serval-dna/rhizome_direct_http.c

/*
Serval Mesh Software
Copyright (C) 2010-2012 Paul Gardner-Stephen

This program 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
of the License, or (at your option) any later version.

This program 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 this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/

#include "serval.h"
#include "rhizome.h"
#include "str.h"
#include <assert.h>


int rhizome_direct_clear_temporary_files(rhizome_http_request *r)
{
  char filename[1024];
  char *fields[]={"manifest","data","unknown",NULL};
  int i;

  for(i=0;fields[i];i++) {
    snprintf(filename,1024,"rhizomedirect.%d.%s",r->alarm.poll.fd,fields[i]);
    filename[1023]=0;
    DEBUGF("Unlinking '%s'",filename);
  }
  return 0;
}

int rhizome_direct_form_received(rhizome_http_request *r)
{
  /* XXX This needs to be implemented.
     For now we just put out a "no content" response that makes testing convenient
  */

  /* XXX process completed form based on the set of fields seen */
  if (!strcmp(r->path,"/rhizome/import"))
    {
      switch(r->fields_seen) {
      case RD_MIME_STATE_MANIFESTHEADERS
	|RD_MIME_STATE_DATAHEADERS:
	/* A bundle to import */
	DEBUGF("Call bundle import for rhizomedata.%d.{data,file}",
	       r->alarm.poll.fd);
	char cmd[1024];
	snprintf(cmd,1024,
		 "servald rhizome import bundle rhizomedirect.%d.data rhizomedirect.%d.manifest",
		 r->alarm.poll.fd,r->alarm.poll.fd);
	cmd[1023]=0;
	int rv=system(cmd);
	int status=-1;
	
	if (rv!=-1) status=WEXITSTATUS(rv);
	
	DEBUGF("Import returned %d",status);
	
	/* clean up after ourselves */
	rhizome_direct_clear_temporary_files(r);
	/* and report back to caller.
	   200 = ok, which is probably appropriate for when we already had the bundle.
	   201 = content created, which is probably appropriate for when we successfully
	   import a bundle (or if we already have it).
	   403 = forbidden, which might be appropriate if we refuse to accept it, e.g.,
	   the import fails due to malformed data etc.
	   (should probably also indicate if we have a newer version if possible)
	   
	   For now we are just returning "no content" as a place-holder while debugging.
	*/
	rhizome_server_simple_http_response(r, 204, "Move along. Nothing to see.");
	break;     
      default:
	/* Clean up after ourselves */
	rhizome_direct_clear_temporary_files(r);	     
      }
    } else if (!strcmp(r->path,"/rhizome/enquiry")) {
    int fd=-1;
    char file[1024];
    switch(r->fields_seen) {
    case RD_MIME_STATE_DATAHEADERS:
      /* Read data buffer in, pass to rhizome direct for comparison with local
	 rhizome database, and send back responses. */
      snprintf(file,1024,"rhizomedirect.%d.%s",r->alarm.poll.fd,"data");
      fd=open(file,O_RDONLY);
      if (fd == -1) {
	/* Clean up after ourselves */
	rhizome_direct_clear_temporary_files(r);	     
	return rhizome_server_simple_http_response(r,500,"Couldn't read a file");
      }
      struct stat stat;
      if (fstat(fd,&stat)) {
	/* Clean up after ourselves */
	close(fd);
	rhizome_direct_clear_temporary_files(r);	     
	return rhizome_server_simple_http_response(r,500,"Couldn't stat a file");
      }
      unsigned char *addr = mmap(NULL, stat.st_size, PROT_READ, 
				 MAP_FILE|MAP_SHARED, fd, 0);
      if (addr==MAP_FAILED) {
	/* Clean up after ourselves */
	close(fd);
	rhizome_direct_clear_temporary_files(r);	     
	return rhizome_server_simple_http_response(r,500,"Couldn't mmap() a file");
      }
      rhizome_direct_bundle_cursor *c=rhizome_direct_get_fill_response(addr,stat.st_size);
      munmap(addr,stat.st_size);
      close(fd);

      if (c)
	{
	  /* TODO: Write out_buffer as the body of the response.
	     We should be able to do this using the async framework fairly easily.
	  */
	  
	  int bytes=c->buffer_offset_bytes+c->buffer_used;
	  r->buffer=malloc(bytes+1024);
	  r->buffer_size=bytes+1024;
	  r->buffer_offset=0;
	  assert(r->buffer);

	  /* Write HTTP response header */
	  struct http_response hr;
	  hr.result_code=200;
	  hr.content_type="binary/octet-stream";
	  hr.content_length=bytes;
	  r->request_type=0;
	  rhizome_server_set_response(r,&hr);
	  assert(r->buffer_offset<1024);

	  /* Now append body and send it back. */
	  bcopy(c->buffer,&r->buffer[r->buffer_offset],bytes);
	  r->buffer_length+=bytes;
	  r->buffer_offset=0;

	  /* Clean up cursor after sending response */
	  rhizome_direct_bundle_iterator_free(&c);
	  /* Clean up after ourselves */
	  rhizome_direct_clear_temporary_files(r);	     

	  return 0;
	}
      else
	{
	  return rhizome_server_simple_http_response(r,500,"Could not get response to enquiry");
	}

      /* Clean up after ourselves */
      rhizome_direct_clear_temporary_files(r);	     
      break;
    default:
      /* Clean up after ourselves */
      rhizome_direct_clear_temporary_files(r);	     

      return rhizome_server_simple_http_response(r, 404, "/rhizome/enquiry requires 'data' field");
    }

  }

  /* Clean up after ourselves */
  rhizome_direct_clear_temporary_files(r);	     
  /* Report error */
  return rhizome_server_simple_http_response(r, 500, "Something went wrong.  Probably a missing data or manifest part, or invalid combination of URI and data/manifest provision.");

}


int rhizome_direct_process_mime_line(rhizome_http_request *r,char *buffer,int count)
{
  /* Check for boundary line at start of buffer.
     Boundary line = CRLF + "--" + boundary_string + optional whitespace + CRLF
     EXCEPT end of form boundary, which is:
     CRLF + "--" + boundary_string + "--" + CRLF

     NOTE: We attach the "--" to boundary_string when setting things up so that
     we don't have to keep manually checking for it here.

     NOTE: The parser eats the CRLF from the front, and attaches it to the end
     of the previous line.  This means we need to rewind 2 bytes from whatever
     file we were writing to whenever we encounter a boundary line, at least
     if those last two bytes were CRLF. That can be safely assumed if we
     assume that the boundary string has been chosen to be a string never appearing
     anywhere in the contents of the form.  In practice, that is only "almost
     certain" (according to the mathematical meaning of that phrase) if boundary
     strings are randomly selected and are of sufficient length.
   
     NOTE: We are not supporting nested/mixed parts, as that would considerably
     complicate the parser.  If the need arises in future, we will deal with it
     then.  In the meantime, we will have something that meets our immediate
     needs for Rhizome Direct and a variety of use cases.
  */

  /* Regardless of the state of the parser, the presence of boundary lines
     is significant, so lets just check once, and remember the result.
     Similarly check a few other conditions. */
  int boundaryLine=0;
  if (!bcmp(buffer,r->boundary_string,r->boundary_string_length))
    boundaryLine=1;

  int endOfForm=0;
  if (boundaryLine&&
      buffer[r->boundary_string_length]=='-'&&
      buffer[r->boundary_string_length+1]=='-')
    endOfForm=1;
  int blankLine=0;
  if (!strcmp(buffer,"\r\n")) blankLine=1;

  DEBUGF("mime state: 0x%x, blankLine=%d, boundary=%d, EOF=%d, bytes=%d",
	 r->source_flags,blankLine,boundaryLine,endOfForm,count);
  switch(r->source_flags) {
  case RD_MIME_STATE_INITIAL:
    if (boundaryLine) r->source_flags=RD_MIME_STATE_PARTHEADERS;
    break;
  case RD_MIME_STATE_PARTHEADERS:
  case RD_MIME_STATE_MANIFESTHEADERS:
  case RD_MIME_STATE_DATAHEADERS:
    DEBUGF("mime line: %s",r->request);
    if (blankLine) {
      /* End of headers */
      if (r->source_flags==RD_MIME_STATE_PARTHEADERS)
	{
	  /* Multiple content-disposition lines.  This is very naughty. */
	  rhizome_server_simple_http_response
	    (r, 400, "<html><h1>Malformed multi-part form POST: Missing content-disposition lines in MIME encoded part.</h1></html>\r\n");
	  return -1;
	}
      
      /* Prepare to write to file for field.
	 We may have multiple rhizome direct transactions running at the same
	 time on different TCP connections.  So serialise using file descriptor.
	 We could use the boundary string or some other random thing, but using
	 the file descriptor places a reasonable upper limit on the clutter that
	 is possible, while still preventing collisions -- provided that we don't
	 close the file descriptor until we have completed processing the 
	 request. */
      r->field_file=NULL;
      char filename[1024];
      char *field="unknown";
      switch(r->source_flags) {
      case RD_MIME_STATE_DATAHEADERS: field="data"; break;
      case RD_MIME_STATE_MANIFESTHEADERS: field="manifest"; break;
      }
      snprintf(filename,1024,"rhizomedirect.%d.%s",r->alarm.poll.fd,field);
      filename[1023]=0;
      DEBUGF("Writing to '%s'",filename);
      r->field_file=fopen(filename,"w");
      if (!r->field_file) {
	rhizome_direct_clear_temporary_files(r);
	rhizome_server_simple_http_response
	  (r, 500, "<html><h1>Sorry, couldn't complete your request, reasonable as it was.  Perhaps try again later.</h1></html>\r\n");
	return -1;
      }
      r->source_flags=RD_MIME_STATE_BODY;
    } else {
      char name[1024];
      char field[1024];
      if (sscanf(buffer,
		 "Content-Disposition: form-data; name=\"%[^\"]\";"
		 " filename=\"%[^\"]\"",field,name)==2)
	{
	  if (r->source_flags!=RD_MIME_STATE_PARTHEADERS)
	    {
	      /* Multiple content-disposition lines.  This is very naughty. */
	      rhizome_server_simple_http_response
		(r, 400, "<html><h1>Malformed multi-part form POST: Multiple content-disposition lines in single MIME encoded part.</h1></html>\r\n");
	      return -1;
	    }
	  DEBUGF("Found form part '%s' name '%s'",field,name);
	  if (!strcasecmp(field,"manifest")) 
	    r->source_flags=RD_MIME_STATE_MANIFESTHEADERS;
	  if (!strcasecmp(field,"data")) 
	    r->source_flags=RD_MIME_STATE_DATAHEADERS;
	  if (r->source_flags!=RD_MIME_STATE_PARTHEADERS)
	    r->fields_seen|=r->source_flags;
	} 
    }
    break;
  case RD_MIME_STATE_BODY:
    if (boundaryLine) {
      r->source_flags=RD_MIME_STATE_PARTHEADERS;

      /* We will have written an extra CRLF to the end of the file,
	 so prune that off. */
      fflush(r->field_file);
      int fd=fileno(r->field_file);
      off_t correct_size=ftell(r->field_file)-2;
      ftruncate(fd,correct_size);
      fclose(r->field_file);
      r->field_file=NULL;
    }
    else {
      int written=fwrite(r->request,count,1,r->field_file);
      DEBUGF("wrote %d lump of %d bytes",written,count);
    }
    break;
  }

  if (endOfForm) {
    /* End of form marker found. 
       Pass it to function that deals with what has been received,
       and will also send response or close the http request if required. */

    /* XXX Rewind last two bytes from file if open, and close file */

    DEBUGF("Found end of form");
    return rhizome_direct_form_received(r);
  }
  return 0;
}

int rhizome_direct_process_post_multipart_bytes
(rhizome_http_request *r,const char *bytes,int count)
{
  {
    DEBUGF("Saw %d multi-part form bytes",count);
    FILE *f=fopen("post.log","a"); 
    if (f) fwrite(bytes,count,1,f);
    if (f) fclose(f);
  }

  /* This function looks for multi-part form separators and descriptor lines,
     and streams any "manifest" or "data" blocks to respectively named files.

     The challenge is that we might only get a partial boundary string passed
     to us.  So we need to remember the last KB or so of data and glue it to
     the front of the current set of bytes.

     In multi-part form parsing we don't need r->request for anything, so if
     we are not in a form part already, then we can stow the bytes there
     for reexamination when more bytes arrive.
     
     Side effect will be that the entire boundary string and associated bits will
     need to be <=1KB, the size of r->request.  This seems quite reasonable.

     Example of such a block is:

     ------WebKitFormBoundaryEoJwSoSVW4qsrBZW
     Content-Disposition: form-data; name="manifest"; filename="spleen"
     Content-Type: application/octet-stream     
  */

  int o;

  /* Split into lines and process each line separately using a
     simple state machine. 
     Lines containing binary are truncated into arbitrarily length pieces, but
     a newline will ALWAYS break the line.
  */

  for(o=0;o<count;o++)
    {
      int newline=0;
      if (bytes[o]=='\n')
	if (r->request_length>0&&r->request[r->request_length-1]=='\r')
	  { newline=1; r->request_length--; }
      if (r->request_length>1020) newline=2;
      if (newline) {	
	/* Found end of line, so process it */
	if (newline==1) {
	  /* Put the real new line onto the end if it was present, so that
	     we don't go doing anything silly, like joining lines in files
	     that really were separated by CRLF, or similarly inserting CRLF
	     in the middle of slabs of bytes that were not CRLF terminated.
	  */
	  r->request[r->request_length++]='\r';
	  r->request[r->request_length++]='\n';
	}
	r->request[r->request_length]=0;
	if (rhizome_direct_process_mime_line(r,r->request,r->request_length)) 
	  return -1;
	r->request_length=0;
	/* If a real new line was detected, then
	   don't include the \n as part of the next line.
	   But if it wasn't a real new line, then make sure we
	   don't loose the byte. */
	if (newline==1) continue;
      }

      r->request[r->request_length++]=bytes[o];
    }

  r->source_count-=count;
  if (r->source_count<=0) {
    DEBUGF("Got to end of multi-part form data");

    /* If the form is still being processed, then flush things through */
    if (r->request_type<0) {
      /* Flush out any remaining data */
      if (r->request_length) {
	DEBUGF("Flushing last %d bytes",r->request_length);
	r->request[r->request_length]=0;
	rhizome_direct_process_mime_line(r,r->request,r->request_length);
      }      
      return rhizome_direct_form_received(r);
    } else {
      /* Form has already been processed, so do nothing */
    }
  }
  return 0;
}

int rhizome_direct_parse_http_request(rhizome_http_request *r)
{
  /* Switching to writing, so update the call-back */
  r->alarm.poll.events=POLLOUT;
  watch(&r->alarm);
  // Start building up a response.
  r->request_type = 0;
  // Parse the HTTP "GET" line.
  char *path = NULL;
  size_t pathlen = 0;
  if (str_startswith(r->request, "GET ", &path)) {
    char *p;
    // This loop is guaranteed to terminate before the end of the buffer, because we know that the
    // buffer contains at least "\n\n" and maybe "\r\n\r\n" at the end of the header block.
    for (p = path; !isspace(*p); ++p)
      ;
    pathlen = p - path;
    if ( str_startswith(p, " HTTP/1.", &p)
      && (str_startswith(p, "0", &p) || str_startswith(p, "1", &p))
      && (str_startswith(p, "\r\n", &p) || str_startswith(p, "\n", &p))
    )
      path[pathlen] = '\0';
    else
      path = NULL;
 
    if (path) {
      char *id = NULL;
      INFOF("RHIZOME HTTP SERVER, GET %s", alloca_toprint(1024, path, pathlen));
      if (strcmp(path, "/favicon.ico") == 0) {
	r->request_type = RHIZOME_HTTP_REQUEST_FAVICON;
	rhizome_server_http_response_header(r, 200, "image/vnd.microsoft.icon", favicon_len);
      } else {
	rhizome_server_simple_http_response(r, 404, "<html><h1>Not found</h1></html>\r\n");
      }
    }
  } else   if (str_startswith(r->request, "POST ", &path)) {
    char *p;
        
    // This loop is guaranteed to terminate before the end of the buffer, because we know that the
    // buffer contains at least "\n\n" and maybe "\r\n\r\n" at the end of the header block.
    for (p = path; !isspace(*p); ++p)
      ;
    pathlen = p - path;
    if ( str_startswith(p, " HTTP/1.", &p)
      && (str_startswith(p, "0", &p) || str_startswith(p, "1", &p))
      && (str_startswith(p, "\r\n", &p) || str_startswith(p, "\n", &p))
    )
	path[pathlen] = '\0';
    else
      path = NULL;
 
    if (path) {
      char *id = NULL;
      INFOF("RHIZOME HTTP SERVER, POST %s", alloca_toprint(1024, path, pathlen));
      if ((strcmp(path, "/rhizome/import") == 0) 
	  ||(strcmp(path, "/rhizome/enquiry") == 0))
	{
	/*
	  We know we have the complete header, so get the content length and content type
	  fields. From those we work out what to do with the body. */
	char *headers=&path[pathlen+1];
	int headerlen=r->request_length-(headers-r->request);
	const char *cl_str=str_str(headers,"Content-Length: ",headerlen);
	const char *ct_str=str_str(headers,"Content-Type: multipart/form-data; boundary=",headerlen);
	if (!cl_str)
	  return 
	    rhizome_server_simple_http_response(r,400,"<html><h1>POST without content-length</h1></html>\r\n");
	if (!ct_str)
	  return 
	    rhizome_server_simple_http_response(r,400,"<html><h1>POST without content-type (or unsupported content-type)</h1></html>\r\n");
	/* ok, we have content-type and content-length, now make sure they are
	   well formed. */
	long long cl;
	if (sscanf(cl_str,"Content-Length: %lld",&cl)!=1)
	  return 
	    rhizome_server_simple_http_response(r,400,"<html><h1>malformed Content-Length: header</h1></html>\r\n");
	char boundary_string[1024];
	int i;
	ct_str+=strlen("Content-Type: multipart/form-data; boundary=");
	for(i=0;i<1023&&*ct_str&&*ct_str!='\n'&&*ct_str!='\r';i++,ct_str++)
	  boundary_string[i]=*ct_str;
	boundary_string[i]=0;
	if (i<4||i>128)
	  return 
	    rhizome_server_simple_http_response(r,400,"<html><h1>malformed Content-Type: header</h1></html>\r\n");

	DEBUGF("HTTP POST content-length=%lld, boundary string='%s'",
	       cl,boundary_string);

	/* Now start receiving and parsing multi-part data.
	   We may have already received some of the post-header data, so 
	   rewind that if necessary. Need to start by finding actual end of
	   headers, and passing any body bytes to the parser.
	   Also need to tell the HTTP request that it has moved to multipart
	   form data parsing, and what the actual requested action is.
	*/

	/* Remember boundary string and source path.
	   Put the preceeding -- on the front to make our life easier when
	   parsing the rest later. */
	snprintf(&r->boundary_string[0],1023,"--%s",boundary_string);
	r->boundary_string[1023]=0;
	r->boundary_string_length=strlen(r->boundary_string);
	r->source_index=0;
	r->source_count=cl;
	snprintf(&r->path[0],1023,"%s",path);
	r->path[1023]=0;
	r->request_type=RHIZOME_HTTP_REQUEST_RECEIVING_MULTIPART;

	/* Find the end of the headers and start of any body bytes that we
	   have read so far. */
	{
	  const char *eoh="\r\n\r\n";
	  int i=0;
	  for(i=0;i<r->request_length;i++) {
	    if (!strncmp(eoh,&r->request[i],strlen(eoh)))
	      break;
	  }
	  if (i>=r->request_length) {
	    /* Couldn't find the end of the headers, but this routine should
	       not be called if the end of headers has not been found.
	       Complain and go home. */
	    return 
	      rhizome_server_simple_http_response(r, 404, "<html><h1>End of headers seems to have gone missing</h1></html>\r\n");
	  }

	  /* Process any outstanding bytes.
	     We need to copy the bytes to a separate buffer, because 
	     r->request and r->request_length get used internally in the 
	     parser, which is also why we need to zero r->request_length.
	     We also zero r->source_flags, which is used as the state
	     counter for parsing the multi-part form data.
	   */
	  int count=r->request_length-i;
	  char buffer[count];
	  bcopy(&r->request[i],&buffer[0],count);
	  r->request_length=0;
	  r->source_flags=0;
	  rhizome_direct_process_post_multipart_bytes(r,buffer,count);
	}

	/* Handle the rest of the transfer asynchronously. */
	return 0;
      } else {
	rhizome_server_simple_http_response(r, 404, "<html><h1>Not found</h1></html>\r\n");
      }
    }
  } else {
    if (debug & DEBUG_RHIZOME_TX)
      DEBUGF("Received malformed HTTP request: %s", alloca_toprint(120, (const char *)r->request, r->request_length));
    rhizome_server_simple_http_response(r, 400, "<html><h1>Malformed request</h1></html>\r\n");
  }
  
  /* Try sending data immediately. */
  rhizome_server_http_send_bytes(r);

  return 0;
}

void rhizome_direct_http_dispatch(rhizome_direct_sync_request *r)
{
  DEBUGF("Dispatch size_high=%lld",r->cursor->size_high);
  rhizome_direct_transport_state_http *state=r->transport_specific_state;

  int sock=socket(AF_INET, SOCK_STREAM, 0);
  if (sock==-1) {
    DEBUGF("could not open socket");    
    goto end;
  } 

  struct hostent *hostent;
  hostent = gethostbyname(state->host);
  if (!hostent) {
    DEBUGF("could not resolve hostname");
    goto end;
  }

  struct sockaddr_in addr;  
  addr.sin_family = AF_INET;     
  addr.sin_port = htons(state->port);   
  addr.sin_addr = *((struct in_addr *)hostent->h_addr);
  bzero(&(addr.sin_zero),8);     

  if (connect(sock,(struct sockaddr *)&addr,sizeof(struct sockaddr)) == -1)
    {
      close(sock);
      DEBUGF("Could not connect to remote");
      goto end;
    }
  
  /* Okay, we have open socket */
  char boundary[1024];
  snprintf(boundary,1024,"----%08lx%08lx",random(),random());

  /* TODO: Refactor this code so that it uses our asynchronous framework.
   */

  int content_length=
    strlen("--")+strlen(boundary)+strlen("\r\n")+
    strlen("Content-Disposition: form-data; name=\"data\"; filename=\"IHAVEs\"\r\n"
	   "Content-Type: application/octet-stream\r\n"
	   "\r\n")+
    r->cursor->buffer_offset_bytes+r->cursor->buffer_used+
    strlen("\r\n--")+strlen(boundary)+strlen("--\r\n");

  char buffer[8192];
  snprintf(buffer,8192,
	   "POST /rhizome/enquiry HTTP/1.0\r\n"
	   "Content-Length: %d\r\n"
	   "Content-Type: multipart/form-data; boundary=%s\r\n"
	   "\r\n"
	   "--%s\r\n"
	   "Content-Disposition: form-data; name=\"data\"; filename=\"IHAVEs\"\r\n"
	   "Content-Type: application/octet-stream\r\n"
	   "\r\n",
	   content_length,
	   boundary,boundary);
  int len=strlen(buffer);
  int sent=0;
  while(sent<len) {
    errno=0;
    int count=write(sock,&buffer[sent],len-sent);
    if (count<1) {
      DEBUGF("errno=%d, count=%d",errno,count);
      if (errno==EPIPE) goto rx;
      close(sock);
      goto end;
    }
    sent+=count;
  }

  len=r->cursor->buffer_offset_bytes+r->cursor->buffer_used;
  sent=0;
  while(sent<len) {
    errno=0;
    int count=write(sock,&r->cursor->buffer[sent],len-sent);
    if (count<1) {
      DEBUGF("errno=%d, count=%d",errno,count);
      if (errno==EPIPE) goto rx;
      close(sock);
      goto end;
    }
    sent+=count;
  }

  snprintf(buffer,8192,"\r\n--%s--\r\n",boundary);
  len=strlen(buffer);
  sent=0;
  while(sent<len) {
    errno=0;
    int count=write(sock,&buffer[sent],len-sent);
    if (count<1) {
      DEBUGF("errno=%d, count=%d",errno,count);
      if (errno==EPIPE) goto rx;
      close(sock);
      goto end;
    }
    sent+=count;
  }

 rx:
  /* request sent, now get response back. */
  buffer[0]=0; len=0;
  while(!http_header_complete(buffer,len,len)&&(len<8192))
    {
      int count=read(sock,&buffer[len],8192-len);
      if (count<1) {
	DEBUGF("errno=%d, count=%d",errno,count);
	close(sock);
	goto end;
      }
      len+=count;
      if (len>=8000) {
	DEBUGF("reply header too long");
	close(sock);
	goto end;
      }
    }

  DEBUGF("Got HTTP header");
  dump("reply",(unsigned char *)buffer,len);

  char *p = NULL;
  if (!str_startswith(buffer, "HTTP/1.0 ", &p)) {
    DEBUGF("Malformed HTTP reply: missing HTTP/1.0 preamble");
    close(sock); goto end;
  }
  int http_response_code = 0;
  char *nump;
  for (nump = p; isdigit(*p); ++p)
    http_response_code = http_response_code * 10 + *p - '0';
  if (p == nump || *p != ' ') {
      DEBUGF("Malformed HTTP reply: missing decimal status code");
    close(sock); goto end;
  }
  if (http_response_code != 200) {
    DEBUGF("Failed HTTP request: rhizome server returned %d != 200 OK", http_response_code);
    close(sock); goto end;
  }
  // This loop will terminate, because http_header_complete() above found at least
  // "\n\n" at the end of the header, and probably "\r\n\r\n".
  while (*p++ != '\n')
    ;
  // Iterate over header lines until the last blank line.
  while (*p != '\r' && *p != '\n') {
    if (strcase_startswith(p, "Content-Length:", &p)) {
      while (*p == ' ')
	++p;
      content_length = 0;
      for (nump = p; isdigit(*p); ++p)
	content_length = content_length * 10 + *p - '0';
      if (p == nump || (*p != '\r' && *p != '\n')) {
	DEBUGF("Invalid HTTP reply: malformed Content-Length header");
	close(sock); goto end;	
      }
    }
    while (*p++ != '\n')
      ;
  }
  if (*p == '\r')
    ++p;
  ++p; // skip '\n' at end of blank line
  if (content_length == -1) {
    DEBUGF("Invalid HTTP reply: missing Content-Length header");
    close(sock); goto end;
  }

  end:
  /* Warning: tail recursion when done this way. 
     Should be triggered by an asynchronous event.
     But this will do for now. */
  rhizome_direct_continue_sync_request(r);
}