connection.c

一个 http 服务器的框架实现

/*
     This file is part of libmicrohttpd
     (C) 2007 Daniel Pittman and Christian Grothoff

     libmicrohttpd is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 2, or (at your
     option) any later version.

     libmicrohttpd is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with libmicrohttpd; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file connection.c
 * @brief  Methods for managing connections
 * @author Daniel Pittman
 * @author Christian Grothoff
 */

#include "internal.h"
#include "connection.h"
#include "memorypool.h"
#include "response.h"

/**
 * Message to transmit when http 1.1 request is received
 */
#define HTTP_100_CONTINUE "HTTP/1.1 100 Continue\r\n\r\n"

/**
 * Response used when the request (http header) is too big to
 * be processed.
 */
#define REQUEST_TOO_BIG ""

/**
 * Get all of the headers from the request.
 *
 * @param iterator callback to call on each header;
 *        maybe NULL (then just count headers)
 * @param iterator_cls extra argument to iterator
 * @return number of entries iterated over
 */
int
MHD_get_connection_values (struct MHD_Connection *connection,
                           enum MHD_ValueKind kind,
                           MHD_KeyValueIterator iterator, void *iterator_cls)
{
  int ret;
  struct MHD_HTTP_Header *pos;

  if (connection == NULL)
    return -1;
  ret = 0;
  pos = connection->headers_received;
  while (pos != NULL)
    {
      if (0 != (pos->kind & kind))
        {
          ret++;
          if ((iterator != NULL) &&
              (MHD_YES != iterator (iterator_cls,
                                    kind, pos->header, pos->value)))
            return ret;
        }
      pos = pos->next;
    }
  return ret;
}


/**
 * Get a particular header value.  If multiple
 * values match the kind, return any one of them.
 *
 * @param key the header to look for
 * @return NULL if no such item was found
 */
const char *
MHD_lookup_connection_value (struct MHD_Connection *connection,
                             enum MHD_ValueKind kind, const char *key)
{
  struct MHD_HTTP_Header *pos;

  if (connection == NULL)
    return NULL;
  pos = connection->headers_received;
  while (pos != NULL)
    {
      if ((0 != (pos->kind & kind)) && (0 == strcasecmp (key, pos->header)))
        return pos->value;
      pos = pos->next;
    }
  return NULL;
}

/**
 * Queue a response to be transmitted to the client (as soon as
 * possible).
 *
 * @param connection the connection identifying the client
 * @param status_code HTTP status code (i.e. 200 for OK)
 * @param response response to transmit
 * @return MHD_NO on error (i.e. reply already sent),
 *         MHD_YES on success or if message has been queued
 */
int
MHD_queue_response (struct MHD_Connection *connection,
                    unsigned int status_code, struct MHD_Response *response)
{
  if ((connection == NULL) ||
      (response == NULL) ||
      (connection->response != NULL) ||
      (connection->bodyReceived == 0) || (connection->headersReceived == 0))
    return MHD_NO;
  MHD_increment_response_rc (response);
  connection->response = response;
  connection->responseCode = status_code;
  if ((connection->method != NULL) &&
      (0 == strcasecmp (connection->method, MHD_HTTP_METHOD_HEAD)))
    {
      /* if this is a "HEAD" request, pretend that we
         have already sent the full message body */
      connection->messagePos = response->total_size;
    }
  return MHD_YES;
}

/**
 * Do we (still) need to send a 100 continue
 * message for this connection?
 */
static int
MHD_need_100_continue (struct MHD_Connection *connection)
{
  const char *expect;

  return ((connection->version != NULL) &&
          (0 == strcasecmp (connection->version,
                            MHD_HTTP_VERSION_1_1)) &&
          (connection->headersReceived == 1) &&
          (NULL != (expect = MHD_lookup_connection_value (connection,
                                                          MHD_HEADER_KIND,
                                                          MHD_HTTP_HEADER_EXPECT)))
          && (0 == strcasecmp (expect, "100-continue"))
          && (connection->continuePos < strlen (HTTP_100_CONTINUE)));
}

/**
 * Obtain the select sets for this connection
 *
 * @return MHD_YES on success
 */
int
MHD_connection_get_fdset (struct MHD_Connection *connection,
                          fd_set * read_fd_set,
                          fd_set * write_fd_set,
                          fd_set * except_fd_set, int *max_fd)
{
  int fd;
  void *buf;

  fd = connection->socket_fd;
  if (fd == -1)
    return MHD_YES;
  if ((connection->read_close == MHD_NO) &&
      ((connection->headersReceived == 0) ||
       (connection->readLoc < connection->read_buffer_size)))
    {
      FD_SET (fd, read_fd_set);
      if (fd > *max_fd)
        *max_fd = fd;
    }
  else
    {
      if ((connection->read_close == MHD_NO) &&
          ((connection->headersReceived == 1) &&
           (connection->post_processed == MHD_NO) &&
           (connection->readLoc == connection->read_buffer_size)))
        {
          /* try growing the read buffer, just in case */
          buf = MHD_pool_reallocate (connection->pool,
                                     connection->read_buffer,
                                     connection->read_buffer_size,
                                     connection->read_buffer_size * 2 +
                                     MHD_BUF_INC_SIZE);
          if (buf != NULL)
            {
              /* we can actually grow the buffer, do it! */
              connection->read_buffer = buf;
              connection->read_buffer_size =
                connection->read_buffer_size * 2 + MHD_BUF_INC_SIZE;
              FD_SET (fd, read_fd_set);
              if (fd > *max_fd)
                *max_fd = fd;
            }
        }
    }
  if ((connection->response != NULL) || MHD_need_100_continue (connection))
    {
      FD_SET (fd, write_fd_set);
      if (fd > *max_fd)
        *max_fd = fd;
    }
  return MHD_YES;
}

/**
 * We ran out of memory processing the
 * header.  Handle it properly by stopping to read data
 * and sending a HTTP 413 or HTTP 414 response.
 * 
 * @param status_code the response code to send (413 or 414)
 */
static void
MHD_excessive_data_handler (struct MHD_Connection *connection,
                            unsigned int status_code)
{
  struct MHD_Response *response;

  /* die, header far too long to be reasonable;
     FIXME: send proper response to client
     (stop reading, queue proper response) */
  connection->read_close = MHD_YES;
  connection->headersReceived = MHD_YES;
  connection->bodyReceived = MHD_YES;
  MHD_DLOG (connection->daemon,
            "Received excessively long header, closing connection.\n");
  response = MHD_create_response_from_data (strlen (REQUEST_TOO_BIG),
                                            REQUEST_TOO_BIG, MHD_NO, MHD_NO);
  MHD_queue_response (connection, status_code, response);
  MHD_destroy_response (response);
}

/**
 * Parse a single line of the HTTP header.  Advance
 * read_buffer (!) appropriately.  If the current line does not
 * fit, consider growing the buffer.  If the line is
 * far too long, close the connection.  If no line is
 * found (incomplete, buffer too small, line too long),
 * return NULL.  Otherwise return a pointer to the line.
 */
static char *
MHD_get_next_header_line (struct MHD_Connection *connection)
{
  char *rbuf;
  size_t pos;

  if (connection->readLoc == 0)
    return NULL;
  pos = 0;
  rbuf = connection->read_buffer;
  while ((pos < connection->readLoc - 1) &&
         (rbuf[pos] != '\r') && (rbuf[pos] != '\n'))
    pos++;
  if (pos == connection->readLoc - 1)
    {
      /* not found, consider growing... */
      if (connection->readLoc == connection->read_buffer_size)
        {
          rbuf = MHD_pool_reallocate (connection->pool,
                                      connection->read_buffer,
                                      connection->read_buffer_size,
                                      connection->read_buffer_size * 2 +
                                      MHD_BUF_INC_SIZE);
          if (rbuf == NULL)
            {
              MHD_excessive_data_handler (connection,
                                          (connection->url != NULL)
                                          ? MHD_HTTP_REQUEST_ENTITY_TOO_LARGE
                                          : MHD_HTTP_REQUEST_URI_TOO_LONG);
            }
          else
            {
              connection->read_buffer_size =
                connection->read_buffer_size * 2 + MHD_BUF_INC_SIZE;
              connection->read_buffer = rbuf;
            }
        }
      return NULL;
    }
  /* found, check if we have proper CRLF */
  if ((rbuf[pos] == '\r') && (rbuf[pos + 1] == '\n'))
    rbuf[pos++] = '\0';         /* skip both r and n */
  rbuf[pos++] = '\0';
  connection->read_buffer += pos;
  connection->read_buffer_size -= pos;
  connection->readLoc -= pos;
  return rbuf;
}

/**
 * @return MHD_NO on failure (out of memory), MHD_YES for success
 */
static int
MHD_connection_add_header (struct MHD_Connection *connection,
                           char *key, char *value, enum MHD_ValueKind kind)
{
  struct MHD_HTTP_Header *hdr;

  hdr = MHD_pool_allocate (connection->pool,
                           sizeof (struct MHD_HTTP_Header), MHD_YES);
  if (hdr == NULL)
    {
      MHD_DLOG (connection->daemon,
                "Not enough memory to allocate header record!\n");
      MHD_excessive_data_handler (connection,
                                  MHD_HTTP_REQUEST_ENTITY_TOO_LARGE);
      return MHD_NO;
    }
  hdr->next = connection->headers_received;
  hdr->header = key;
  hdr->value = value;
  hdr->kind = kind;
  connection->headers_received = hdr;
  return MHD_YES;
}

/**
 * Process escape sequences ('+'=space, %HH)
 */
static void
MHD_http_unescape (char *val)
{
  char *esc;
  unsigned int num;

  while (NULL != (esc = strstr (val, "+")))
    *esc = ' ';
  while (NULL != (esc = strstr (val, "%")))
    {
      if ((1 == sscanf (&esc[1],
                        "%2x", &num)) || (1 == sscanf (&esc[1], "%2X", &num)))
        {
          esc[0] = (unsigned char) num;
          memmove (&esc[1], &esc[3], strlen (&esc[3]));
        }
      val = esc + 1;
    }
}

/**
 * @return MHD_NO on failure (out of memory), MHD_YES for success
 */
static int
parse_arguments (enum MHD_ValueKind kind,
                 struct MHD_Connection *connection, char *args)
{
  char *equals;
  char *amper;

  while (args != NULL)
    {
      equals = strstr (args, "=");
      if (equals == NULL)
        return MHD_NO;          /* invalid, ignore */
      equals[0] = '\0';
      equals++;
      amper = strstr (equals, "&");
      if (amper != NULL)
        {
          amper[0] = '\0';
          amper++;
        }
      MHD_http_unescape (args);
      MHD_http_unescape (equals);
      if (MHD_NO == MHD_connection_add_header (connection,
                                               args, equals, kind))
        return MHD_NO;
      args = amper;
    }
  return MHD_YES;
}

/**
 * Parse the cookie header (see RFC 2109).
 * 
 * @return MHD_YES for success, MHD_NO for failure (malformed, out of memory)
 */
static int
MHD_parse_cookie_header (struct MHD_Connection *connection)
{
  const char *hdr;
  char *cpy;
  char *pos;