On Sun, Dec 30, 2012 at 07:11:28PM -0300, Jorge Arellano Cid wrote:
Hi,
On Sat, Dec 29, 2012 at 05:44:22AM +0400, p37sitdu at lavabit.com wrote:
On Thu, Dec 27, 2012 at 04:37:36PM -0300, Jorge Arellano Cid wrote:
As from the patch you sent (same as before), and the explanation you give (ignoring my explanation), I guess you're making conclusions out of reading the code in Dpi_connect_socket() *only*.
I made conclusions from reading Dpi_connect_socket() only, because in the case of error in Dpi_blocking_write file descriptor is left open and not passed anywhere else. If it was passed somewhere else, I would read the code there and check if file descriptor was closed there.
Have you checked what you state as fact? (i.e. that the FD is leaked and not closed by the CCC). FWIW, I did check before writing my previous answer.
Patch that I did for checking is attached. It replaces Dpi_blocking_write call with -1 to simulate fault in Dpi_blocking_write for Dpi_connect_socket().
Introducing the error in Dpi_blocking_write for all functions doesn't work, in this case Dpi_connect_socket is not called at all (because Dpi_start_dpid fails).
With this patch applied, I recompiled dillo and pressed "bookmarks" button several times to trigger dpi code. Each time I pressed "bookmarks" button, new descriptor was leaked:
% ls /proc/$(pidof dillo)/fd 0 1 2 3 4 5 % ls /proc/$(pidof dillo)/fd 0 1 2 3 4 5 6 % ls /proc/$(pidof dillo)/fd 0 1 2 3 4 5 6 % ls /proc/$(pidof dillo)/fd 0 1 2 3 4 5 6 7 % ls /proc/$(pidof dillo)/fd 0 1 2 3 4 5 6 7 8
Then I applied the patch I sent before (with hg qpush) on top of the fault patch and rebuilt dillo: "make clean && make". I ran dillo again with ./src/dillo and did the same test with bookmarks button:
% ls /proc/$(pidof dillo)/fd 0 1 2 3 4 5 % ls /proc/$(pidof dillo)/fd 0 1 2 3 4 5 % ls /proc/$(pidof dillo)/fd 0 1 2 3 4 5
diff -r 8e10859b2aab src/IO/dpi.c --- a/src/IO/dpi.c +++ b/src/IO/dpi.c @@ -641,7 +641,7 @@ /* send authentication Key (the server closes sock_fd on error) */ } else if (!(cmd = a_Dpip_build_cmd("cmd=%s msg=%s", "auth", SharedKey))) { MSG_ERR("[Dpi_connect_socket] Can't make auth message.\n"); - } else if (Dpi_blocking_write(sock_fd, cmd, strlen(cmd)) == -1) { + } else if (-1 == -1) { MSG_ERR("[Dpi_connect_socket] Can't send auth message.\n"); } else { ret = sock_fd;
Ah, OK, now I see what you mean.
There's a semantic ambiguity, the comment:
/* send authentication Key (the server closes sock_fd on error) */
means: "if there's an error with the authentication" (I know because I wrote the comment).
(and as the patch removed this comment) I made the same test but with:
- } else if (!(cmd = a_Dpip_build_cmd("cmd=%s msg=%s", "auth", SharedKey))) { + } else if (!(cmd = a_Dpip_build_cmd("cmd=%s msg=%s","auth",SharedKey+1))) {
and the CCC closes the file descriptor as expected.
The error case you noticed exists, and although highly unlikely to happen, requires some thought. As from the test above, the socket is connected, then nothing is written to simulate an error, but the OS never sees an error, as it doesn't exist, and doesn't notify either end (IOW, it leaves the socket passively expecting for data to come).
Now, the canonical way to handle the whole process should have been to build the CCC upon connect(), then try to authenticate, and let the CCC handle any errors that may come, but this is probably too much code for little gain, so it was all coded in Dpi_connect_socket().
The problem with closing FDs outside the CCC is that it can introduce race conditions, but in this case the CCC is partially built, so your patch suggestion may be OK.
I'll have to give it some more thought and tests...
OK, just committed a slightly modified and bigger patch that also corrects the wrong error error message given (CCC side). Please check how it works, and send feedback. -- Cheers Jorge.-