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() {
  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(sizeof(char[256][256]))) == NULL) {
 133                 printf("Can't malloc buffers; dropping connection.\n");
 134                 close (sock);
 135                 return NULL;
 136                 }
 137
 138         printf("Reading request from socket %d\n", sock);
 139
 140         /*
 141          * Find out what it is that the web browser is asking for
 142          */
 143         ContentLength = 0;
 144         do {
 145                 req_gets(sock, buf, hold);
 146                 if (!strncasecmp(buf, "Cookie: wc_session=", 19)) {
 147                         desired_session = atoi(&buf[19]);
 148                         }
 149                 if (!strncasecmp(buf, "Content-length: ", 16)) {
 150                         ContentLength = atoi(&buf[16]);
 151                         }
 152                 strcpy(&req[num_lines++][0], buf);
 153                 } while(strlen(buf)>0);
 154
 155         /*
 156          * See if there's an existing session open with the desired ID
 157          */
 158         TheSession = NULL;
 159         if (desired_session != 0) {
 160                 pthread_mutex_lock(&MasterCritter);
 161                 for (sptr=SessionList; sptr!=NULL; sptr=sptr->next) {
 162                         if (sptr->session_id == desired_session) {
 163                                 TheSession = sptr;
 164                                 lock_session(TheSession);
 165                                 }
 166                         }
 167                 pthread_mutex_unlock(&MasterCritter);
 168                 }
 169
 170         /*
 171          * Create a new session if we have to
 172          */
 173         if (TheSession == NULL) {
 174                 printf("Creating a new session\n");
 175                 pthread_mutex_lock(&MasterCritter);
 176                 TheSession = (struct wc_session *)
 177                         malloc(sizeof(struct wc_session));
 178                 TheSession->session_id = GenerateSessionID();
 179                 pipe(TheSession->inpipe);
 180                 pipe(TheSession->outpipe);
 181                 pthread_mutex_init(&TheSession->critter, NULL);
 182                 lock_session(TheSession);
 183                 TheSession->next = SessionList;
 184                 SessionList = TheSession;
 185                 pthread_mutex_unlock(&MasterCritter);
 186                 sprintf(str_session, "%d", TheSession->session_id);
 187                 f = fork();
 188                 fflush(stdout); fflush(stdin);
 189                 if (f==0) {
 190                         dup2(TheSession->inpipe[0], 0);
 191                         dup2(TheSession->outpipe[1], 1);
 192                         /* Close the ends of the pipes that we're not using */
 193                         close(TheSession->inpipe[1]);
 194                         close(TheSession->outpipe[0]);
 195                         execlp("./webcit", "webcit", str_session, defaulthost,
 196                                defaultport, NULL);
 197                         printf("HTTP/1.0 404 WebCit Failure\n\n");
 198                         printf("Server: %s\n", SERVER);
 199                         printf("Content-type: text/html\n");
 200                         printf("Content-length: 76\n");
 201                         printf("\n");
 202                         printf("<HTML><HEAD><TITLE>Error</TITLE></HEAD>\n");
 203                         printf("<BODY>execlp() failed</BODY></HTML>\n");
 204                         exit(0);
 205                         }
 206                 /* Close the ends of the pipes that we're not using */
 207                 close(TheSession->inpipe[0]);
 208                 close(TheSession->outpipe[1]);
 209                 }
 210
 211         /*
 212          * Send the request to the appropriate session...
 213          */
 214         printf("   Writing %d lines of command\n", num_lines);
 215         printf("%s\n", &req[0][0]);
 216         for (a=0; a<num_lines; ++a) {
 217                 write(TheSession->inpipe[1], &req[a][0], strlen(&req[a][0]));
 218                 write(TheSession->inpipe[1], "\n", 1);
 219                 }
 220         printf("   Writing %d bytes of content\n", ContentLength);
 221         while (ContentLength--) {
 222                 read(sock, buf, 1);
 223                 write(TheSession->inpipe[1], buf, 1);
 224                 }
 225
 226         /*
 227          * ...and get the response.
 228          */
 229         printf("   Reading response\n");
 230         ContentLength = 0;
 231         do {
 232                 gets0(TheSession->outpipe[0], buf);
 233                 write(sock, buf, strlen(buf));
 234                 write(sock, "\n", 1);
 235                 if (!strncasecmp(buf, "Content-length: ", 16))
 236                         ContentLength = atoi(&buf[16]);
 237                 if (!strcasecmp(buf, "X-WebCit-Session: close")) {
 238                         CloseSession = 1;
 239                         }
 240                 } while (strlen(buf) > 0);
 241
 242         printf("   Reading %d bytes of content\n", ContentLength);
 243         while(ContentLength--) {
 244                 read(TheSession->outpipe[0], buf, 1);
 245                 write(sock, buf, 1);
 246                 }
 247
 248         /*
 249          * Now our HTTP connection is done.  It would be relatively easy
 250          * to support HTTP/1.1 "persistent" connections by looping back to
 251          * the top of this function.  For now, we'll just close.
 252          */
 253         printf("   Closing socket\n");
 254         close(sock);
 255
 256         unlock_session(TheSession);
 257
 258         /*
 259          * If the last response included a "close session" directive,
 260          * remove the context now.
 261          */
 262         if (CloseSession) {
 263                 printf("Removing session.\n");
 264                 pthread_mutex_lock(&MasterCritter);
 265
 266                 lock_session(TheSession);
 267
 268                 if (SessionList==TheSession) {
 269                         SessionList = SessionList->next;
 270                         }
 271                 else {
 272                         for (sptr=SessionList; sptr!=NULL; sptr=sptr->next) {
 273                                 if (sptr->next == TheSession) {
 274                                         sptr->next = TheSession->next;
 275                                         }
 276                                 }
 277                         }
 278
 279                 close(TheSession->inpipe[1]);
 280                 close(TheSession->outpipe[0]);
 281                 unlock_session(TheSession);
 282                 free(TheSession);
 283
 284                 pthread_mutex_unlock(&MasterCritter);
 285                 }
 286
 287         free(req);
 288
 289         /*
 290          * The thread handling this HTTP connection is now finished.
 291          */
 292         return NULL;
 293         }