webcit/context_loop.c

   1 /*
   2  * context_loop.c
   3  *
   4  * This is the other half of the webserver.  It handles the task of hooking
   5  * up HTTP requests with the session they belong to, using HTTP cookies to
   6  * keep track of things.  If the HTTP request doesn't belong to any currently
   7  * active session, a new session is spawned.
   8  */
   9
  10 #include <stdlib.h>
  11 #include <unistd.h>
  12 #include <stdio.h>
  13 #include <fcntl.h>
  14 #include <signal.h>
  15 #include <sys/types.h>
  16 #include <sys/wait.h>
  17 #include <sys/socket.h>
  18 #include <sys/time.h>
  19 #include <limits.h>
  20 #include <netinet/in.h>
  21 #include <netdb.h>
  22 #include <string.h>
  23 #include <errno.h>
  24 #include <stdarg.h>
  25 #include <pthread.h>
  26 #include "webcit.h"
  27
  28 /*
  29  * We keep one of these around for each active session
  30  */
  31 struct wc_session {
  32         struct wc_session *next;        /* Next session in list */
  33         int session_id;                 /* Session ID */
  34         int inpipe[2];                  /* Data from webserver to session */
  35         int outpipe[2];                 /* Data from session to webserver */
  36         pthread_mutex_t critter;        /* Critical section uses pipes */
  37         };
  38
  39 struct wc_session *SessionList = NULL;
  40
  41 int GenerateSessionID() {
  42         return getpid();
  43         }
  44
  45
  46 void gets0(int fd, char buf[]) {
  47
  48         buf[0] = 0;
  49         do {
  50                 buf[strlen(buf)+1] = 0;
  51                 read(fd, &buf[strlen(buf)], 1);
  52                 } while (buf[strlen(buf)-1] >= 32);
  53         buf[strlen(buf)-1] = 0;
  54         }
  55
  56
  57 /*
  58  * This loop gets called once for every HTTP connection made to WebCit.
  59  */
  60 void *context_loop(int *socknumptr) {
  61         char req[256][256];
  62         char buf[256];
  63         int num_lines = 0;
  64         int a;
  65         int f;
  66         int sock;
  67         int desired_session = 0;
  68         char str_session[256];
  69         struct wc_session *sptr;
  70         struct wc_session *TheSession;
  71         int ContentLength;
  72
  73         sock = *socknumptr;
  74
  75         /*
  76          * Find out what it is that the web browser is asking for
  77          */
  78         ContentLength = 0;
  79         do {
  80                 client_gets(sock, buf);
  81                 if (!strncasecmp(buf, "Cookie: wc_session=", 19)) {
  82                         desired_session = atoi(&buf[19]);
  83                         }
  84                 if (!strncasecmp(buf, "Content-length: ", 16)) {
  85                         ContentLength = atoi(&buf[16]);
  86                         }
  87                 strcpy(&req[num_lines++][0], buf);
  88                 } while(strlen(buf)>0);
  89
  90         /*
  91          * See if there's an existing session open with the desired ID
  92          */
  93         TheSession = NULL;
  94         if (desired_session != 0) {
  95                 for (sptr=SessionList; sptr!=NULL; sptr=sptr->next) {
  96                         if (sptr->session_id == desired_session) {
  97                                 TheSession = sptr;
  98                                 }
  99                         }
 100                 }
 101
 102         /*
 103          * Create a new session if we have to
 104          */
 105         if (TheSession == NULL) {
 106                 printf("Creating a new session\n");
 107                 TheSession = (struct wc_session *)
 108                         malloc(sizeof(struct wc_session));
 109                 TheSession->session_id = GenerateSessionID();
 110                 pthread_mutex_init(&TheSession->critter, NULL);
 111                 pipe(TheSession->inpipe);
 112                 pipe(TheSession->outpipe);
 113                 TheSession->next = SessionList;
 114                 SessionList = TheSession;
 115                 sprintf(str_session, "%d", TheSession->session_id);
 116                 f = fork();
 117                 fflush(stdout); fflush(stdin);
 118                 if (f==0) {
 119                         dup2(TheSession->inpipe[0], 0);
 120                         dup2(TheSession->outpipe[1], 1);
 121                         execlp("./webcit", "webcit", str_session, NULL);
 122                         printf("HTTP/1.0 404 WebCit Failure\n\n");
 123                         printf("Server: %s\n", SERVER);
 124                         printf("Content-type: text/html\n");
 125                         printf("Content-length: 76\n");
 126                         printf("\n");
 127                         printf("<HTML><HEAD><TITLE>Error</TITLE></HEAD>\n");
 128                         printf("<BODY>execlp() failed</BODY></HTML>\n");
 129                         exit(0);
 130                         }
 131                 }
 132
 133         /*
 134          * Send the request to the appropriate session
 135          */
 136         pthread_mutex_lock(&TheSession->critter);
 137         for (a=0; a<num_lines; ++a) {
 138                 write(TheSession->inpipe[1], &req[a][0], strlen(&req[a][0]));
 139                 write(TheSession->inpipe[1], "\n", 1);
 140                 }
 141         while (ContentLength--) {
 142                 read(sock, buf, 1);
 143                 write(TheSession->inpipe[1], buf, 1);
 144                 }
 145
 146         /*
 147          * ...and get the response (FIX for non-text)
 148          */
 149         ContentLength = 0;
 150         do {
 151                 gets0(TheSession->outpipe[0], buf);
 152                 write(sock, buf, strlen(buf));
 153                 write(sock, "\n", 1);
 154                 if (!strncasecmp(buf, "Content-length: ", 16))
 155                         ContentLength = atoi(&buf[16]);
 156                 } while (strlen(buf) > 0);
 157
 158         while(ContentLength--) {
 159                 read(TheSession->outpipe[0], buf, 1);
 160                 write(sock, buf, 1);
 161                 }
 162
 163         pthread_mutex_unlock(&TheSession->critter);
 164
 165         /*
 166          * Now our HTTP connection is done.  It would be relatively easy
 167          * to support HTTP/1.1 "persistent" connections by looping back to
 168          * the top of this function.  For now, we'll just exit.
 169          */
 170         close(sock);
 171         pthread_exit(NULL);
 172         }