Commit 0e4084c6 authored by Bill Stoddard's avatar Bill Stoddard
Browse files

It is not sufficient to reset the file pointer before each call to ap_send_fd. A better solution 

is to make certain that only apr_sendfile() will be used to send content with a cached file handle.
This assumes that apr_sendfile() should not rely on the position of the file pointer. I suspect that
sendfile implementations that rely on the position of the file pointer are broken and we should not
use sendfile on those platforms.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87654 13f79535-47bb-0310-9956-ffa450edef68
parent 53be4943

modules/cache/mod_file_cache.c

+26 −5
Original line number Diff line number Diff line
@@ -216,6 +216,12 @@ static apr_status_t cleanup_file_cache(void *sconfv) 
static const char *cachefile(cmd_parms *cmd, void *dummy, const char *filename)



{

    /* ToDo:

     * Disable the file cache on a Windows 9X box. APR_HAS_SENDFILE will be

     * defined in an Apache for Windows build, but apr_sendfile is not

     * implemened on Windows 9X because TransmitFile is not available.

     */



#if APR_HAS_SENDFILE

    a_server_config *sconf;

    a_file *new_file;
@@ -400,13 +406,28 @@ static int sendfile_handler(request_rec *r, a_file *file) 
    apr_status_t rv = APR_EINIT;

    apr_off_t offset = 0;



    rv = apr_seek(file->file, APR_SET, &offset);

    if (rv != APR_SUCCESS) {

        ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r,

                      "seek failed");

        return HTTP_INTERNAL_SERVER_ERROR;

    /* A cached file handle (more importantly, its file pointer) is 

     * shared by all threads in the process. The file pointer will 

     * be corrupted if multiple threads attempt to read from the 

     * cached file handle. The sendfile API does not rely on the position 

     * of the file pointer instead taking explicit file offset and 

     * length arguments. 

     *

     * We should call ap_send_fd with a cached file handle IFF 

     * we are CERTAIN the file will be served with apr_sendfile(). 

     * The presense of an AP_FTYPE_FILTER in the filter chain nearly

     * guarantees that apr_sendfile will NOT be used to send the file.

     * Furthermore, AP_FTYPE_CONTENT filters will be at the beginning

     * of the chain, so it should suffice to just check the first 

     * filter in the chain. If the first filter is not a content filter, 

     * assume apr_sendfile() will be used to send the content.

     */

    if (r->output_filters && r->output_filters->frec) {

        if (r->output_filters->frec->ftype == AP_FTYPE_CONTENT)

            return DECLINED;

    }





    rv = ap_send_fd(file->file, r, 0, file->finfo.size, &nbytes);

    if (rv != APR_SUCCESS) {

        /* ap_send_fd will log the error */