From: | Bruce Momjian <bruce(at)momjian(dot)us> |
---|---|
To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
Cc: | Joel Jacobson <joel(at)trustly(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [BUG FIX] Compare returned value by socket() against PGINVALID_SOCKET instead of < 0 |
Date: | 2014-04-08 18:02:51 |
Message-ID: | 20140408180251.GA8685@momjian.us |
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Thread: | |
Lists: | pgsql-hackers |
On Sun, Apr 6, 2014 at 11:45:59AM +0530, Amit Kapila wrote:
> On Tue, Apr 1, 2014 at 6:31 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > I reviewed this patch and you are correct that we are not handling
> > socket() and accept() returns properly on Windows. We were doing it
> > properly in most place in the backend, but your patch fixes the
> > remaining places:
> >
> > http://msdn.microsoft.com/en-us/library/windows/desktop/ms740516%28v=vs.85%29.aspx
> >
> > However, libpq doesn't seem to be doing much to handle Windows properly
> > in this area. I have adjusted libpq to map socket to -1, but the proper
> > fix is to distribute pgsocket and PGINVALID_SOCKET checks throughout the
> > libpq code. I am not sure how to handle PQsocket() --- should it still
> > return -1?
>
> I think changing PQsocket() can impact all existing applications as
> it is mentioned in docs that "result of -1 indicates that no server
> connection is currently open.". Do you see any compelling need to
> change return value of PQSocket() after your patch?
No, I do not. In fact, the SSL_get_fd() call in secure_read() returns a
signed integer too, and that is passed around like a socket, so in fact
the SSL API doesn't even allow us to get an unsigned value on Windows in
all cases.
> > Having the return value be conditional on the operating
> > system is ugly. How much of this should be backpatched?
>
> I think it's okay to back patch all the changes.
> Is there any part in patch which you feel is risky to back patch?
Well, we would not backpatch this if it is just a stylistic fix, and I
am starting to think it just a style issue. This MSDN website says -1,
SOCKET_ERROR, and INVALID_SOCKET are very similar:
http://msdn.microsoft.com/en-us/library/windows/desktop/cc507522%28v=vs.85%29.aspx
and this Stackoverflow thread says the same:
http://stackoverflow.com/questions/10817252/why-is-invalid-socket-defined-as-0-in-winsock2-h-c
In fact, this C program compiled by gcc on Debian issues no compiler
warnings and returns 'hello', showing that -1 and ~0 compare as equal:
int
main(int argc, char **argv)
{
int i;
unsigned int j;
i = -1;
j = ~0;
if (i == j)
printf("hello\n");
return 0;
}
meaning our incorrect syntax is computed correctly.
> > Why aren't we
> > getting warnings on Windows about assigning the socket() return value to
> > an integer?
>
> I think by default Windows doesn't give warning for such code even at Warning
> level 4. I have found one related link:
> http://stackoverflow.com/questions/75385/make-vs-compiler-catch-signed-unsigned-assignments
>
> > Updated patch attached.
>
> It seems you have missed to change at below places.
>
> 1.
> int
> pg_foreach_ifaddr(PgIfAddrCallback callback, void *cb_data)
> sock = WSASocket(AF_INET, SOCK_DGRAM, 0, 0, 0, 0);
> if (sock == SOCKET_ERROR)
Well, the actual problem here is that WSASocket() returns INVALID_SOCKET
per the documentation, not SOCKET_ERROR. I did not use PGINVALID_SOCKET
here because this is Windows-specific code, defining 'sock' as SOCKET.
We could have sock defined as pgsocket, but because this is Windows code
already, it doesn't seem wise to mix portability code in there.
> 2.
> pgwin32_waitforsinglesocket(SOCKET s, int what, int timeout)
> {
> static HANDLE waitevent = INVALID_HANDLE_VALUE;
> static SOCKET current_socket = -1;
Yes, that -1 is wrong and I have changed it to INVALID_SOCKET, again
using the same rules that say PGINVALID_SOCKET doesn't make sense here
as it is Windows-specific code.
I am attaching an updated patch, which explains the PQsocket() return
value issue, and fixes the items listed above. I am inclined to apply
this just to head for correctness, and modify libpq to use pgsocket
consistently in a follow-up patch.
This is not like the readdir() fix we had to backpatch because that was
clearly not catching errors.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
Attachment | Content-Type | Size |
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socket.diff | text/x-diff | 9.8 KB |
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