Methods and apparatus for intercepting control and data connections

• US 7,161,947 B1
• Filed: 07/30/2002
• Issued: 01/09/2007
• Est. Priority Date: 07/30/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Desai, Arun Raghavendra
• Primary Examiner(s): HO, DUC CHI
• Application Number:
  US10/208,540
• Time in Patent Office: 1,624 Days
• Field of Search: None
• US Class Current: 370/401
• CPC Class Codes: H04L 67/06 specially adapted for file transfer, e.g. file transfer protocol [FTP]
• CPC Class Codes: H04L 67/568 Storing data temporarily at an intermediate stage, e.g. caching

Abstract

A system provides a proxy connection by intercepting a control connection and a data connection between a client and a server. A proxy device receives a control connection request from a client and establishes a proxy control connection with a server in response to the control connection request from the client. The proxy device then receives a data connection request from the client. In response to the data connection request, the proxy device establishes a data connection with the server at a server-selected or dynamic port of the server and establishes a data connection with the client at a fixed port of the proxy device. Using this technique, the proxy device transparently intercepts both the control connection and the data connection from the client and transmits data received from the server-selected port of the server to the client through the fixed port of the proxy device.

Claims

1. In a proxy device, a method for intercepting a control connection and a data connection between a client and a server comprising the steps of:

receiving a control connection request from a client;

establishing a proxy control connection with a server in response to the control connection request from the client;

receiving a data connection request from the client;

establishing a data connection with the server at a server-selected port of the server;

establishing a data connection with the client at a fixed port of the proxy device; and

transmitting to the client, through the fixed port of the proxy device, data received from the server-selected port of the server.

2. The method of claim 1 wherein the step of receiving a data connection request from the client comprises the steps of receiving a passive data connection request from the client and establishing a passive data connection with the server.

3. The method of claim 2 wherein the step of receiving the control connection request from the client further comprises establishing an acceptance criteria that acts as a condition for establishing the data connection with the client.

4. The method of claim 3 wherein the step of establishing an acceptance criteria comprises establishing a transmission protocol, a source Internet protocol address, a source port number, a destination Internet protocol address, and a destination port number for the acceptance criteria.

5. The method of claim 3 further comprising the step of maintaining the acceptance criteria in a storage location.

6. The method of claim 5 wherein the step of maintaining comprises creating an entry in a conditional acceptance table.

7. The method of claim 5 further comprising the steps of:

detecting termination of the data connection with the server; and

removing the acceptance criteria from the storage location.

8. The method of claim 3 further comprising the step of establishing a data connection with the client based upon the acceptance criteria.

9. The method of claim 8 wherein the step of establishing a data connection with the client comprises the steps of:

receiving a data connection request from the client, the request having a header portion;

comparing the header portion of the data connection request from the client with the acceptance criteria; and

detecting a correspondence between the header portion of the data connection request and the acceptance criteria.

10. The method of claim 1 further comprising the step of mapping the server selected port of the server with the fixed port of the proxy device.

11. The method of claim 1 wherein the step of receiving a data connection request from the client comprises the steps of receiving an active connection request from the client and establishing a passive data connection with the server.

12. A proxy device comprising:

at least one communications interface;

a processor;

a memory; and

an interconnection mechanism coupling the at least one communications interface, the processor, and the memory;

wherein the proxy device is configured to;

receive a control connection request from a client;

establish a proxy control connection with a server in response to the control connection request from the client;

receive a data connection request from the client;

establish a data connection with the server at a server-selected port of the server;

establish a data connection with the client at a fixed port of the proxy device; and

transmit to the client, through the fixed port of the proxy device, data received from the server-selected port of the server.

13. The proxy device of claim 12 wherein the proxy device, while receiving a data connection request from the client, is configured to receive a passive data connection request from the client and establish a passive data connection with the server.

14. The proxy device of claim 13 wherein the proxy device, while detecting the control connection request from the client, is further configured to establish an acceptance criteria that acts as a condition for establishing the data connection with the client.

15. The proxy device of claim 14 wherein, while establishing an acceptance criteria, the proxy device is configured to establish a transmission protocol, a source Internet protocol address, a source port number, a destination Internet protocol address, and a destination port number for the acceptance criteria.

16. The proxy device of claim 14 wherein the proxy device is further configured to maintain the acceptance criteria in a storage location.

17. The proxy device claim 16 wherein, while maintaining the acceptance criteria in a storage location, the proxy device is further configured to create an entry in a conditional acceptance table.

18. The proxy device claim 16 wherein the proxy device is further configured to:

detect termination of the data connection with the server; and

remove the acceptance criteria from the storage location.

19. The proxy device of claim 14 wherein the proxy device is further configured to establishing a data connection with the client based upon the acceptance criteria.

20. The proxy device of claim 19 wherein the proxy device, while establishing a data connection with the client, is configured to:

receive a data connection request from the client, the request having a header portion;

compare the header portion of the data connection request from the client with the acceptance criteria; and

detect a correspondence between the header portion of the data connection request and the acceptance criteria.

21. The proxy device of claim 12 wherein the proxy device is further configured to map the server selected port of the server with the fixed port of the proxy device.

22. The proxy device of claim 12 wherein the proxy device, while receiving a data connection request from the client, is configured to receive an active connection request from the client to establish an active data connection and establish a passive data connection with the server.

23. A computer program product having a computer-readable medium including computer program logic encoded thereon that, when performed on a processor in a computerized device having a coupling of a memory, a processor, and at least one communications interface provides a method for performing the operations of:

receiving a control connection request from a client;

establishing a proxy control connection with a server in response to the control connection request from the client;

receiving a data connection request from the client;

establishing a data connection with the server at a server-selected port of the server;

establishing a data connection with the client at a fixed port of the proxy device; and

transmitting to the client, through the fixed port of the proxy device, data received from the server-selected port of the server.

24. A proxy device comprising:

at least one communications interface;

a processor;

a memory; and

an interconnection mechanism coupling the at least one communications interface, the processor, and the memory;

wherein the proxy device is configured to produce a means for intercepting a control connection and a data connection between a client and a server, such means including;

means for receiving a control connection request from a client;

means for establishing a proxy control connection with a server in response to the control connection request from the client;

means for receiving a data connection request from the client;

means for establishing a data connection with the server at a server-selected port of the server;

means for establishing a data connection with the client at a fixed port of the proxy device; and

means for transmitting to the client, through the fixed port of the proxy device, data received from the server-selected port of the server.