I'm trying to write a simple sniffer-driver for linux, which will redirect all the requests to the real serial port (and also will print all the messages into system log). I found some examples on the Internet and implemented few functions. For example, function that invokes when ouw fake device is opened:
static int dev_open(struct inode *inodep, struct file *filep) {
numberOpens++;
printk(KERN_INFO "sniffer: Device has been opened %d time(s)\n", numberOpens);
/// Connecting to real device
fd = open (real_device, O_RDWR | O_NOCTTY | O_SYNC);
if (fd < 0) {
printk(KERN_INFO "sniffer: cannot open device %s\n", real_device);
return 1;
}
set_interface_attribs (fd, B115200, 0); // set speed to 115,200 bps, 8n1 (no parity)
set_blocking (fd, 0); // set no blocking
return 0;
}
As you can see, this function just opens the real device using standart linux open system call. Or function that sets real device settings (speed and parity):
int set_interface_attribs (int fd, int speed, int parity) {
struct termios tty;
memset (&tty, 0, sizeof tty);
if (tcgetattr (fd, &tty) != 0) {
// error_message ("error %d from tcgetattr", errno);
printk(KERN_INFO "sniffer: cannot get device attributes\n");
return -1;
}
cfsetospeed (&tty, speed);
cfsetispeed (&tty, speed);
tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8; // 8-bit chars
// disable IGNBRK for mismatched speed tests; otherwise receive break
// as \000 chars
tty.c_iflag &= ~IGNBRK; // disable break processing
tty.c_lflag = 0; // no signaling chars, no echo,
// no canonical processing
tty.c_oflag = 0; // no remapping, no delays
tty.c_cc[VMIN] = 0; // read doesn't block
tty.c_cc[VTIME] = 5; // 0.5 seconds read timeout
tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl
tty.c_cflag |= (CLOCAL | CREAD);// ignore modem controls,
// enable reading
tty.c_cflag &= ~(PARENB | PARODD); // shut off parity
tty.c_cflag |= parity;
tty.c_cflag &= ~CSTOPB;
tty.c_cflag &= ~CRTSCTS;
if (tcsetattr (fd, TCSANOW, &tty) != 0) {
printk(KERN_INFO "sniffer: cannot set device attributes\n");
return -1;
}
return -1;
}
It uses tcgetattr and tcsetattr system calls.
I included all required header files:
#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
#include <linux/unistd.h>
#include <linux/string.h>
#include <linux/termios.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
But when I try to compile this module i get "implicit declaration of function" errors for this system calls.
My Makefile:
obj-m += sniffer.o
all:
$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
Compile errors:
sniffer.c: In function ‘set_interface_attribs’:
sniffer.c:51:9: error: implicit declaration of function ‘tcgetattr’ [-Werror=implicit-function-declaration]
if (tcgetattr (fd, &tty) != 0) {
^
sniffer.c:57:5: error: implicit declaration of function ‘cfsetospeed’ [-Werror=implicit-function-declaration]
cfsetospeed (&tty, speed);
^
sniffer.c:58:5: error: implicit declaration of function ‘cfsetispeed’ [-Werror=implicit-function-declaration]
cfsetispeed (&tty, speed);
^
sniffer.c:79:9: error: implicit declaration of function ‘tcsetattr’ [-Werror=implicit-function-declaration]
if (tcsetattr (fd, TCSANOW, &tty) != 0) {
^
sniffer.c: In function ‘dev_open’:
sniffer.c:151:9: error: implicit declaration of function ‘open’ [-Werror=implicit-function-declaration]
fd = open (real_device, O_RDWR | O_NOCTTY | O_SYNC);
^
sniffer.c: In function ‘dev_read’:
sniffer.c:164:18: error: implicit declaration of function ‘read’ [-Werror=implicit-function-declaration]
error_count = read(fd, buffer, len);
^
sniffer.c: In function ‘dev_write’:
sniffer.c:177:4: error: implicit declaration of function ‘write’ [-Werror=implicit-function-declaration]
write (fd, buffer, len);
^
sniffer.c: In function ‘dev_release’:
sniffer.c:184:4: error: implicit declaration of function ‘close’ [-Werror=implicit-function-declaration]
close(fd);
^
What can it be? All the examples that i found just say that I should include <linux/unistd.h> and <linux/termios.h>.
