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This article introduces the relevant knowledge of "what is the type and principle of reptile agent IP". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

1. Agent type: transparent agent IP, anonymous agent IP, high anonymous agent

Proxy IP can be divided into four types. In addition to transparent agent IP, anonymous agent IP, high anonymous agent IP, there is another kind of obfuscation agent IP. In terms of basic security, they are arranged in the order of high concealment > confusion > anonymity > transparency.

2. Agency principle: REMOTE_ADDR, X-Forwarded-For (XFF), HTTP_VIA.

The proxy type mainly depends on the configuration of the proxy server, and different configurations form different proxy types. In the configuration, these three variables REMOTE_ADDR, HTTP_VIA, and HTTP_X_FORWARDED_FOR are the determining factors.

(1) REMOTE_ADDR

REMOTE_ADDR represents the IP of the client, but its value is not provided by the client, but is specified by the server based on the IP.

If you use a browser to access the site directly, the site's web server (Nginx, Apache, and so on) sets REMOTE_ADDR to the IP address of the client.

If we set up a proxy for the browser, our request to access the target site first passes through the proxy server, and then the proxy server converts the request to the target site. The web proxy server of the Web site sets REMOTE_ADDR as the IP of the proxy server.

2. X-Forwarded-For (XFF)

X-Forwarded-For is the HTTP extension header that represents the real IP of the HTTP client. When a client uses a proxy, the network proxy server does not know the real IP address of the client. To avoid this, the proxy server usually adds the header information of the X-Forwarded-For and the IP of the client to the header information.

The format of the X-Forwarded-For request header is as follows:

Xmuri ForwardedPROXYCLENE proxy1proxy2

Client represents the IP address of the client; proxy1 is the device farthest from the server. IP;proxy2 is the IP; of the secondary proxy device. From the format, you can see that there can be multiple layers of agents from client to server.

Before the HTTP request arrives at the server, through three agents, Proxy1, Proxy2, Proxy3,IP are IP1, IP2, IP3, respectively, and when the actual IP of the user is IP0, according to the XFF standard, the server will eventually receive the following information

Xmuri ForwardedFollowing IP0pr iP1Magi IP2

Proxy3 connects directly to the server and adds IP2 to XFF to help Proxy2 forward requests. There is no IP3,IP3 in the list that is available on the server through the RemoteAddress field. As we all know, the HTTP connection is based on the TCP connection. There is no concept of IP in the HTTP protocol. RemoteAddress comes from the TCP connection, which means that the device IP that establishes the TCP connection with the server is IP3. Here I suggest that when using http, reptiles try to use regular products like Sun http.

(3) HTTP_VIA

Via is the header of HTTP protocol, which records the proxy and gateway of HTTP request, adds one proxy server through one proxy server, and adds two through two.

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