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Re: [Qemu-devel] [PATCH] Proposed fix broken RST response to a slirp red
From: |
Edgar E. Iglesias |
Subject: |
Re: [Qemu-devel] [PATCH] Proposed fix broken RST response to a slirp redirect socket |
Date: |
Wed, 11 Jun 2008 21:37:12 +0200 |
User-agent: |
Mutt/1.5.16 (2007-06-09) |
On Wed, Jun 11, 2008 at 08:07:39PM +0200, Edgar E. Iglesias wrote:
> On Wed, Jun 11, 2008 at 12:21:45PM -0500, Jason Wessel wrote:
> >
> > When using slirp networking with a redirected tcp socket, the qemu guest
> > os does not receive RST packets when a redirected, accepted socket goes
> > into the FIN_WAIT_2 status. Presently slirp sends ACKs instead of RST
> > packets, which means the guest os application socket writes do not fail
> > event after the client has terminated the socket.
> >
> > Here is a simple way to demonstrate the problem.
> >
> > * Start qemu with user mode networking plus:
> > -redir tcp:4441::4441
> >
> > * Assuming you booted a linux guest os you could run:
> > cat /dev/zero | nc -p 4441 -l
> >
> > * On the host run the following command and you
> > must hit control-c after about 1 second
> > nc localhost 4441
>
> Hello Jason,
>
> IIRC connections in FIN_WAIT_2 can continue to receive data.
>
> If I might take a wild guess at whats going on:
> The host closed the receiving socket when you ctrl-c nc. That socket still has
> data in it's rcvbuf so the stack aborts the connection and sends a RST. The
> slirp code should now see a -1 on it's next write to that socket and an errno
> ECONNRESET but it's not correctly taking care of that case, instead it's
> incorrectly setting the TCP state to FIN_WAIT_2. It should have set it to
> CLOSED and sent a RST to the guest.
Heh, that guess wasn't entirely correct...
Anyway, here is a patch that hopefully helps.
Best regards
--
Edgar E. Iglesias
Axis Communications AB
diff --git a/slirp/socket.c b/slirp/socket.c
index 75003af..2a459a1 100644
--- a/slirp/socket.c
+++ b/slirp/socket.c
@@ -165,9 +165,21 @@ soread(so)
if (nn < 0 && (errno == EINTR || errno == EAGAIN))
return 0;
else {
+ int err;
+ socklen_t slen;
+
+ err = errno;
+ if (nn == 0)
+ getsockopt(so->s, SOL_SOCKET, SO_ERROR,
+ &err, &slen);
+
DEBUG_MISC((dfd, " --- soread() disconnected, nn = %d,
errno = %d-%s\n", nn, errno,strerror(errno)));
sofcantrcvmore(so);
- tcp_sockclosed(sototcpcb(so));
+ if (err == ECONNRESET
+ || err == ENOTCONN || err == EPIPE)
+ tcp_drop(sototcpcb(so), err);
+ else
+ tcp_sockclosed(sototcpcb(so));
return -1;
}
}