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  * $Id$
  10  */
  11
  12 #include <ctype.h>
  13 #include <stdlib.h>
  14 #ifdef HAVE_UNISTD_H
  15 #include <unistd.h>
  16 #endif
  17 #include <stdio.h>
  18 #ifdef HAVE_FCNTL_H
  19 #include <fcntl.h>
  20 #endif
  21 #include <signal.h>
  22 #include <sys/types.h>
  23 #include <sys/wait.h>
  24 #include <sys/socket.h>
  25 #ifdef HAVE_SYS_TIME_H
  26 #include <sys/time.h>
  27 #endif
  28 #ifdef HAVE_LIMITS_H
  29 #include <limits.h>
  30 #endif
  31 #include <netinet/in.h>
  32 #include <netdb.h>
  33 #include <string.h>
  34 #include <errno.h>
  35 #include <stdarg.h>
  36 #include <pthread.h>
  37 #include "webcit.h"
  38 #include "webserver.h"
  39
  40 /*
  41  * We keep one of these around for each active session
  42  */
  43 struct wc_session {
  44         struct wc_session *next;        /* Next session in list */
  45         int session_id;                 /* Session ID */
  46         int inpipe[2];                  /* Data from webserver to session */
  47         int outpipe[2];                 /* Data from session to webserver */
  48         pthread_mutex_t critter;        /* Critical section uses pipes */
  49         };
  50
  51 struct wc_session *SessionList = NULL;
  52
  53 /* Only one thread may manipulate SessionList at a time... */
  54 pthread_mutex_t MasterCritter;
  55
  56 int GenerateSessionID(void) {
  57         return getpid();
  58         }
  59
  60
  61 void gets0(int fd, char buf[]) {
  62
  63         buf[0] = 0;
  64         do {
  65                 buf[strlen(buf)+1] = 0;
  66                 read(fd, &buf[strlen(buf)], 1);
  67                 } while (buf[strlen(buf)-1] >= 32);
  68         buf[strlen(buf)-1] = 0;
  69         }
  70
  71 /*
  72  * Collapse multiple cookies on one line
  73  */
  74 void req_gets(int sock, char *buf, char *hold) {
  75         int a;
  76
  77         if (strlen(hold)==0) {
  78                 client_gets(sock, buf);
  79                 }
  80         else {
  81                 strcpy(buf, hold);
  82                 }
  83         strcpy(hold, "");
  84
  85         if (!strncasecmp(buf, "Cookie: ", 8)) {
  86                 for (a=0; a<strlen(buf); ++a) if (buf[a]==';') {
  87                         sprintf(hold, "Cookie: %s", &buf[a+1]);
  88                         buf[a]=0;
  89                         while (isspace(hold[8])) strcpy(&hold[8], &hold[9]);
  90                         return;
  91                         }
  92                 }
  93         }
  94
  95 /*
  96  * Grab a lock on the session, so other threads don't try to access
  97  * the pipes at the same time.
  98  */
  99 static void lock_session(struct wc_session *session) {
 100         printf("Locking session %d...\n", session->session_id);
 101         pthread_mutex_lock(&session->critter);
 102         printf("   ...got lock\n");
 103         }
 104
 105 /*
 106  * Let go of the lock.
 107  */
 108 static void unlock_session(struct wc_session *session) {
 109         printf("Unlocking.\n");
 110         pthread_mutex_unlock(&session->critter);
 111         }
 112
 113 extern const char *defaulthost;
 114 extern const char *defaultport;
 115
 116 /*
 117  * This loop gets called once for every HTTP connection made to WebCit.
 118  */
 119 void *context_loop(int sock) {
 120         char (*req)[256];
 121         char buf[256], hold[256];
 122         int num_lines = 0;
 123         int a;
 124         int f;
 125         int desired_session = 0;
 126         char str_session[256];
 127         struct wc_session *sptr;
 128         struct wc_session *TheSession;
 129         int ContentLength;
 130         int CloseSession = 0;
 131
 132         if ((req = malloc((long)sizeof(char[256][256]))) == NULL) {
 133                 sprintf(buf, "Can't malloc buffers; dropping connection.\n");
 134                 fprintf(stderr, "%s", buf);
 135                 write(sock, buf, strlen(buf));
 136                 close (sock);
 137                 pthread_exit(NULL);
 138                 }
 139
 140         printf("Reading request from socket %d\n", sock);
 141
 142         /*
 143          * Find out what it is that the web browser is asking for
 144          */
 145         ContentLength = 0;
 146         do {
 147                 req_gets(sock, buf, hold);
 148                 if (!strncasecmp(buf, "Cookie: wc_session=", 19)) {
 149                         desired_session = atoi(&buf[19]);
 150                         }
 151                 if (!strncasecmp(buf, "Content-length: ", 16)) {
 152                         ContentLength = atoi(&buf[16]);
 153                         }
 154                 strcpy(&req[num_lines++][0], buf);
 155                 } while(strlen(buf)>0);
 156
 157         /*
 158          * See if there's an existing session open with the desired ID
 159          */
 160         TheSession = NULL;
 161         if (desired_session != 0) {
 162                 pthread_mutex_lock(&MasterCritter);
 163                 for (sptr=SessionList; sptr!=NULL; sptr=sptr->next) {
 164                         if (sptr->session_id == desired_session) {
 165                                 TheSession = sptr;
 166                                 lock_session(TheSession);
 167                                 }
 168                         }
 169                 pthread_mutex_unlock(&MasterCritter);
 170                 }
 171
 172         /*
 173          * Create a new session if we have to
 174          */
 175         if (TheSession == NULL) {
 176                 printf("Creating a new session\n");
 177                 pthread_mutex_lock(&MasterCritter);
 178                 TheSession = (struct wc_session *)
 179                         malloc(sizeof(struct wc_session));
 180                 TheSession->session_id = GenerateSessionID();
 181                 pipe(TheSession->inpipe);
 182                 pipe(TheSession->outpipe);
 183                 pthread_mutex_init(&TheSession->critter, NULL);
 184                 lock_session(TheSession);
 185                 TheSession->next = SessionList;
 186                 SessionList = TheSession;
 187                 pthread_mutex_unlock(&MasterCritter);
 188                 sprintf(str_session, "%d", TheSession->session_id);
 189                 f = fork();
 190                 fflush(stdout); fflush(stdin);
 191                 if (f==0) {
 192                         dup2(TheSession->inpipe[0], 0);
 193                         dup2(TheSession->outpipe[1], 1);
 194                         /* Close the ends of the pipes that we're not using */
 195                         close(TheSession->inpipe[1]);
 196                         close(TheSession->outpipe[0]);
 197                         execlp("./webcit", "webcit", str_session, defaulthost,
 198                                defaultport, NULL);
 199                         printf("HTTP/1.0 404 WebCit Failure\n\n");
 200                         printf("Server: %s\n", SERVER);
 201                         printf("Content-type: text/html\n");
 202                         printf("Content-length: 76\n");
 203                         printf("\n");
 204                         printf("<HTML><HEAD><TITLE>Error</TITLE></HEAD>\n");
 205                         printf("<BODY>execlp() failed</BODY></HTML>\n");
 206                         exit(0);
 207                         }
 208                 /* Close the ends of the pipes that we're not using */
 209                 close(TheSession->inpipe[0]);
 210                 close(TheSession->outpipe[1]);
 211                 }
 212
 213         /*
 214          * Send the request to the appropriate session...
 215          */
 216         printf("   Writing %d lines of command\n", num_lines);
 217         printf("%s\n", &req[0][0]);
 218         for (a=0; a<num_lines; ++a) {
 219                 write(TheSession->inpipe[1], &req[a][0], strlen(&req[a][0]));
 220                 write(TheSession->inpipe[1], "\n", 1);
 221                 }
 222         printf("   Writing %d bytes of content\n", ContentLength);
 223         if (ContentLength > 0) {
 224                 while (ContentLength > 0) {
 225                         a = ContentLength;
 226                         if (a > sizeof buf) a = sizeof buf;
 227                         if (!client_read(sock, buf, a)) goto end;
 228                         if (write(TheSession->inpipe[1], buf, a) != a) goto end;
 229                         ContentLength -= a;
 230                         }
 231
 232                 /* Discard the CRLF following the POST data. Yes, this is
 233                  * necessary. No, you don't want to know why. */
 234                 if (!client_read(sock, buf, 2)) goto end;
 235                 }
 236
 237         /*
 238          * ...and get the response.
 239          */
 240         printf("   Reading response\n");
 241         ContentLength = 0;
 242         do {
 243                 gets0(TheSession->outpipe[0], buf);
 244                 write(sock, buf, strlen(buf));
 245                 write(sock, "\n", 1);
 246                 if (!strncasecmp(buf, "Content-length: ", 16))
 247                         ContentLength = atoi(&buf[16]);
 248                 if (!strcasecmp(buf, "X-WebCit-Session: close")) {
 249                         CloseSession = 1;
 250                         }
 251                 } while (strlen(buf) > 0);
 252
 253         printf("   Reading %d bytes of content\n", ContentLength);
 254         while(ContentLength--) {
 255                 read(TheSession->outpipe[0], buf, 1);
 256                 write(sock, buf, 1);
 257                 }
 258
 259         /*
 260          * If the last response included a "close session" directive,
 261          * remove the context now.
 262          */
 263         if (CloseSession) {
 264                 printf("Removing session.\n");
 265                 pthread_mutex_lock(&MasterCritter);
 266
 267                 if (SessionList==TheSession) {
 268                         SessionList = SessionList->next;
 269                         }
 270                 else {
 271                         for (sptr=SessionList; sptr!=NULL; sptr=sptr->next) {
 272                                 if (sptr->next == TheSession) {
 273                                         sptr->next = TheSession->next;
 274                                         }
 275                                 }
 276                         }
 277
 278                 close(TheSession->inpipe[1]);
 279                 close(TheSession->outpipe[0]);
 280                 unlock_session(TheSession);
 281                 free(TheSession);
 282
 283                 pthread_mutex_unlock(&MasterCritter);
 284                 }
 285         else {
 286         end:
 287                 unlock_session(TheSession);
 288                 }
 289
 290         /*
 291          * Now our HTTP connection is done.  It would be relatively easy
 292          * to support HTTP/1.1 "persistent" connections by looping back to
 293          * the top of this function.  For now, we'll just close.
 294          */
 295
 296         free(req);
 297         printf("   Closing socket\n");
 298         close(sock);
 299
 300         /*
 301          * The thread handling this HTTP connection is now finished.
 302          */
 303         pthread_exit(NULL);
 304         }