Server Access Processing System

Abstract

A method, programmed medium and system are provided for preventing the denial of file system access to a plurality of clients accessing a NFS server. In one example, an NFS server is configured to listen on a server port. The server runs a separate daemon which “watches” client requests as they are received at the NFS server. The server processing system tracks the number of times a client sends consecutive TCP zero-window packets in response to a data packet from the server. If the number of zero-window packets crosses a user-defined threshold, then a routine is called to stop responding to that client using a backoff algorithm. When the server reaches a point where the number of available threads or any other relevant resource dips below a user-defined threshold, the server process starts terminating connections to the clients starting from the ones with the oldest entry in the table.

1 . A method for server access processing, said method comprising:
 determining when a data packet is sent from a server to a client device;   counting a number of zero window packets (ZWPs) received from said client device by said server following said data packet being sent to provide a ZWP count; and   using said ZWP count to control access to said server by said client device.   
     
     
         2 . The method as set forth in  claim 1  wherein said ZWP count includes a total count of consecutive ZWPs received by said server. 
     
     
         3 . The method as set forth in  claim 2  and further including:
 disconnecting said client device from said server after said total count exceeds a first predetermined number. 
 
     
     
         4 . The method as set forth in  claim 2  and further including:
 determining a resource availability level of said server when said total count exceeds a first predetermined number; and 
 disconnecting said client device from said server when said resource availability level is below a predetermined level or said total count exceeds a first predetermined number. 
 
     
     
         5 . The method as set forth in  claim 2  and further including:
 disabling said server from responding to said client device for a first time period after said total count exceeds a first predetermined number; 
 
     
     
         6 . The method as set forth in  claim 5  and further including enabling said server to respond to said client device after said first time period if no ZWPs are received by said server from said client device during said first time period. 
     
     
         7 . The method as set forth in  claim 5  and further including:
 disabling said server from responding to said client device for a second time period after said total count exceeds a second predetermined number at a completion of said first time period, said second time period being greater than said first time period. 
 
     
     
         8 . The method as set forth in  claim 7  and further including enabling said server to respond to said client device after said second time period if no ZWPs are received by said server from said client device during said second time period. 
     
     
         9 . A computer program product for enabling server access processing, the computer program product comprising computer readable program code configured such that when such program code is read by said server, the server is effective for:
 determining when a data packet is sent from said server to a client device;   counting a number of zero window packets (ZWPs) received from said client device by said server following said data packet being sent to provide a ZWP count; and   using said ZWP count to control access to said server by said client device.   
     
     
         10 . The program product as set forth in  claim 9  wherein said ZWP count includes a total count of consecutive ZWPs received by said server. 
     
     
         11 . The program product as set forth in  claim 10  and further including:
 disconnecting said client device from said server after said total count exceeds a first predetermined number. 
 
     
     
         12 . The program product as set forth in  claim 10  and further including:
 determining a resource availability level of said server when said total count exceeds a first predetermined number; and 
 disconnecting said client device from said server when said resource availability level is below a predetermined level and said total count exceeds a first predetermined number. 
 
     
     
         13 . The program product as set forth in  claim 10  and further including:
 disabling said server from responding to said client device for a first time period after said total count exceeds a first predetermined number; 
 
     
     
         14 . The program product as set forth in  claim 13  and further including enabling said server to respond to said client device after said first time period if no ZWPs are received by said server from said client device during said first time period. 
     
     
         15 . The program product as set forth in  claim 13  and further including:
 disabling said server from responding to said client device for a second time period after said total count exceeds a second predetermined number at a completion of said first time period, said second time period being greater than said first time period. 
 
     
     
         16 . The program product as set forth in  claim 15  and further including enabling said server to respond to said client device after said second time period if no ZWPs are received by said server from said client device during said second time period. 
     
     
         17 . A server enabled to manage server access requests from a client device, said server comprising:
 means for determining when a data packet is sent from said server to said client device;   means for counting a number of zero window packets (ZWPs) received from said client device by said server following said data packet being sent to provide a ZWP count; and   means for using said ZWP count to control access to said server by said client device.   
     
     
         18 . The server as set forth in  claim 17  wherein said ZWP count includes a total count of consecutive ZWPs received by said server. 
     
     
         19 . The server as set forth in  claim 18  and further including:
 means for disconnecting said client device from said server after said total count exceeds a first predetermined number. 
 
     
     
         20 . The server as set forth in  claim 18  and further including:
 means for determining a resource availability level of said server when said total count exceeds a first predetermined number; and 
 means for disconnecting said client device from said server when said resource availability level is below a predetermined level and said total count exceeds a first predetermined number. 
 
     
     
         21 . The server as set forth in  claim 18  and further including:
 means for disabling said server from responding to said client device for a first time period after said total count exceeds a first predetermined number; 
 
     
     
         22 . The server as set forth in  claim 21  and further including means for enabling said server to respond to said client device after said first time period if no ZWPs are received by said server from said client device during said first time period. 
     
     
         23 . The server as set forth in  claim 21  and further including:
 means for disabling said server from responding to said client device for a second time period after said total count exceeds a second predetermined number at a completion of said first time period, said second time period being greater than said first time period. 
 
     
     
         24 . The server as set forth in  claim 23  and further including means for enabling said server to respond to said client device after said second time period if no ZWPs are received by said server from said client device during said second time period. 
     
     
         25 . A computer system including a server and at least one client device accessing said server, said server being enabled for managing access to said server by said client device, said server including:
 means for determining when a data packet is sent from said server to said client device;   means for counting a number of zero window packets (ZWPs) received from said client device by said server following said data packet being sent to provide a ZWP count, said ZWP count including a total count of consecutive ZWPs received by said server;   means for disabling said server from responding to said client device for a first time period after said total count exceeds a first predetermined number;   means for enabling said server to respond to said client device after said first time period if no ZWPs are received by said server from said client device during said first time period;   means for determining a resource availability level of said server when said total count exceeds said first predetermined number;   means for disabling said server from responding to said client device for a second time period after said total count exceeds a second predetermined number at a completion of said first time period, said second time period being greater than said first time period;   means for enabling said server to respond to said client device after said second time period if no ZWPs are received by said server from said client device during said second time period; and   means for disconnecting said client device from said server when said resource availability level is below a predetermined level and said total count exceeds said second predetermined number after said second time period.