Re: (ITS#7937) back-sock does not flush data to socket

[hyc@symas.com]

pdg@uow.edu.au wrote:
> Full_Name: Peter Gray
> Version: 2.4.39
> OS: solaris 10
> URL: ftp://ftp.openldap.org/incoming/
> Submission from: (NULL) (130.130.37.84)
>
>
> The code in back-sock seems to have an error.
>
> It opens a socket, converts the socket fd to a FILE *, and uses fprintf to send
> data to the socket. For example, from search.c:

Thanks for the report, fixed in git master.
>
>
>          fprintf( fp, "SEARCH\n" );
>          fprintf( fp, "msgid: %ld\n", (long) op->o_msgid );
>          sock_print_conn( fp, op->o_conn, si );
>          sock_print_suffixes( fp, op->o_bd );
>          fprintf( fp, "base: %s\n", op->o_req_dn.bv_val );
>          fprintf( fp, "scope: %d\n", op->oq_search.rs_scope );
>          fprintf( fp, "deref: %d\n", op->oq_search.rs_deref );
>          fprintf( fp, "sizelimit: %d\n", op->oq_search.rs_slimit );
>          fprintf( fp, "timelimit: %d\n", op->oq_search.rs_tlimit );
>          fprintf( fp, "filter: %s\n", op->_s_search.rs_filterstr.bv_val );
>          fprintf( fp, "attrsonly: %d\n", op->oq_search.rs_attrsonly ? 1 : 0 );
>          fprintf( fp, "attrs:%s", op->oq_search.rs_attrs == NULL ? " all" : ""
> );
>          for ( an = op->oq_search.rs_attrs; an && an->an_name.bv_val; an++ ) {
>                  fprintf( fp, " %s", an->an_name.bv_val );
>          }
>          fprintf( fp, "\n\n" );  /* end of attr line plus blank line */
>
>          /* read in the results and send them along */
>          rs->sr_attrs = op->oq_search.rs_attrs;
>          sock_read_and_send_results( op, rs, fp );
>
> However, it fails to flush the stream, so in sock_read_and_send_results when it
> issues a read from the socket, the data written has not been seen by the socket
> endpoint.
>
> This results in deadlock when slapd is waiting on the read, and the daemon on
> the other end of the socket is waiting on the ldap query.
>
> My fix is to call fflush as the first operation on sock_read_and_send_results
> and this worked fine.
>
> Here is the diff.
> *** .snapshot/nightly.0/result.c        Sun Jan 26 00:36:15 2014
> --- result.c    Thu Sep 11 11:25:07 2014
> ***************
> *** 48,53 ****
> --- 48,54 ----
>          char    line[BUFSIZ];
>          char    ebuf[128];
>
> +       (void) fflush(fp);
>          /* read in the result and send it along */
>          buf = (char *) ch_malloc( BUFSIZ );
>          buf[0] = '\0';
>
>
>
>


-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/