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proxy_server_with_cache.c
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proxy_server_with_cache.c
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#include "proxy_parse.h"
#include <asm-generic/socket.h>
#include <stdio.h>
#include <string.h>
#include <strings.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 <error.h>
#include <pthread.h>
#include <semaphore.h>
#define MAX_CLIENTS 10
#define MAX_BYTES 4096 // bytes allocation space - 4KB
#define MAX_ELEMENT_SIZE 10 * (1<<10)
#define MAX_SIZE 200 * (1<<20) // size of cache
typedef struct cache_element cache_element ;
// Implementing the cache element for LRU cache (time-based)
struct cache_element {
char* data;
int len;
char* url;
time_t lru_time_track;
cache_element* next;
// We need a linked-list to access corresponding cache elements
};
cache_element* find(char* url);
int add_cache_element(char* data, int size, char* url);
void remove_cache_element();
int port_number = 8080;
int proxy_socketId;
// Creating new thread for each socket connection with client
// 1. Defining max-limit = 10 (array containig thread-ids)
pthread_t tid[MAX_CLIENTS];
// 2. LRU cache is a shared resource. When multiple threads access it there
// can be a race condition. Hence, we setup a lock.
pthread_mutex_t lock;
// 3. As we have setup a limit of 10 client connections, we might run out of
// client connections. In which case, we need to hold the further incoming
// requests till a connection becomes free.
sem_t semaphore;
// Global HEAD for the linkedlist which contains the LRU cache
cache_element* head;
int cache_size;
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:
sprintf(str, sizeof(str),
"HTTP/1.1 400 Bad Request\r\n\
Content-Length: 95\r\n\
Connection: keep-alive\r\n\
Content-Type: text/html\r\n\
Date: %s\r\n\
Server: Ritesh-Server\r\n\r\n\
<html>\
<head>\
<title>400 Bad Request</title>\
</head>\n\
<body>\
<h1>400 Bad Request</h1>\n\
</body>\
</html>", currentTime);
printf("400 Bad Request\n");
send(socket, str, strlen(str), 0);
break;
case 403:
sprintf(str, sizeof(str),
"HTTP/1.1 403 Forbidden\r\n\
Content-Length: 112\r\n\
Connection: keep-alive\r\n\
Content-Type: text/html\r\n\
Date: %s\r\n\
Server: Ritesh-Serves\r\n\r\n\
<html>\
<head>\
<title>403 Forbidden</title>\
</head>\n\
<body>\
<h1>403 Forbidden</h1>\n\
</body>\
</html>", currentTime);
printf("403 Forbidden\n");
send(socket, str, strlen(str), 0);
break;
case 404:
sprintf(str, sizeof(str),
"HTTP/1.1 404 Not Found\r\n\
Content-Length: 91\r\n\
Connection: keep-alive\r\n\
Content-Type: text/html\r\n\
Date: %s\r\n\
Server: Ritesh-Serves\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:
sprintf(str, sizeof(str),
"HTTP/1.1 500 Interal Server Error\r\n\
Content-Length: 115\r\n\
Connection: keep-alive\r\n\
Content-Type: text/html\r\n\
Date: %s\r\n\
Server: Ritesh-Serves\r\n\r\n\
<html>\
<head>\
<title>500 Interal Server Error</title>\
</head>\n\
<body>\
<h1>500 Interal Server Error</h1>\n\
</body>\
</html>", currentTime);
printf("500 Interal Server Error\n");
send(socket, str, strlen(str), 0);
break;
case 501:
sprintf(str, sizeof(str),
"HTTP/1.1 501 Not Implemented\r\n\
Content-Length: 103\r\n\
Connection: keep-alive\r\n\
Content-Type: text/html\r\n\
Date: %s\r\n\
Server: Ritesh-Serves\r\n\r\n\
<html>\
<head>\
<title>501 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:
sprintf(str, sizeof(str),
"HTTP/1.1 505 HTTP Version Not Supported\r\n\
Content-Length: 125\r\n\
Connection: keep-alive\r\n\
Content-Type: text/html\r\n\
Date: %s\r\n\
Server: Ritesh-Serves\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 0;
}
int connectRemoteServer(char* host_addr, int port_num){
// Creating remote server socket
int remoteSocket = socket(AF_INET, SOCK_STREAM, 0);
if(remoteSocket < 0){
printf("Error in creating your socket\n");
return -1;
}
struct hostent* host = gethostbyname(host_addr);
if(host == NULL){
fprintf(stderr, "No such host exists\n");
return -1;
}
struct sockaddr_in server_addr;
bzero((char *)&server_addr, sizeof(server_addr));
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);
if(connect(remoteSocket, (struct sockaddr *)&server_addr,
(size_t)sizeof(server_addr) < 0)){
fprintf(stderr, "Error in connecting\n");
return -1;
}
// If connected successfully, return the socket (which is an integer)
return remoteSocket;
}
int handle_request(int clientSocketId, struct ParsedRequest* request, char* tempReq){
char* buf = (char *)malloc(sizeof(char)*MAX_BYTES);
strcpy(buf, "GET ");
strcat(buf, request->path);
strcat(buf, " ");
strcat(buf, request->version);
strcat(buf, "\r\n");
size_t len = strlen(buf);
// Connection - header
if(ParsedHeader_set(request, "Connection", "close") < 0){
printf("Set header key is not working");
}
// Host - header
if(ParsedHeader_get(request, "Host") == NULL){
if(ParsedHeader_set(request, "Host", request->host) < 0){
printf("Set Host header key is not working");
}
}
if(ParsedRequest_unparse_headers(request, buf + len,
(size_t)MAX_BYTES - len) < 0){
printf("Unparse failed");
}
// End-server
int server_port = 80;
if(request->port != NULL){
server_port = atoi(request->port);
}
// Remote socket
int remoteSocketId = connectRemoteServer(request->host, server_port);
if(remoteSocketId < 0){
return -1;
}
int bytes_send = send(remoteSocketId, buf, strlen(buf), 0);
bzero(buf, MAX_BYTES);
// Keep receiving till response keeps coming
bytes_send = recv(remoteSocketId, buf, MAX_BYTES - 1, 0);
char* temp_buffer = (char*)malloc(sizeof(char)*MAX_BYTES);
int temp_buffer_size = MAX_BYTES;
int temp_buffer_index = 0;
while(bytes_send > 0){
bytes_send = send(clientSocketId, buf, bytes_send, 0);
for(int i = 0; i < bytes_send/sizeof(char); i++){
// Accept all incoming responses into temp buffer as this has to
// be stored in the LRU cache later on
temp_buffer[temp_buffer_index] = buf[i];
temp_buffer_index++;
}
temp_buffer_size += MAX_BYTES;
// Dynamically allocating more space to temporary buffer to
// accomodate huge incoming responses
temp_buffer = (char*)realloc(temp_buffer, temp_buffer_size);
if(bytes_send < 0){
perror("Error in sending data to the client\n");
break;
}
bzero(buf, MAX_BYTES);
bytes_send = recv(remoteSocketId, buf, MAX_BYTES - 1, 0);
}
free(buf);
add_cache_element(temp_buffer, strlen(temp_buffer), tempReq);
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;
} else {
version = -1;
}
return version;
}
void *thread_fn(void *socketNew){
// Using a semaphore. If the value has become negative then it waits,
// otherwise it proceeds.
sem_wait(&semaphore);
int p;
sem_getvalue(&semaphore, &p);
printf("Semaphore value is %d\n", p);
// Making a pointer
int *t = (int*) socketNew;
// Getting the value out of the pointer
int socket = *t;
// Now that a thread + socket has been allocated to the client, he will
// start sending bytes. We need to receive them.
int bytes_send_client, len;
char *buffer = (char*)calloc(MAX_BYTES, sizeof(char));
bzero(buffer, MAX_BYTES);
// Params -
bytes_send_client = recv(socket, buffer, MAX_BYTES, 0);
while(bytes_send_client > 0){
len = strlen(buffer);
// Any HTTP request ends with "\r\n\r\n", we need to compare substring
// and see if we have reached that spot or not. If no then we must
// keep reading else break out of the loop
if (strstr(buffer, "\r\n\r\n") == NULL){
bytes_send_client = recv(socket, buffer + len, MAX_BYTES - len, 0);
} else {
break;
}
}
// Dynamically allocating this because sizeof-character tends to
// differ from OS-to-OS so we cannot hardcode this value
char *tempReq = (char *)malloc(strlen(buffer) * sizeof(char) + 1);
for(int i = 0; i < strlen(buffer); i++){
tempReq[i] = buffer[i];
}
struct cache_element* temp = find(tempReq);
// if the element is found in LRU cache
if(temp != NULL){
int size = temp -> len / sizeof(char);
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[i];
pos++;
}
send(socket, response, MAX_BYTES, 0);
}
printf("Data retrived from the cache");
printf("%s\n\n", response);
}
// if element is not found in LRU cache, then first check if the bytes
// send by the client is greater than 0 or not (managing invalid requests)
else if (bytes_send_client > 0){
len = strlen(buffer);
struct ParsedRequest* request = ParsedRequest_create();
if(ParsedRequest_parse(request, buffer, len) < 0){
printf("Parsing failed\n");
} else {
bzero(buffer, MAX_BYTES);
if(!strcmp(request -> method, "GET")){
if(request->host &&
request->path &&
checkHTTPversion(request->version) == 1){
bytes_send_client = handle_request(socket, request, tempReq);
if(bytes_send_client == -1){
// Internal server error - due to main server
sendErrorMessage(socket, 500);
}
} else {
// Internal server error - due to proxy server
sendErrorMessage(socket, 500);
}
} else {
printf("This code does not support any method except GET\n");
}
}
// Free everything
ParsedRequest_destroy(request);
} else if (bytes_send_client == 0){
printf("Client is disconnected");
}
shutdown(socket, SHUT_RDWR);
close(socket);
free(buffer);
// Release semaphore
sem_post(&semaphore);
sem_getvalue(&semaphore, &p);
printf("Semaphore post value is %d\n", p);
free(tempReq);
return NULL;
}
int main(int argc, char* argv[]){
int client_socketId, client_len;
// When we open a socket, it returns a descriptor (same as opening files)
struct sockaddr_in server_addr, client_addr;
// Semaphore - minVal = 0, maxVal = 10
sem_init(&semaphore, 0, MAX_CLIENTS);
// Initializing lock with NULL
pthread_mutex_init(&lock, NULL);
if(argv == 2){
// ./proxy 9090 (takes two args)
port_number = atoi(argv[1]);
} else {
printf("Too few arguments");
exit(1); // sys-call
}
printf("Starting Proxy server at port: %d\n", port_number);
proxy_socketId = socket(AF_INET, SOCK_STREAM, 0);
// If socket creation fails, it returns a negative value and exit
if (proxy_socketId < 0) {
perror("Failed to create a socket\n");
exit(1);
}
int reuse = 1;
if (setsockopt(proxy_socketId, SOL_SOCKET, SO_REUSEADDR,
(const char*)&reuse, sizeof(reuse)) < 0) {
perror("setSockOpt failed\n");
}
bzero((char*)&server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(port_number);
server_addr.sin_addr.s_addr = INADDR_ANY;
// Port binding
if(bind(proxy_socketId,
(struct sockaddr*)&server_addr, sizeof(server_addr) < 0)){
perror("Port is not available");
exit(1);
}
printf("Binding on port %d\n", port_number);
int listen_status = listen(proxy_socketId, MAX_CLIENTS);
if (listen_status < 0){
perror("Error in listening\n");
exit(1);
}
int i = 0;
int Connected_socketId[MAX_CLIENTS];
while(1){
bzero((char *)&client_addr, sizeof(client_addr));
client_len = sizeof(client_addr);
client_socketId = accept(proxy_socketId,
(struct sockaddr *)&client_addr,
(socklen_t *)&client_addr
);
if(client_socketId < 0){
printf("Not able to connect");
exit(1);
} else {
Connected_socketId[i] = client_socketId;
}
struct sockaddr_in* client_pt = (struct sockaddr_in *)&client_addr;
// Extract the client address from whichever socket that was opened
struct in_addr ip_addr = client_pt -> sin_addr;
char str[INET_ADDRSTRLEN];
// The function converts the address from network format to presentation
// format. Returns null if system error occurs.
inet_ntop(AF_INET, &ip_addr, str, INET_ADDRSTRLEN);
printf("Client is connected with port number %d and ip address is %s\n",
ntohs(client_addr.sin_port), str);
// All connections are open and have been accepted by the client
// Provide a socket to the thread so that other clients can come and
// then a new socket is created and given to them.
pthread_create(&tid[i], NULL, thread_fn, (void *)&Connected_socketId[i]);
i++;
}
// Deallocate the socket memory
close(proxy_socketId);
return 1;
}
cache_element *find(char* url){
// finding element inside linked-list
cache_element* site = NULL;
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("\n URL found\n");
site->lru_time_track = time(NULL);
printf("LRU time track after %ld", site->lru_time_track);
break;
}
site = site->next;
}
} else {
printf("URL not found in cache");
}
temp_lock_val = pthread_mutex_unlock(&lock);
printf("Lock is unlocked");
return site;
}
void remove_cache_element(){
// if cache is not empty, search for the node which has the least
// lru_time_track and delete it.
cache_element *p;
cache_element *q;
cache_element *temp;
// Removing elements from a linked list but with a mutex-lock
int temp_lock_val = pthread_mutex_lock(&lock);
printf("Lock is acquired\n");
if(head != NULL){
for(q=head, p=head, temp=head; q->next != NULL; q = q->next){
if(((q->next)->lru_time_track) < (temp->lru_time_track)){
temp = q->next;
p = q;
}
}
if(temp==head){
head = head->next;
} else {
// Removing the least recently used
p->next = temp->next;
}
cache_size = cache_size - (temp->len) - sizeof(cache_element)
- strlen(temp->url) - 1;
// Deallocate things one by one
free(temp->data);
free(temp->url);
free(temp);
}
temp_lock_val = pthread_mutex_unlock(&lock);
printf("Remove cache lock\n");
}
int add_cache_element(char *data, int size, char* url){
int temp_lock_val = pthread_mutex_lock(&lock);
printf("Remove cache Lock acquired %d\n", temp_lock_val);
int element_size = size + 1 + strlen(url) + sizeof(cache_element);
if(element_size > MAX_ELEMENT_SIZE){
// element is too big, do something else
temp_lock_val = pthread_mutex_unlock(&lock);
printf("Add cache lock is unlocked");
} else {
while(cache_size + element_size > MAX_SIZE){
remove_cache_element();
}
cache_element* element = (cache_element*)malloc(sizeof(cache_element));
element->data = (char*)malloc(size+1);
strcpy(element->data, data);
element->url = (char*)malloc(1 + (strlen(url) * sizeof(char)));
strcpy(element->url, url);
element->lru_time_track = time(NULL);
element->next = head;
element->len = size;
cache_size += element_size;
temp_lock_val = pthread_mutex_unlock(&lock);
printf("Add cache lock is unlocked\n");
return 1;
}
return 0;
}