2021/07/09

使用sshfs比samba安全方便. 但是 Geany 存取 sshfs-win 掛載進來的檔案, 在存檔時會抱怨 Permission denied.

解決的方式是撤銷 use_gio_unsafe_file_saving. 操作如下:

1. 拉下【編輯(E)】選單, 點擊【偏好設定(S)】

2. 切換到【各種類型】, 取消勾選 files.use_gio_unsafe_file_saving. 然後套用並確定.

參考資訊:

Geany: All you never wanted to know about file saving

2021/05/26

debug function for LUCI

local debug = 0

function dbg_print(...)

if 1 == debug then

local dbg = io.open("/dev/console", "w")

if dbg then

dbg:write(os.date("[%H:%M:%S]: "))

for _, o in ipairs({...}) do

dbg:write(tostring(o)..' ')

end

dbg:write("\n")

dbg:close()

end

2021/03/17

C 將 stdout 轉給 console

daemon 的除錯訊息被殼層吃掉的時候, 將訊息丟到 console 可以方便除錯, 如果是每次呼叫 debug 時都 openfile 和 closefile 會有點浪費資源, 所以直接將 stdout 轉給 console, 就能繼續用 printf 來送出除錯訊息了.

做法就是開個 file handler 給 console, 然後重新將 stdout 設定給 console 的 file handler. 範例程式如下:

#include <stdio.h>
int main()
{
	FILE *stdout_bk;
	FILE *fpout = fopen("/dev/console" ,"w" );
	stdout_bk = stdout;
	printf("printf not to console\n");
	stdout = fpout;
	printf("printf to console\n");
	stdout = stdout_bk;
	return 0;
}

做成 MACRO

#ifdef AIMDBG
#undef AIMDBG
#endif
#define AIMDBG(fmt,...) \
do { \
    FILE *console = fopen("/dev/console" ,"w" ); \
    if (console) { \
        fprintf(console, fmt, __VA_ARGS__); \
        fflush(console); \
        fclose(console); \
    } \
} while(0)

追加 Hexdump

static void hexdump (uint8_t* ptr, int len) {
    int i;
    for (i=0; i<len; i++) {
        if (15 == (i % 16)) {
            AIMDBG("%02X\n", ptr[i]);
        }
        else if (7 == (i % 8)) {
            AIMDBG("%02X   ", ptr[i]);
        }
        else {
            AIMDBG("%02X ", ptr[i]);
        }
    }
    AIMDBG("%s", "\n");
}

類似 printf 的用法直接輸出到 console

void console_debug(const char *fmt, ...)
{
    static FILE *console_fp = NULL;
    static int tried_open = 0;

    if (!tried_open) {
        console_fp = fopen("/dev/console", "w");
        if (console_fp == NULL) {
            perror("Warning: Cannot open /dev/console, fallback to stderr");
            console_fp = stderr;
        }
        tried_open = 1;
    }
    char log_buf[1024];
    va_list args;
    va_start(args, fmt);
    vsnprintf(log_buf, sizeof(log_buf), fmt, args);
    va_end(args);
    fprintf(console_fp, "[SYSLOGD] %s", log_buf);
    fflush(console_fp);
}

2021/03/05

快速重製 oom 確認 memory leak 的問題

memory leak 會造成記憶體不足而引發 linux 的 oom kill 機制. 假如有 memory leak 的情況發生, 記憶體應該會被佔用而越來越少, 所以要認或是驗證有沒有解決 memory leak, 最簡單的方式就是寫一隻程式來把記憶體占用, 藉此縮短驗證所需的時間.

typedef struct S_ROBBER
{
	char occupy[1024];
} C_ROBBER;

void syntax(char *command)
{
	printf("Syntax:\n");
	printf("\t%s mem_request(MB)\n", command);
	printf("\t\t mem_request between 1 and 128\n", command);
}

int main( int argc, char **argv)
{
	int memreq;
	int i, j;
	char *robber[128][1024];
	C_ROBBER *ptr;
	
	if (argc != 2) {
		syntax(argv[0]);
		return 0;
	}
	
	memreq = atoi(argv[1]);
	
	if (memreq < 1 || memreq > 128) {
		syntax(argv[0]);
		return 0;
	}
	
	for (i=0; i<memreq; i++) {
		for (j=0; j<1024; j++) {
			ptr = (C_ROBBER *)malloc(sizeof(C_ROBBER));
			if (ptr)
			{
				robber[i][j] = ptr;
			} else {
				printf("Your system was very very poor!\n");
				break;
			}
		}
		if (j < 1024) {
			break;
		}
	}
	printf("Robber occupy %dMB memory, now.\n", i);
	
	while(1) {
		sleep(3600);
	}
}

這隻程式會根據船進去的參數, 以 MB 為單位, 霸佔記憶體. 最大占用限制 128MB.

一般系統在記憶體不足時會觸發 oom kill, 而強盜程式會是被殺的最大目標, 所以要把 oom kill 機制關閉, 讓系統直接 panic. 指令如下

1	echo 1 > /proc/sys/vm/panic_on_oom

這樣就可以先用強盜程式將記憶體占用到只剩下一點點, 當記憶體不足的情形發生時, 會直接 panic 而不是把強盜砍掉, 就可以大幅度的縮短重製及驗證的時間.

2021/02/20

Install tor as proxy

Install tor

sudo apt-get install tor

Test tor

curl --socks5 localhost:9050 --socks5-hostname localhost:9050 --insecure -s https://check.torproject.org/ | cat | grep -m 1 Congratulations | xargs

You will get message "Congratulations. This browser is configured to use Tor." if tor work.

Edit tor config to open listen port on lan

sudo nano /etc/tor/torrc

Search for "SocksPort 9050" and replace with:

SocksPort 9050

SocksPort 192.168.56.4:9051 # open sock port for other stations.

# restart tor service

sudo service tor restart

# check listen port

ss -nlt

Setup your browser proxy

Check if you are tor

https://check.torproject.org/

Aim Wang