I am developing a WiFi tool in Ubuntu Linux 12.04 environment and I need to switch the WiFi interface between different channels.
Currently I found the solution in Wireshark source code ws80211_utils.c in function called ws80211_set_freq but I do not know how to implement it into my source code and which libs to include and how to compile so I could test it.
The problem is that there are too many arguments and flags you have to use. Also, this is the first time I develop a netlink wifi tool.
If there are any good manuals available where to start and how to use netlink calls for WiFi please provide me with the link.
Thanks a lot i advance!
In current Linux versions, nl80211 is the right way to "talk" to the wireless subsystem. Be aware that you cannot arbitrarily set a channel with every driver and every operating mode (master, client, monitor etc.) Some drivers allow a channel change only when the corresponding interface is "down". In modes such as client ("managed"), the channel cannot be set at all because it is defined by the access point.
Also note that not all wireless device drivers use mac80211/cfg80211. For those drivers not using it, you either have to use the old wireless extensions API or (even worse) a driver-specific proprietary API.
Sadly, there seems to be no up-to-date and complete documentation of the nl80211 interface. Please correct me if I am wrong!
Your approach of looking into the source code of other programs seems to be a reasonable way. You could also use the source code of the iw command line utility. iw has an option to set the channel:
$ iw --help
Usage: iw [options] command
Options:
--debug enable netlink debugging
--version show version (3.2)
Commands:
…
dev <devname> set channel <channel> [HT20|HT40+|HT40-]
…
In iw's phy.c, line 91ff. you can find the code called when iw wlan0 set channel is executed. However, this code is definitely not easy to read. It looks like the
NL80211_CMD_SET_WIPHYcommand in conjunction with the NL80211_ATTR_WIPHY_FREQ attribute is the way to go.
In this SO answer you can find a skeleton program for using nl80211. Also, the code of Aircrack-ng (src/osdep/linux.c, function linux_set_channel_nl80211) could act as a blueprint.
The accepted answer is currently correct, but there's no example code posted yet which solves the OP's question (even if nearly 4 years late), so I thought I would add this here for any future search engine users. It's adapted from this SO question and the specific Aircrack-ng file (/src/aircrack-osdep/linux.c, line 1050) that were both previously mentioned.
#include <net/if.h>
#include <netlink/netlink.h>
#include <netlink/genl/genl.h>
#include <netlink/genl/ctrl.h>
#include <linux/nl80211.h>
int main(int argc, char *argv[])
{
/* The device's name and the frequency we wish to set it to. */
char *device = "wlan1";
int frequencyMhz = 2442;
/* Create the socket and connect to it. */
struct nl_sock *sckt = nl_socket_alloc();
genl_connect(sckt);
/* Allocate a new message. */
struct nl_msg *mesg = nlmsg_alloc();
/* Check /usr/include/linux/nl80211.h for a list of commands and attributes. */
enum nl80211_commands command = NL80211_CMD_SET_WIPHY;
/* Create the message so it will send a command to the nl80211 interface. */
genlmsg_put(mesg, 0, 0, genl_ctrl_resolve(sckt, "nl80211"), 0, 0, command, 0);
/* Add specific attributes to change the frequency of the device. */
NLA_PUT_U32(mesg, NL80211_ATTR_IFINDEX, if_nametoindex(device));
NLA_PUT_U32(mesg, NL80211_ATTR_WIPHY_FREQ, frequencyMhz);
/* Finally send it and receive the amount of bytes sent. */
int ret = nl_send_auto_complete(sckt, mesg);
printf("%d Bytes Sent\n", ret);
nlmsg_free(mesg);
return EXIT_SUCCESS;
nla_put_failure:
nlmsg_free(mesg);
printf("PUT Failure\n");
return EXIT_FAILURE;
}
Compile this with gcc main.c $(pkg-config --cflags --libs libnl-3.0 libnl-genl-3.0).
Once executed, check the frequency/channel of your device with e.g. iw wlan1 info or iwconfig. There's no serious error checking here, so all you will notice is if the message was sent or not. Hopefully this helps anyone like me making the transition from Wireless Extensions to cfg80211 and nl80211.
Related
Since the RPL border router example works as either a Cooja mote or a native mote, I thought using the SLIP code in /services/rpl-border-router/native might work. I made a copy of hello-world. I edited hello-world.c to read
#include "contiki.h"
#include "services/rpl-border-router/native/border-router.h"
#include <stdio.h> /* For printf() */
extern int contiki_argc;
extern char **contiki_argv;
/*---------------------------------------------------------------------------*/
PROCESS(hello_world_process, "Hello world process");
AUTOSTART_PROCESSES(&hello_world_process);
/*---------------------------------------------------------------------------*/
PROCESS_THREAD(hello_world_process, ev, data)
{
static struct etimer timer;
PROCESS_BEGIN();
/* Setup a periodic timer that expires after 10 seconds. */
etimer_set(&timer, CLOCK_SECOND * 10);
slip_config_handle_arguments(contiki_argc, contiki_argv);
slip_init();
while(1) {
printf("Hello, world\n");
/* Wait for the periodic timer to expire and then restart the timer. */
PROCESS_WAIT_EVENT_UNTIL(etimer_expired(&timer));
etimer_reset(&timer);
}
PROCESS_END();
}
And edited the makefile:
CONTIKI_PROJECT = hello-world
all: $(CONTIKI_PROJECT)
CONTIKI = ../..
include $(CONTIKI)/Makefile.dir-variables
MODULES += $(CONTIKI_NG_SERVICES_DIR)/rpl-border-router
include $(CONTIKI)/Makefile.include
This inclusion of rpl-border-router module was done because I was getting undefined reference to ‘slip_init()’... and undefined reference to ‘slip_config_handle_arguments(contiki_argc, contiki_argv);’... errors when compiling, despite the #include "services/rpl-border-router/native/border-router.h" line in hello-world.c. This does appear to be the right header to include for declarations of these functions, but if I am mistaken please say so.
From the folder where the edited hello-world code resides, I did make distclean, and then make TARGET=native. If I run this edited hello-world with
sudo ./hello-world.native fd00::3 -s ttyS0
it looks like it is starting up, but I see:
…[INFO: Native ] Added global IPv6 address fd00::302:304:506:708
********SLIP started on ``/dev/ttyS0''
Hello, world
[INFO: BR ] RPL-Border router started
********SLIP started on ``/dev/ttyS0''
opened tun device ``/dev/tun0''
So it is trying to start up the border router as well as opening the SLIP interface, and just below the ifconfig tun0 output (which looks fine) I see
…hello-world.native: serial_input: read: Success
ifconfig tun0 down
netstat -nr | awk '{ if ($2 == "tun0") print "route delete -net "$1; }' | sh
So, it seems I need to do something to stop from starting the border router module. I have seen that there are 'slip.c' and 'slip.h' in os/dev/, used in the slip-radio example but the declaration of 'slip_arch_init()' in slip.h without a definition of slip_arch_init() in slip.c has me confused, and motivated me to use 'slip_init()' from the /services/rpl-border-router/native folder, since in there I can see a pretty normal bit of code opening up a serial interface.
I have done a lot of google searching and searched through several of the more complex examples for something similar to what I am trying to do, but haven’t found anything that seems very close. If there is something ready made then or course that would be the greatest help, but I am sure it must be obvious that my understanding of Make and file interrelations is nowhere near where it needs to be.
Just to be clear, my goal at the moment is to get a SLIP interface up and running on the remote VM so that I can get a ping6 response on the VM with the border router. I will worry about writing the callback once I have some baseline connectivity. Maybe this is a misunderstanding on my part as well.
For unit testing purposes, I want to be able to run a bare-metal binary with qemu and capture it's output.
Sample file:
#include <stdio.h>
#include <stdint.h>
static void qemu_exit() {
register uint32_t r0 __asm__("r0");
r0 = 0x18;
register uint32_t r1 __asm__("r1");
r1 = 0x20026;
__asm__ volatile("bkpt #0xAB");
}
int main(void) {
puts("This is some example text that I want to capture");
qemu_exit();
return 0;
}
Running with:
qemu-system-gnuarmeclipse --nographic --no-reboot \
--board STM32F4-Discovery --mcu STM32F429ZI \
--semihosting-config enable=on,target=native \
--image <binary>
Displayed to the console is:
QEMU 2.8.0-13 monitor - type 'help' for more information
(qemu) This is some example text that I want to capture
This 'example text' is generated within QEMU and so redirecting stdout to a file does not capture it (only: QEMU 2.8.0-13 monitor - type 'help' for more information
(qemu)). Looking at the available qemu logging options -d help does not offer anything as far as I can see.
EDIT
A hacky solution is to use script to capture terminal session:
script --quiet --command <qemu-shell-script-wrapper>
That's not an upstream QEMU, and 2.8 is also quite old, but hopefully the same things that work with upstream QEMU will work there.
Firstly, assuming you're not actually using the monitor, you can get rid of that part of the output by dropping '--nographic' and instead using '-display none'. (--nographic does a lot of things all at once, including both "no graphical display" and also "default serial output to the terminal, add a QEMU monitor and multiplex the monitor and the serial", among other things. It's convenient if that's what you want but sometimes it's less confusing to specify everything separately.)
Secondly, you say you're using semihosting output but is the guest's stdlib definitely using semihosting for its puts() string output and not serial port (UART) output? The output will come out on the terminal either way but how you tell QEMU to redirect it somewhere else will differ. (I suspect it may be using UART output, because if it were using semihosting output then the redirection of stdout that you tried should have worked.)
If the output from the guest is via the serial port then you can control where it goes using the '-serial' option (most simply, "-serial stdio" to send to stdout, but you can also do more complicated things like sending to files, pipes or TCP sockets.). If it's via semihosting then you can control where it goes using the 'chardev=id' suboption of -semihosting-config.
I would like to get a list of the wireless networks available. Ideally this would be via some C call, but I don't mind if I have to kludge it with a system call. Even better if the required C call or program doesn't require some exotic 3rd party package.
The internet seems to suggest I use sudo iwlist <interface> scan which does seem to do the trick from the command line, but I'd rather not require root permissions. I only want to see the basics, not change anything.
It's pretty easy to do a scan in the command line. The man pages are your friend here (check out iwconfig and iwlist). But using the C interface is a little more difficult so I'll focus on that.
First of all, as other people have mentioned, definitely download out the wireless tools source code. All the documentation for the programming interface is in the .c files. As far as I can tell, there is no web documentation for the api. However, the source code is pretty easy to read through. You pretty much only need iwlib.h and iwlib.c for this question.
While you can use iw_set_ext and iw_get_ext, the libiw implements a basic scanning function iw_scan, from which you can extract most of the information that you need.
Here is a simple program to get the ESSID for all available wireless networks. Compile with -liw and run with sudo.
#include <stdio.h>
#include <time.h>
#include <iwlib.h>
int main(void) {
wireless_scan_head head;
wireless_scan *result;
iwrange range;
int sock;
/* Open socket to kernel */
sock = iw_sockets_open();
/* Get some metadata to use for scanning */
if (iw_get_range_info(sock, "wlan0", &range) < 0) {
printf("Error during iw_get_range_info. Aborting.\n");
exit(2);
}
/* Perform the scan */
if (iw_scan(sock, "wlan0", range.we_version_compiled, &head) < 0) {
printf("Error during iw_scan. Aborting.\n");
exit(2);
}
/* Traverse the results */
result = head.result;
while (NULL != result) {
printf("%s\n", result->b.essid);
result = result->next;
}
exit(0);
}
DISCLAIMER: This is just a demonstration program. It's possible for some results to not have an essid. In addition, this assumes your wireless interface is "wlan0". You get the idea.
Read the iwlib source code!
The Wireless Tools package -- of which iwlist is a part -- also contains a Wireless Tools Helper Library. You need to include iwlib.h and link with libiw.a (i.e. add -liw). Then look up the documentation for the iw_set_ext function. The SIOCSIWSCAN parameter will be of most use. For an example of how to use this interface, take a look at the KWifiManager source in the KDE library (see: Interface_wireless_wirelessextensions::get_available_networks method). Alternatively, you can also download the Wireless Tools source code and take a look at how the iwlib iw_set_ext function is also used for scanning in iwlist.c.
As for privileges, I imagine the process will need to run as root to perform the scan. I'd love to know if this could be done otherwise as well.
Since you are using Ubuntu 8.04 the libiw-dev package should be of use.
You can use nmcli which does not require root permissions or name of WIFI interface.
nmcli -t -f ssid dev wifi
I generated a code for "stm32f103c8t6" with CubeMX for USB VCP, when I add "CDC_Transmit_FS" command to send data, the port isn't recognized by windows10!
what should I do? Here is the code which is compiled without error:
#include "stm32f1xx_hal.h"
#include "usb_device.h"
#include "usbd_cdc_if.h"
int main(void)
{
uint8_t Text[] = "Hello\r\n";
while (1)
{
CDC_Transmit_FS(Text,6); /*when commented the port is recognized*/
HAL_Delay(1000);
}
}
There are three things you need to check in my experience:
startup_stm32f405xx.s --> Increase the Heap size. I use heap size 800 and stack size 800 as well.
usbd_cdc_if.c --> APP_RX_DATA_SIZE 64 and APP_TX_DATA_SIZE 64
usbd_cdc_if.c --> add below code to the CDC_Control_FS() function
Code:
case CDC_SET_LINE_CODING:
tempbuf[0]=pbuf[0];
tempbuf[1]=pbuf[1];
tempbuf[2]=pbuf[2];
tempbuf[3]=pbuf[3];
tempbuf[4]=pbuf[4];
tempbuf[5]=pbuf[5];
tempbuf[6]=pbuf[6];
break;
case CDC_GET_LINE_CODING:
pbuf[0]=tempbuf[0];
pbuf[1]=tempbuf[1];
pbuf[2]=tempbuf[2];
pbuf[3]=tempbuf[3];
pbuf[4]=tempbuf[4];
pbuf[5]=tempbuf[5];
pbuf[6]=tempbuf[6];
break;
and define the uint8_t tempbuf[7]; in the user private_variables section.
Without the increased heap size, Windows does not react at all.
Without the point 3, Windows will send the baud rate information and then read the baud rate, expecting to get back the same values. Since you do not return any values, the virtual com port remains as driver-not-loaded.
If you do all of that, the Windows 10 out-of-the-box VCP driver can be used. No need to install the very old ST VCP driver on your system.
PS: I read somewhere turning on VSense makes problems, too. Don't know, I have not configured it and all works like a charm.
Put delay before CDC_Transmit_FS call - it will wait for the initiatialization. Your code should be like this
int main(void)
{
uint8_t Text[] = "Hello\r\n";
HAL_Delay(1000);
while (1)
{
CDC_Transmit_FS(Text,6); /*when commented the port is recognized*/
HAL_Delay(1000);
}
}
I had similar issue. I couldn't connect to a port and the port appears as just "virtual com port". I added while loop to wait for USBD_OK from CDC_Transmit_FS. Then it stars work even with out it or a delay after init function. I am not sure what the issue was.
while(CDC_Transmit_FS((uint8_t*)txBuf, strlen(txBuf))!=USBD_OK)
{
}
you may have to install driver to get device recognized as com port
you can get it from st site
if not installed the device is listed with question or exclamation mark on device manager
note that you cannot send until device get connected to host!
not sure that CubeMX CDC_Transmit_FS is checking for this
also instead of delay to resend you shall check the CDC class data "TXSstate"
is 0 mean tx is over.
I know it's a bit late, but I stumbled upon this post and it was extremely helpful.
Here is what I needed to do:
do the Line-Coding (I think only necessary on Windows-Systems)
increase Heap (Stack was left at default 0x200)
Here is what wasn't necessary for me (on a STM32F405RGT6 Chip):
change APP_RX_DATA_SIZE / APP_TX_DATA_SIZE (left it at 2048)
add a delay befor running CDC_Tranmit_FS()
Also some things to consider that happened to me in the past:
be sure to use a USB-Cable with data lines (most charging-cables don't have them)
double check the traces/connections if you use a custom board
I want to capture packets going out of my machine, and I'm using libpcap (version 1.0.0-1) for the same. The problem is, that a basic program like this -
#include <stdio.h>
#include <pcap.h>
int main(int argc, char *argv[]) {
char *dev, errbuf[PCAP_ERRBUF_SIZE];
dev = pcap_lookupdev(errbuf);
if (dev == NULL) {
fprintf(stderr, "%s\n", errbuf);
return (2);
}
printf("Device : %s\n", dev);
return (0);
}
does not seem to display the wireless interface. Everytime I compile and run the program, it detects eth0. How can I make it capture the wireless interfaces as well?
pcap_lookupdev() returns the default networking device on the system, which is usually the first device listed. pcap_findalldevs() returns an enumeration of all devices in the system, which you can use to select a device and capture from it.
try using pcap_findalldevs(). i guess pcap_lookupdev() matches the first entry in the list is suitable interfaces
As others have stated, pcap_lookupdev() simply returns the first device found. You need to use pcap_findalldevs() to build a list of all available devices, then prompt the user to pick one (or let the user specify a number n on the command line, and then use the _n_th device).
But, if this is just a quick-and-dirty test program, you can find out the interface name and code it directly into your program. You can use ifconfig or tcpdump -D to find out the interface names on your system, then make a call like pcap_create("en1", errbuf).