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 #include <unistd.h>
  15 #include <stdio.h>
  16 #include <fcntl.h>
  17 #include <signal.h>
  18 #include <sys/types.h>
  19 #include <sys/wait.h>
  20 #include <sys/socket.h>
  21 #include <sys/time.h>
  22 #include <limits.h>
  23 #include <netinet/in.h>
  24 #include <netdb.h>
  25 #include <string.h>
  26 #include <errno.h>
  27 #include <stdarg.h>
  28 #include <pthread.h>
  29 #include "webcit.h"
  30 #include "webserver.h"
  31
  32 /*
  33  * We keep one of these around for each active session
  34  */
  35 struct wc_session {
  36         struct wc_session *next;        /* Next session in list */
  37         int session_id;                 /* Session ID */
  38         int inpipe[2];                  /* Data from webserver to session */
  39         int outpipe[2];                 /* Data from session to webserver */
  40         pthread_mutex_t critter;        /* Critical section uses pipes */
  41         };
  42
  43 struct wc_session *SessionList = NULL;
  44
  45 /* Only one thread may manipulate SessionList at a time... */
  46 pthread_mutex_t MasterCritter;
  47
  48 int GenerateSessionID() {
  49         return getpid();
  50         }
  51
  52
  53 void gets0(int fd, char buf[]) {
  54
  55         buf[0] = 0;
  56         do {
  57                 buf[strlen(buf)+1] = 0;
  58                 read(fd, &buf[strlen(buf)], 1);
  59                 } while (buf[strlen(buf)-1] >= 32);
  60         buf[strlen(buf)-1] = 0;
  61         }
  62
  63 /*
  64  * Collapse multiple cookies on one line
  65  */
  66 void req_gets(int sock, char *buf, char *hold) {
  67         int a;
  68
  69         if (strlen(hold)==0) {
  70                 client_gets(sock, buf);
  71                 }
  72         else {
  73                 strcpy(buf, hold);
  74                 }
  75         strcpy(hold, "");
  76
  77         if (!strncasecmp(buf, "Cookie: ", 8)) {
  78                 for (a=0; a<strlen(buf); ++a) if (buf[a]==';') {
  79                         sprintf(hold, "Cookie: %s", &buf[a+1]);
  80                         buf[a]=0;
  81                         while (isspace(hold[8])) strcpy(&hold[8], &hold[9]);
  82                         return;
  83                         }
  84                 }
  85         }
  86
  87 extern const char *defaulthost;
  88 extern const char *defaultport;
  89
  90 /*
  91  * This loop gets called once for every HTTP connection made to WebCit.
  92  */
  93 void *context_loop(int sock) {
  94         char (*req)[256];
  95         char buf[256], hold[256];
  96         int num_lines = 0;
  97         int a;
  98         int f;
  99         int desired_session = 0;
 100         char str_session[256];
 101         struct wc_session *sptr;
 102         struct wc_session *TheSession;
 103         int ContentLength;
 104         int CloseSession = 0;
 105
 106         if ((req = malloc(sizeof(char[256][256]))) == NULL) {
 107                 printf("Can't malloc buffers; dropping connection.\n");
 108                 close (sock);
 109                 return NULL;
 110                 }
 111
 112         printf("Reading request from socket %d\n", sock);
 113
 114         /*
 115          * Find out what it is that the web browser is asking for
 116          */
 117         ContentLength = 0;
 118         do {
 119                 req_gets(sock, buf, hold);
 120                 if (!strncasecmp(buf, "Cookie: wc_session=", 19)) {
 121                         desired_session = atoi(&buf[19]);
 122                         }
 123                 if (!strncasecmp(buf, "Content-length: ", 16)) {
 124                         ContentLength = atoi(&buf[16]);
 125                         }
 126                 strcpy(&req[num_lines++][0], buf);
 127                 } while(strlen(buf)>0);
 128
 129         /*
 130          * See if there's an existing session open with the desired ID
 131          */
 132         TheSession = NULL;
 133         if (desired_session != 0) {
 134                 pthread_mutex_lock(&MasterCritter);
 135                 for (sptr=SessionList; sptr!=NULL; sptr=sptr->next) {
 136                         if (sptr->session_id == desired_session) {
 137                                 TheSession = sptr;
 138                                 }
 139                         }
 140                 pthread_mutex_unlock(&MasterCritter);
 141                 }
 142
 143         /*
 144          * Create a new session if we have to
 145          */
 146         if (TheSession == NULL) {
 147                 printf("Creating a new session\n");
 148                 pthread_mutex_lock(&MasterCritter);
 149                 TheSession = (struct wc_session *)
 150                         malloc(sizeof(struct wc_session));
 151                 TheSession->session_id = GenerateSessionID();
 152                 pipe(TheSession->inpipe);
 153                 pipe(TheSession->outpipe);
 154                 pthread_mutex_init(&TheSession->critter, NULL);
 155                 TheSession->next = SessionList;
 156                 SessionList = TheSession;
 157                 sprintf(str_session, "%d", TheSession->session_id);
 158                 f = fork();
 159                 fflush(stdout); fflush(stdin);
 160                 if (f==0) {
 161                         dup2(TheSession->inpipe[0], 0);
 162                         dup2(TheSession->outpipe[1], 1);
 163                         execlp("./webcit", "webcit", str_session, defaulthost,
 164                                defaultport, NULL);
 165                         printf("HTTP/1.0 404 WebCit Failure\n\n");
 166                         printf("Server: %s\n", SERVER);
 167                         printf("Content-type: text/html\n");
 168                         printf("Content-length: 76\n");
 169                         printf("\n");
 170                         printf("<HTML><HEAD><TITLE>Error</TITLE></HEAD>\n");
 171                         printf("<BODY>execlp() failed</BODY></HTML>\n");
 172                         exit(0);
 173                         }
 174                 pthread_mutex_unlock(&MasterCritter);
 175                 }
 176
 177         /*
 178          * Grab a lock on the session, so other threads don't try to access
 179          * the pipes at the same time.
 180          */
 181         printf("Locking session %d...\n", TheSession->session_id);
 182         pthread_mutex_lock(&TheSession->critter);
 183         printf("   ...got lock\n");
 184
 185         /*
 186          * Send the request to the appropriate session...
 187          */
 188         printf("   Writing %d lines of command\n", num_lines);
 189         printf("%s\n", &req[0][0]);
 190         for (a=0; a<num_lines; ++a) {
 191                 write(TheSession->inpipe[1], &req[a][0], strlen(&req[a][0]));
 192                 write(TheSession->inpipe[1], "\n", 1);
 193                 }
 194         printf("   Writing %d bytes of content\n", ContentLength);
 195         while (ContentLength--) {
 196                 read(sock, buf, 1);
 197                 write(TheSession->inpipe[1], buf, 1);
 198                 }
 199
 200         /*
 201          * ...and get the response.
 202          */
 203         printf("   Reading response\n");
 204         ContentLength = 0;
 205         do {
 206                 gets0(TheSession->outpipe[0], buf);
 207                 write(sock, buf, strlen(buf));
 208                 write(sock, "\n", 1);
 209                 if (!strncasecmp(buf, "Content-length: ", 16))
 210                         ContentLength = atoi(&buf[16]);
 211                 if (!strcasecmp(buf, "X-WebCit-Session: close")) {
 212                         CloseSession = 1;
 213                         }
 214                 } while (strlen(buf) > 0);
 215
 216         printf("   Reading %d bytes of content\n", ContentLength);
 217         while(ContentLength--) {
 218                 read(TheSession->outpipe[0], buf, 1);
 219                 write(sock, buf, 1);
 220                 }
 221
 222         /*
 223          * Now our HTTP connection is done.  It would be relatively easy
 224          * to support HTTP/1.1 "persistent" connections by looping back to
 225          * the top of this function.  For now, we'll just close.
 226          */
 227         printf("   Closing socket\n");
 228         close(sock);
 229
 230         /*
 231          * Let go of the lock
 232          */
 233         printf("Unlocking.\n");
 234         pthread_mutex_unlock(&TheSession->critter);
 235
 236
 237
 238         /*
 239          * If the last response included a "close session" directive,
 240          * remove the context now.
 241          */
 242         if (CloseSession) {
 243                 printf("Removing session.\n");
 244                 pthread_mutex_lock(&MasterCritter);
 245
 246                 if (SessionList==TheSession) {
 247                         SessionList = SessionList->next;
 248                         }
 249                 else {
 250                         for (sptr=SessionList; sptr!=NULL; sptr=sptr->next) {
 251                                 if (sptr->next == TheSession) {
 252                                         sptr->next = TheSession->next;
 253                                         }
 254                                 }
 255                         }
 256
 257                 free(TheSession);
 258
 259                 pthread_mutex_unlock(&MasterCritter);
 260                 }
 261
 262
 263
 264         /*
 265          * The thread handling this HTTP connection is now finished.
 266          */
 267         return NULL;
 268         }