This is the mail archive of the
cygwin@cygwin.com
mailing list for the Cygwin project.
BUG - 1.3.n accept fails if NULL sockaddr * argument and other related stuff.
- To: <cygwin at cygwin dot com>
- Subject: BUG - 1.3.n accept fails if NULL sockaddr * argument and other related stuff.
- From: "Mike Thomas" <miketh at brisbane dot paradigmgeo dot com>
- Date: Wed, 1 Aug 2001 13:25:29 +1000
- Cc: "Andreas. Lange" <Andreas dot Lange at Rhein-Main dot de>, "Glynn Clements" <glynn dot clements at virgin dot net>
Hi there.
The following function (open source GIS package GRASS) dies when accept
is called. Replacing the NULL argument with a valid pointer stopped the
crash. I am told that "accept()" should be able to deal with a NULL
argument - certainly this code works on several Unices.
----------------------------------------------------------------------------
----------------------
/* -----------------------------------------------------------------------
* G_sock_accept (int sockfd):
* Wrapper around the accept() function. No client info is returned, but
* that's not generally useful for local sockets anyway. Function returns
* the file descriptor or an error code generated by accept(). Note,
* this call will usually block until a connection arrives. You can use
* select() for a time out on the call.
* ---------------------------------------------------------------------*/
int
G_sock_accept (int sockfd)
{
return accept (sockfd, (struct sockaddr *) NULL, NULL);
}
------------------------------------------------------------------------------------------------
Looking at the Cygwin source below, I see that if the length argument is too small
it is corrected, but no similar check is made for the argument "peer".
------------------------------------------------------------------------------------------------
cygwin_accept (int fd, struct sockaddr *peer, int *len)
{
int res = -1;
BOOL secret_check_failed = FALSE;
BOOL in_progress = FALSE;
sigframe thisframe (mainthread);
fhandler_socket *sock = get (fd);
if (sock)
{
/* accept on NT fails if len < sizeof (sockaddr_in)
* some programs set len to
* sizeof (name.sun_family) + strlen (name.sun_path) for UNIX domain
*/
if (len && ((unsigned) *len < sizeof (struct sockaddr_in)))
*len = sizeof (struct sockaddr_in);
res = accept (sock->get_socket (), peer, len); // can't use a blocking call inside a lock
---------------------------------------------
---------------------------------------------------
QUESTION:
Is the "accept()" call inside "cygwin_accept()" the winsock.dll "accept()"?
OTHER ISSUES:
I point these two out for attention from the Cygwin experts on socket
implementation.
1. socket.h does not include a type "socklen_t" which is apparently defined
on some Unix platforms.
2. Although not relevant to the code above, I noticed while looking in
socket.h and friends that Cygwin provides sockaddr and sockaddr_un, which
differ in terms of how much space is made for the name of the socket. The
sockaddr member sa_data is only very short (14 bytes, compared to
UNIX_PATH_LEN for the sun_path member of sockaddr_un) which would not
suffice for a long file name. Unfortunately accept is defined in terms of
sockaddr rather than sockaddr_un which could potentially cause string
overwrites.
Cheers
Mike Thomas.
--
Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
Bug reporting: http://cygwin.com/bugs.html
Documentation: http://cygwin.com/docs.html
FAQ: http://cygwin.com/faq/