从字节缓冲区中提取IP [英] extract IP from a buffer of bytes

问题描述

如果我有一个包含此字节的缓冲区：

510175126-94-51080

If I have a buffer containing this bytes:
510175126-94-51080

如何从中提取 75126-94-51 部分（这是ip）并打印正确的IP？
感谢高级。

How can I extract the 75126-94-51 part from it(which is the ip) and print the correct IP ? Thanks in advanced.

for（int i = 0; i< bytes_recv; i ++）

{

cout < static_cast< int>（temp [i]）;

}

cout< endl;

edit：这是我的输出：5 1 0 1 75 126 -94 -51 0 80

for(int i = 0; i < bytes_recv; i++)
{
cout << static_cast<int>(temp[i]);
}
cout << endl;
edit: this is my output: 5 1 0 1 75 126 -94 -51 0 80

推荐答案

问题中缺少很多信息。所以，你正在从SOCKS协议读取服务器回复。首先，缓冲区不应该和将不具有10字节的固定大小。它有10个字节，如果你的地址是IPv4（这巧合是几天前耗尽，考虑IPv6的时间）。如果来源具有IPv6地址，则服务器响应的大小不同。

A lot of information is missing from the question. So, you are reading the server reply from the SOCKS protocol. First, the buffer should not and will not have a fixed size of 10 bytes. It has 10 bytes if your address is IPv4 (which coincidently was exhausted a few days ago, time to think about IPv6). If the origin has a IPv6 address, the size of the server response is different.

从 RFC 1928 ，第6节，服务器回复具有以下格式：

From RFC 1928, section 6, the server reply has this format:

+----+-----+-------+------+----------+----------+
|VER | REP |  RSV  | ATYP | BND.ADDR | BND.PORT |
+----+-----+-------+------+----------+----------+
| 1  |  1  | X'00' |  1   | Variable |    2     |
+----+-----+-------+------+----------+----------+

请注意，地址字段具有可变大小。对于IPv4，具体来说，ATYP == 0x01和BND.ADDR具有大小4，这使得1 + 1 + 1 + 1 + 4 + 2 = 10字节。但你应该考虑其他大小是可能的，特别是如果ATYP == 0x03，这使得BND.ADDR的长度真正变量。

Note that the address field has variable size. For IPv4, specifically, ATYP == 0x01 and BND.ADDR has size 4, which makes 1+1+1+1+4+2 = 10 bytes. But you should consider that other sizes are possible, specially if ATYP == 0x03, which makes BND.ADDR truly variable in length.

所以，回答你的问题，你在 char buffer [] 数组（或指针）中有这些字节，你必须首先检查地址的类型，然后像这样提取：

So, answering your question, considering that you have these bytes in a char buffer[] array (or pointer), you must first check the type of the address, then extract it like this:

#include <arpa/inet.h>

switch (buffer[3]) {
  case 0x01: {    /* IPv4 address */
    char result[INET_ADDRSTRLEN];
    inet_ntop(AF_INET, (void*)(&buffer[4]), result, sizeof result);
    std::cout << "IPv4: " << result << "\n";
    break;
  }

  case 0x04: {    /* IPv6 address */
    char result[INET6_ADDRSTRLEN];
    inet_ntop(AF_INET6, (void*)(&buffer[4]), result, sizeof result);
    std::cout << "IPv6: " << result << "\n";
    break;
  }

  default:
    std::cout << "Unsupported format.\n";
    break;
}

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