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chardev: disallow TLS/telnet/websocket with tcp_chr_wait_connected

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In the previous commit

    commit 1dc8a6695c
    Author: Marc-André Lureau <marcandre.lureau@redhat.com>
    Date:   Tue Aug 16 12:33:32 2016 +0400

      char: fix waiting for TLS and telnet connection

the tcp_chr_wait_connected() method was changed to check for a non-NULL
's->ioc' as a sign that there is already a connection present, as
opposed to checking the "connected" flag to supposedly fix handling of
TLS/telnet connections.

The original code would repeatedly call tcp_chr_wait_connected creating
many connections as 'connected' would never become true. The changed
code would still repeatedly call tcp_chr_wait_connected busy waiting
because s->ioc is set but the chardev will never see CHR_EVENT_OPENED.
IOW, the code is still broken with TLS/telnet, but in a different way.

Checking for a non-NULL 's->ioc' does not mean that a CHR_EVENT_OPENED
will be ready for a TLS/telnet connection. These protocols (and the
websocket protocol) all require the main loop to be running in order
to complete the protocol handshake before emitting CHR_EVENT_OPENED.
The tcp_chr_wait_connected() method is only used during early startup
before a main loop is running, so TLS/telnet/websock connections can
never complete initialization.

Making this work would require changing tcp_chr_wait_connected to run
a main loop. This is quite complex since we must not allow GSource's
that other parts of QEMU have registered to run yet. The current callers
of tcp_chr_wait_connected do not require use of the TLS/telnet/websocket
protocols, so the simplest option is to just forbid this combination
completely for now.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20190211182442.8542-14-berrange@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2019-02-11 18:24:39 +00:00 committed by Marc-André Lureau
parent 25d93b6a11
commit d1885e549d
1 changed files with 14 additions and 2 deletions
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16
chardev/char-socket.c
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@ -951,8 +951,20 @@ static void tcp_chr_accept_server_sync(Chardev *chr)
static int tcp_chr_wait_connected(Chardev *chr, Error **errp)
{
SocketChardev *s = SOCKET_CHARDEV(chr);
/* It can't wait on s->connected, since it is set asynchronously
* in TLS and telnet cases, only wait for an accepted socket */
const char *opts[] = { "telnet", "tn3270", "websock", "tls-creds" };
bool optset[] = { s->is_telnet, s->is_tn3270, s->is_websock, s->tls_creds };
size_t i;
QEMU_BUILD_BUG_ON(G_N_ELEMENTS(opts) != G_N_ELEMENTS(optset));
for (i = 0; i < G_N_ELEMENTS(opts); i++) {
if (optset[i]) {
error_setg(errp,
"'%s' option is incompatible with waiting for "
"connection completion", opts[i]);
return -1;
}
}
while (!s->ioc) {
if (s->is_listen) {
tcp_chr_accept_server_sync(chr);