+	    for (w = wi; ndes > 0 && w != wi_roof; w++)
+	    {
+		if (w->busy && FD_ISSET(w->afd, &readfds))
+		{
+		    answer(w);
+		    ndes--;
+		}
+	    }
+	}
+    }
+}
+
+/* Not to be invoked by strangers -- user hostile.
+ * Mandatory args: query-fd answer-fd
+ * Optional arg: -d, signifying "debug".
+ */
+
+static void
+adns_usage(const char *fmt, const char *arg)
+{
+    const char **sp = ipsec_copyright_notice();
+
+    fprintf(stderr, "INTERNAL TO PLUTO: DO NOT EXECUTE\n");
+
+    fprintf(stderr, fmt, arg);
+    fprintf(stderr, "\n%s\n", ipsec_version_string());
+
+    for (; *sp != NULL; sp++)
+	fprintf(stderr, "%s\n", *sp);
+
+    syslog(LOG_ERR, fmt, arg);
+    exit(HES_INVOCATION);
+}
+
+int
+main(int argc UNUSED, char **argv)
+{
+    int i = 1;
+
+    name = argv[0];
+
+    while (i < argc)
+    {
+	if (streq(argv[i], "-d"))
+	{
+	    i++;
+	    debug = TRUE;
+	}
+	else
+	{
+	    adns_usage("unexpected argument \"%s\"", argv[i]);
+	    /*NOTREACHED*/
+	}
+    }
+
+    return master();
+}
+
+#endif /* !USE_LWRES */