Connect two native Contiki NG motes over SLIP - c

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.

Related

Capture QEMU Semihosted I/O

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.

How do I get a list of available wifi-connections? [duplicate]

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

Mac kernel programming generic kernel extension prinf() not working

I've followed the Creating a Generic Kernel Extension with Xcode tutorial.
MyKext.c:
#include <sys/systm.h>
#include <mach/mach_types.h>
kern_return_t MyKext_start (kmod_info_t * ki, void * d)
{
printf("MyKext has started.\n");
return KERN_SUCCESS;
}
kern_return_t MyKext_stop (kmod_info_t * ki, void * d)
{
printf("MyKext has stopped.\n");
return KERN_SUCCESS;
}
I've also disabled the csrutil, which allow me to load my own kext.
# csrutil disable
When I load my own kext into kernel
$ sudo kextload -v /tmp/MyKext.kext
The result of printf() not write into /var/log/system.log.
I've also set boot-args
$ sudo nvram boot-args="original_contents debug=0x4"
Can anyone help me out?
Apparently, since Sierra (10.12) at least, they reorganized the way the logs are written (iOS support?), so you cannot see it in system.log anymore. Still, in your Console application, you have in the sidebar a Devices section, where you can select your device (usually your Mac system) and see real-time log limited to "kernel" in the search box. So I can see these when using kext load/kextunload:
default 11:58:27.608228 +0200 kernel MyKext has started.
default 11:58:34.446824 +0200 kernel MyKext has stopped.
default 11:58:44.803350 +0200 kernel MyKext has started.
There is no need for the csrutil and nvram changes.
Important For some freaky reason, I needed to restart the Console to reflect my messages changes, otherwise it has showing the ones (start & stop) from the previous build. Very strange indeed!
Later To recover old logs, try sudo log collect --last 1d and open the result with Console(more here).
Sorry to necro-post, but I found it useful to use log(1) with one of its many commands (as suggested by #pmdj in the comments above) rather than use Console. From the manual:
log -- Access system wide log messages created by os_log, os_trace and other log-
ging systems.
For example, one can run:
log stream
to see real-time output of the system, including printf() from the MacOS kernel extension.

Function XOpenDisplay with and without parameter

I have little issue with XOpenDisplay function. In school I can run program and it works good when using XOpenDisplay("ip:0"), but on my local machine in home when I run program (changed ip on current) got "Segmentation fault (core dumped)", but with empy string XOpenDisplay("") it works fine. I need to be able to use ip. Used host +, but nothing changes.
My system is Kubuntu 14.04.1: 3.16.0-30-generic #40~14.04.1-Ubuntu SMP Thu Jan 15 17:43:14 UTC 2015
Here is code of program:
#include <X11/Xlib.h>
#include <X11/X.h>
#include <stdio.h>
Display *mydisplay;
Window mywindow;
XSetWindowAttributes mywindowattributes;
XGCValues mygcvalues;
GC mygc;
Visual *myvisual;
int mydepth;
int myscreen;
Colormap mycolormap;
XColor mycolor,mycolor1,dummy;
int i;
main()
{
mydisplay = XOpenDisplay("192.168.0.12:0");
myscreen = DefaultScreen(mydisplay);
myvisual = DefaultVisual(mydisplay,myscreen);
mydepth = DefaultDepth(mydisplay,myscreen);
mywindowattributes.background_pixel = XWhitePixel(mydisplay,myscreen);
mywindowattributes.override_redirect = True;
mywindow = XCreateWindow(mydisplay,XRootWindow(mydisplay,myscreen),
0,0,500,500,10,mydepth,InputOutput,
myvisual,CWBackPixel|CWOverrideRedirect,
&mywindowattributes);
mycolormap = DefaultColormap(mydisplay,myscreen);
XAllocNamedColor(mydisplay,mycolormap,"cyan",&mycolor,&dummy);
XAllocNamedColor(mydisplay,mycolormap,"red",&mycolor1,&dummy);
XMapWindow(mydisplay,mywindow);
mygc = DefaultGC(mydisplay,myscreen);
XSetForeground(mydisplay,mygc,mycolor.pixel);
XFillRectangle(mydisplay,mywindow,mygc,100,100,300,300);
XSetForeground(mydisplay,mygc,mycolor1.pixel);
XSetFunction(mydisplay,mygc,GXcopy);
XSetLineAttributes(mydisplay,mygc,10,LineSolid,CapProjecting,JoinMiter);
XDrawLine(mydisplay,mywindow,mygc,100,100,400,400);
XDrawLine(mydisplay,mywindow,mygc,100,400,400,100);
XFlush(mydisplay);
sleep(10);
XCloseDisplay(mydisplay);
exit(0);
}
I can only guess that need to set something, but have no idea where is that option.
You shall always check whether functions returned successfully, or not. It is not a Haskell, where all the checking done for you by monad, it is C. As for your particular case, the problem is that the function XOpenDisplay fails and returns null for you. In the next line you're trying to use DefaultScreen with the result. The DefaultScreen is defined as
#define DefaultScreen(dpy) ((dpy)->default_screen)
I.e. it just a macro, which using the first argument as a pointer. In your case it does ((0)->default_screen), i.e. it dereferencing the null pointer, and that leads to the segfault you see.
Also, about the XOpenDisplay("192.168.0.12:0"); — you didn't mentioned that you're trying to connect to another PC, so, if it's the same computer where the app running, try to call the function as XOpenDisplay("127.0.0.1:0");
UPD: okay, I tried to run the code at my PC, and the function doesn't work for me too. To find the reason I started the code under strace app, and saw
…
connect(3, {sa_family=AF_INET, sin_port=htons(6000), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 ECONNREFUSED (Connection refused)
…
Aha! So, the app trying to connect to XServer, but Xserver refuses the connection. Actually, it have a security reason to disable it by default — so, that nobody would connect to your XServer from a network unless you specifically allowed it. For the function to work you need to launch your XServer with the option that allows such a connection. Right now DisplayManagers are the ones, who manages xsessions, so you need to set some option depending on your DM.
The solution for lightdm
Open the /etc/lightdm/lightdm.conf, and paste the line xserver-allow-tcp=true in the section [SeatDefaults](you will see it).
The solution for gdm
Edit the file /etc/gdm/gdm.schemas, you will find there something like
<schema>
<key>security/DisallowTCP</key>
<signature>b</signature>
<default>true</default>
</schema>
Change the true to false.

Set wireless channel using netlink API

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.

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