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