We very occasionally see a problem that goes like this:

1) Send an LDAP search request to a Windows DC

2) Call ldap_int_select from result.c - wait4msg()

3) After ldap_int_select returns okay - (eventually) call down into the sockbuf.c function sb_stream_read() which calls read(...)

4) The read() hangs forever if it has to do multiple calls to get the entire response (very very occasionally)

I was not able to get a network trace to see why recv() hangs forever (AIX 5.3 BTW), but it does have to do with a large response that comes back in several TCP fragments.

I solved the issue by adding an additional select() call in sb_stream_read()

Here is what I did in code base 2.2.6

static ber_slen_t

sb_stream_read( Sockbuf_IO_Desc *sbiod, void *buf, ber_len_t len )

...

#elif defined( HAVE_NCSA )

/*

* NCSA Telnet TCP/IP stack (under DOS)

*/

return nread( sbiod->sbiod_sb->sb_fd, buf, len );

#else

{

int rc = ber_int_sb_read_wait(sbiod->sbiod_sb); <- The new check

if (rc > 0)

{

rc = read( sbiod->sbiod_sb->sb_fd, buf, len );

}

return rc;

}

#endif

}

New Function

/**

* If there is a timeout - wait for data, to avoid

* permanent blocking on a read.

*

* @param sb Socket buf with socket id and timeout

* @return -1=error : 0=timeout : 1=proceed

*/

static int

ber_int_sb_read_wait(Sockbuf *sb)

{

struct timeval tm = sb->sb_timeout;

int rc = 1;

/* If no timeout was specified skip the select */

if (tm.tv_sec || tm.tv_usec)

{

int sock = sb->sb_fd;

fd_set rfds;

FD_ZERO(&rfds);

FD_SET(sock, &rfds);

ber_log_printf(LDAP_DEBUG_PACKETS, sb->sb_debug,

"ber_int_sb_read_wait start: timeout is %d %d",

(int)tm.tv_sec, (int)tm.tv_usec);

rc = select(sock+1, &rfds, NULL, NULL, &tm);

ber_log_printf(LDAP_DEBUG_PACKETS, sb->sb_debug,

"ber_int_sb_read_wait end: sock=%d rc=%d %s\n",

sock, rc, (rc >= 0) ? "" : STRERROR(errno));

}

return rc;

}

In open.c - ldap_int_open_connection(), I added some code to propagate the timeout down to ber_int_sb_read_wait((

{

/*

* Propagate the network timeout to sockbuf layer for

* select calls.

*/

struct timeval *tm = 0;

int ret = ldap_get_option(ld, LDAP_OPT_NETWORK_TIMEOUT,

(void *)&tm);

if (ret == LDAP_OPT_SUCCESS && tm) {

ber_sockbuf_ctrl(conn->lconn_sb, LBER_SB_OPT_SET_TIMEOUT, tm);

LDAP_FREE(tm);

}

}

Regards

Dave Daugherty

Centrify Corp.