使用gdb打印ip地址

时间:2009-11-29 20:13:49

标签: c++ printing gdb ip-address

我正在调试网络代码,并希望打印声明为int32的IP地址。   当我使用gdb打印命令打印它时,我得到一些没有太大意义的值。

我怎么可能以有意义的格式打印它们?

7 个答案:

答案 0 :(得分:9)

只需使用inet_ntoa(3)

(gdb) p (char*)inet_ntoa(0x01234567)  # Replace with your IP address
$1 = 0xa000b660 "103.69.35.1"

答案 1 :(得分:6)

如果您正在调试核心文件但无法使用inet_ntoa(),那么您还可以执行以下操作:

(gdb) set $int_ip = 0x01234567
(gdb) printf "%d.%d.%d.%d\n", ($int_ip & 0xff), ($int_ip >> 8) & 0xff, ($int_ip >> 16) & 0xff, ($int_ip >> 24)
103.69.35.1
(gdb) 

答案 2 :(得分:3)

但inet_ntoa()不接受u_int32_t参数,而是采用struct in_addr参数,所以先前的答案是:      p(char *)inet_ntoa(3) 对我来说似乎不对。

这是一种在名为gdb.cmd.txt的文件中定义函数的方法,因此在启动时调用“gdb -x gdb.cmd.txt”。

在gdb.cmd.txt中,输入:

define ntoa
        set $ipv4 = $arg0
        echo IPV4 =.
        p $ipv4
        set $val1 = ($ipv4 >> 24) & 0xff
        set $val2 = ($ipv4 >> 16) & 0xff
        set $val3 = ($ipv4 >>  8) & 0xff
        set $val4 = ($ipv4 >>  0) & 0xff
       printf "IPV4=%u=0x%02x.%02x.%02x.%02x =%d.%d.%d.%d\n", $ipv4, $val1, $val2, $val3, $val4, $val1, $val2, $val3, $val4
    end

然后运行gdb,并按如下方式调用ntoa“用户定义函数”:

(gdb) ntoa(0x01020304)
IPV4 =.$10 = 16909060
IPV4=16909060=0x01.02.03.04 =1.2.3.4
(gdb) ntoa(-1)
IPV4 =.$10 = -1
IPV4=4294967295=0xff.ff.ff.ff =255.255.255.255

(gdb) ntoa(0x01020304) IPV4 =.$10 = 16909060 IPV4=16909060=0x01.02.03.04 =1.2.3.4 (gdb) ntoa(-1) IPV4 =.$10 = -1 IPV4=4294967295=0xff.ff.ff.ff =255.255.255.255

BTW:我现在正在搜索gdb中是否有方法让函数返回格式化字符串,这样我就可以运行命令“p ntoa(0x01020304)”或“p ntoa(ptr-> ipv4_addresss)” (假设ptr是包含u_int32_t ipv4_address“数据元素”的结构的有效ptr。)但似乎gdb用户定义的函数不允许sprintf()调用。

-dennis bednar 2012年12月

答案 3 :(得分:1)

创建一个调用inet_ntoa的函数,然后在int上的gdb中使用'p'命令调用它。

答案 4 :(得分:1)

解释Gopinath的回答:

(gdb) p/uc (char[4]) 342757386
$4 = {10 '\n', 16 '\020', 110 'n', 20 '\024'}

p/uc:告诉gdb将数据视为未签名的char内容。

(char[4]) 342757386:将IP转换为4个char元素的数组,每个char元素代表一个字节/八位字节。

因此,您要告诉gdb将IP的十进制表示形式视为四个字节(四个八位字节)的数组,然后将它们打印为无符号字符。

如果忽略每个字节的ASCII表示形式,则您的IP地址为10.16.110.20

答案 5 :(得分:0)

这是另一个有趣的方式:

#include <sys/types.h>  // u_int32_t


// next 3 for inet_ntoa() call
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

// C++ headers
#include <iostream> // std::cout
#include <string>
#include <sstream>  // ostringstream


// class to aid in using the gdb(3) debugger to print a u_int32_t ip_address as a string.
// The toString() is a static method!!
// How to call a C++ method from the gdb debugger, to simulate the inet_nto(3) method
//
// From within gdb debugger, you must have a process, so first stop at main:
//  b main
//  r
//
//  (gdb) p MYIP4::toString(0x0fffefdfc)
//  $1 = "255.254.253.252"
//
//  (gdb) p MYIP4::toString(-1)
//  $2 = "255.255.255.255"
//
//  (gdb) p MYIP4::toString(65536)
//  $3 = "0.1.0.0"
//
// Drawbacks: the a.out executable that you are debugging needs the MYIP4 class already
// compiled and linked into the executable that you are debugging.
//
// PS: I don't know if there is a "slick way" where the MyIP4 class could dynamically be loaded,
// within gdb(), if the executable failed to contain the MYIP4 class.
//
// PS: I had trouble with my operator() idea.. If you know how to improve on it, post away!
//
// @author 1201207 dpb  created
//=============================

class MYIP4
{
public:
    static std::string toString(u_int32_t ipv4_address )
    {
        struct in_addr temp_addr;

        // inet_ntoa() returns a char * to a buffer which may be overwritten
        // soon, so convert char* to a string for extra safety.
        temp_addr.s_addr = htonl(ipv4_address);
        std::string ipv4String = std::string(inet_ntoa( temp_addr ));
        return ipv4String;
    }

#if 0
    // this idea did NOT work, so it is commented out.
    //
    // overload the () operator, so that, within gdb, we can simply type:
    //  p MYIP4(0x01020304)
    // instead of:
    //  p MYIP4::toString(0x01020304)

    std::string operator() ( u_int32_t ipv4_address )
    {
        return toString(ipv4_address);
    }
#endif

};


void test1();

int main()
{
    test1();
    return 0;
}

void test1()
{
    u_int32_t   ipv4Address = 0x01020304;   // host byte order for 1.2.3.4
    std::cout << "Test1: IPAddress=" << MYIP4::toString(ipv4Address) << "\n";
}

答案 6 :(得分:-1)

尝试此命令:

(gdb) p/uc (char[4])342757386
$1 = {10 '\n', 16 '\020', 110 'n', 20 '\024'}