Hi all,
Since yesterday I have been trying to understand why "char**
essid_list" is working inside getInstalledEssidList(&count,
essid_list) but failing as soon as I try to access essid_list[0]
outside the function.
Both the source and the gdb text output are attached.
Any helpful pointers are appreciated.
Edward.
gdb auto-conn
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Reading symbols from auto-conn...done.
(gdb) b 202
Breakpoint 1 at 0x401223: file automated_scanner.c, line 202.
(gdb) r
Starting program: /home/edbarx/netman/backend_src/src/auto-conn
Breakpoint 1, autoWirelessScanPlus () at automated_scanner.c:202
202 getInstalledEssidList(&count, essid_list);
(gdb) s
getInstalledEssidList (count=0x7fffffffe284, essid_list=0x1) at
automated_scanner.c:48
48 int el_size = 0; // stands for essid_list size
(gdb) n
51 if ((dir = opendir(IFACES_PATH)) != 0) {
(gdb) n
52 while ((ent = readdir (dir)) != 0)
(gdb) n
54 strcmp(".", ent->d_name) != 0 &&
(gdb) n
53 if(
(gdb) n
52 while ((ent = readdir (dir)) != 0)
(gdb) n
54 strcmp(".", ent->d_name) != 0 &&
(gdb) n
53 if(
(gdb) n
55 strcmp("..", ent->d_name) != 0
(gdb) n
54 strcmp(".", ent->d_name) != 0 &&
(gdb) n
57 (*count)++;
(gdb) n
62 encoded_essid = ent->d_name;
(gdb) n
63 if (el_size < *count) {
(gdb) p encoded_essid
$1 = 0x60206b "EB-TP-LNK67"
(gdb) n
64 el_size =+ 10;
(gdb) n
65 if (el_size == 10)
(gdb) n
66 essid_list =
calloc(*count + 9, sizeof(char*));
(gdb) n
70 essid_list[*count - 1] =
calloc(strlen(encoded_essid) + 1, sizeof(char));
(gdb) n
71 strcpy(essid_list[*count - 1],
encoded_essid);
(gdb) n
52 while ((ent = readdir (dir)) != 0)
(gdb) p essid_list[0]
$2 = 0x60a0b0 "EB-TP-LNK67"
(gdb) n
54 strcmp(".", ent->d_name) != 0 &&
(gdb) n
53 if(
(gdb) n
55 strcmp("..", ent->d_name) != 0
(gdb) n
54 strcmp(".", ent->d_name) != 0 &&
(gdb) n
52 while ((ent = readdir (dir)) != 0)
(gdb) n
73 closedir(dir);
(gdb) n
87 return 0;
(gdb) n
88 }
(gdb) n
autoWirelessScanPlus () at automated_scanner.c:206
206 getRadiatingWifiList(&active_wifis, active_wifi_list);
(gdb) p essid_list[0]
Cannot access memory at address 0x1
(gdb) s
getRadiatingWifiList (active_wifis=0x7fffffffe280, active_wifi_list=0x0) at
automated_scanner.c:94
94 char * scan_buffer = NULL;
(gdb) n
96 scan_buffer = calloc(1024, 1);
(gdb) n
99 shell_reader = popen("/sbin/iwlist wlan0 scan | grep
\"Quality=\\|ESSID:\"", "r");
(gdb) n
101 if(!shell_reader) {
(gdb) n
113 int z = 0;
(gdb) n
115 *active_wifis = -1;
(gdb) n
116 while((scan_buffer = fgets(scan_buffer, 1024, shell_reader)))
(gdb) n
118 z++;
(gdb) n
119 if (z == 1)
(gdb) n
120 active_wifi_list = calloc(sizeof(void*), 10);
(gdb) n
124 if (z % 2 == 1) {
(gdb) n
125 active_wifis++;
(gdb) n
126 tmp_wifi_quality =
calloc(sizeof(wifi_quality), 1);
(gdb) n
127 active_wifi_list[*active_wifis] =
tmp_wifi_quality;
(gdb) n
129 char* substr = strstr((char *)
scan_buffer, "Signal level=");
(gdb) n
130 substr = strstr(substr, "=");
(gdb) n
131 char* endstr = strstr(substr + 1, " ");
(gdb) n
133 strncpy(tmpstr, substr + 1, endstr -
substr - 1);
(gdb) n
134 tmpstr[endstr - substr + 1] = '\0';
(gdb) n
136 tmp_wifi_quality->quality =
strtod(tmpstr, NULL);
(gdb) n
144 double log_quality =
(tmp_wifi_quality->quality)/10;
(gdb) n
145 tmp_wifi_quality->quality = pow(10,
log_quality);
(gdb) n
116 while((scan_buffer = fgets(scan_buffer, 1024, shell_reader)))
(gdb) n
118 z++;
(gdb) n
119 if (z == 1)
(gdb) n
121 else if (z % 20 == 0)
(gdb) n
124 if (z % 2 == 1) {
(gdb) n
148 char* tmpstr = strtok((char*)
scan_buffer, "\"");
(gdb) n
149 tmpstr = strtok(NULL, "\"");
(gdb) n
151 strncpy(tmp_wifi_quality->name,
tmpstr, strlen(tmpstr));
(gdb) n
116 while((scan_buffer = fgets(scan_buffer, 1024, shell_reader)))
(gdb) n
156 if (scan_buffer != NULL) free(scan_buffer);
(gdb) n
157 pclose(shell_reader);
(gdb) n
158 }
(gdb) n
autoWirelessScanPlus () at automated_scanner.c:209
209 sortRadiatingWifisList(active_wifis, active_wifi_list);
(gdb) s
sortRadiatingWifisList (active_wifis=-1, active_wifi_list=0x0) at
automated_scanner.c:163
163 int i, j = 0;
(gdb) n
164 while (j < active_wifis) {
(gdb) n
177 }
(gdb) n
autoWirelessScanPlus () at automated_scanner.c:212
212 int wireless = 0;
(gdb) s
214 for (counter = 0; counter < count; counter++) {
(gdb) n
215 char* tmp_essid_list_item = essid_list[counter];
(gdb) n
Program received signal SIGSEGV, Segmentation fault.
0x0000000000401281 in autoWirelessScanPlus () at automated_scanner.c:215
215 char* tmp_essid_list_item = essid_list[counter];
(gdb)
/*
netman - A Network Connection Manager
Copyright (C) 2015 Edward Bartolo
"netman" is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
"netman" is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with "netman". If not, see <http://www.gnu.org/licenses/>.
*/
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <dirent.h>
#include <alloca.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <math.h>
//#include "core_functions.h"
//#include "essid_encoder.h"
#include "paths.h"
#define MAX_ESSID_LENGTH 1024
typedef struct {
double quality;
char name[MAX_ESSID_LENGTH];
} wifi_quality;
int getInstalledEssidList(int* count, char** essid_list)
{
DIR * dir;
struct dirent * ent;
int el_size = 0; // stands for essid_list size
// First get a list of installed wireless "interfaces" files
if ((dir = opendir(IFACES_PATH)) != 0) {
while ((ent = readdir (dir)) != 0)
if(
strcmp(".", ent->d_name) != 0 &&
strcmp("..", ent->d_name) != 0
) {
(*count)++;
char* encoded_essid;
int err;
encoded_essid = ent->d_name;
if (el_size < *count) {
el_size =+ 10;
if (el_size == 10)
essid_list = calloc(*count + 9, sizeof(char*));
else essid_list = realloc(essid_list, (*count + 9)*sizeof(char*));
}
essid_list[*count - 1] = calloc(strlen(encoded_essid) + 1, sizeof(char));
strcpy(essid_list[*count - 1], encoded_essid);
}
closedir(dir);
}
else {
int old_errno = errno;
fprintf(
stderr, "Error: "
"loadExisting(): opendir(%s) failed (Error: %s)\n",
IFACES_PATH, strerror(errno)
);
return old_errno;
}
return 0;
}
int getRadiatingWifiList(int* active_wifis, void** active_wifi_list)
{
// Hopefully, here we have a list of installed essid interfaces files
FILE * shell_reader;
char * scan_buffer = NULL;
int err;
scan_buffer = calloc(1024, 1);
// read output lines containing 'Quality=' and 'ESSID:'
shell_reader = popen("/sbin/iwlist wlan0 scan | grep \"Quality=\\|ESSID:\"", "r");
if(!shell_reader) {
fprintf(
stderr,
"ERROR: power_scan(): "
"popen() failed (Error: %s)\n",
strerror(errno)
);
return -1;
}
wifi_quality* tmp_wifi_quality;
int z = 0;
*active_wifis = -1;
while((scan_buffer = fgets(scan_buffer, 1024, shell_reader)))
{
z++;
if (z == 1)
active_wifi_list = calloc(sizeof(void*), 10);
else if (z % 20 == 0)
active_wifi_list = realloc(active_wifis + 10, sizeof(void*));
if (z % 2 == 1) {
active_wifis++;
tmp_wifi_quality = calloc(sizeof(wifi_quality), 1);
active_wifi_list[*active_wifis] = tmp_wifi_quality;
char* substr = strstr((char *) scan_buffer, "Signal level=");
substr = strstr(substr, "=");
char* endstr = strstr(substr + 1, " ");
char tmpstr[MAX_ESSID_LENGTH];
strncpy(tmpstr, substr + 1, endstr - substr - 1);
tmpstr[endstr - substr + 1] = '\0';
tmp_wifi_quality->quality = strtod(tmpstr, NULL);
// P(dBm) = 10 · log10( P(mW) / 1mW)
// we want the absolute power
// P(mW) / 1mW = P*
// P* = antilog(P/10)
double log_quality = (tmp_wifi_quality->quality)/10;
tmp_wifi_quality->quality = pow(10, log_quality);
}
else {
char* tmpstr = strtok((char*) scan_buffer, "\"");
tmpstr = strtok(NULL, "\"");
strncpy(tmp_wifi_quality->name, tmpstr, strlen(tmpstr));
}
//printf("%s", scan_buffer);
}
if (scan_buffer != NULL) free(scan_buffer);
pclose(shell_reader);
}
// sort radiating wifis according to signal strength
int sortRadiatingWifisList(const int active_wifis, void** active_wifi_list)
{
int i, j = 0;
while (j < active_wifis) {
for (i = active_wifis - j - 1; i == 0; i--)
if (
((wifi_quality*) active_wifi_list[i - 1])->quality <
((wifi_quality*) active_wifi_list[i])->quality
) {
wifi_quality* awifi_quality = (wifi_quality*) active_wifi_list[i - 1];
active_wifi_list[i - 1] = active_wifi_list[i];
active_wifi_list[i] = awifi_quality;
}
j++;
}
}
int wifiEssidInstalled(const int active_wifis, void** active_wifi_list, char* essid)
{
int i;
for (i = 0; i <= active_wifis; i++) {
if (strcmp(((wifi_quality*) active_wifi_list[i])->name, essid) == 0) {
return i;
}
}
return -1; // ie not found
}
int autoWirelessScanPlus()
{
char** essid_list;
int count = 0;
int active_wifis;
void** active_wifi_list;
char* scan_buffer;
// get a list of currently installed wifi essids
getInstalledEssidList(&count, essid_list);
//fprintf(stdout, essid_list[0], "\n");
// get a list of irradiating wifis
getRadiatingWifiList(&active_wifis, active_wifi_list);
// sort the radiating wifis in descending order according to strength
sortRadiatingWifisList(active_wifis, active_wifi_list);
int connection_result;
int wireless = 0;
int counter;
for (counter = 0; counter < count; counter++) {
char* tmp_essid_list_item = essid_list[counter];
if (wifiEssidInstalled(active_wifis, active_wifi_list, tmp_essid_list_item) > -1) {
FILE * shell_reader;
// required command for popen: /sbin/ifup wlan0 -i IFACES_PATH"/"essid_list[counter]
char ifup_cmd[40 + MAX_ESSID_LENGTH];
strncpy(ifup_cmd, "/sbin/ifup wlan0 -i "IFACES_PATH"/", 38);
strncat(ifup_cmd, essid_list[counter], strlen(essid_list[counter]));
shell_reader = popen(ifup_cmd, "r");
if(!shell_reader) {
fprintf(
stderr,
"ERROR: autoWirelessScanPlus(): "
"popen() failed (Error: %s)\n",
strerror(errno)
);
}
pclose(shell_reader);
shell_reader = popen(
"/bin/ip a | grep \"state UP\"", "r"
);
if(!shell_reader) {
fprintf(
stderr,
"ERROR: autoWirelessScanPlus(): "
"popen() failed (Error: %s)\n",
strerror(errno)
);
}
scan_buffer = (char *) calloc(1025, 1);
if (scan_buffer == NULL)
{
fprintf(
stderr,
"ERROR: autoWirelessScanPlus(): "
"popen() failed (Error: %s)\n",
strerror(errno)
);
}
while((scan_buffer = fgets(scan_buffer, 1024, shell_reader))) {
if (strstr((char *) scan_buffer, "wlan0") != NULL)
wireless++;
//else if (strstr((char *) scan_buffer, "eth0") != NULL)
// wired++;
}
pclose(shell_reader);
free(scan_buffer);
if (wireless) break; // if connected to wireless stop iterating
}
}
// free all the allocated memory
// free the essid string list
int u;
for (u = 0; u < count; u++)
free(essid_list[u]);
free(essid_list);
// free the radiating wifis list
for (u = 0; u <= active_wifis; u++)
free((wifi_quality*) active_wifi_list[u]);
free((void*) active_wifi_list);
}
int main(int argc, char *argv[])
{
autoWirelessScanPlus();
return 0;
}_______________________________________________
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