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Proxy_Phase1.c
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Proxy_Phase1.c
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#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<strings.h>
#include<string.h>
#include<stdlib.h>
#include<netdb.h>
#include<stdbool.h>
#include<sys/select.h>
#define BACKLOG_QUEUE 1 //Number of connections to listen.
int main(int arg_cnt,char *arg_val[])
{
int proxy_sock,action_sock,clilen,n,web_sock; //Declaring all sockets.
char buffer[655350],temp_buffer[10]; //Declaring read,write buffer.
struct sockaddr_in proxy_addr,accept_addr,web_addr; //Declaring internet addresses object of structures for proxy and webserver.
struct hostent *webserver;
if(arg_cnt<2) //Arguments provided while running less than 1
{
fprintf(stderr,"\nError, No port provided ");
exit(1); //Can't continue without port, Exit!
}
proxy_sock=socket(AF_INET,SOCK_STREAM,0); //initializing socket for proxy.
if(proxy_sock<0) //Error initializing proxy socket.
{
perror("\nError in opening proxy socket ");
close(proxy_sock);
exit(1); //Can't continue initializing proxy socket, Exit!
}
bzero((char *)&proxy_addr,sizeof(proxy_addr)); //}Initializing proxy address and accept address objects with 0
bzero((char *)&accept_addr,sizeof(accept_addr)); //}
proxy_addr.sin_family=AF_INET; //initializing for code for the address family.
proxy_addr.sin_addr.s_addr=INADDR_ANY; //Initializing for the IP address of the host/machine.
proxy_addr.sin_port=htons(atoi(arg_val[1])); //Initializing for port number using arguments.
if(bind(proxy_sock,(struct sockaddr *)&proxy_addr,sizeof(proxy_addr))<0) //Bind the Socket and Addresses and check for error
{
perror("\nError in binding proxy socket and proxy addresses ");
close(proxy_sock);
exit(1); //Can't continue without proper binding, Exit!
}
listen(proxy_sock,BACKLOG_QUEUE); //Start listening from the proxy socket.
clilen=sizeof(accept_addr); //Store the size and addresses of the proxy.
while(1) //Run proxy, until killed.
{
char host[1024],request[512],site[2048],*trim_host=NULL,*find_conn=NULL,sitecpy[2048],*trim_port=NULL; //}Declaring required variables.
bool portprovided=false,proceed=false; //}
int port=80,i; //}Default port is 80.
action_sock=accept(proxy_sock,(struct sockaddr *)&accept_addr,&clilen); //open socket to accept traffic from proxy.
if(action_sock<0) //Error opening accepting socket.
{
perror("\nError in accepting socket on proxy ");
close(proxy_sock);
close(action_sock);
exit(1); //Can't continue without accepting socket, Exit!
}
bzero(buffer,sizeof(buffer)); //Initializing buffer with 0.
do //Read while all the data is read
{
bzero(temp_buffer,sizeof(temp_buffer)); //Initialize temp buffer with zero
n=read(action_sock,temp_buffer,sizeof(temp_buffer)-1); //Read contents from the proxy through accepting socket.
if(n!=0) //If some content is read.
strcat(buffer,temp_buffer); //Concatenate everything to make the entire buffer.
}while(buffer[strlen(buffer)-1]!='\n'||buffer[strlen(buffer)-2]!='\r'||buffer[strlen(buffer)-3]!='\n'||buffer[strlen(buffer)-4]!='\r'); //Exit loop when contents are completely read.
sscanf(buffer,"%s %s ",request,site); //Store the request type and website from the request stored in buffer.
if((strncmp(request,"GET",3)!=0)) //Check if the request is a GET request.
{
printf("\nNot a GET Request!");
proceed=false;
}
else if((strncmp(site,"http://",7)!=0)) //Check if the protocol is HTTP.
{
printf("\nNot a HTTP Request!");
proceed=false;
}
else
proceed=true;
if(proceed==true) //If valid request(checked above).
{
for(i=7;i<strlen(site);i++) //Check if port number is provided or not.
{
if(site[i]==':')
{
memcpy(sitecpy,&site[i],strlen(site)-i); //Copy everything from ':' if port provided to sitecpy.
sitecpy[strlen(site)-i]='\0'; //Insert null character for end of string
trim_port=strtok(sitecpy,":/"); //Extract only port from sitecpy. eg: :2222/hello.php will result in 2222
for(i=0;i<strlen(trim_port);i++) //Check if trim_port stores number and not alphabets(exceptional cases request had unusual ':'.
{
if(trim_port[i]<'0'||trim_port[i]>'9')
{
portprovided=false;
break;
}
else
portprovided=true;
}
break;
}
}
if(portprovided==true)
port=atoi(trim_port); //Store the extracted port number from request if provided.
find_conn=strstr(buffer,"keep-alive"); //Find keep_alive in request(buffer).
if(find_conn!=NULL) //If keep-alive found.
strncpy(find_conn,"close\r\n\r\n\r",10); //Change it to close.
trim_host=strtok(site,"//"); //}Extract host name from request thorugh webstite requested.
trim_host=strtok(NULL,"/:"); //}
sprintf(host,"%s",trim_host); //}Store host in the host variable.
web_sock=socket(AF_INET,SOCK_STREAM,0); //initialize the socket for webserver connection.
if(web_sock<0) //Error opening web socket.
{
perror("\nError in opening web socket ");
close(proxy_sock);
close(action_sock);
close(web_sock);
exit(1); //Can't continue without web socket initialization, Exit!.
}
webserver=gethostbyname(host); //Store host name in the webserver.
if(webserver==NULL) //If bad host or error getting host.
{
printf("\nBad host or error in host");
char bad_req[]="400 : BAD REQUEST\n\nNo Such host!"; //Send bad request to browser thorugh proxy.
write(action_sock,bad_req,strlen(bad_req));
close(action_sock);
continue; //Skip loop once since error in host name.
}
bzero((char *)&web_addr,sizeof(web_addr)); //Initializing web address object with 0.
web_addr.sin_port=htons(port); //Initialize with port number of web server to connect to.
web_addr.sin_family=AF_INET; //initializing for code for the address family.
bcopy((char *)webserver->h_addr,(char *)&web_addr.sin_addr.s_addr,webserver->h_length); //Set all the feilds in Web address object.
if(connect(web_sock,(struct sockaddr *)&web_addr,sizeof(web_addr))<0) //Connect to the web server.
{
perror("\nError connecting to webserver ");
char bad_req[]="400 : BAD REQUEST\n\nConnection timed out";
write(action_sock,bad_req,strlen(bad_req)); //Write to browser for not a valid request.
close(action_sock); //close the proxy socket to reset for next iteration.
continue; //Skip loop once since error connecting to webserver.
}
write(web_sock,buffer,strlen(buffer)); //Write the modified request to the webserver.
do //Read the response from web server and write to browser till response is written completely.
{
bzero(buffer,sizeof(buffer));
n=read(web_sock,buffer,sizeof(buffer)-1);
if(n>0)
write(action_sock,buffer,strlen(buffer));
}while(n>0);
close(action_sock); //close the proxy socket to reset for next iteration.
}
else //If not GET request or not HTTP protocol in request.
{
char bad_req[]="400 : BAD REQUEST\n\nOnly HTTP Protocols and GET requests accepted";
write(action_sock,bad_req,strlen(bad_req)); //Write to browser for not a valid request.
close(action_sock); //close the proxy socket to reset for next iteration.
}
}
close(proxy_sock); //}Free Sockets.
close(web_sock); //}
return 0;
}