initial

.gitignore

@@ -0,0 +1,3 @@
+*.d
+*.o
+telnetproxy

Makefile

@@ -0,0 +1,22 @@
+VERSION := v0.01
+
+CFLAGS := -O2 -pipe -Wall -DVERSION='"$(VERSION)"'
+
+OBJS := configfile.o connection.o event.o logging.o network.o telnetproxy.o
+
+all: telnetproxy
+
+telnetproxy: $(OBJS)
+	$(CC) $(CFLAGS) $^ -o $@
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+%.d: %.c
+	$(CC) $(CFLAGS) -MM -c $< -o $@
+
+clean:
+	rm -f telnetproxy *.d *.o *.log
+
+DEPS := $(wildcard *.c)
+-include $(DEPS:.c=.d)

configfile.c

@@ -0,0 +1,200 @@
+/***************************************************************************
+ *   Copyright (C) 06/2006 by Olaf Rempel                                  *
+ *   razzor@kopf-tisch.de                                                  *
+ *                                                                         *
+ *   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.                                   *
+ *                                                                         *
+ *   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.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program; if not, write to the                         *
+ *   Free Software Foundation, Inc.,                                       *
+ *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
+ ***************************************************************************/
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <arpa/inet.h>
+
+#include "configfile.h"
+#include "list.h"
+#include "logging.h"
+
+#define BUFSIZE 1024
+
+struct conf_section {
+	struct list_head list;
+	struct list_head tupel_list;
+	char *name;
+};
+
+struct conf_tupel {
+	struct list_head list;
+	char *option;
+	char *parameter;
+};
+
+static LIST_HEAD(config_list);
+
+static struct conf_section * config_add_section(const char *name)
+{
+	struct conf_section *section;
+	section = malloc(sizeof(struct conf_section) + strlen(name));
+	if (section == NULL)
+		return NULL;
+
+	INIT_LIST_HEAD(&section->list);
+	INIT_LIST_HEAD(&section->tupel_list);
+
+	section->name = strdup(name);
+	if (section->name == NULL) {
+		free(section);
+		return NULL;
+	}
+
+	list_add_tail(&section->list, &config_list);
+	return section;
+}
+
+static int config_add_tupel(struct conf_section *section, const char *option, const char *parameter)
+{
+	struct conf_tupel *tupel = malloc(sizeof(struct conf_tupel));
+	if (tupel == NULL)
+		return -1;
+
+	INIT_LIST_HEAD(&tupel->list);
+	tupel->option = strdup(option);
+	tupel->parameter = strdup(parameter);
+
+	if (tupel->option == NULL || tupel->parameter == NULL) {
+		free(tupel);
+		return -1;
+	}
+
+	list_add_tail(&tupel->list, &section->tupel_list);
+	return 0;
+}
+
+int config_parse(const char *config)
+{
+	FILE *fz = fopen(config, "r");
+	if (fz == NULL) {
+		log_print(LOG_ERROR, "config_parse(): %s", config);
+		return -1;
+	}
+
+	char *line = malloc(BUFSIZE);
+	if (line == NULL) {
+		log_print(LOG_ERROR, "config_parse(): out of memory");
+		fclose(fz);
+		return -1;
+	}
+
+	int linenum = 0;
+	struct conf_section *section = NULL;
+	while (fgets(line, BUFSIZE, fz) != NULL) {
+		linenum++;
+
+		if (line[0] == '#' || line[0] <= ' ') {
+			continue;
+
+		} else if (line[0] == '[') {
+			char *tok = strtok(line +1, " ]\n");
+
+			if (tok == NULL || (section = config_add_section(tok)) == NULL) {
+				log_print(LOG_WARN, "config_parse(): invalid section in row %d", linenum);
+				free(line);
+				fclose(fz);
+				return -1;
+			}
+			continue;
+
+		} else if (section == NULL) {
+			log_print(LOG_WARN, "config_parse(): missing section in row %d", linenum);
+			free(line);
+			fclose(fz);
+			return -1;
+		}
+
+		char *tok = strtok(line, " \n");
+		if (tok != NULL) {
+			char *tok2;
+			while ((tok2 = strtok(NULL, " \n"))) {
+				if (config_add_tupel(section, tok, tok2) != 0)
+					log_print(LOG_WARN, "config_parse(): invalid row %d", linenum);
+			}
+		}
+	}
+
+	fclose(fz);
+	free(line);
+	return 0;
+}
+
+static struct conf_section * config_get_section(const char *name)
+{
+	struct conf_section *section;
+
+	list_for_each_entry(section, &config_list, list) {
+		if (!strcmp(section->name, name))
+			return section;
+	}
+	return NULL;
+}
+
+char * config_get_string(const char *section_str, const char *option, char *def)
+{
+	struct conf_section *section = config_get_section(section_str);
+	if (section != NULL) {
+		struct conf_tupel *tupel;
+		list_for_each_entry(tupel, &section->tupel_list, list) {
+			if (!strcmp(tupel->option, option))
+				return tupel->parameter;
+		}
+	}
+
+	if (def != NULL)
+		log_print(LOG_WARN, "config [%s:%s] not found, using default: '%s'",
+			section_str, option, def);
+	return def;
+}
+
+int config_get_int(const char *section, const char *option, int def)
+{
+	char *ret = config_get_string(section, option, NULL);
+	if (ret == NULL) {
+		log_print(LOG_WARN, "config [%s:%s] not found, using default: '%d'",
+			section, option, def);
+		return def;
+	}
+	return atoi(ret);
+}
+
+int config_get_strings(const char *section_str, const char *option,
+			int (*callback)(const char *value, void *privdata),
+			void *privdata)
+{
+	struct conf_section *section = config_get_section(section_str);
+	if (section == NULL)
+		return -1;
+
+	int cnt = 0;
+	struct conf_tupel *tupel;
+	list_for_each_entry(tupel, &section->tupel_list, list) {
+		if (!strcmp(tupel->option, option))
+			if (callback(tupel->parameter, privdata) == 0)
+				cnt++;
+	}
+	return cnt;
+}

configfile.h

@@ -0,0 +1,16 @@
+#ifndef _CONFIG_H_
+#define _CONFIG_H_
+
+#include <netinet/in.h>
+
+int config_parse(const char *config);
+
+char * config_get_string(const char *section_str, const char *option, char *def);
+
+int config_get_int(const char *section, const char *option, int def);
+
+int config_get_strings(const char *section_str, const char *option,
+			int (*callback)(const char *value, void *privdata),
+			void *privdata);
+
+#endif /* _CONFIG_H_ */

connection.c

@@ -0,0 +1,5 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include "connection.h"

connection.h

@@ -0,0 +1,23 @@
+#ifndef _CONNECTION_H_
+#define _CONNECTION_H_
+
+#include <netinet/ip.h>
+
+#include "list.h"
+
+struct connection {
+	struct list_head list;
+
+	struct sockaddr_in src_addr;
+	struct sockaddr_in dst_addr;
+
+	int src_fd;
+	int dst_fd;
+
+	unsigned long login_time;
+	unsigned long idle_time;
+
+	char user[32];
+};
+
+#endif // _CONNECTION_H_

event.c

@@ -0,0 +1,310 @@
+/***************************************************************************
+ *   Copyright (C) 10/2006 by Olaf Rempel                                  *
+ *   razzor@kopf-tisch.de                                                  *
+ *                                                                         *
+ *   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.                                   *
+ *                                                                         *
+ *   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.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program; if not, write to the                         *
+ *   Free Software Foundation, Inc.,                                       *
+ *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
+ ***************************************************************************/
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+
+#include <sys/time.h>
+#include <sys/types.h>
+
+#include "list.h"
+#include "logging.h"
+
+#include "event.h"
+
+static LIST_HEAD(readfd_list);
+static LIST_HEAD(writefd_list);
+static LIST_HEAD(exceptfd_list);
+static LIST_HEAD(timeout_list);
+
+struct fd_entry {
+	struct list_head list;
+	int fd;
+	int type;
+	int (*callback)(int fd, void *privdata);
+	void *privdata;
+};
+
+struct timeout_entry {
+	struct list_head list;
+	struct timeval timeout;
+	struct timeval nextrun;
+	int (*callback)(void *privdata);
+	void *privdata;
+};
+
+int event_add_fd(int fd, int type, int (*callback)(int fd, void *privdata), void *privdata)
+{
+	if (fd < 0 || fd > FD_SETSIZE)
+		return -1;
+
+	struct fd_entry *entry;
+	entry = malloc(sizeof(struct fd_entry));
+	if (entry == NULL) {
+		log_print(LOG_ERROR, "event_add_fd(): out of memory");
+		return -1;
+	}
+
+	entry->fd = fd;
+	entry->type = type;
+	entry->callback = callback;
+	entry->privdata = privdata;
+
+	switch (type) {
+	case FD_READ:
+		list_add_tail(&entry->list, &readfd_list);
+		break;
+
+	case FD_WRITE:
+		list_add_tail(&entry->list, &writefd_list);
+		break;
+
+	case FD_EXCEPT:
+		list_add_tail(&entry->list, &exceptfd_list);
+		break;
+
+	default:
+		log_print(LOG_ERROR, "add_fd(): unknown type");
+		free(entry);
+		return -1;
+	}
+
+	return 0;
+}
+
+int event_remove_fd(int fd)
+{
+	struct fd_entry *entry, *tmp;
+	list_for_each_entry_safe(entry, tmp, &readfd_list, list) {
+		if (entry->fd == fd) {
+			list_del(&entry->list);
+			free(entry);
+			return 0;
+		}
+	}
+
+	list_for_each_entry_safe(entry, tmp, &writefd_list, list) {
+		if (entry->fd == fd) {
+			list_del(&entry->list);
+			free(entry);
+			return 0;
+		}
+	}
+
+	list_for_each_entry_safe(entry, tmp, &exceptfd_list, list) {
+		if (entry->fd == fd) {
+			list_del(&entry->list);
+			free(entry);
+			return 0;
+		}
+	}
+
+	return -1;
+}
+
+static void calc_nextrun(struct timeval *timeout, struct timeval *nextrun)
+{
+	struct timeval now;
+	gettimeofday(&now, NULL);
+
+	nextrun->tv_usec = now.tv_usec + timeout->tv_usec;
+	nextrun->tv_sec = now.tv_sec + timeout->tv_sec;
+
+	if (nextrun->tv_usec >= 1000000) {
+		nextrun->tv_usec -= 1000000;
+		nextrun->tv_sec++;
+	}
+}
+
+static void calc_timeout(struct timeval *timeout, struct timeval *nextrun)
+{
+	struct timeval now;
+	gettimeofday(&now, NULL);
+
+	timeout->tv_usec = nextrun->tv_usec - now.tv_usec;
+	timeout->tv_sec = nextrun->tv_sec - now.tv_sec;
+
+	if (timeout->tv_usec < 0) {
+		timeout->tv_usec += 1000000;
+		timeout->tv_sec--;
+	}
+}
+
+static void schedule_nextrun(struct timeout_entry *entry)
+{
+	struct timeout_entry *search;
+
+	list_for_each_entry(search, &timeout_list, list) {
+		if (search->nextrun.tv_sec > entry->nextrun.tv_sec) {
+			list_add_tail(&entry->list, &search->list);
+			return;
+
+		} else if (search->nextrun.tv_sec == entry->nextrun.tv_sec &&
+			   search->nextrun.tv_usec > entry->nextrun.tv_usec) {
+				list_add_tail(&entry->list, &search->list);
+				return;
+		}
+	}
+	list_add_tail(&entry->list, &timeout_list);
+}
+
+int event_add_timeout(struct timeval *timeout, int (*callback)(void *privdata), void *privdata)
+{
+	struct timeout_entry *entry;
+	entry = malloc(sizeof(struct timeout_entry));
+	if (entry == NULL) {
+		log_print(LOG_ERROR, "event_add_timeout(): out of memory");
+		return -1;
+	}
+
+	memcpy(&entry->timeout, timeout, sizeof(entry->timeout));
+	entry->callback = callback;
+	entry->privdata = privdata;
+
+	calc_nextrun(&entry->timeout, &entry->nextrun);
+	schedule_nextrun(entry);
+	return 0;
+}
+
+void event_loop(void)
+{
+	while (1) {
+		fd_set readfds, *readfds_p = NULL;
+		fd_set writefds, *writefds_p = NULL;
+		fd_set exceptfds, *exceptfds_p =NULL;
+		struct timeval timeout, *timeout_p = NULL;
+
+		if (!list_empty(&readfd_list)) {
+			struct fd_entry *entry;
+
+			FD_ZERO(&readfds);
+			list_for_each_entry(entry, &readfd_list, list)
+				FD_SET(entry->fd, &readfds);
+
+			readfds_p = &readfds;
+		}
+
+		if (!list_empty(&writefd_list)) {
+			struct fd_entry *entry;
+
+			FD_ZERO(&writefds);
+			list_for_each_entry(entry, &writefd_list, list)
+				FD_SET(entry->fd, &writefds);
+
+			writefds_p = &writefds;
+		}
+
+		if (!list_empty(&exceptfd_list)) {
+			struct fd_entry *entry;
+
+			FD_ZERO(&exceptfds);
+			list_for_each_entry(entry, &exceptfd_list, list)
+				FD_SET(entry->fd, &exceptfds);
+
+			exceptfds_p = &exceptfds;
+		}
+
+		if (!list_empty(&timeout_list)) {
+			struct timeout_entry *entry, *tmp;
+			list_for_each_entry_safe(entry, tmp, &timeout_list, list) {
+
+				calc_timeout(&timeout, &entry->nextrun);
+				if (timeout.tv_sec >= 0 && timeout.tv_usec > 0) {
+					timeout_p = &timeout;
+					break;
+				}
+
+				// delayed timeout, exec NOW!
+				list_del(&entry->list);
+				int ret = entry->callback(entry->privdata);
+				if (ret == 0) {
+					calc_nextrun(&entry->timeout, &entry->nextrun);
+					schedule_nextrun(entry);
+
+				} else {
+					free(entry);
+				}
+			}
+		}
+
+		int i = select(FD_SETSIZE, readfds_p, writefds_p, exceptfds_p, timeout_p);
+		if (i < 0) {
+			/* On error, -1 is returned, and errno is set
+				* appropriately; the sets and timeout become
+				* undefined, so do not rely on their contents
+				* after an error.
+				*/
+			continue;
+
+		} else if (i == 0 && !list_empty(&timeout_list)) {
+			struct timeout_entry *entry;
+			entry = list_entry(timeout_list.next, typeof(*entry), list);
+			list_del(&entry->list);
+
+			int ret = entry->callback(entry->privdata);
+			if (ret == 0) {
+				calc_nextrun(&entry->timeout, &entry->nextrun);
+				schedule_nextrun(entry);
+
+			} else {
+				free(entry);
+			}
+		}
+
+		if (readfds_p) {
+			struct fd_entry *entry, *tmp;
+			list_for_each_entry_safe(entry, tmp, &readfd_list, list) {
+				if (!FD_ISSET(entry->fd, &readfds))
+					continue;
+
+				if (entry->callback(entry->fd, entry->privdata) != 0) {
+					list_del(&entry->list);
+					free(entry);
+				}
+			}
+		}
+
+		if (writefds_p) {
+			struct fd_entry *entry, *tmp;
+			list_for_each_entry_safe(entry, tmp, &writefd_list, list) {
+				if (FD_ISSET(entry->fd, &writefds))
+					continue;
+
+				if (entry->callback(entry->fd, entry->privdata) != 0) {
+					list_del(&entry->list);
+					free(entry);
+				}
+			}
+		}
+
+		if (exceptfds_p) {
+			struct fd_entry *entry, *tmp;
+			list_for_each_entry_safe(entry, tmp, &exceptfd_list, list) {
+				if (FD_ISSET(entry->fd, &exceptfds))
+					continue;
+
+				if (entry->callback(entry->fd, entry->privdata) != 0) {
+					list_del(&entry->list);
+					free(entry);
+				}
+			}
+		}
+	}
+}

event.h

@@ -0,0 +1,26 @@
+#ifndef _EVENT_H_
+#define _EVENT_H_
+
+#include <sys/time.h>
+
+#define FD_READ		0x01
+#define FD_WRITE	0x02
+#define FD_EXCEPT	0x04
+
+#define event_add_readfd(fd, callback, privdata) \
+	event_add_fd(fd, FD_READ, callback, privdata)
+
+#define event_add_writefd(fd, callback, privdata) \
+	event_add_fd(fd, FD_WRITE, callback, privdata)
+
+#define event_add_exceptfd(fd, callback, privdata) \
+	event_add_fd(fd, FD_EXCEPT, callback, privdata)
+
+int event_add_fd(int fd, int type, int (*callback)(int fd, void *privdata), void *privdata);
+int event_add_timeout(struct timeval *timeout, int (*callback)(void *privdata), void *privdata);
+
+int event_remove_fd(int fd);
+
+void event_loop(void);
+
+#endif /* _EVENT_H_ */

list.h

@@ -0,0 +1,268 @@
+#ifndef _LIST_H_
+#define _LIST_H_
+
+/*
+ * stolen from linux kernel 2.6.11 (http://kernel.org/)
+ * linux/include/linux/stddef.h (offsetoff)
+ * linux/include/linux/kernel.h (container_of)
+ * linux/include/linux/list.h (*list*)
+ * linux/include/linux/netfilter_ipv4/listhelp.h (LIST_FIND)
+ *
+ * modified by Olaf Rempel <razzor@kopf-tisch.de>
+ */
+#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
+
+#define container_of(ptr, type, member) ({ \
+		const typeof( ((type *)0)->member ) *__mptr = (ptr); \
+		(type *)( (char *)__mptr - offsetof(type,member) );})
+
+struct list_head {
+	struct list_head *next, *prev;
+};
+
+#define LIST_HEAD_INIT(name) { &(name), &(name) }
+
+#define LIST_HEAD(name) \
+	struct list_head name = LIST_HEAD_INIT(name)
+
+#define INIT_LIST_HEAD(ptr) do { \
+	(ptr)->next = (ptr); (ptr)->prev = (ptr); \
+} while (0)
+
+/*
+ * Insert a new entry between two known consecutive entries.
+ *
+ * This is only for internal list manipulation where we know
+ * the prev/next entries already!
+ */
+static inline void __list_add(struct list_head *new,
+			      struct list_head *prev,
+			      struct list_head *next)
+{
+	next->prev = new;
+	new->next = next;
+	new->prev = prev;
+	prev->next = new;
+}
+
+/*
+ * list_add - add a new entry
+ * @new: new entry to be added
+ * @head: list head to add it after
+ *
+ * Insert a new entry after the specified head.
+ * This is good for implementing stacks.
+ */
+static inline void list_add(struct list_head *new, struct list_head *head)
+{
+	__list_add(new, head, head->next);
+}
+
+/*
+ * list_add_tail - add a new entry
+ * @new: new entry to be added
+ * @head: list head to add it before
+ *
+ * Insert a new entry before the specified head.
+ * This is useful for implementing queues.
+ */
+static inline void list_add_tail(struct list_head *new, struct list_head *head)
+{
+	__list_add(new, head->prev, head);
+}
+
+/*
+ * Delete a list entry by making the prev/next entries
+ * point to each other.
+ *
+ * This is only for internal list manipulation where we know
+ * the prev/next entries already!
+ */
+static inline void __list_del(struct list_head * prev, struct list_head * next)
+{
+	next->prev = prev;
+	prev->next = next;
+}
+
+/*
+ * list_del - deletes entry from list.
+ * @entry: the element to delete from the list.
+ * Note: list_empty on entry does not return true after this, the entry is
+ * in an undefined state.
+ */
+static inline void list_del(struct list_head *entry)
+{
+	__list_del(entry->prev, entry->next);
+	entry->next = NULL;
+	entry->prev = NULL;
+}
+
+/*
+ * list_del_init - deletes entry from list and reinitialize it.
+ * entry: the element to delete from the list.
+ */
+static inline void list_del_init(struct list_head *entry)
+{
+	__list_del(entry->prev, entry->next);
+	INIT_LIST_HEAD(entry);
+}
+
+/*
+ * list_move - delete from one list and add as another's head
+ * @list: the entry to move
+ * @head: the head that will precede our entry
+ */
+static inline void list_move(struct list_head *list, struct list_head *head)
+{
+        __list_del(list->prev, list->next);
+        list_add(list, head);
+}
+
+/*
+ * list_move_tail - delete from one list and add as another's tail
+ * @list: the entry to move
+ * @head: the head that will follow our entry
+ */
+static inline void list_move_tail(struct list_head *list,
+				  struct list_head *head)
+{
+        __list_del(list->prev, list->next);
+        list_add_tail(list, head);
+}
+
+/*
+ * list_empty - tests whether a list is empty
+ * @head: the list to test.
+ */
+static inline int list_empty(const struct list_head *head)
+{
+	return head->next == head;
+}
+
+static inline void __list_splice(struct list_head *list,
+				 struct list_head *head)
+{
+	struct list_head *first = list->next;
+	struct list_head *last = list->prev;
+	struct list_head *at = head->next;
+
+	first->prev = head;
+	head->next = first;
+
+	last->next = at;
+	at->prev = last;
+}
+
+/*
+ * list_splice - join two lists
+ * @list: the new list to add.
+ * @head: the place to add it in the first list.
+ */
+static inline void list_splice(struct list_head *list, struct list_head *head)
+{
+	if (!list_empty(list))
+		__list_splice(list, head);
+}
+
+/*
+ * list_splice_init - join two lists and reinitialise the emptied list.
+ * @list: the new list to add.
+ * @head: the place to add it in the first list.
+ *
+ * The list at @list is reinitialised
+ */
+static inline void list_splice_init(struct list_head *list,
+				    struct list_head *head)
+{
+	if (!list_empty(list)) {
+		__list_splice(list, head);
+		INIT_LIST_HEAD(list);
+	}
+}
+
+/*
+ * list_entry - get the struct for this entry
+ * @ptr:	the &struct list_head pointer.
+ * @type:	the type of the struct this is embedded in.
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_entry(ptr, type, member) \
+	container_of(ptr, type, member)
+
+/*
+ * list_for_each	-	iterate over a list
+ * @pos:	the &struct list_head to use as a loop counter.
+ * @head:	the head for your list.
+ */
+#define list_for_each(pos, head) \
+	for (pos = (head)->next; pos != (head); pos = pos->next)
+
+/*
+ * list_for_each_prev	-	iterate over a list backwards
+ * @pos:	the &struct list_head to use as a loop counter.
+ * @head:	the head for your list.
+ */
+#define list_for_each_prev(pos, head) \
+	for (pos = (head)->prev; pos != (head); pos = pos->prev)
+
+/*
+ * list_for_each_safe	-	iterate over a list safe against removal of list entry
+ * @pos:	the &struct list_head to use as a loop counter.
+ * @n:		another &struct list_head to use as temporary storage
+ * @head:	the head for your list.
+ */
+#define list_for_each_safe(pos, n, head) \
+	for (pos = (head)->next, n = pos->next; pos != (head); \
+		pos = n, n = pos->next)
+
+/*
+ * list_for_each_entry	-	iterate over list of given type
+ * @pos:	the type * to use as a loop counter.
+ * @head:	the head for your list.
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_for_each_entry(pos, head, member)				\
+	for (pos = list_entry((head)->next, typeof(*pos), member);	\
+	     &pos->member != (head); 					\
+	     pos = list_entry(pos->member.next, typeof(*pos), member))
+
+/*
+ * list_for_each_entry_reverse - iterate backwards over list of given type.
+ * @pos:	the type * to use as a loop counter.
+ * @head:	the head for your list.
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_for_each_entry_reverse(pos, head, member)			\
+	for (pos = list_entry((head)->prev, typeof(*pos), member);	\
+	     &pos->member != (head); 					\
+	     pos = list_entry(pos->member.prev, typeof(*pos), member))
+
+/*
+ * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
+ * @pos:	the type * to use as a loop counter.
+ * @n:		another type * to use as temporary storage
+ * @head:	the head for your list.
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_for_each_entry_safe(pos, n, head, member)			\
+	for (pos = list_entry((head)->next, typeof(*pos), member),	\
+		n = list_entry(pos->member.next, typeof(*pos), member);	\
+	     &pos->member != (head); 					\
+	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
+
+
+/* Return pointer to first true entry, if any, or NULL.  A macro
+   required to allow inlining of cmpfn. */
+#define LIST_FIND(head, cmpfn, type, args...)           \
+({                                                      \
+        const struct list_head *__i, *__j = NULL;       \
+                                                        \
+        list_for_each(__i, (head))                      \
+                if (cmpfn((const type)__i , ## args)) { \
+                        __j = __i;                      \
+                        break;                          \
+                }                                       \
+        (type)__j;                                      \
+})
+
+#endif /* _LIST_H_ */

logging.c

@@ -0,0 +1,103 @@
+/***************************************************************************
+ *   Copyright (C) 06/2006 by Olaf Rempel                                  *
+ *   razzor@kopf-tisch.de                                                  *
+ *                                                                         *
+ *   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.                                   *
+ *                                                                         *
+ *   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.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program; if not, write to the                         *
+ *   Free Software Foundation, Inc.,                                       *
+ *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
+ ***************************************************************************/
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <string.h>
+
+#include "logging.h"
+
+#define BUFSIZE 8192
+
+static FILE *log_fd = NULL;
+static char *buffer = NULL;
+
+void log_print(int prio, const char *fmt, ...)
+{
+	va_list az;
+	int len;
+
+	if (buffer == NULL) {
+		buffer = malloc(BUFSIZE);
+		if (buffer == NULL) {
+			fprintf(stderr, "log_print: out of memory\nBailing out!\n");
+			exit(-1);
+		}
+	}
+
+	va_start(az, fmt);
+	len = vsnprintf(buffer, BUFSIZE, fmt, az);
+	va_end(az);
+
+	if (len < 0 || len >= BUFSIZE) {
+		log_print(LOG_ERROR, "log_print: arguments too long");
+		errno = 0;
+		return;
+	}
+
+	if (errno) {
+		strncpy(buffer + len, ": ", BUFSIZE - len);
+		len += 2;
+		strncpy(buffer + len, strerror(errno), BUFSIZE - len);
+	}
+
+	if (log_fd) {
+		char    tbuf[64];
+		time_t  tzgr;
+
+		time(&tzgr);
+		strftime(tbuf, sizeof(tbuf), "%b %d %H:%M:%S :", localtime(&tzgr));
+
+		fprintf(log_fd, "%s %s\n", tbuf, buffer);
+		fflush(log_fd);
+
+	} else {
+		fprintf(stderr, "%s\n", buffer);
+	}
+
+	errno = 0;
+}
+
+static void log_close(void)
+{
+	if (buffer)
+		free(buffer);
+
+	fclose(log_fd);
+}
+
+int log_init(char *logfile)
+{
+	log_fd = fopen(logfile, "a");
+	if (log_fd == NULL) {
+		log_print(LOG_ERROR, "log_open('%s'): %s", logfile);
+		return 0;
+	}
+
+	if (atexit(log_close) != 0) {
+		log_print(LOG_ERROR, "log_open(): atexit()");
+		return 0;
+	}
+
+	log_print(LOG_EVERYTIME, "==========================");
+	return 1;
+}

logging.h

@@ -0,0 +1,16 @@
+#ifndef _LOGGING_H_
+#define _LOGGING_H_
+
+#define LOG_DEBUG 5
+#define LOG_INFO  4
+#define LOG_NOTICE 3
+#define LOG_WARN 2
+#define LOG_ERROR 1
+#define LOG_CRIT 0
+
+#define LOG_EVERYTIME 0
+
+int log_init(char *logfile);
+void log_print(int prio, const char *fmt, ... );
+
+#endif /* _LOGGING_H_ */

network.c

@@ -0,0 +1,78 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <netinet/ip.h>
+#include <arpa/inet.h>
+
+#include "logging.h"
+
+int parse_saddr(const char *addr, struct sockaddr_in *sa)
+{
+	char *addr_cpy = strdup(addr);
+	if (addr_cpy == NULL) {
+		log_print(LOG_WARN, "parse_saddr(): out of memory");
+		return -1;
+	}
+
+	char *tmp;
+	char *ip = strtok_r(addr_cpy, ":", &tmp);
+	if (ip == NULL) {
+		free(addr_cpy);
+		return -1;
+	}
+
+	char *port = strtok_r(NULL, ":", &tmp);
+	if (port == NULL) {
+		free(addr_cpy);
+		return -1;
+	}
+
+	sa->sin_family = AF_INET;
+	sa->sin_port = htons(atoi(port));
+	int ret = inet_aton(ip, &sa->sin_addr);
+
+	free(addr_cpy);
+	return (ret != 0) ? 0 : -1;
+}
+
+int get_sockaddr(struct sockaddr_in *sa, char *buf, int size)
+{
+	return snprintf(buf, size, "%s:%d", inet_ntoa(sa->sin_addr), ntohs(sa->sin_port));
+}
+
+char * get_sockaddr_buf(struct sockaddr_in *sa)
+{
+	static char buf[24];
+	get_sockaddr(sa, buf, sizeof(buf));
+	return buf;
+}
+
+int tcp_listen_socket(struct sockaddr_in *sa, int cnt)
+{
+	int sock = socket(AF_INET, SOCK_STREAM, 0);
+	if (sock < 0 ) {
+		log_print(LOG_ERROR, "tcp_listen_socket(): socket()");
+		return -1;
+	}
+
+	int i = 1;
+	if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &i, sizeof(i))) {
+		log_print(LOG_ERROR, "tcp_listen_socket(): setsockopt(SO_REUSEADDR)");
+		close(sock);
+		return -1;
+	}
+
+	if (bind(sock, (struct sockaddr *)sa, sizeof(*sa))) {
+		log_print(LOG_ERROR, "tcp_listen_socket(): bind(%s)", get_sockaddr_buf(sa));
+		close(sock);
+		return -1;
+	}
+
+	if (listen(sock, cnt)) {
+		log_print(LOG_ERROR, "tcp_listen_socket(): listen()");
+		close(sock);
+		return -1;
+	}
+	return sock;
+}

network.h

@@ -0,0 +1,12 @@
+#ifndef _NETWORK_H_
+#define _NETWORK_H_
+
+#include <netinet/ip.h>
+
+int parse_saddr(const char *addr, struct sockaddr_in *sa);
+int tcp_listen_socket(struct sockaddr_in *sa, int cnt);
+
+int get_sockaddr(struct sockaddr_in *sa, char *buf, int size);
+char * get_sockaddr_buf(struct sockaddr_in *sa);
+
+#endif // _NETWORK_H_

telnetproxy.c

@@ -0,0 +1,117 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "configfile.h"
+#include "connection.h"
+#include "event.h"
+#include "list.h"
+#include "logging.h"
+#include "network.h"
+
+static LIST_HEAD(connection_list);
+
+static int server_handler(int fd, void *privdata)
+{
+	struct connection *con = (struct connection *)privdata;
+	char buf[256];
+
+	int len = read(fd, buf, sizeof(buf));
+	if (len <= 0) {
+		list_del(&con->list);
+		destroy_connection(con);
+		return -1;
+	}
+
+	write(con->src_fd, buf, len);
+	return 0;
+}
+
+static int client_handler(int fd, void *privdata)
+{
+	struct connection *con = (struct connection *)privdata;
+	char buf[256];
+
+	int len = read(fd, buf, sizeof(buf));
+	if (len <= 0) {
+		list_del(&con->list);
+		destroy_connection(con);
+		return -1;
+	}
+
+	if (con->dst_fd != -1) {
+		write(con->dst_fd, buf, len);
+		return 0;
+	}
+
+	// check destination
+	int sock = tcp_connect_socket(&con->dst_addr);
+	if (sock < 0) {
+		list_del(&con->list);
+		destroy_connection(con);
+		return -1;
+	}
+
+	event_add_readfd(sock, server_handler, con);
+	log_print(LOG_INFO, "forwarding to %s", get_sockaddr_buf(&con->dst_addr));
+	return 0;
+}
+
+static int listen_handler(int fd, void *privdata)
+{
+	struct connection *con = malloc(sizeof(struct connection));
+	if (con == NULL) {
+		log_print(LOG_WARN, "listen_handler(): out of memory");
+		return 0;
+	}
+
+	int i = sizeof(con->src_addr);
+	con->src_fd = accept(fd, (struct sockaddr *)&con->src_addr, &i);
+	if (con->src_fd < 0) {
+		free(con);
+		return 0;
+	}
+
+	con->dst_fd = -1;
+	con->login_time = con->idle_time = time(NULL);
+
+	log_print(LOG_INFO, "accepted connection from %s", get_sockaddr_buf(&con->src_addr));
+
+	list_add_tail(&con->list, &connection_list);
+	event_add_readfd(con->src_fd, client_handler, con);
+	return 0;
+}
+
+static int listen_init(const char *value, void *privdata)
+{
+	struct sockaddr_in addr;
+
+	if (parse_saddr(value, &addr) == -1) {
+		log_print(LOG_WARN, "invalid listen addr: '%s'", value);
+		return -1;
+	}
+
+	int sock = tcp_listen_socket(&addr, 10);
+	if (sock < 0)
+		return -1;
+
+	event_add_readfd(sock, listen_handler, NULL);
+	log_print(LOG_INFO, "listen on %s", get_sockaddr_buf(&addr));
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	if (config_parse("telnetproxy.conf") == -1)
+		return -1;
+
+	int cnt = config_get_strings("global", "listen", listen_init, NULL);
+	if (cnt <= 0) {
+		log_print(LOG_ERROR, "no listen sockets defined!");
+		return -1;
+	}
+
+	event_loop();
+
+	return 0;
+}

telnetproxy.conf

@@ -0,0 +1,2 @@
+[global]
+listen 0.0.0.0:8000