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Extract telnet functions into a separate header

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This commit is contained in:
Igor Socec 2016-11-18 22:42:29 +01:00
parent f1372827c1
commit c59b2138f4
4 changed files with 110 additions and 108 deletions
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4
moxerver.c
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@ -193,7 +193,9 @@ int main(int argc, char *argv[]) {
continue; continue;
} }
/* put client in "character" mode */ /* put client in "character" mode */
telnet_set_character_mode(&client); char msg[TELNET_MSG_SIZE_CHARMODE];
telnet_message_set_character_mode(msg);
client_write(&client, msg, TELNET_MSG_SIZE_CHARMODE);
} }
/* setup parameters for select() */ /* setup parameters for select() */

29
moxerver.h
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@ -12,6 +12,8 @@
#include <termios.h> #include <termios.h>
#include <time.h> #include <time.h>
#include <telnet.h>
#define DATABUF_LEN 128 #define DATABUF_LEN 128
#define DEV_PATH 128 #define DEV_PATH 128
#define TIMESTAMP_FORMAT "%Y-%m-%dT%H:%M:%S" /* ISO 8601 */ #define TIMESTAMP_FORMAT "%Y-%m-%dT%H:%M:%S" /* ISO 8601 */
@ -159,34 +161,7 @@ int client_wait_line(client_t *client);
int client_ask_username(client_t *client); int client_ask_username(client_t *client);
/* Functions handling details related to telnet protocol. */
/**
* Tells client to go into "character" mode.
*
* Returns:
* - 0 on success
* - negative value if error occurred
*/
int telnet_set_character_mode(client_t *client);
/**
* Handles special characters in data buffer after receiving them from client.
* Used to filter out handshake commands of telnet protocol.
*
* Returns:
* 0 always
*/
int telnet_handle_client_read(char *databuf, int *datalen);
/**
* Handles special characters in data buffer before sending to client.
* Used for echoing characters correctly to telnet client.
*
* Returns:
* 0 always
*/
int telnet_handle_client_write(char *databuf, int *datalen);
/* Functions handling communication with tty device. */ /* Functions handling communication with tty device. */

156
telnet.c
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@ -1,8 +1,5 @@
/* #include <telnet.h>
* Handling details related to telnet protocol. #include <moxerver.h>
*/
#include "moxerver.h"
/* structure for holding telnet option name and value */ /* structure for holding telnet option name and value */
typedef struct typedef struct
@ -12,7 +9,8 @@ typedef struct
} telnet_option_t; } telnet_option_t;
/* supported telnet option values */ /* supported telnet option values */
telnet_option_t telnet_options[] = { telnet_option_t telnet_options[] =
{
{"WILL", 251}, {"WILL", 251},
{"WONT", 252}, {"WONT", 252},
{"DO", 253}, {"DO", 253},
@ -25,118 +23,118 @@ telnet_option_t telnet_options[] = {
/* this list must end with {NULL, 0} */ /* this list must end with {NULL, 0} */
}; };
/* Returns telnet option name based on the value. */ /* Returns the name of a telnet option based on the value. */
static const char* telnet_option_name(int value) { static const char* telnet_option_name(int value)
int i = 0; {
while (telnet_options[i].name) { int i;
if (telnet_options[i].value == value) return telnet_options[i].name; for (i = 0; telnet_options[i].name != NULL; i++)
i++; {
if (telnet_options[i].value == value)
{
return telnet_options[i].name;
}
} }
/* default value */
return '\0'; return '\0';
} }
/* Returns telnet option value based on the name. */ /* Returns the value of a telnet option based on the name. */
static char telnet_option_value(const char* name) { static char telnet_option_value(const char* name)
int i = 0; {
while (telnet_options[i].name) { int i;
if (!strcmp(telnet_options[i].name, name)) return telnet_options[i].value; for (i = 0; telnet_options[i].name != NULL; i++)
i++; {
if (strcmp(telnet_options[i].name, name) == 0)
{
return telnet_options[i].value;
}
} }
/* default value */
return 0; return 0;
} }
/* Sends telnet option command. Returns 0 on success, -1 on failure. */ /* Handles a received telnet option command. */
static int telnet_send_command(client_t *client, const char* option, const char* command) { static void telnet_handle_command(char *databuf, int datalen)
{
char data[3]; /* just print received commands:
* we set the client, we don't adapt to client commands */
/* pack command */ if (databuf[0] == telnet_option_value("IAC"))
data[0] = telnet_option_value("IAC"); {
data[1] = telnet_option_value(option);
data[2] = telnet_option_value(command);
/* send command */
if (client_write(client, data, 3) <= 0) {
fprintf(stderr, "[%s:%d] failed sending %s %s\n", __func__, __LINE__, option, command);
return -1;
}
fprintf(stderr, "[%s] sent %s %s\n", __func__, option, command);
return 0;
}
/* Handles received telnet option command. Always returns 0.*/
static int telnet_handle_command(char *databuf, int datalen) {
/* currently just print received commands because we set the client, we don't adapt to client commands */
if (databuf[0] == telnet_option_value("IAC")) {
fprintf(stderr, "[%s] received %s %s\n", __func__, fprintf(stderr, "[%s] received %s %s\n", __func__,
telnet_option_name(databuf[1]), telnet_option_name(databuf[2])); telnet_option_name(databuf[1]),
telnet_option_name(databuf[2]));
} }
return 0;
} }
/* Tells client to go into "character" mode. */ void telnet_message_set_character_mode(char *databuf)
int telnet_set_character_mode(client_t *client) { {
/* send a predefined set of commands proven to work */
int err = 0; databuf[0] = telnet_option_value("IAC");
databuf[1] = telnet_option_value("WILL");
databuf[2] = telnet_option_value("ECHO");
/* send predefined commands and add up their return vaules */ databuf[3] = telnet_option_value("IAC");
err += telnet_send_command(client, "WILL", "ECHO"); databuf[4] = telnet_option_value("WILL");
err += telnet_send_command(client, "WILL", "SGA"); databuf[5] = telnet_option_value("SGA");
err += telnet_send_command(client, "WONT", "LINEMODE"); /* this depends on telnet client */
/* this one really depends on telnet client */
databuf[6] = telnet_option_value("IAC");
databuf[7] = telnet_option_value("WONT");
databuf[8] = telnet_option_value("LINEMODE");
//TODO Do we verify client response? What do we do if the response is not how we expected? //TODO Do we verify client response? What do we do if the response is not how we expected?
return err;
} }
/* Handles special characters in data buffer after receiving them from client. void telnet_handle_client_read(char *databuf, int *datalen)
* Used to filter out handshake commands of telnet protocol. */ {
int telnet_handle_client_read(char *databuf, int *datalen) {
int i; int i;
char newdata[DATABUF_LEN]; char newdata[DATABUF_LEN];
int newlen = 0; int newlen = 0;
/* process data using a new buffer */ /* process data using a new buffer */
for (i = 0; i < *datalen; i++) { for (i = 0; i < *datalen; i++)
{
/* handle and discard telnet commands */ /* handle and discard telnet commands */
if (databuf[i] == telnet_option_value("IAC")) { if (databuf[i] == telnet_option_value("IAC"))
{
telnet_handle_command((databuf+i), 3); telnet_handle_command((databuf+i), 3);
i += 2; i += 2;
} }
/* let other data pass through */ /* let other data pass through */
else { else
{
newdata[newlen++] = databuf[i]; newdata[newlen++] = databuf[i];
} }
} }
/* overwrite data with new buffer */ /* overwrite the data with the new buffer */
for (i = 0; i < newlen; i++) databuf[i] = newdata[i]; for (i = 0; i < newlen; i++)
{
databuf[i] = newdata[i];
}
/* update data length */
*datalen = newlen; *datalen = newlen;
return 0;
} }
/* Handles special characters in data buffer before sending to client. void telnet_handle_client_write(char *databuf, int *datalen)
* Used for echoing characters correctly to telnet client. */ {
int telnet_handle_client_write(char *databuf, int *datalen) {
int i; int i;
char newdata[DATABUF_LEN]; char newdata[DATABUF_LEN]; // TODO: maybe use realloc, this is risky
int newlen = 0; int newlen = 0;
/* process data using a new buffer */ /* process data using a new buffer */
for (i = 0; i < *datalen; i++) { for (i = 0; i < *datalen; i++)
{
/* pressed ENTER */ /* pressed ENTER */
if (databuf[i] == 13) { if (databuf[i] == 13)
{
fprintf(stderr, "[%s] handling ENTER\n", __func__); fprintf(stderr, "[%s] handling ENTER\n", __func__);
newdata[newlen++] = '\r'; newdata[newlen++] = '\r';
newdata[newlen++] = '\n'; newdata[newlen++] = '\n';
} }
/* pressed BACKSPACE */ /* pressed BACKSPACE */
if (databuf[i] == 127) { if (databuf[i] == 127)
{
fprintf(stderr, "[%s] handling BACKSPACE\n", __func__); fprintf(stderr, "[%s] handling BACKSPACE\n", __func__);
newdata[newlen++] = 8; newdata[newlen++] = 8;
newdata[newlen++] = ' '; newdata[newlen++] = ' ';
@ -146,9 +144,11 @@ int telnet_handle_client_write(char *databuf, int *datalen) {
newdata[newlen++] = databuf[i]; newdata[newlen++] = databuf[i];
} }
} }
/* overwrite data with new buffer */ /* overwrite the data with the new buffer */
for (i = 0; i < newlen; i++) databuf[i] = newdata[i]; for (i = 0; i < newlen; i++)
{
databuf[i] = newdata[i];
}
/* update data length */
*datalen = newlen; *datalen = newlen;
return 0;
} }

25
telnet.h Normal file
View file

@ -0,0 +1,25 @@
/* Handles details related to telnet protocol. */
#define TELNET_MSG_SIZE_CHARMODE 9
/**
* Creates a telnet protocol message that tells client to go into "character"
* mode. The passed data buffer must be big enough to hold the message payload
* with the size defined by TELNET_MSG_SIZE_CHARMODE.
* Operates directly on the passed data buffer.
*/
void telnet_message_set_character_mode(char *databuf);
/**
* Handles special characters in the data buffer after receiving them from the
* client. Used to filter out the handshake commands of telnet protocol.
* Operates directly on the passed data buffer and modifies the payload length.
*/
void telnet_handle_client_read(char *databuf, int *datalen);
/**
* Handles special characters in the data buffer before sending them to the
* client. Used to correctly echo the characters to the telnet client.
* Operates directly on the passed data buffer and modifies the payload length.
*/
void telnet_handle_client_write(char *databuf, int *datalen);