cs-3516-assignment-1/server/socket_server.c

#include "socket_server.h"
#include "request_handling.h"
#include "../common/http_types.h"
#include "../common/socket_helper.h"
#include "../common/buffer_helper.h"
#include "status_codes.h"
#include <errno.h>
#include <math.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <time.h>
#include <unistd.h>

/**
 * Gets the address info for the given port, such that the server will listen on 0.0.0.
 *
 * @param port The port to listen on.
 * @param info A pointer to a location where getaddrinfo can store data.
 *
 * @return The result of getaddrinfo. See `man getaddrinfo` for details.
 */
static int build_addr_info(int port, struct addrinfo **info) {
    struct addrinfo hints = {.ai_family = AF_UNSPEC, .ai_socktype = SOCK_STREAM};
    // Get the number of chars in the port
    int port_length = floor(log10(port)) + 1;
    char *port_string = malloc((port_length + 1) * sizeof(char));
    sprintf(port_string, "%d", port);

    int addr_status = getaddrinfo(LISTEN_ADDR, port_string, &hints, info);
    free(port_string);

    return addr_status;
}

/**
 * Setup the server's socket for listening.
 *
 * @param port The port to listen on.
 *
 * @return A server_info representing the result of setting up the socket.
 */
struct server_info setup(int port) {
    struct server_info info = {.sock_fd = -1};
    struct addrinfo *addr_info;
    int addr_status = build_addr_info(port, &addr_info);
    if (addr_status != 0) {
        freeaddrinfo(addr_info);
        info.status = STATUS_ERROR;
        return info;
    }

    info.sock_fd = socket(addr_info->ai_family, addr_info->ai_socktype, addr_info->ai_protocol);
    if (info.sock_fd == -1) {
        freeaddrinfo(addr_info);
        info.status = STATUS_ERROR;
        return info;
    }

    int bind_result = bind(info.sock_fd, addr_info->ai_addr, addr_info->ai_addrlen);
    if (bind_result == -1) {
        freeaddrinfo(addr_info);
        close(info.sock_fd);
        info.sock_fd = -1;
        info.status = STATUS_ERROR;
        return info;
    }

    freeaddrinfo(addr_info);
    int listen_result = listen(info.sock_fd, BACKLOG_SIZE);
    if (listen_result == -1) {
        close(info.sock_fd);
        info.sock_fd = -1;
        info.status = STATUS_ERROR;
        return info;
    }
    info.status = STATUS_LISTENING;

    return info;
}

/**
 * Make an HTTP date for the date header
 *
 * @param buffer The buffer to write into
 * @param buffer_size The max size of the buffer
 *
 * @return The number of bytes the format takes up, excluding the null term.
 */
static size_t make_http_date(char *buffer, size_t buffer_size) {
    time_t current_time = time(NULL);
    struct tm *utc_time = gmtime(&current_time);

    return strftime(buffer, buffer_size, DATE_FORMAT, utc_time);
}

/**
 * Sends the headers and status line of the response
 *
 * @param status_code The status code to send
 * @param client_socket The socket to send the message on
 * @param content_length The content length of the file-to-send
 *
 * @return -1 on error, 0 otherwise.
 */
static int send_headers(int status_code, int client_socket, long content_length) {
    const char *status_code_message = get_message_from_status_code(status_code);
    if (status_code_message == NULL) {
        return -1;
    }
    // All status codes are three digits, plus the space for the null term.
    char *status_code_string = malloc(4 * sizeof(char));
    snprintf(status_code_string, 4, "%d", status_code);
    const char *status_line_components[] = {HTTP_VERSION, " ", status_code_string, " ", status_code_message, "\r\n"};
    int status_line_buffer_size = get_buffer_size(status_line_components, 6) + 1;
    char *status_line_buffer = malloc(status_line_buffer_size * sizeof(char));
    sprintf(status_line_buffer, "%s %s %s\r\n", HTTP_VERSION, status_code_string, status_code_message);
    free(status_code_string);

    // RFC2616 states that if we don't intend to persist the connection, we must send "Connection: close"
    const char *connection_header_components[] = {HEADER_CONNECTION, ": close\r\n"};
    char *content_length_header_buffer = "";
    // Include space for the CRLF and null term
    int header_buffer_size = get_buffer_size(connection_header_components, 2) + 3;
    if (content_length > 0) {
        // Get the number of chars in the port
        int content_length_length = floor(log10(content_length)) + 1;
        char *content_length_string = malloc((content_length_length + 1) * sizeof(char));
        sprintf(content_length_string, "%ld", content_length);
        const char *content_length_header_components[] = {HEADER_CONTENT_LENGTH, ": ", content_length_string, "\r\n"};
        int content_length_header_length = get_buffer_size(content_length_header_components, 4) + 1;
        header_buffer_size += content_length_header_length - 1;
        content_length_header_buffer = malloc(content_length_header_length * sizeof(char));
        sprintf(content_length_header_buffer, "%s: %s\r\n", HEADER_CONTENT_LENGTH, content_length_string);
        free(content_length_string);
    }

    // The 1024 is somewhat arbitrary, but everything should fit.
    char *date_header_buffer = malloc(1024 * sizeof(char));
    header_buffer_size += make_http_date(date_header_buffer, 1024);
    // +4 is ': \r\n'
    header_buffer_size += strlen(HEADER_DATE) + 4;

    char *header_buffer = malloc(header_buffer_size * sizeof(char));
    sprintf(header_buffer, "%s: close\r\n%s: %s\r\n%s\r\n", HEADER_CONNECTION, HEADER_DATE, date_header_buffer, content_length_header_buffer);
    free(date_header_buffer);
    if (content_length > 0) {
        free(content_length_header_buffer);
    }

    int send_result = send(client_socket, status_line_buffer, status_line_buffer_size - 1, 0);
    if (send_result == -1) {
        free(status_line_buffer);
        free(header_buffer);
        return -1;
    }
    send_result = send(client_socket, header_buffer, header_buffer_size - 1, 0);
    if (send_result == -1) {
        free(status_line_buffer);
        free(header_buffer);
        return -1;
    }
    free(status_line_buffer);
    free(header_buffer);

    return 0;
}

/**
 * Send a file over the socket.
 *
 * @param client_fd The file descriptor to send on.
 * @param file The file to read
 *
 * @return -1 on error, 0 on success.
 */
static int send_file(int client_fd, struct requested_file file) {
    char *buffer = malloc(FILE_BUFFER_SIZE * sizeof(char));
    int bytes_read;
    while ((bytes_read = fread(buffer, sizeof(char), FILE_BUFFER_SIZE, file.file)) != 0) {
        int send_result = send(client_fd, buffer, bytes_read, 0);
        if (send_result == -1) {
            free(buffer);
            return -1;
        }
    }
    free(buffer);

    return 0;
}

/**
 * Parse and validate a request line
 *
 * @param message An http_message with a start_line.
 * @param req_line The request line of the request to write to.
 *
 * @return PARSE_RESULT_OK if ok, other value otherwise, depending on the state of the start line..
 */
static enum request_parse_result parse_and_validate_request(struct http_message message, struct request_line *req_line) {
    int parse_result = parse_request_line(message.start_line, req_line);
    if (parse_result == -1) {
        return PARSE_RESULT_MALFORMED;
    } else if (strcmp(req_line->http_version, HTTP_VERSION) != 0) {
        return PARSE_RESULT_BAD_VERSION;
    } else if (strcmp(req_line->method, "GET") != 0) {
        return PARSE_RESULT_BAD_METHOD;
    }

    return PARSE_RESULT_OK;
}

static void free_request_items(struct http_message message) {
    if (message.start_line != NULL) {
        free(message.start_line);
    }
    if (message.contents != NULL) {
        free(message.contents);
    }
    if (message.headers != NULL) {
        free_headers(message.headers);
    }
}

/**
 * Serve a single request.
 *
 * @param sock_fd The socket file descriptor of the server
 *
 * @return A socket_result representing the status of the serve.
 */
enum socket_result serve_one_request(int sock_fd) {
    int client_fd = accept(sock_fd, NULL, NULL);
    if (client_fd == -1) {
        return RESULT_WRITE_ERROR;
    }
    struct http_message message = {};
    enum socket_result read_result = get_all_remote_parts(client_fd, TYPE_SERVER, &message);
    if (read_result == RESULT_MALFORMED) {
        send_headers(400, client_fd, -1);
        close(client_fd);
        free_request_items(message);
        return RESULT_MALFORMED;
    } else if (read_result != RESULT_OK){
        send_headers(500, client_fd, -1);
        free_request_items(message);
        close(client_fd);
        return RESULT_READ_ERROR;
    }
    struct request_line parsed_request_line = {};
    enum request_parse_result parse_result = parse_and_validate_request(message, &parsed_request_line);
    // Ensure our the request line's info is congruent with the server's expectations.
    if (parse_result != PARSE_RESULT_OK) {
        int status_code = 500;
        if (parse_result == PARSE_RESULT_MALFORMED) {
            status_code = 400;
        } else if (parse_result == PARSE_RESULT_BAD_VERSION) {
            status_code = 505;
        } else if (parse_result == PARSE_RESULT_BAD_METHOD) {
            status_code = 405;
        }
        send_headers(status_code, client_fd, -1);
        free_request_line_items(&parsed_request_line);
        free_request_items(message);
        close(client_fd);
        return RESULT_PROCESSING_ERROR;
    }
    // Attempt to read the file and return it.
    struct requested_file file = {};
    enum file_result file_get_result = get_file_from_uri(parsed_request_line.uri, &file);
    if (file_get_result != RESULT_FILE_OK) {
        int send_result = 0;
        if (file_get_result == RESULT_NOT_FILE || (file_get_result == RESULT_IO_ERROR && errno == ENOENT)) {
            send_result = send_headers(404, client_fd, -1);
        } else if (file_get_result == RESULT_IO_ERROR && errno == EACCES) {
            send_result = send_headers(403, client_fd, -1);
        } else {
            free_request_line_items(&parsed_request_line);
            free_request_items(message);
            send_headers(500, client_fd, -1);
            shutdown(client_fd, SHUT_RDWR);
            close(client_fd);
            return RESULT_PROCESSING_ERROR;
        }

        if (send_result != 0) {
            free_request_line_items(&parsed_request_line);
            free_request_items(message);
            shutdown(client_fd, SHUT_RDWR);
            close(client_fd);
            return RESULT_WRITE_ERROR;
        }
    } else {
        send_headers(200, client_fd, file.size);
        send_file(client_fd, file);
    }
    free_request_line_items(&parsed_request_line);
    free_request_items(message);
    if (file_get_result == RESULT_FILE_OK) {
        fclose(file.file);
    }

    shutdown(client_fd, SHUT_RDWR);
    close(client_fd);
    return RESULT_OK;
}