Sunday, November 22, 2015
How to prevent realtek Wi-Fi from sleep mode?
http://raspberrypi.stackexchange.com/questions/1384/how-do-i-disable-suspend-mode
Friday, May 22, 2015
Tuesday, May 5, 2015
Saturday, April 4, 2015
Git: How to add all untrackable file in command line?
You can try either of the following:
Reference: http://stackoverflow.com/questions/3498035/git-add-all-files-modified-deleted-and-untracked
git add -A
Warning, starting git 2.0 (mid 2013), this will always stage files on the all working tree.
If you want to stage files that are only under the current path of your working tree, then you need to use:
If you want to stage files that are only under the current path of your working tree, then you need to use:
$ git add -A .
Reference: http://stackoverflow.com/questions/3498035/git-add-all-files-modified-deleted-and-untracked
Sunday, March 29, 2015
How to resolve 500.19 error during running Bonobo Git server
1. Run the following command on the prompt:
>%windir%\system32\inetsrv\appcmd unlock config -section:system.webServer/modules
(Reference: http://stackoverflow.com/questions/26633346/bonobo-git-server-http-error-500-19-code-0x80070021)
2-1. Windows 7
Run the following command on the prompt:
>Run %windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis.exe -ir with administrator privileges
2-2. Windows 8 or higher
Add the Windows features: IIS -> WWWS -> Application Development Features -> ASP.NET 4.5
(Reference: https://groups.google.com/forum/#!topic/bonobo-git-server/V3UmArM0r4I)
>%windir%\system32\inetsrv\appcmd unlock config -section:system.webServer/modules
(Reference: http://stackoverflow.com/questions/26633346/bonobo-git-server-http-error-500-19-code-0x80070021)
2-1. Windows 7
Run the following command on the prompt:
>Run %windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis.exe -ir with administrator privileges
2-2. Windows 8 or higher
Add the Windows features: IIS -> WWWS -> Application Development Features -> ASP.NET 4.5
(Reference: https://groups.google.com/forum/#!topic/bonobo-git-server/V3UmArM0r4I)
Monday, March 9, 2015
Wireless tools for Android
Note that Android uses libnl2.0 which is not compatible with source code for libnl3.0
https://github.com/nvamelichev/wireless-tools-android
https://github.com/nvamelichev/wireless-tools-android
If you want to specify the path to git.exe and are using GitHub for Windows
You can find it from the path like:
C:\Users\<username>\AppData\Local\GitHub\PortableGit_<numbersandletters>\bin\git.exe
Reference: http://stackoverflow.com/a/16127984/3534219
C:\Users\<username>\AppData\Local\GitHub\PortableGit_<numbersandletters>\bin\git.exe
Reference: http://stackoverflow.com/a/16127984/3534219
Wednesday, February 11, 2015
How to scan Wi-Fi AP list using libnl library?
/*
* scan_access_points.c: Prints all detected access points with wlan0 using NL80211 (netlink).
*
* Only works on network interfaces whose drivers are compatible with Netlink. Test this by running `iw list`.
*
* Since only privileged users may submit NL80211_CMD_TRIGGER_SCAN, you'll have to run the compiled program as root.
*
* Build with: gcc $(pkg-config --cflags --libs libnl-genl-3.0) scan_access_points.c
*
* Raspbian prerequisites:
* sudo apt-get install libnl-genl-3-dev
*
* Resources:
* http://git.kernel.org/cgit/linux/kernel/git/jberg/iw.git/tree/scan.c
* http://stackoverflow.com/questions/21601521/how-to-use-the-libnl-library-to-trigger-nl80211-commands
* http://stackoverflow.com/questions/23760780/how-to-send-single-channel-scan-request-to-libnl-and-receive-single-
*
* Expected output (as root):
* NL80211_CMD_TRIGGER_SCAN sent 36 bytes to the kernel.
* Waiting for scan to complete...
* Got NL80211_CMD_NEW_SCAN_RESULTS.
* Scan is done.
* NL80211_CMD_GET_SCAN sent 28 bytes to the kernel.
* 47:be:34:f0:bb:be, 2457 MHz, NETGEAR16
* 6b:db:ed:85:ef:42, 2432 MHz, NETGEAR31
* d8:06:ef:a7:f9:80, 2412 MHz, ATT912
* a7:0d:af:0a:19:08, 2462 MHz, ATT185
*
* Expected output (without root):
* NL80211_CMD_TRIGGER_SCAN sent 36 bytes to the kernel.
* Waiting for scan to complete...
* error_handler() called.
* WARNING: err has a value of -1.
* ERROR: nl_recvmsgs() returned -28 (Operation not permitted).
* do_scan_trigger() failed with -28.
*
*/
#include <errno.h>
#include <netlink/errno.h>
#include <netlink/netlink.h>
#include <netlink/genl/genl.h>
#include <linux/nl80211.h>
struct trigger_results {
int done;
int aborted;
};
struct handler_args { // For family_handler() and nl_get_multicast_id().
const char *group;
int id;
};
static int error_handler(struct sockaddr_nl *nla, struct nlmsgerr *err, void *arg) {
// Callback for errors.
printf("error_handler() called.\n");
int *ret = arg;
*ret = err->error;
return NL_STOP;
}
static int finish_handler(struct nl_msg *msg, void *arg) {
// Callback for NL_CB_FINISH.
int *ret = arg;
*ret = 0;
return NL_SKIP;
}
static int ack_handler(struct nl_msg *msg, void *arg) {
// Callback for NL_CB_ACK.
int *ret = arg;
*ret = 0;
return NL_STOP;
}
static int no_seq_check(struct nl_msg *msg, void *arg) {
// Callback for NL_CB_SEQ_CHECK.
return NL_OK;
}
static int family_handler(struct nl_msg *msg, void *arg) {
// Callback for NL_CB_VALID within nl_get_multicast_id(). From http://sourcecodebrowser.com/iw/0.9.14/genl_8c.html.
struct handler_args *grp = arg;
struct nlattr *tb[CTRL_ATTR_MAX + 1];
struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
struct nlattr *mcgrp;
int rem_mcgrp;
nla_parse(tb, CTRL_ATTR_MAX, genlmsg_attrdata(gnlh, 0), genlmsg_attrlen(gnlh, 0), NULL);
if (!tb[CTRL_ATTR_MCAST_GROUPS]) return NL_SKIP;
nla_for_each_nested(mcgrp, tb[CTRL_ATTR_MCAST_GROUPS], rem_mcgrp) { // This is a loop.
struct nlattr *tb_mcgrp[CTRL_ATTR_MCAST_GRP_MAX + 1];
nla_parse(tb_mcgrp, CTRL_ATTR_MCAST_GRP_MAX, nla_data(mcgrp), nla_len(mcgrp), NULL);
if (!tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME] || !tb_mcgrp[CTRL_ATTR_MCAST_GRP_ID]) continue;
if (strncmp(nla_data(tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME]), grp->group,
nla_len(tb_mcgrp[CTRL_ATTR_MCAST_GRP_NAME]))) {
continue;
}
grp->id = nla_get_u32(tb_mcgrp[CTRL_ATTR_MCAST_GRP_ID]);
break;
}
return NL_SKIP;
}
int nl_get_multicast_id(struct nl_sock *sock, const char *family, const char *group) {
// From http://sourcecodebrowser.com/iw/0.9.14/genl_8c.html.
struct nl_msg *msg;
struct nl_cb *cb;
int ret, ctrlid;
struct handler_args grp = { .group = group, .id = -ENOENT, };
msg = nlmsg_alloc();
if (!msg) return -ENOMEM;
cb = nl_cb_alloc(NL_CB_DEFAULT);
if (!cb) {
ret = -ENOMEM;
goto out_fail_cb;
}
ctrlid = genl_ctrl_resolve(sock, "nlctrl");
genlmsg_put(msg, 0, 0, ctrlid, 0, 0, CTRL_CMD_GETFAMILY, 0);
ret = -ENOBUFS;
NLA_PUT_STRING(msg, CTRL_ATTR_FAMILY_NAME, family);
ret = nl_send_auto_complete(sock, msg);
if (ret < 0) goto out;
ret = 1;
nl_cb_err(cb, NL_CB_CUSTOM, error_handler, &ret);
nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_handler, &ret);
nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, family_handler, &grp);
while (ret > 0) nl_recvmsgs(sock, cb);
if (ret == 0) ret = grp.id;
nla_put_failure:
out:
nl_cb_put(cb);
out_fail_cb:
nlmsg_free(msg);
return ret;
}
void mac_addr_n2a(char *mac_addr, unsigned char *arg) {
// From http://git.kernel.org/cgit/linux/kernel/git/jberg/iw.git/tree/util.c.
int i, l;
l = 0;
for (i = 0; i < 6; i++) {
if (i == 0) {
sprintf(mac_addr+l, "%02x", arg[i]);
l += 2;
} else {
sprintf(mac_addr+l, ":%02x", arg[i]);
l += 3;
}
}
}
void print_ssid(unsigned char *ie, int ielen) {
uint8_t len;
uint8_t *data;
int i;
while (ielen >= 2 && ielen >= ie[1]) {
if (ie[0] == 0 && ie[1] >= 0 && ie[1] <= 32) {
len = ie[1];
data = ie + 2;
for (i = 0; i < len; i++) {
if (isprint(data[i]) && data[i] != ' ' && data[i] != '\\') printf("%c", data[i]);
else if (data[i] == ' ' && (i != 0 && i != len -1)) printf(" ");
else printf("\\x%.2x", data[i]);
}
break;
}
ielen -= ie[1] + 2;
ie += ie[1] + 2;
}
}
static int callback_trigger(struct nl_msg *msg, void *arg) {
// Called by the kernel when the scan is done or has been aborted.
struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
struct trigger_results *results = arg;
//printf("Got something.\n");
//printf("%d\n", arg);
//nl_msg_dump(msg, stdout);
if (gnlh->cmd == NL80211_CMD_SCAN_ABORTED) {
printf("Got NL80211_CMD_SCAN_ABORTED.\n");
results->done = 1;
results->aborted = 1;
} else if (gnlh->cmd == NL80211_CMD_NEW_SCAN_RESULTS) {
printf("Got NL80211_CMD_NEW_SCAN_RESULTS.\n");
results->done = 1;
results->aborted = 0;
} // else probably an uninteresting multicast message.
return NL_SKIP;
}
static int callback_dump(struct nl_msg *msg, void *arg) {
// Called by the kernel with a dump of the successful scan's data. Called for each SSID.
struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
char mac_addr[20];
struct nlattr *tb[NL80211_ATTR_MAX + 1];
struct nlattr *bss[NL80211_BSS_MAX + 1];
static struct nla_policy bss_policy[NL80211_BSS_MAX + 1] = {
[NL80211_BSS_TSF] = { .type = NLA_U64 },
[NL80211_BSS_FREQUENCY] = { .type = NLA_U32 },
[NL80211_BSS_BSSID] = { },
[NL80211_BSS_BEACON_INTERVAL] = { .type = NLA_U16 },
[NL80211_BSS_CAPABILITY] = { .type = NLA_U16 },
[NL80211_BSS_INFORMATION_ELEMENTS] = { },
[NL80211_BSS_SIGNAL_MBM] = { .type = NLA_U32 },
[NL80211_BSS_SIGNAL_UNSPEC] = { .type = NLA_U8 },
[NL80211_BSS_STATUS] = { .type = NLA_U32 },
[NL80211_BSS_SEEN_MS_AGO] = { .type = NLA_U32 },
[NL80211_BSS_BEACON_IES] = { },
};
// Parse and error check.
nla_parse(tb, NL80211_ATTR_MAX, genlmsg_attrdata(gnlh, 0), genlmsg_attrlen(gnlh, 0), NULL);
if (!tb[NL80211_ATTR_BSS]) {
printf("bss info missing!\n");
return NL_SKIP;
}
if (nla_parse_nested(bss, NL80211_BSS_MAX, tb[NL80211_ATTR_BSS], bss_policy)) {
printf("failed to parse nested attributes!\n");
return NL_SKIP;
}
if (!bss[NL80211_BSS_BSSID]) return NL_SKIP;
if (!bss[NL80211_BSS_INFORMATION_ELEMENTS]) return NL_SKIP;
// Start printing.
mac_addr_n2a(mac_addr, nla_data(bss[NL80211_BSS_BSSID]));
printf("%s, ", mac_addr);
printf("%d MHz, ", nla_get_u32(bss[NL80211_BSS_FREQUENCY]));
print_ssid(nla_data(bss[NL80211_BSS_INFORMATION_ELEMENTS]), nla_len(bss[NL80211_BSS_INFORMATION_ELEMENTS]));
printf("\n");
return NL_SKIP;
}
int do_scan_trigger(struct nl_sock *socket, int if_index, int driver_id) {
// Starts the scan and waits for it to finish. Does not return until the scan is done or has been aborted.
struct trigger_results results = { .done = 0, .aborted = 0 };
struct nl_msg *msg;
struct nl_cb *cb;
struct nl_msg *ssids_to_scan;
int err;
int ret;
int mcid = nl_get_multicast_id(socket, "nl80211", "scan");
nl_socket_add_membership(socket, mcid); // Without this, callback_trigger() won't be called.
// Allocate the messages and callback handler.
msg = nlmsg_alloc();
if (!msg) {
printf("ERROR: Failed to allocate netlink message for msg.\n");
return -ENOMEM;
}
ssids_to_scan = nlmsg_alloc();
if (!ssids_to_scan) {
printf("ERROR: Failed to allocate netlink message for ssids_to_scan.\n");
nlmsg_free(msg);
return -ENOMEM;
}
cb = nl_cb_alloc(NL_CB_DEFAULT);
if (!cb) {
printf("ERROR: Failed to allocate netlink callbacks.\n");
nlmsg_free(msg);
nlmsg_free(ssids_to_scan);
return -ENOMEM;
}
// Setup the messages and callback handler.
genlmsg_put(msg, 0, 0, driver_id, 0, 0, NL80211_CMD_TRIGGER_SCAN, 0); // Setup which command to run.
nla_put_u32(msg, NL80211_ATTR_IFINDEX, if_index); // Add message attribute, which interface to use.
nla_put(ssids_to_scan, 1, 0, ""); // Scan all SSIDs.
nla_put_nested(msg, NL80211_ATTR_SCAN_SSIDS, ssids_to_scan); // Add message attribute, which SSIDs to scan for.
nlmsg_free(ssids_to_scan); // Copied to `msg` above, no longer need this.
nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, callback_trigger, &results); // Add the callback.
nl_cb_err(cb, NL_CB_CUSTOM, error_handler, &err);
nl_cb_set(cb, NL_CB_FINISH, NL_CB_CUSTOM, finish_handler, &err);
nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_handler, &err);
nl_cb_set(cb, NL_CB_SEQ_CHECK, NL_CB_CUSTOM, no_seq_check, NULL); // No sequence checking for multicast messages.
// Send NL80211_CMD_TRIGGER_SCAN to start the scan. The kernel may reply with NL80211_CMD_NEW_SCAN_RESULTS on
// success or NL80211_CMD_SCAN_ABORTED if another scan was started by another process.
err = 1;
ret = nl_send_auto(socket, msg); // Send the message.
printf("NL80211_CMD_TRIGGER_SCAN sent %d bytes to the kernel.\n", ret);
printf("Waiting for scan to complete...\n");
while (err > 0) ret = nl_recvmsgs(socket, cb); // First wait for ack_handler(). This helps with basic errors.
if (err < 0) {
printf("WARNING: err has a value of %d.\n", err);
}
if (ret < 0) {
printf("ERROR: nl_recvmsgs() returned %d (%s).\n", ret, nl_geterror(-ret));
return ret;
}
while (!results.done) nl_recvmsgs(socket, cb); // Now wait until the scan is done or aborted.
if (results.aborted) {
printf("ERROR: Kernel aborted scan.\n");
return 1;
}
printf("Scan is done.\n");
// Cleanup.
nlmsg_free(msg);
nl_cb_put(cb);
nl_socket_drop_membership(socket, mcid); // No longer need this.
return 0;
}
int main() {
int if_index = if_nametoindex("wlan0"); // Use this wireless interface for scanning.
// Open socket to kernel.
struct nl_sock *socket = nl_socket_alloc(); // Allocate new netlink socket in memory.
genl_connect(socket); // Create file descriptor and bind socket.
int driver_id = genl_ctrl_resolve(socket, "nl80211"); // Find the nl80211 driver ID.
// Issue NL80211_CMD_TRIGGER_SCAN to the kernel and wait for it to finish.
int err = do_scan_trigger(socket, if_index, driver_id);
if (err != 0) {
printf("do_scan_trigger() failed with %d.\n", err);
return err;
}
// Now get info for all SSIDs detected.
struct nl_msg *msg = nlmsg_alloc(); // Allocate a message.
genlmsg_put(msg, 0, 0, driver_id, 0, NLM_F_DUMP, NL80211_CMD_GET_SCAN, 0); // Setup which command to run.
nla_put_u32(msg, NL80211_ATTR_IFINDEX, if_index); // Add message attribute, which interface to use.
nl_socket_modify_cb(socket, NL_CB_VALID, NL_CB_CUSTOM, callback_dump, NULL); // Add the callback.
int ret = nl_send_auto(socket, msg); // Send the message.
printf("NL80211_CMD_GET_SCAN sent %d bytes to the kernel.\n", ret);
ret = nl_recvmsgs_default(socket); // Retrieve the kernel's answer. callback_dump() prints SSIDs to stdout.
nlmsg_free(msg);
if (ret < 0) {
printf("ERROR: nl_recvmsgs_default() returned %d (%s).\n", ret, nl_geterror(-ret));
return ret;
}
return 0;
}
Reference: http://stackoverflow.com/questions/18062268/using-nl80211-h-to-scan-access-points
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