unix/http/server.c

#define _GNU_SOURCE ///< in order for optarg to be defined
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include "shared/http.h"

#define LISTEN_BACKLOG 5 //< Define maximum size of the input queue

static int create_server_socket(uint16_t port, struct sockaddr_in incoming);
static char * setup_server_response(char* dir, char* ifile, char* request);
static char * get_file_contents(char* dir, char* filename);

int main(int argc, char *argv[]) {
    check_opts_number(argc);

    char *cport = "8080";
    char *ifile = "index.html";
    char *dir = NULL;
    char *response; //< To hold the server response
    int c;

    /// Process the options
    while((c = getopt(argc, argv, "p:i:h")) != -1) {
        switch(c) {
            case 'p':
                cport = optarg;
                break;
            case 'i':
                ifile = optarg;
                break;
            case 'h':
                printf("Command usage:\n");
                print_usage();
                exit(EXIT_SUCCESS);
            case '?':
                print_usage();
                exit(EXIT_FAILURE);
            default:
                abort();
        }
    }

    /// Check if the required argument is there
    if(argv[optind] == NULL) {
        fprintf(stderr, "Mandatory argument 'doc_root' missing.\n");
        print_usage();
        exit(EXIT_FAILURE);
    } else {
        dir = argv[optind];
    }

    uint16_t port = atoi(cport); //< Convert the argument to integer

    struct sockaddr_in incoming; //< Basic incoming config

    incoming.sin_addr.s_addr = INADDR_ANY; //< Allow 0.0.0.0 to access the server
	incoming.sin_port = htons(port); //< Set the port to work on
	incoming.sin_family = AF_INET; //< Use IPv4

    int sockfd = create_server_socket(port, incoming); //< Define a server socket
    int current_session = 0;

    socklen_t peer_addr_size = sizeof(struct sockaddr_in);

    while(1) { //< Accept connections until terminated
        /// Start accepting connections
        current_session = accept(sockfd, (struct sockaddr*) &incoming, &peer_addr_size); //< Save the current session

        if(current_session < 0) {
            (void) fprintf(stderr, "ERROR: Could not start accepting connections\n");
            close(current_session);
            close(sockfd);
            exit(EXIT_FAILURE);
        } else {
            char *request = malloc (sizeof (char) * __INT16_MAX__);

            if(recv(current_session, request, strlen(request) - 1, 0) < 0) {
                (void) fprintf(stderr, "ERROR: Could not receive connection from client\n");
                close(current_session);
                close(sockfd);
                exit(EXIT_FAILURE);
            }

            /// Setup the server response
            response = setup_server_response(dir, ifile, request);

            /// Send the response to the client
            if(send(current_session, response, strlen(response) + 1, 0) < 0) {
                (void) fprintf(stderr, "ERROR: Could not send the response to the client\n");
                close(current_session);
                close(sockfd);
                exit(EXIT_FAILURE);
            }
        }
    }

    close(current_session);
    close(sockfd);
    exit(EXIT_SUCCESS);
}

static void print_usage(void) {
    printf("server [-p PORT] [ -i INDEX ] DOC_ROOT\n");
}

/**
 * @brief Function to check the number of arguments
 * @details Checks the number of arguments supplied to the command line.
 *          If the arguments are less than the required or more than possible, it exits
 * @param argc - Number of arguments obtained from the command line
 * @return none
 *
 **/
static void check_opts_number(int argc) {
    if(argc <= 1) {
        fprintf(stderr, "At least one argument expected.\n");
        print_usage();
        exit(EXIT_FAILURE);
    } else if(argc > 6) {
        fprintf(stderr, "Too many arguments supplied.\n");
        print_usage();
        exit(EXIT_FAILURE);
    }
}

/**
 * @brief Function to create a socket using a default configuration for a server
 * @details Creates a socket using a default configuration for a server
 *          If there was no error, it returns the socket
 *          If there was an error, it exits and displays an error message
 * @param port     - the port to bind the server to
 *        incoming - basic incoming sockaddr config
 * @return sockfd - The socket obtained from the socket creation
 **/
static int create_server_socket(uint16_t port, struct sockaddr_in incoming) {
    int sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); //< Define socket with default configuration

    if(sockfd < 0) {
		(void) fprintf(stderr, "ERROR: Socket creation failed.\n");
		exit(EXIT_FAILURE);
	}

    /// Bind to a port
    if(bind(sockfd, (struct sockaddr*) &incoming, sizeof(struct sockaddr_in)) < 0) {
		(void) fprintf(stderr, "ERROR: Could not bind server to port %d!\n", port);
		close(sockfd);
		exit(EXIT_FAILURE);
	}

    /// Start listening on the socket
	if(listen(sockfd, LISTEN_BACKLOG) < 0)
	{
		(void) fprintf(stderr, "ERROR: Could not start listening\n");
		close(sockfd);
		exit(EXIT_FAILURE);
	} else {
        (void) fprintf(stdout, "Listening on port %d...\n", port);
    }

    return sockfd;
}

/**
 * @brief Function to create the HTTP response
 * @details Gets the client request
 *          If the server receives an invalid requests, a 400 header is build and the function adds it to response
 *          If a GET request is received, the function tries to open the resource:
 *              - if it could open it, it builds a 200 header and the file contents as body and adds them to response
 *              - if it could not open it, it builds a 404 header and adds it to response
 *          If anything other than a GET request is received, a 501 header is build and the function adds it to response
 *          At the end, it returns the server response with header and body (if available)
 * @param dir             - the directory of the file
 *        ifile           - the name of the indexfile
 *        request         - the request of the client
 * @return response - A header with the status code and a body (if available)
 **/
static char * setup_server_response(char* dir, char* ifile, char* request) {
    char *response = malloc (sizeof (char) * __INT16_MAX__);

    char method[4];
    strncpy(method, request, 3); //< Get the request type
    method[3] = 0; //< Add terminating string

    char header[__INT8_MAX__ + 100];

    if(strcmp(method, "GET") == 0) {
        char *body = NULL;
        char *delim = strstr(request, "/");
        char *req_file = strtok(delim, " "); //< Get the requested file

        if(strlen(req_file) == 1) {
            body = get_file_contents(dir, ifile);
        }
        else {
            char *rest = strstr(request, "HTTP/1.1");
            rest = strtok(rest, "\r\n");
            if(rest == NULL) {
                strcpy(
                    header,
                    "HTTP/1.1 400 Bad Request\r\nConnection: close\r\n\r\n"
                ); //< Build the 400 header
                strcat(response, header);
            } else {
                body = get_file_contents(dir, req_file + 1);
                (void) fprintf(stdout, "GET: %s\n", req_file);
            }
        }

        if(body != NULL) {
            time_t current_time;
            time(&current_time);
            struct tm * tm = gmtime(&current_time);
            char time_string[50];

            strftime(time_string, 50, "%a, %d %b %y %H:%M:%S %Z", tm);

            snprintf(
                header,
                sizeof header,
                "HTTP/1.1 200 OK\r\nDate: %s\r\nContent-Length: %ld\r\nConnection: close\r\n\r\n",
                time_string, strlen(body)
            ); //< Build the 200 header
            strcat(response, header);
            strcat(response, body);
        } else {
            strcpy(
                header,
                "HTTP/1.1 404 Not Found\r\nConnection: close\r\n\r\n"
            ); //< Build the 404 header
            strcat(response, header);
        }
    } else {
        strcpy(
            header,
            "HTTP/1.1 501 Not Implemented\r\nConnection: close\r\n\r\n"
        ); //< Build 501 the header
        strcat(response, header);
    }
    return response;
}

/**
 * @brief Function to take the contents of a specified file
 * @details Gets the contents of the file specified
 *          If there is no file, it returns NULL
 *          If the file is empty, it returns " "
 *          If the file is not empty, it returns its contents
 * @param dir      - the directory of the file
 *        filename - the name of the file
 * @return res - The contents of the file, formatted as a string
 **/
static char * get_file_contents(char *dir, char *filename) {
    char path[strlen(dir) + strlen(filename) + 100]; //< set the variable for the path with a reasonable length
    snprintf(path, sizeof path, "%s%s", dir, filename);

    FILE *file = NULL;

    file = fopen(path, "r");

    if(file == NULL) {
        return NULL;
    } else {
        char *res = 0;

        fseek(file, 0, SEEK_END); //< Set position to end of stream
        int file_length = ftell(file); //< Get file length
        fseek(file, 0, SEEK_SET); //< Set the position to begining of stream
        res = malloc(file_length); //< Allocate memory for the file contents
        fread(res, 1, file_length, file); //< Read the contents into res

        return res;
    }
}