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
  24 #include <errno.h>
  25 #include <stdarg.h>
  26 #include <pthread.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         };
  37
  38 struct wc_session *SessionList = NULL;
  39
  40 int GenerateSessionID() {
  41         return getpid();
  42         }
  43
  44
  45 void gets0(int fd, char buf[]) {
  46
  47         buf[0] = 0;
  48         do {
  49                 buf[strlen(buf)+1] = 0;
  50                 read(fd, &buf[strlen(buf)], 1);
  51                 } while (buf[strlen(buf)-1] >= 32);
  52         buf[strlen(buf)-1] = 0;
  53         }
  54
  55
  56 /*
  57  * This loop gets called once for every HTTP connection made to WebCit.
  58  */
  59 void *context_loop(int *socknumptr) {
  60         char req[256][256];
  61         char buf[256];
  62         int num_lines = 0;
  63         int a;
  64         int f;
  65         int sock;
  66         int desired_session = 0;
  67         char str_session[256];
  68         struct wc_session *sptr;
  69         struct wc_session *TheSession;
  70         int ContentLength;
  71
  72         sock = *socknumptr;
  73
  74         /*
  75          * Find out what it is that the web browser is asking for
  76          */
  77         do {
  78                 client_gets(sock, buf);
  79                 if (!strncasecmp(buf, "Cookie: wc_session=", 19)) {
  80                         desired_session = atoi(&buf[19]);
  81                         }
  82
  83
  84                 strcpy(&req[num_lines++][0], buf);
  85                 } while(strlen(buf)>0);
  86
  87         /*
  88          * See if there's an existing session open with the desired ID
  89          */
  90         TheSession = NULL;
  91         if (desired_session != 0) {
  92                 for (sptr=SessionList; sptr!=NULL; sptr=sptr->next) {
  93                         if (sptr->session_id == desired_session) {
  94                                 TheSession = sptr;
  95                                 }
  96                         }
  97                 }
  98
  99         /*
 100          * Create a new session if we have to
 101          */
 102         if (TheSession == NULL) {
 103                 printf("Creating a new session\n");
 104                 TheSession = (struct wc_session *)
 105                         malloc(sizeof(struct wc_session));
 106                 TheSession->session_id = GenerateSessionID();
 107                 pipe(TheSession->inpipe);
 108                 pipe(TheSession->outpipe);
 109                 TheSession->next = SessionList;
 110                 SessionList = TheSession;
 111                 sprintf(str_session, "%d", TheSession->session_id);
 112                 f = fork();
 113                 fflush(stdout); fflush(stdin);
 114                 if (f==0) {
 115                         dup2(TheSession->inpipe[0], 0);
 116                         dup2(TheSession->outpipe[1], 1);
 117                         execlp("./webcit", "webcit", str_session, NULL);
 118                         printf("HTTP/1.0 404 WebCit Failure\n\n");
 119                         printf("Content-type: text/html\n");
 120                         printf("Content-length: 76\n");
 121                         printf("\n");
 122                         printf("<HTML><HEAD><TITLE>Error</TITLE></HEAD>\n");
 123                         printf("<BODY>execlp() failed</BODY></HTML>\n");
 124                         exit(0);
 125                         }
 126                 }
 127
 128         /*
 129          * Send the request to the appropriate session
 130          */
 131         for (a=0; a<num_lines; ++a) {
 132                 write(TheSession->inpipe[1], &req[a][0], strlen(&req[a][0]));
 133                 write(TheSession->inpipe[1], "\n", 1);
 134                 }
 135         write(TheSession->inpipe[1], "\n", 1);
 136
 137         /*
 138          * ...and get the response (FIX for non-text)
 139          */
 140         ContentLength = 0;
 141         do {
 142                 gets0(TheSession->outpipe[0], buf);
 143                 write(sock, buf, strlen(buf));
 144                 write(sock, "\n", 1);
 145                 if (!strncasecmp(buf, "Content-length: ", 16))
 146                         ContentLength = atoi(&buf[16]);
 147                 } while (strlen(buf) > 0);
 148
 149         while(ContentLength--) {
 150                 read(TheSession->outpipe[0], buf, 1);
 151                 write(sock, buf, 1);
 152                 }
 153
 154         /*
 155          * Now our HTTP connection is done.  It would be relatively easy
 156          * to support HTTP/1.1 "persistent" connections by looping back to
 157          * the top of this function.  For now, we'll just exit.
 158          */
 159         close(sock);
 160         pthread_exit(NULL);
 161         }