CacheCow/proxy_server_with_cache.c at main · hemanggs/CacheCow · GitHub

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#include "proxy_parse.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
#include <sys/wait.h>
#include <errno.h>
#include <pthread.h>
#include <semaphore.h>
#include <time.h>

#define MAX_CLIENTS 10
#define MAX_BYTES (4096);

typedef struct cache_element cache_element;

struct cache_element
{
    char *data;
    int len;
    char *url;
    time_t lru_time_track;
    cache_element *next;
}

cache_element *
find(char *url);
int add_cache_element(char *data, int size, char *url);

int port_no = 8080;
int proxy_socket_id =           // each  request has its own socket
    pthread_t tid[MAX_CLIENTS]; // no of requests = no of sockets =no of threads

sem_t semaphore; //  a type of lock , having multiple values

pthread_mutex_t lock; // mutex lock
                      // to avoid concurrency problems  when mutliple threads access same shared resource(LRU cache here)
                      // when a thread wants to access , it will  check lock -> locked -> wait to be unlocked -> unlocked -> add own lock ->  complete access -> unlock -> next thread lock

cache_element *head;
int cache_size;


// Handling Error Message
int sendErrorMessage(int socket, int status_code)
{
	char str[1024];
	char currentTime[50];
	time_t now = time(0);

	struct tm data = *gmtime(&now);
	strftime(currentTime,sizeof(currentTime),"%a, %d %b %Y %H:%M:%S %Z", &data);

	switch(status_code)
	{
		case 400: snprintf(str, sizeof(str), "HTTP/1.1 400 Bad Request\r\nContent-Length: 95\r\nConnection: keep-alive\r\nContent-Type: text/html\r\nDate: %s\r\nServer: VaibhavN/14785\r\n\r\n<HTML><HEAD><TITLE>400 Bad Request</TITLE></HEAD>\n<BODY><H1>400 Bad Rqeuest</H1>\n</BODY></HTML>", currentTime);
				  printf("400 Bad Request\n");
				  send(socket, str, strlen(str), 0);
				  break;

		case 403: snprintf(str, sizeof(str), "HTTP/1.1 403 Forbidden\r\nContent-Length: 112\r\nContent-Type: text/html\r\nConnection: keep-alive\r\nDate: %s\r\nServer: VaibhavN/14785\r\n\r\n<HTML><HEAD><TITLE>403 Forbidden</TITLE></HEAD>\n<BODY><H1>403 Forbidden</H1><br>Permission Denied\n</BODY></HTML>", currentTime);
				  printf("403 Forbidden\n");
				  send(socket, str, strlen(str), 0);
				  break;

		case 404: snprintf(str, sizeof(str), "HTTP/1.1 404 Not Found\r\nContent-Length: 91\r\nContent-Type: text/html\r\nConnection: keep-alive\r\nDate: %s\r\nServer: VaibhavN/14785\r\n\r\n<HTML><HEAD><TITLE>404 Not Found</TITLE></HEAD>\n<BODY><H1>404 Not Found</H1>\n</BODY></HTML>", currentTime);
				  printf("404 Not Found\n");
				  send(socket, str, strlen(str), 0);
				  break;

		case 500: snprintf(str, sizeof(str), "HTTP/1.1 500 Internal Server Error\r\nContent-Length: 115\r\nConnection: keep-alive\r\nContent-Type: text/html\r\nDate: %s\r\nServer: VaibhavN/14785\r\n\r\n<HTML><HEAD><TITLE>500 Internal Server Error</TITLE></HEAD>\n<BODY><H1>500 Internal Server Error</H1>\n</BODY></HTML>", currentTime);
				  //printf("500 Internal Server Error\n");
				  send(socket, str, strlen(str), 0);
				  break;

		case 501: snprintf(str, sizeof(str), "HTTP/1.1 501 Not Implemented\r\nContent-Length: 103\r\nConnection: keep-alive\r\nContent-Type: text/html\r\nDate: %s\r\nServer: VaibhavN/14785\r\n\r\n<HTML><HEAD><TITLE>404 Not Implemented</TITLE></HEAD>\n<BODY><H1>501 Not Implemented</H1>\n</BODY></HTML>", currentTime);
				  printf("501 Not Implemented\n");
				  send(socket, str, strlen(str), 0);
				  break;

		case 505: snprintf(str, sizeof(str), "HTTP/1.1 505 HTTP Version Not Supported\r\nContent-Length: 125\r\nConnection: keep-alive\r\nContent-Type: text/html\r\nDate: %s\r\nServer: VaibhavN/14785\r\n\r\n<HTML><HEAD><TITLE>505 HTTP Version Not Supported</TITLE></HEAD>\n<BODY><H1>505 HTTP Version Not Supported</H1>\n</BODY></HTML>", currentTime);
				  printf("505 HTTP Version Not Supported\n");
				  send(socket, str, strlen(str), 0);
				  break;

		default:  return -1;

	}
	return 1;
}


// Connect Proxy Server to Backend/Remote Server
int connectRemoteServer(char* host_addr, int port_num)
{
	// Creating Socket for proxy to remote server ---------------------------
	int remoteSocket = socket(AF_INET, SOCK_STREAM, 0);

	if( remoteSocket < 0)
	{
		printf("Error in Creating Socket.\n");
		return -1;
	}

	// Get host by the name or ip address provided

	struct hostent *host = gethostbyname(host_addr);
	if(host == NULL)
	{
		fprintf(stderr, "No such host exists.\n");	 // standard error stream
		return -1;
	}

	// inserts ip address and port number of host in struct `server_addr`
	struct sockaddr_in server_addr;

	bzero((char*)&server_addr, sizeof(server_addr)); // clear garbage values
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(port_num);


	bcopy((char *)host->h_addr,(char *)&server_addr.sin_addr.s_addr,host->h_length); // copy host ip address into server_addr

	// Connect Proxy server to Remote server ----------------------------------------------------
    // each connection requires a socket
	if( connect(remoteSocket, (struct sockaddr*)&server_addr, (socklen_t)sizeof(server_addr)) < 0 )
	{
		fprintf(stderr, "Error in connecting !\n");
		return -1;
	}
	// free(host_addr);
	return remoteSocket;
}


int handle_request(int clientSocket, ParsedRequest *request, char *tempReq)
{
    char *buf = (char *)malloc(sizeof(char) * MAX_BYTES); // put GET request to buffer
    strcpy(buf, "GET ");                                  // I have only Implemented GET requests
    strcat(buf, request->path);
    strcat(buf, " ");
    strcat(buf, request->version);
    strcat(buf, "\r\n");

    size_t len = strlen(buf);

    if (ParsedHeader_set(request, "Connection", "close") < 0) // setting Connection part of header to close , if <0 error encountered
    {
        printf("set header key not work\n"); // error in setting header
    }

    if (ParsedHeader_get(request, "Host") == NULL) // Checking if Header is set already
    {
        if (ParsedHeader_set(request, "Host", request->host) < 0)  // Setting Host part of header to request->Host
        {
            printf("Set \"Host\" header key not working\n");// error in setting header
        }
    }

    if (ParsedRequest_unparse_headers(request, buf + len, (size_t)MAX_BYTES - len) < 0) // Unparsing (Convert Back to Raw String data to be sent) and appending to  buffer contents
    {
        printf("unparse failed\n");
        // return -1;				// If this happens Still try to send request without header
    }

    int server_port = 80; // Default Remote Server Port
    if (request->port != NULL)
        server_port = atoi(request->port);

    int remoteSocketID = connectRemoteServer(request->host, server_port); // Connected to Remote server

    if (remoteSocketID < 0)
        return -1;

    int bytes_send = send(remoteSocketID, buf, strlen(buf), 0);

    bzero(buf, MAX_BYTES); // clear buffer

    bytes_send = recv(remoteSocketID, buf, MAX_BYTES - 1, 0); // recieve bytes into buffer

    char *temp_buffer = (char *)malloc(sizeof(char) * MAX_BYTES); // temp buffer
    int temp_buffer_size = MAX_BYTES;
    int temp_buffer_index = 0;

    while (bytes_send > 0) // while we keep  recieving bytes from remote server
    {
        bytes_send = send(clientSocket, buf, bytes_send, 0); // (Proxy to client) sending response of the request to the Client

        for (int i = 0; i < bytes_send / sizeof(char); i++)
        {
            temp_buffer[temp_buffer_index] = buf[i]; //  Storing  it in Temp Buffer so that we can Store it later in LRU Cache
            // printf("%c",buf[i]); // Response Printing
            temp_buffer_index++;
        }
        temp_buffer_size += MAX_BYTES; // 2x temp buffer size when its filled
        temp_buffer = (char *)realloc(temp_buffer, temp_buffer_size); // C dosent have dynamic array , so i have to 2x the size of buffer every time its filled

        if (bytes_send < 0)
        {
            perror("Error in sending data to client socket.\n");
            break;
        }

         // We have Successfully Sent to Client , now lets recieve from remote server Socket again
        bzero(buf, MAX_BYTES); // clear buffer
        bytes_send = recv(remoteSocketID, buf, MAX_BYTES - 1, 0);
    }


    temp_buffer[temp_buffer_index] = '\0';
    free(buf); // we have to free the buffer array (Dynamic Allocation)
    add_cache_element(temp_buffer, strlen(temp_buffer), tempReq);      // Adding TempBuffer to LRU Cache
    printf("Done\n");
    free(temp_buffer);

    close(remoteSocketID);
    return 0;
}

int checkHTTPversion(char *msg)
{
	int version = -1;

	if(strncmp(msg, "HTTP/1.1", 8) == 0)
	{
		version = 1;
	}
	else if(strncmp(msg, "HTTP/1.0", 8) == 0)
	{
		version = 1;										// Handling this similar to version 1.1
	}
	else
		version = -1;

	return version;
}


void *thread_fn(void *socketNew) // init thread
{
    sem_wait(&seamaphore);
    int p;
    sem_getvalue(&seamaphore, &p);
    printf("semaphore value:%d\n", p);
    int *t = (int *)(socketNew);
    int socket = *t;            // Socket is socket descriptor of the connected Client
    int bytes_send_client, len; // Bytes Transferred

    char *buffer = (char *)calloc(MAX_BYTES, sizeof(char)); // Creating buffer of 4kb for a client , To process Request 4kb at a time

    bzero(buffer, MAX_BYTES);                               // Making buffer zero
    bytes_send_client = recv(socket, buffer, MAX_BYTES, 0); // Receiving the Request from client

    while (bytes_send_client > 0)
    {
        len = strlen(buffer);
        // recieve loop until u find "\r\n\r\n"(ending of http request) in the buffer
        if (strstr(buffer, "\r\n\r\n") == NULL)
        {
            bytes_send_client = recv(socket, buffer + len, MAX_BYTES - len, 0);
        }
        else
        {
            break;
        }
    }

    // printf("--------------------------------------------\n");
    // printf("%s\n",buffer);
    // printf("----------------------%d----------------------\n",strlen(buffer));

    char *tempReq = (char *)malloc(strlen(buffer) * sizeof(char) + 1);
    // tempReq &  buffer both store the http request sent by client
    for (int i = 0; i < strlen(buffer); i++)
    {
        tempReq[i] = buffer[i];
    }

    // checking if current  request is in cache
    struct cache_element *temp = find(tempReq);

    // Request is present is cache = Loop Linked list to get response from cache
    if (temp != NULL)
    {
        // request found in cache, so sending the response to client from proxy's cache
        int size = temp->len / sizeof(char); // Lenght of request
        int pos = 0;
        char response[MAX_BYTES];
        while (pos < size)
        {
            bzero(response, MAX_BYTES);
            for (int i = 0; i < MAX_BYTES; i++)
            {
                response[i] = temp->data[pos];
                pos++;
            }
            send(socket, response, MAX_BYTES, 0);
        }
        printf("Data retrived from the Cache\n\n");
        printf("%s\n\n", response);
        // close(socketNew);
        // sem_post(&seamaphore);
        // return NULL;
    }

    // Not in LRU Cache , so treated as New Request
    else if (bytes_send_client > 0)
    {
        len = strlen(buffer);
        // Parsing the request
        ParsedRequest *request = ParsedRequest_create(); // storing  the buffer in this parsed request variable

        // ParsedRequest_parse returns 0 on success and -1 on failure.On success it stores parsed request in
        //  the request
        if (ParsedRequest_parse(request, buffer, len) < 0)
        {
            printf("Parsing failed\n");
        }
        else
        {
            bzero(buffer, MAX_BYTES);
            if (!strcmp(request->method, "GET")) // its a GET
            {

                if (request->host && request->path && (checkHTTPversion(request->version) == 1)) // only HTTP version 1.0 supported by this lib
                {
                    bytes_send_client = handle_request(socket, request, tempReq); // Handle GET request
                    if (bytes_send_client == -1)
                    {
                        sendErrorMessage(socket, 500);
                    }
                }
                else
                    sendErrorMessage(socket, 500); // 500 Internal Error
            }
            else
            {
                printf("This code doesn't support any method other than GET\n");
            }
        }
        // freeing up the request pointer
        ParsedRequest_destroy(request);
    }
    // corrupted send from client
    else if (bytes_send_client < 0)
    {
        perror("Error in receiving from client.\n");
    }
    // no request from client
    else if (bytes_send_client == 0)
    {
        printf("Client disconnected!\n");
    }
    // close socket
    shutdown(socket, SHUT_RDWR);
    close(socket);
    free(buffer); // buffer stores both incoming request or response during the processing time

    sem_post(&seamaphore);
    sem_getvalue(&seamaphore, &p);
    printf("Semaphore post value:%d\n", p);

    free(tempReq);
    return NULL;
}

int main(int argc, char *argv[])
{
    int client_socketId, client_len;
    struct sockaddr server_addr, client_addr;
    sem_init(&semaphore, MAX_CLIENTS);
    pthread_mutex_init(&lock, NULL);

    if (argv == 2)
    { // can use custom port
        // ./proxy   9090
        //  arg[0]  arg[1]
        port_number = atoi(argv[1]);
    }
    else
    {
        printf({"Too few arguments\n"});
        exit(1); // exit system call
    }

    printf("Starting Proxy Server at port: %d \n", port_no);
    proxy_socket_id = socket(AF_INET, SOCK_STREAM, 0);

    if (proxy_socket_id < 0)
    {
        perror("Failed to create socket.\n");
        exit(1);
    }

    int reuse = 1;

    if (setsockopt(proxy_socket_id, SOL_SOCKET, SO_REUSEADDR, (const char *)&reuse, sizeof(reuse)) < 0)
        perror("setsockopt(SO_REUSEADDR) failed\n");

    bzero((char *)&server_addr, sizeof(server_addr)); // clean default garbage values that C sets

    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port_number); // Assigning port to the Proxy
    server_addr.sin_addr.s_addr = INADDR_ANY;  // Any available adress assigned

    // Binding the socket
    if (bind(proxy_socket_id, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
    {
        perror("Port is not free\n");
        exit(1);
    }
    printf("Binding on port: %d\n", port_number);

    int listen_status = listen(proxy_socket_id, MAX_CLIENTS);
    if (listen_status < 0)
    {
        perror("Error in Listening \n");
        exit(1);
    }

    int i = 0;
    int Connected_socketid[MAX_CLIENTS];

    // continuously check for client requests
    while (1)
    {
        {
            bzero((char *)&client_addr, sizeof(client_addr));
            client_len = sizeof(client_addr);
            client_socketId = accept(proxy_socket_id, (struct sockaddr *)&client_addr, (socklen_t *)&client_len);
        }
        if (client_socketId < 0)
        {
            fprintf(stderr, "Error in Accepting connection !\n");
            exit(1);
        }
        else
        {
            Connected_socketid[i] = client_socketId; // Storing accepted client into array
            // opened sockets
        }

        // Getting IP address and port number of client
        struct sockaddr_in *client_pt = (struct sockaddr_in *)&client_addr;
        struct in_addr ip_addr = client_pt->sin_addr;
        char str[INET_ADDRSTRLEN];                          // INET_ADDRSTRLEN: Default ip address size
        inet_ntop(AF_INET, &ip_addr, str, INET_ADDRSTRLEN); // convert ipaddr to standard readable format
        printf("Client is connected with port number: %d and ip address: %s \n", ntohs(client_addr.sin_port), str);
        // printf("Socket values of index %d in main function is %d\n",i, client_socketId);

        pthread_create(&tid[i], NULL, thread_fn, (void *)&Connected_socketId[i]); // Creating a thread for each client accepted
        // This Thread is responsible for handling request and response for the its client
        i++;
    }
    close(proxy_socketId); // Close socket
    return 0;
}


// Find Node in Linked List ( LRU Cache)
cache_element* find(char* url){

// Checks for url in the cache if found returns pointer to the respective cache element or else returns NULL
    cache_element* site=NULL;
	//sem_wait(&cache_lock);
    int temp_lock_val = pthread_mutex_lock(&lock);
	printf("Remove Cache Lock Acquired %d\n",temp_lock_val);


    if(head!=NULL){
        site = head;
        while (site!=NULL)
        {
            if(!strcmp(site->url,url)){
				printf("LRU Time Track Before : %ld", site->lru_time_track);
                printf("\nurl found\n");
				// Updating the time_track
				site->lru_time_track = time(NULL);
				printf("LRU Time Track After : %ld", site->lru_time_track);
				break;
            }
            site=site->next;
        }
    }
	else {
    printf("\nurl not found\n");
	}
	//sem_post(&cache_lock);
    temp_lock_val = pthread_mutex_unlock(&lock);
	printf("Remove Cache Lock Unlocked %d\n",temp_lock_val);
    return site;
}

// Remove Linked List Node
void remove_cache_element(){
    // If cache is not empty searches for the node which has the least lru_time_track and deletes it
    cache_element * p ;  	// Cache_element Pointer (Prev. Pointer)
	cache_element * q ;		// Cache_element Pointer (Next Pointer)
	cache_element * temp;	// Cache element to remove
    //sem_wait(&cache_lock);
    int temp_lock_val = pthread_mutex_lock(&lock);
	printf("Remove Cache Lock Acquired %d\n",temp_lock_val);
	if( head != NULL) { // Cache != empty
		for (q = head, p = head, temp =head ; q -> next != NULL;
			q = q -> next) { // Iterate through entire cache and search for oldest time track
			if(( (q -> next) -> lru_time_track) < (temp -> lru_time_track)) {
				temp = q -> next;
				p = q;
			}
		}
		if(temp == head) {
			head = head -> next; /*Handle the base case*/
		} else {
			p->next = temp->next;
		}
		cache_size = cache_size - (temp -> len) - sizeof(cache_element) -
		strlen(temp -> url) - 1;     //updating the cache size
		free(temp->data);
		free(temp->url); // Free the removed element
		free(temp);
	}
	//sem_post(&cache_lock);
    temp_lock_val = pthread_mutex_unlock(&lock);
	printf("Remove Cache Lock Unlocked %d\n",temp_lock_val);
}


// Add Element to Linked list
int add_cache_element(char* data,int size,char* url){
    // Adds element to the cache
	// sem_wait(&cache_lock);
    int temp_lock_val = pthread_mutex_lock(&lock);
	printf("Add Cache Lock Acquired %d\n", temp_lock_val);
    int element_size=size+1+strlen(url)+sizeof(cache_element); // Size of the new element which will be added to the cache
    if(element_size>MAX_ELEMENT_SIZE){
		//sem_post(&cache_lock);
        // If element size is greater than MAX_ELEMENT_SIZE we don't add the element to the cache
        temp_lock_val = pthread_mutex_unlock(&lock);
		printf("Add Cache Lock Unlocked %d\n", temp_lock_val);
		// free(data);
		// printf("--\n");
		// free(url);
        return 0;
    }
    else
    {   while(cache_size+element_size>MAX_SIZE){
            // We keep removing elements from cache until we get enough space to add the element
            remove_cache_element();
        }
        cache_element* element = (cache_element*) malloc(sizeof(cache_element)); // Allocating memory for the new cache element
        element->data= (char*)malloc(size+1); // Allocating memory for the response to be stored in the cache element
		strcpy(element->data,data);
        element -> url = (char*)malloc(1+( strlen( url )*sizeof(char)  )); // Allocating memory for the request to be stored in the cache element (as a key)
		strcpy( element -> url, url );
		element->lru_time_track=time(NULL);    // Updating the time_track
        element->next=head;
        element->len=size;
        head=element;
        cache_size+=element_size;
        temp_lock_val = pthread_mutex_unlock(&lock);
		printf("Add Cache Lock Unlocked %d\n", temp_lock_val);
		//sem_post(&cache_lock);
		// free(data);
		// printf("--\n");
		// free(url);
        return 1;
    }
    return 0;
}