main.cpp

/* These lines of comments are from original author */
/* J. David's webserver */
/* This is a simple webserver.
 * Created November 1999 by J. David Blackstone.
 * CSE 4344 (Network concepts), Prof. Zeigler
 * University of Texas at Arlington
 */
/* Following lines of comments are from Komoriii */
/* This program compiles for macOS Catalina. It is pthread free.*/
/*
    Thanks to J.David for the idea.
    Also, thanks github user cbsheng for Chinese comment, which helps me a lot for my study.
*/
#if !defined(__unix__) && !defined(__APPLE__)
#error THIS OPERATING SYSTEM DOES NOT SUPPORT KQUEUE API
#endif

#include <iostream>
#include <sstream>
#include <sys/socket.h>
#include <sys/event.h>
#include <sys/uio.h>
#include <sys/stat.h>
#include <arpa/inet.h>
#include <cctype>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <functional>

#define SERVER_STRING "SERVER: httpd/0.1.0\r\n"

void bad_request(int);
void cat(int, FILE *);
void cannot_execute(int);
int get_line(int, char *, int);
void headers(int, const char *);
void not_found(int);
void serve_file(int, const char *);
void unimplemented(int);
void setNonBlock(int fd);
void accept_request(int client);
void execute_cgi(int client, const char *path,
                 const char *method, const char *query_string);
void handleAccept(int efd, int fd);
static const int kReadEvent = 1;
static const int kWriteEvent = 2;

static char buf[1024];
static char method[255];
static char url[255];
static char path[512];


/**********************************************************************/
/* A request has caused a call to accept() on the server port to
 * return.  Process the request appropriately.
 * Parameters: the socket connected to the client */
/**********************************************************************/
void accept_request(int client)
{
    int numchars;
    size_t i, j;
    struct stat st;
    int cgi = 0;      /* becomes true if server decides this is a CGI
                       * program */
    char *query_string = NULL;

    numchars = get_line(client, buf, sizeof(buf));
    i = 0; j = 0;
    while (!isspace(buf[j]) && (i < sizeof(method) - 1))
    {
        method[i] = buf[j];
        i++; j++;
    }
    method[i] = '\0';

    if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
    {
        unimplemented(client);
        return;
    }

    if (strcasecmp(method, "POST") == 0)
        cgi = 1;

    i = 0;
    while (isspace(buf[j]) && (j < sizeof(buf)))
        j++;
    while (!isspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))
    {
        url[i] = buf[j];
        i++; j++;
    }
    url[i] = '\0';

    if (strcasecmp(method, "GET") == 0)
    {
        query_string = url;
        while ((*query_string != '?') && (*query_string != '\0'))
            query_string++;
        if (*query_string == '?')
        {
            cgi = 1;
            *query_string = '\0';
            query_string++;
        }
    }

    sprintf(path, "statics%s", url);
    printf(path);
    printf("\n");
    if (path[strlen(path) - 1] == '/')
        strcat(path, "index.html");
    if (stat(path, &st) == -1) {
        while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */
            numchars = get_line(client, buf, sizeof(buf));
        not_found(client);
    }
    else
    {
        if ((st.st_mode & S_IFMT) == S_IFDIR)
            strcat(path, "/index.html");
        if ((st.st_mode & S_IXUSR) ||
            (st.st_mode & S_IXGRP) ||
            (st.st_mode & S_IXOTH))
            cgi = 1;
        if (!cgi)
            serve_file(client, path);
        else
            //perror("cgi needed");
            execute_cgi(client, path, method, query_string);
    }

    close(client);
}

/**********************************************************************/
/* Inform the client that a request it has made has a problem.
 * Parameters: client socket */
/**********************************************************************/
void bad_request(int client)
{
    //char buf[1024];

    sprintf(buf, "HTTP/1.0 400 BAD REQUEST\r\n");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "Content-type: text/html\r\n");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "\r\n");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "<P>Your browser sent a bad request, ");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "such as a POST without a Content-Length.\r\n");
    send(client, buf, sizeof(buf), 0);
}

/**********************************************************************/
/* Put the entire contents of a file out on a socket.  This function
 * is named after the UNIX "cat" command, because it might have been
 * easier just to do something like pipe, fork, and exec("cat").
 * Parameters: the client socket descriptor
 *             FILE pointer for the file to cat */
/**********************************************************************/
void cat(int client, FILE *resource)
{

    char buf[1024];

    fgets(buf, sizeof(buf), resource);
    while (!feof(resource))
    {
        send(client, buf, strlen(buf), 0);
        fgets(buf, sizeof(buf), resource);
    }
}

/**********************************************************************/
/* Inform the client that a CGI script could not be executed.
 * Parameter: the client socket descriptor. */
/**********************************************************************/
void cannot_execute(int client)
{
    char buf[1024];

    sprintf(buf, "HTTP/1.0 500 Internal Server Error\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "Content-type: text/html\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<P>Error prohibited CGI execution.\r\n");
    send(client, buf, strlen(buf), 0);
}

/**********************************************************************/
/* Print out an error message with perror() (for system errors; based
 * on value of errno, which indicates system call errors) and exit the
 * program indicating an error. */
/**********************************************************************/
inline void error_die(const char * sc)
{
    perror(sc);
    exit(1);
}
/**********************************************************************/
/* Update the status of fds
 * Parameter: the socket descriptor for listening new connection
 *            the socket descriptor for update event
 *            the */
/**********************************************************************/
static void updateEvents(int efd, int fd, int events, bool modify)
{
    struct kevent ev[2];
    int n = 0;
    if (events & kReadEvent) {
        EV_SET(&ev[n++], fd, EVFILT_READ, EV_ADD|EV_ENABLE, 0, 0, (void*)(intptr_t)fd);
    } else if (modify){
        EV_SET(&ev[n++], fd, EVFILT_READ, EV_DELETE, 0, 0, (void*)(intptr_t)fd);
    }
    if (events & kWriteEvent) {
        EV_SET(&ev[n++], fd, EVFILT_WRITE, EV_ADD|EV_ENABLE, 0, 0, (void*)(intptr_t)fd);
    } else if (modify){
        EV_SET(&ev[n++], fd, EVFILT_WRITE, EV_DELETE, 0, 0, (void*)(intptr_t)fd);
    }
    printf("%s fd %d events read %d write %d\n",
           modify ? "mod" : "add", fd, events & kReadEvent, events & kWriteEvent);
    int r = kevent(efd, ev, n, NULL, 0, NULL);
    if(r < 0 ) error_die("kevent failed");
}

/**********************************************************************/
/* NOT IN USED
 * Execute a CGI script.  Will need to set environment variables as
 * appropriate.
 * Parameters: client socket descriptor
 *             path to the CGI script */
/**********************************************************************/
void execute_cgi(int client, const char *path,
                 const char *method, const char *query_string)
{
    //char buf[1024];
    int cgi_output[2];
    int cgi_input[2];
    pid_t pid;
    int status;
    int i;
    char c;
    int numchars = 1;
    int content_length = -1;

    buf[0] = 'A'; buf[1] = '\0';
    if (strcasecmp(method, "GET") == 0)
        while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */
            numchars = get_line(client, buf, sizeof(buf));
    else    /* POST */
    {
        numchars = get_line(client, buf, sizeof(buf));
        while ((numchars > 0) && strcmp("\n", buf))
        {
            buf[15] = '\0';
            if (strcasecmp(buf, "Content-Length:") == 0)
                content_length = atoi(&(buf[16]));
            numchars = get_line(client, buf, sizeof(buf));
        }
        if (content_length == -1) {
            bad_request(client);
            return;
        }
    }

    sprintf(buf, "HTTP/1.0 200 OK\r\n");
    send(client, buf, strlen(buf), 0);

    if (pipe(cgi_output) < 0) {
        cannot_execute(client);
        return;
    }
    if (pipe(cgi_input) < 0) {
        cannot_execute(client);
        return;
    }

    if ( (pid = fork()) < 0 ) {
        cannot_execute(client);
        return;
    }
    if (pid == 0)  /* child: CGI script */
    {
        char meth_env[255];
        char query_env[255];
        char length_env[255];

        dup2(cgi_output[1], 1);
        dup2(cgi_input[0], 0);
        close(cgi_output[0]);
        close(cgi_input[1]);
        sprintf(meth_env, "REQUEST_METHOD=%s", method);
        putenv(meth_env);
        if (strcasecmp(method, "GET") == 0) {
            sprintf(query_env, "QUERY_STRING=%s", query_string);
            putenv(query_env);
        }
        else {   /* POST */
            sprintf(length_env, "CONTENT_LENGTH=%d", content_length);
            putenv(length_env);
        }
        execl(path, path, NULL);
        exit(0);
    } else {    /* parent */
        close(cgi_output[1]);
        close(cgi_input[0]);
        if (strcasecmp(method, "POST") == 0)
            for (i = 0; i < content_length; i++) {
                recv(client, &c, 1, 0);
                write(cgi_input[1], &c, 1);
            }
        while (read(cgi_output[0], &c, 1) > 0)
            send(client, &c, 1, 0);

        close(cgi_output[0]);
        close(cgi_input[1]);
        waitpid(pid, &status, 0);
    }
}


void handleAccept(int efd, int fd) {
    struct sockaddr_in raddr;
    socklen_t rsz = sizeof(raddr);
    int cfd = accept(fd,(struct sockaddr *)&raddr,&rsz);
    if(cfd < 0) error_die("socket error");
    sockaddr_in peer, local;
    socklen_t alen = sizeof(peer);
    int r = getpeername(cfd, (sockaddr*)&peer, &alen);
    if(r < 0) error_die("get peer name failed");
    printf("accept a connection from %s\n", inet_ntoa(raddr.sin_addr));
    setNonBlock(cfd);
    updateEvents(efd, cfd, kReadEvent|kWriteEvent, false);
}

/**********************************************************************/
/* callback function for EVFILT_READ
 * Parameters: the socket descriptor for listening new connection
 *             the socket descriptor for specific connection
/**********************************************************************/
void handleRead(int efd, int fd)
{
  //deal with a new connection
  accept_request(fd);
}

/**********************************************************************/
/* callback function for EVFILT_WRITE
 * fill your code if you want to call some procedure on this event
 * Parameters: the socket descriptor for listening new connection
 *             the socket descriptor for specific connection
/**********************************************************************/
void handleWrite(int efd, int fd) {
    //just update
    //updateEvents(efd, fd, kReadEvent, true);
}

/**********************************************************************/
/* Get a line from a socket, whether the line ends in a newline,
 * carriage return, or a CRLF combination.  Terminates the string read
 * with a null character.  If no newline indicator is found before the
 * end of the buffer, the string is terminated with a null.  If any of
 * the above three line terminators is read, the last character of the
 * string will be a linefeed and the string will be terminated with a
 * null character.
 * Parameters: the socket descriptor
 *             the buffer to save the data in
 *             the size of the buffer
 * Returns: the number of bytes stored (excluding null) */
/**********************************************************************/
int get_line(int sock, char *buf, int size)
{
    int i = 0;
    char c = '\0';
    int n;

    while ((i < size - 1) && (c != '\n'))
    {
        n = recv(sock, &c, 1, 0);
        /* DEBUG printf("%02X\n", c); */
        if (-1 == n && errno == EAGAIN) {
            //printf("never be here?\n");
            continue;
        }
        else if (n > 0)
        {
            if (c == '\r')
            {
                n = recv(sock, &c, 1, MSG_PEEK);
                /* DEBUG printf("%02X\n", c); */
                if ((n > 0) && (c == '\n'))
                    recv(sock, &c, 1, 0);
                else
                    c = '\n';
            }
            buf[i] = c;
            i++;
        }
        else
            c = '\n';
    }
    buf[i] = '\0';

    return(i);
}

/**********************************************************************/
/* Return the informational HTTP headers about a file. */
/* Parameters: the socket to print the headers on
 *             the name of the file */
/**********************************************************************/
void headers(int client, const char *filename)
{
    //char buf[1024];
    (void)filename;  /* could use filename to determine file type */

    strcpy(buf, "HTTP/1.0 200 OK\r\n");
    send(client, buf, strlen(buf), 0);
    strcpy(buf, SERVER_STRING);
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "Content-Type: text/html\r\n");
    send(client, buf, strlen(buf), 0);
    strcpy(buf, "\r\n");
    send(client, buf, strlen(buf), 0);
}

/**********************************************************************/
/* Give a client a 404 not found status message. */
/**********************************************************************/
void not_found(int client)
{
    //char buf[1024];

    sprintf(buf, "HTTP/1.0 404 NOT FOUND\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, SERVER_STRING);
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "Content-Type: text/html\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<HTML><TITLE>Not Found</TITLE>\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<BODY><P>The server could not fulfill\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "your request because the resource specified\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "is unavailable or nonexistent.\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "</BODY></HTML>\r\n");
    send(client, buf, strlen(buf), 0);
}

/**********************************************************************/
/* Send a regular file to the client.  Use headers, and report
 * errors to client if they occur.
 * Parameters: a pointer to a file structure produced from the socket
 *              file descriptor
 *             the name of the file to serve */
/**********************************************************************/
void serve_file(int client, const char *filename)
{
    FILE *resource = NULL;
    int numchars = 1;
    //char buf[1024];

    buf[0] = 'A'; buf[1] = '\0';
    while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */
        numchars = get_line(client, buf, sizeof(buf));

    resource = fopen(filename, "r");
    if (resource == NULL)
        not_found(client);
    else
    {
        headers(client, filename);
        cat(client, resource);
    }
    fclose(resource);
}

/**********************************************************************/
/* Inform the client that the requested web method has not been
 * implemented.
 * Parameter: the client socket */
/**********************************************************************/
void unimplemented(int client)
{
    //char buf[1024];

    sprintf(buf, "HTTP/1.0 501 Method Not Implemented\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, SERVER_STRING);
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "Content-Type: text/html\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<HTML><HEAD><TITLE>Method Not Implemented\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "</TITLE></HEAD>\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<BODY><P>HTTP request method not supported.\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "</BODY></HTML>\r\n");
    send(client, buf, strlen(buf), 0);
}


void setNonBlock(int fd)
{
    int flags = fcntl(fd, F_GETFL, 0);
    if(flags < 0) error_die("fcntl failted");
    int r = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
    if(r < 0) error_die("fcntl failed");
}

static void loop_once(int efd, int lfd, int waitms)
{
    struct timespec timeout;
    timeout.tv_sec = waitms / 1000;
    timeout.tv_nsec = (waitms % 1000) * 1000 * 1000;
    const int kMaxEvent = 100;
    struct kevent activeEvs[kMaxEvent];
    // n is the number of fds
    int n = kevent(efd, NULL, 0, activeEvs, kMaxEvent, &timeout);
    // for loop检查每一个file descriptor
    for(int i = 0; i < n; i++)
    {
        int fd = (int)(intptr_t)activeEvs[i].udata;
        int events = activeEvs[i].filter;
        if(events == EVFILT_READ)
        {
            if(fd == lfd)
            {
                handleAccept(efd, fd);
            } else {
                handleRead(efd, fd);
            }
        } else if(events == EVFILT_WRITE)
        {
            handleWrite(efd, fd);
        } else {
            close(fd);
            perror("unkown event");
            continue;
        }
    }
}

int main(int argc, char * argv[]) {
    /*initialization*/
    std::stringstream s(argv[1]);
    short port;
    s >> port;
    int iSetOption = 1;
    int epollfd = kqueue();
    int listenfd = socket(AF_INET, SOCK_STREAM, 0);
    //  set the socket attribute SO_REUSEADDR for non-delaying restart
    if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, (char*)&iSetOption,
             sizeof(iSetOption)) < 0)
       return 1;
    
    // allow bind same port multiple times for local machine LB
    if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEPORT, (char*)&iSetOption,
               sizeof(iSetOption)) < 0)
        return 1;

    struct sockaddr_in addr;
    memset (&addr, 0, sizeof(sockaddr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = INADDR_ANY;
    int r = ::bind(listenfd, (struct sockaddr *) &addr, sizeof(struct sockaddr));
    if(r < 0) error_die("bind failed");
    r = listen(listenfd, 20);
    printf("listen at %d \n", port);
    setNonBlock(listenfd);
    updateEvents(epollfd, listenfd, kReadEvent, false);
    /* main loop */
    for(;;)
    {
        loop_once(epollfd, listenfd, 1000);
    }
    close(listenfd);
    return 0;
}