This is a demo that performs SSL tunneling (client and/or server) and is

built using an abstracted state machine with a non-blocking IP wrapper
around it. README will follow in the next commit.

1 files changed, 733 insertions, 0 deletions

diff --git a/demos/tunala/tunala.c b/demos/tunala/tunala.c
new file mode 100644
index 0000000000..445940fabd
--- /dev/null
+++ b/demos/tunala/tunala.c
@@ -0,0 +1,733 @@
+#if defined(NO_BUFFER) || defined(NO_IP) || defined(NO_OPENSSL)
+#error "Badness, NO_BUFFER, NO_IP or NO_OPENSSL is defined, turn them *off*"
+#endif
+
+/* Include our bits'n'pieces */
+#include "tunala.h"
+
+
+/********************************************/
+/* Our local types that specify our "world" */
+/********************************************/
+
+/* These represent running "tunnels". Eg. if you wanted to do SSL in a
+ * "message-passing" scanario, the "int" file-descriptors might be replaced by
+ * thread or process IDs, and the "select" code might be replaced by message
+ * handling code. Whatever. */
+typedef struct _tunala_item_t {
+	/* The underlying SSL state machine. This is a data-only processing unit
+	 * and we communicate with it by talking to its four "buffers". */
+	state_machine_t sm;
+	/* The file-descriptors for the "dirty" (encrypted) side of the SSL
+	 * setup. In actuality, this is typically a socket and both values are
+	 * identical. */
+	int dirty_read, dirty_send;
+	/* The file-descriptors for the "clean" (unencrypted) side of the SSL
+	 * setup. These could be stdin/stdout, a socket (both values the same),
+	 * or whatever you like. */
+	int clean_read, clean_send;
+} tunala_item_t;
+
+/* This structure is used as the data for running the main loop. Namely, in a
+ * network format such as this, it is stuff for select() - but as pointed out,
+ * when moving the real-world to somewhere else, this might be replaced by
+ * something entirely different. It's basically the stuff that controls when
+ * it's time to do some "work". */
+typedef struct _select_sets_t {
+	int max; /* As required as the first argument to select() */
+	fd_set reads, sends, excepts; /* As passed to select() */
+} select_sets_t;
+typedef struct _tunala_selector_t {
+	select_sets_t last_selected; /* Results of the last select() */
+	select_sets_t next_select; /* What we'll next select on */
+} tunala_selector_t;
+
+/* This structure is *everything*. We do it to avoid the use of globals so that,
+ * for example, it would be easier to shift things around between async-IO,
+ * thread-based, or multi-fork()ed (or combinations thereof). */
+typedef struct _tunala_world_t {
+	/* The file-descriptor we "listen" on for new connections */
+	int listen_fd;
+	/* The array of tunnels */
+	tunala_item_t *tunnels;
+	/* the number of tunnels in use and allocated, respectively */
+	unsigned int tunnels_used, tunnels_size;
+	/* Our outside "loop" context stuff */
+	tunala_selector_t selector;
+	/* Our SSL_CTX, which is configured as the SSL client or server and has
+	 * the various cert-settings and callbacks configured. */
+	SSL_CTX *ssl_ctx;
+	/* Simple flag with complex logic :-) Indicates whether we're an SSL
+	 * server or an SSL client. */
+	int server_mode;
+} tunala_world_t;
+
+/*****************************/
+/* Internal static functions */
+/*****************************/
+
+static SSL_CTX *initialise_ssl_ctx(int server_mode, const char *engine_id,
+		const char *CAfile, const char *cert, const char *key);
+static void selector_init(tunala_selector_t *selector);
+static void selector_add_listener(tunala_selector_t *selector, int fd);
+static void selector_add_tunala(tunala_selector_t *selector, tunala_item_t *t);
+static int selector_select(tunala_selector_t *selector);
+/* This returns -1 for error, 0 for no new connections, or 1 for success, in
+ * which case *newfd is populated. */
+static int selector_get_listener(tunala_selector_t *selector, int fd, int *newfd);
+static int tunala_world_new_item(tunala_world_t *world, int fd,
+		const unsigned char *ip, unsigned short port);
+static void tunala_world_del_item(tunala_world_t *world, unsigned int idx);
+static int tunala_item_io(tunala_selector_t *selector, tunala_item_t *item);
+
+/*********************************************/
+/* MAIN FUNCTION (and its utility functions) */
+/*********************************************/
+
+/* For now, hard-coded as follows;
+ * (a) We're like "tunala -listen 127.0.0.1:9001 -proxy 127.0.0.1:9002"
+ * (b) We max out at 50 simultaneous tunnels, listening will stop while we have
+ *     that many tunnels operating and will recommence as/when tunnels close.
+ * (c) We are an SSL client proxy
+ * (d) We use the "openssl" ENGINE
+ * (e) We use the CA cert file "cacert.pem"
+ * */
+
+static const char *def_proxyhost = "127.0.0.1:443";
+static const char *def_listenhost = "127.0.0.1:8080";
+static int def_max_tunnels = 50;
+static const char *def_cacert = NULL;
+static const char *def_cert = NULL;
+static const char *def_key = NULL;
+static const char *def_engine_id = NULL;
+static int def_server_mode = 0;
+
+static const char *helpstring =
+	"\n'Tunala' (A tunneler with a New Zealand accent)\n"
+	"Usage: tunala [options], where options are from;\n"
+	"    -listen [host:]<port>  (default = 127.0.0.1:8080)\n"
+	"    -proxy <host>:<port>   (default = 127.0.0.1:443)\n"
+	"    -maxtunnels <num>      (default = 50)\n"
+	"    -cacert <path|NULL>    (default = NULL)\n"
+	"    -cert <path|NULL>      (default = NULL)\n"
+	"    -key <path|NULL>       (default = whatever '-cert' is)\n"
+	"    -engine <id|NULL>      (default = NULL)\n"
+	"    -server <0|1>          (default = 0, ie. an SSL client)\n"
+	"    -<h|help|?>            (displays this help screen)\n"
+	"NB: It is recommended to specify a cert+key when operating as an\n"
+	"SSL server. If you only specify '-cert', the same file must\n"
+	"contain a matching private key.\n";
+
+static int usage(const char *errstr, int isunknownarg)
+{
+	if(isunknownarg)
+		fprintf(stderr, "Error: unknown argument '%s'\n", errstr);
+	else
+		fprintf(stderr, "Error: %s\n", errstr);
+	fprintf(stderr, "%s\n", helpstring);
+	return 1;
+}
+
+static int err_str0(const char *str0)
+{
+	fprintf(stderr, str0);
+	fprintf(stderr, "\n");
+	return 1;
+}
+
+static int err_str1(const char *str0, const char *str1)
+{
+	fprintf(stderr, str0, str1);
+	fprintf(stderr, "\n");
+	return 1;
+}
+
+static int parse_max_tunnels(const char *s, unsigned int *maxtunnels)
+{
+	unsigned long l;
+	char *temp;
+	l = strtoul(s, &temp, 10);
+	if((temp == s) || (*temp != '\0') || (l < 1) || (l > 1024)) {
+		fprintf(stderr, "Error, '%s' is an invalid value for "
+				"maxtunnels\n", s);
+		return 0;
+	}
+	*maxtunnels = (unsigned int)l;
+	return 1;
+}
+
+static int parse_server_mode(const char *s, int *servermode)
+{
+	unsigned long l;
+	char *temp;
+	l = strtoul(s, &temp, 10);
+	if((temp == s) || (*temp != '\0') || (l > 1)) {
+		fprintf(stderr, "Error, '%s' is an invalid value for the "
+				"server mode\n", s);
+		return 0;
+	}
+	*servermode = (int)l;
+	return 1;
+}
+
+int main(int argc, char *argv[])
+{
+	unsigned int loop;
+	int newfd;
+	tunala_world_t world;
+	tunala_item_t *t_item;
+	unsigned char *proxy_ip;
+	unsigned short proxy_port;
+	/* Overridables */
+	const char *proxyhost = def_proxyhost;
+	const char *listenhost = def_listenhost;
+	unsigned int max_tunnels = def_max_tunnels;
+	const char *cacert = def_cacert;
+	const char *cert = def_cert;
+	const char *key = def_key;
+	const char *engine_id = def_engine_id;
+	int server_mode = def_server_mode;
+
+/* Parse command-line arguments */
+next_arg:
+	argc--; argv++;
+	if(argc > 0) {
+		if(strcmp(*argv, "-listen") == 0) {
+			if(argc < 2)
+				return usage("-listen requires an argument", 0);
+			argc--; argv++;
+			listenhost = *argv;
+			goto next_arg;
+		} else if(strcmp(*argv, "-proxy") == 0) {
+			if(argc < 2)
+				return usage("-proxy requires an argument", 0);
+			argc--; argv++;
+			proxyhost = *argv;
+			goto next_arg;
+		} else if(strcmp(*argv, "-maxtunnels") == 0) {
+			if(argc < 2)
+				return usage("-maxtunnels requires an argument", 0);
+			argc--; argv++;
+			if(!parse_max_tunnels(*argv, &max_tunnels))
+				return 1;
+			goto next_arg;
+		} else if(strcmp(*argv, "-cacert") == 0) {
+			if(argc < 2)
+				return usage("-cacert requires an argument", 0);
+			argc--; argv++;
+			if(strcmp(*argv, "NULL") == 0)
+				cacert = NULL;
+			else
+				cacert = *argv;
+			goto next_arg;
+		} else if(strcmp(*argv, "-cert") == 0) {
+			if(argc < 2)
+				return usage("-cert requires an argument", 0);
+			argc--; argv++;
+			if(strcmp(*argv, "NULL") == 0)
+				cert = NULL;
+			else
+				cert = *argv;
+			goto next_arg;
+		} else if(strcmp(*argv, "-key") == 0) {
+			if(argc < 2)
+				return usage("-key requires an argument", 0);
+			argc--; argv++;
+			if(strcmp(*argv, "NULL") == 0)
+				key = NULL;
+			else
+				key = *argv;
+			goto next_arg;
+		} else if(strcmp(*argv, "-engine") == 0) {
+			if(argc < 2)
+				return usage("-engine requires an argument", 0);
+			argc--; argv++;
+			engine_id = *argv;
+			goto next_arg;
+		} else if(strcmp(*argv, "-server") == 0) {
+			if(argc < 2)
+				return usage("-server requires an argument", 0);
+			argc--; argv++;
+			if(!parse_server_mode(*argv, &server_mode))
+				return 1;
+			goto next_arg;
+		} else if((strcmp(*argv, "-h") == 0) ||
+				(strcmp(*argv, "-help") == 0) ||
+				(strcmp(*argv, "-?") == 0)) {
+			fprintf(stderr, "%s\n", helpstring);
+			return 0;
+		} else
+			return usage(*argv, 1);
+	}
+
+	/* Initialise network stuff */
+	if(!ip_initialise())
+		return err_str0("ip_initialise failed");
+	err_str0("ip_initialise succeeded");
+	/* Create the SSL_CTX */
+	if((world.ssl_ctx = initialise_ssl_ctx(server_mode, engine_id,
+			cacert, cert, key)) == NULL)
+		return err_str1("initialise_ssl_ctx(engine_id=%s) failed",
+			(engine_id == NULL) ? "NULL" : engine_id);
+	err_str1("initialise_ssl_ctx(engine_id=%s) succeeded",
+			(engine_id == NULL) ? "NULL" : engine_id);
+	/* Create the listener */
+	if((world.listen_fd = ip_create_listener(listenhost)) == -1)
+		return err_str1("ip_create_listener(%s) failed", listenhost);
+	err_str1("ip_create_listener(%s) succeeded", listenhost);
+	if(!ip_parse_address(proxyhost, &proxy_ip, &proxy_port, 0))
+		return err_str1("ip_parse_address(%s) failed", proxyhost);
+	err_str1("ip_parse_address(%s) succeeded", proxyhost);
+	fprintf(stderr, "Info - proxying to %d.%d.%d.%d:%d\n",
+			(int)proxy_ip[0], (int)proxy_ip[1],
+			(int)proxy_ip[2], (int)proxy_ip[3], (int)proxy_port);
+	fprintf(stderr, "Info - set maxtunnels to %d\n", (int)max_tunnels);
+	fprintf(stderr, "Info - set to operate as an SSL %s\n",
+			(server_mode ? "server" : "client"));
+	/* Initialise the rest of the stuff */
+	world.tunnels_used = world.tunnels_size = 0;
+	world.tunnels = NULL;
+	world.server_mode = server_mode;
+	selector_init(&world.selector);
+
+/* We're ready to loop */
+main_loop:
+	/* Should we listen for *new* tunnels? */
+	if(world.tunnels_used < max_tunnels)
+		selector_add_listener(&world.selector, world.listen_fd);
+	/* We should add in our existing tunnels */
+	for(loop = 0; loop < world.tunnels_used; loop++)
+		selector_add_tunala(&world.selector, world.tunnels + loop);
+	/* Now do the select */
+	switch(selector_select(&world.selector)) {
+	case -1:
+		fprintf(stderr, "selector_select returned a badness error.\n");
+		abort();
+	case 0:
+		fprintf(stderr, "Warn, selector_select return 0 - signal??\n");
+		goto main_loop;
+	default:
+		break;
+	}
+	/* Accept new connection if we should and can */
+	if((world.tunnels_used < max_tunnels) && (selector_get_listener(
+					&world.selector, world.listen_fd,
+					&newfd) == 1)) {
+		/* We have a new connection */
+		if(!tunala_world_new_item(&world, newfd,
+					proxy_ip, proxy_port)) {
+			fprintf(stderr, "tunala_world_new_item failed\n");
+			abort();
+		}
+		fprintf(stderr, "Info, new tunnel opened, now up to %d\n",
+				world.tunnels_used);
+	}
+	/* Give each tunnel its moment, note the while loop is because it makes
+	 * the logic easier than with "for" to deal with an array that may shift
+	 * because of deletes. */
+	loop = 0;
+	t_item = world.tunnels;
+	while(loop < world.tunnels_used) {
+		if(!tunala_item_io(&world.selector, t_item)) {
+			/* We're closing whether for reasons of an error or a
+			 * natural close. Don't increment loop or t_item because
+			 * the next item is moving to us! */
+			tunala_world_del_item(&world, loop);
+			fprintf(stderr, "Info, tunnel closed, down to %d\n",
+					world.tunnels_used);
+		}
+		else {
+			/* Move to the next item */
+			loop++;
+			t_item++;
+		}
+	}
+	goto main_loop;
+	/* Should never get here */
+	abort();
+	return 1;
+}
+
+/****************/
+/* OpenSSL bits */
+/****************/
+
+static SSL_CTX *initialise_ssl_ctx(int server_mode, const char *engine_id,
+		const char *CAfile, const char *cert, const char *key)
+{
+	SSL_CTX *ctx, *ret = NULL;
+	SSL_METHOD *meth;
+	ENGINE *e = NULL;
+	FILE *fp = NULL;
+	X509 *x509 = NULL;
+	EVP_PKEY *pkey = NULL;
+
+        OpenSSL_add_ssl_algorithms();
+        SSL_load_error_strings();
+
+	meth = (server_mode ? SSLv23_server_method() : SSLv23_client_method());
+	if(meth == NULL)
+		goto err;
+	if(engine_id) {
+		if((e = ENGINE_by_id(engine_id)) == NULL) {
+			fprintf(stderr, "Error obtaining '%s' engine, openssl "
+					"errors follow\n", engine_id);
+			goto err;
+		}
+		if(!ENGINE_set_default(e, ENGINE_METHOD_ALL)) {
+			fprintf(stderr, "Error assigning '%s' engine, openssl "
+					"errors follow\n", engine_id);
+			goto err;
+		}
+		ENGINE_free(e);
+	}
+	if((ctx = SSL_CTX_new(meth)) == NULL)
+		goto err;
+	/* cacert */
+	if(CAfile) {
+		if(!X509_STORE_load_locations(SSL_CTX_get_cert_store(ctx),
+					CAfile, NULL)) {
+			fprintf(stderr, "Error loading CA cert(s) in '%s'\n",
+					CAfile);
+			goto err;
+		}
+		fprintf(stderr, "Info, operating with CA cert(s) in '%s'\n",
+				CAfile);
+	} else
+		fprintf(stderr, "Info, operating without a CA cert(-list)\n");
+	if(!SSL_CTX_set_default_verify_paths(ctx)) {
+		fprintf(stderr, "Error setting default verify paths\n");
+		goto err;
+	}
+	/* cert */
+	if(cert) {
+		if((fp = fopen(cert, "r")) == NULL) {
+			fprintf(stderr, "Error opening cert file '%s'\n", cert);
+			goto err;
+		}
+		if(!PEM_read_X509(fp, &x509, NULL, NULL)) {
+			fprintf(stderr, "Error reading PEM cert from '%s'\n",
+					cert);
+			goto err;
+		}
+		if(!SSL_CTX_use_certificate(ctx, x509)) {
+			fprintf(stderr, "Error, cert in '%s' can not be used\n",
+					cert);
+			goto err;
+		}
+		fprintf(stderr, "Info, operating with cert in '%s'\n", cert);
+		fclose(fp);
+		fp = NULL;
+		/* If a cert was given without matching key, we assume the same
+		 * file contains the required key. */
+		if(!key)
+			key = cert;
+	} else
+		if(key) {
+			fprintf(stderr, "Error, can't specify a key without a "
+					"corresponding certificate\n");
+			goto err;
+		}
+	/* key */
+	if(key) {
+		if((fp = fopen(key, "r")) == NULL) {
+			fprintf(stderr, "Error opening key file '%s'\n", key);
+			goto err;
+		}
+		if(!PEM_read_PrivateKey(fp, &pkey, NULL, NULL)) {
+			fprintf(stderr, "Error reading PEM key from '%s'\n",
+					key);
+			goto err;
+		}
+		if(!SSL_CTX_use_PrivateKey(ctx, pkey)) {
+			fprintf(stderr, "Error, key in '%s' can not be used\n",
+					key);
+			goto err;
+		}
+		fprintf(stderr, "Info, operating with key in '%s'\n", key);
+	} else
+		fprintf(stderr, "Info, operating without a cert or key\n");
+
+	/* Success! */
+	ret = ctx;
+err:
+	if(!ret) {
+		ERR_print_errors_fp(stderr);
+		if(ctx)
+			SSL_CTX_free(ctx);
+	}
+	if(fp)
+		fclose(fp);
+	if(x509)
+		X509_free(x509);
+	if(pkey)
+		EVP_PKEY_free(pkey);
+	return ret;
+}
+
+/*****************/
+/* Selector bits */
+/*****************/
+
+static void selector_sets_init(select_sets_t *s)
+{
+	s->max = 0;
+	FD_ZERO(&s->reads);
+	FD_ZERO(&s->sends);
+	FD_ZERO(&s->excepts);
+}
+static void selector_init(tunala_selector_t *selector)
+{
+	selector_sets_init(&selector->last_selected);
+	selector_sets_init(&selector->next_select);
+}
+
+#define SEL_EXCEPTS 0x00
+#define SEL_READS   0x01
+#define SEL_SENDS   0x02
+static void selector_add_raw_fd(tunala_selector_t *s, int fd, int flags)
+{
+	FD_SET(fd, &s->next_select.excepts);
+	if(flags & SEL_READS)
+		FD_SET(fd, &s->next_select.reads);
+	if(flags & SEL_SENDS)
+		FD_SET(fd, &s->next_select.sends);
+	/* Adjust "max" */
+	if(s->next_select.max < (fd + 1))
+		s->next_select.max = fd + 1;
+}
+
+static void selector_add_listener(tunala_selector_t *selector, int fd)
+{
+	selector_add_raw_fd(selector, fd, SEL_READS);
+}
+
+static void selector_add_tunala(tunala_selector_t *s, tunala_item_t *t)
+{
+	/* Set clean read if sm.clean_in is not full */
+	if(t->clean_read != -1) {
+		selector_add_raw_fd(s, t->clean_read,
+			(buffer_full(state_machine_get_buffer(&t->sm,
+				SM_CLEAN_IN)) ? SEL_EXCEPTS : SEL_READS));
+	}
+	/* Set clean send if sm.clean_out is not empty */
+	if(t->clean_send != -1) {
+		selector_add_raw_fd(s, t->clean_send,
+			(buffer_empty(state_machine_get_buffer(&t->sm,
+				SM_CLEAN_OUT)) ? SEL_EXCEPTS : SEL_SENDS));
+	}
+	/* Set dirty read if sm.dirty_in is not full */
+	if(t->dirty_read != -1) {
+		selector_add_raw_fd(s, t->dirty_read,
+			(buffer_full(state_machine_get_buffer(&t->sm,
+				SM_DIRTY_IN)) ? SEL_EXCEPTS : SEL_READS));
+	}
+	/* Set dirty send if sm.dirty_out is not empty */
+	if(t->dirty_send != -1) {
+		selector_add_raw_fd(s, t->dirty_send,
+			(buffer_empty(state_machine_get_buffer(&t->sm,
+				SM_DIRTY_OUT)) ? SEL_EXCEPTS : SEL_SENDS));
+	}
+}
+
+static int selector_select(tunala_selector_t *selector)
+{
+	memcpy(&selector->last_selected, &selector->next_select,
+			sizeof(select_sets_t));
+	selector_sets_init(&selector->next_select);
+	return select(selector->last_selected.max,
+			&selector->last_selected.reads,
+			&selector->last_selected.sends,
+			&selector->last_selected.excepts, NULL);
+}
+
+/* This returns -1 for error, 0 for no new connections, or 1 for success, in
+ * which case *newfd is populated. */
+static int selector_get_listener(tunala_selector_t *selector, int fd, int *newfd)
+{
+	if(FD_ISSET(fd, &selector->last_selected.excepts))
+		return -1;
+	if(!FD_ISSET(fd, &selector->last_selected.reads))
+		return 0;
+	if((*newfd = ip_accept_connection(fd)) == -1)
+		return -1;
+	return 1;
+}
+
+/************************/
+/* "Tunala" world stuff */
+/************************/
+
+static int tunala_world_make_room(tunala_world_t *world)
+{
+	unsigned int newsize;
+	tunala_item_t *newarray;
+
+	if(world->tunnels_used < world->tunnels_size)
+		return 1;
+	newsize = (world->tunnels_size == 0 ? 16 :
+			((world->tunnels_size * 3) / 2));
+	if((newarray = malloc(newsize * sizeof(tunala_item_t))) == NULL)
+		return 0;
+	memset(newarray, 0, newsize * sizeof(tunala_item_t));
+	if(world->tunnels_used > 0)
+		memcpy(newarray, world->tunnels,
+			world->tunnels_used * sizeof(tunala_item_t));
+	if(world->tunnels_size > 0)
+		free(world->tunnels);
+	/* migrate */
+	world->tunnels = newarray;
+	world->tunnels_size = newsize;
+	return 1;
+}
+
+static int tunala_world_new_item(tunala_world_t *world, int fd,
+		const unsigned char *ip, unsigned short port)
+{
+	tunala_item_t *item;
+	int newfd;
+
+	if(!tunala_world_make_room(world))
+		return 0;
+	item = world->tunnels + (world->tunnels_used++);
+	state_machine_init(&item->sm);
+	item->clean_read = item->clean_send =
+		item->dirty_read = item->dirty_send = -1;
+	if((newfd = ip_create_connection_split(ip, port)) == -1)
+		goto err;
+	/* Which way round? If we're a server, "fd" is the dirty side and the
+	 * connection we open is the clean one. For a client, it's the other way
+	 * around. */
+	if(world->server_mode) {
+		item->dirty_read = item->dirty_send = fd;
+		item->clean_read = item->clean_send = newfd;
+	} else {
+		item->clean_read = item->clean_send = fd;
+		item->dirty_read = item->dirty_send = newfd;
+	}
+	state_machine_set_SSL(&item->sm, SSL_new(world->ssl_ctx),
+			world->server_mode);
+	return 1;
+err:
+	state_machine_close(&item->sm);
+	return 0;
+
+}
+
+static void tunala_world_del_item(tunala_world_t *world, unsigned int idx)
+{
+	tunala_item_t *item = world->tunnels + idx;
+	if(item->clean_read != -1)
+		close(item->clean_read);
+	if(item->clean_send != item->clean_read)
+		close(item->clean_send);
+	item->clean_read = item->clean_send = -1;
+	if(item->dirty_read != -1)
+		close(item->dirty_read);
+	if(item->dirty_send != item->dirty_read)
+		close(item->dirty_send);
+	item->dirty_read = item->dirty_send = -1;
+	state_machine_close(&item->sm);
+	/* OK, now we fix the item array */
+	if(idx + 1 < world->tunnels_used)
+		/* We need to scroll entries to the left */
+		memmove(world->tunnels + idx,
+				world->tunnels + (idx + 1),
+				(world->tunnels_used - (idx + 1)) *
+					sizeof(tunala_item_t));
+	world->tunnels_used--;
+}
+
+static int tunala_item_io(tunala_selector_t *selector, tunala_item_t *item)
+{
+	int c_r, c_s, d_r, d_s; /* Four boolean flags */
+
+	/* Take ourselves out of the gene-pool if there was an except */
+	if((item->clean_read != -1) && FD_ISSET(item->clean_read,
+				&selector->last_selected.excepts))
+		return 0;
+	if((item->clean_send != -1) && FD_ISSET(item->clean_send,
+				&selector->last_selected.excepts))
+		return 0;
+	if((item->dirty_read != -1) && FD_ISSET(item->dirty_read,
+				&selector->last_selected.excepts))
+		return 0;
+	if((item->dirty_send != -1) && FD_ISSET(item->dirty_send,
+				&selector->last_selected.excepts))
+		return 0;
+	/* Grab our 4 IO flags */
+	c_r = c_s = d_r = d_s = 0;
+	if(item->clean_read != -1)
+		c_r = FD_ISSET(item->clean_read, &selector->last_selected.reads);
+	if(item->clean_send != -1)
+		c_s = FD_ISSET(item->clean_send, &selector->last_selected.sends);
+	if(item->dirty_read != -1)
+		d_r = FD_ISSET(item->dirty_read, &selector->last_selected.reads);
+	if(item->dirty_send != -1)
+		d_s = FD_ISSET(item->dirty_send, &selector->last_selected.sends);
+	/* If no IO has happened for us, skip needless data looping */
+	if(!c_r && !c_s && !d_r && !d_s)
+		return 1;
+	if(c_r)
+		c_r = (buffer_from_fd(state_machine_get_buffer(&item->sm,
+				SM_CLEAN_IN), item->clean_read) <= 0);
+	if(c_s)
+		c_s = (buffer_to_fd(state_machine_get_buffer(&item->sm,
+				SM_CLEAN_OUT), item->clean_send) <= 0);
+	if(d_r)
+		d_r = (buffer_from_fd(state_machine_get_buffer(&item->sm,
+				SM_DIRTY_IN), item->dirty_read) <= 0);
+	if(d_s)
+		d_s = (buffer_to_fd(state_machine_get_buffer(&item->sm,
+				SM_DIRTY_OUT), item->dirty_send) <= 0);
+	/* If any of the flags is non-zero, that means they need closing */
+	if(c_r) {
+		close(item->clean_read);
+		if(item->clean_send == item->clean_read)
+			item->clean_send = -1;
+		item->clean_read = -1;
+	}
+	if(c_s) {
+		close(item->clean_send);
+		if(item->clean_send == item->clean_read)
+			item->clean_read = -1;
+		item->clean_send = -1;
+	}
+	if(d_r) {
+		close(item->dirty_read);
+		if(item->dirty_send == item->dirty_read)
+			item->dirty_send = -1;
+		item->dirty_read = -1;
+	}
+	if(d_s) {
+		close(item->dirty_send);
+		if(item->dirty_send == item->dirty_read)
+			item->dirty_read = -1;
+		item->dirty_send = -1;
+	}
+	/* This function name is attributed to the term donated by David
+	 * Schwartz on openssl-dev, message-ID:
+	 * <NCBBLIEPOCNJOAEKBEAKEEDGLIAA.davids@webmaster.com>. :-) */
+	if(!state_machine_churn(&item->sm))
+		/* If the SSL closes, it will also zero-out the _in buffers
+		 * and will in future process just outgoing data. As and
+		 * when the outgoing data has gone, it will return zero
+		 * here to tell us to bail out. */
+		return 0;
+	/* Otherwise, we return zero if both sides are dead. */
+	if(((item->clean_read == -1) || (item->clean_send == -1)) &&
+			((item->dirty_read == -1) || (item->dirty_send == -1)))
+		return 0;
+	/* If only one side closed, notify the SSL of this so it can take
+	 * appropriate action. */
+	if((item->clean_read == -1) || (item->clean_send == -1)) {
+		if(!state_machine_close_clean(&item->sm))
+			return 0;
+	}
+	if((item->dirty_read == -1) || (item->dirty_send == -1)) {
+		if(state_machine_close_dirty(&item->sm))
+			return 0;
+	}
+	return 1;
+}
+