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Ignore TCP dispatches that have zero references

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The TCP dispatches are removed from the dispatchmgr->list in the
dispatch_destroy() and there's a brief period of time where
dns_dispatch_gettcp() can find a dispatch in connected state that's
being destroyed.

Set the dispatch state to DNS_DISPATCHSTATE_NONE in the TCP connection
callback if there are no responses waiting, and ignore TCP dispatches
with zero references in dns_dispatch_gettcp().
This commit is contained in:
Ondřej Surý 2022-12-20 06:11:26 +01:00
parent 90cd14f620
commit 3fac4ca57e
No known key found for this signature in database
GPG key ID: 2820F37E873DEA41
1 changed files with 38 additions and 26 deletions
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64
lib/dns/dispatch.c
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@ -764,6 +764,7 @@ tcp_recv_shutdown(dns_dispatch_t *disp, dns_displist_t *resps,
next = ISC_LIST_NEXT(resp, alink);
tcp_recv_add(resps, resp, result);
}
disp->state = DNS_DISPATCHSTATE_CANCELED;
}
static void
@ -1258,34 +1259,42 @@ dns_dispatch_gettcp(dns_dispatchmgr_t *mgr, const isc_sockaddr_t *destaddr,
* 2. destination address is same
* 3. local address is either NULL or same
*/
if (disp->socktype == isc_socktype_tcp &&
isc_sockaddr_equal(destaddr, &peeraddr) &&
(localaddr == NULL ||
isc_sockaddr_eqaddr(localaddr, &sockname)))
if (disp->socktype != isc_socktype_tcp ||
!isc_sockaddr_equal(destaddr, &peeraddr) ||
(localaddr != NULL &&
!isc_sockaddr_eqaddr(localaddr, &sockname)))
{
switch (disp->state) {
case DNS_DISPATCHSTATE_NONE:
/* Dispatch in indeterminate state, skip it */
UNLOCK(&disp->lock);
continue;
}
switch (disp->state) {
case DNS_DISPATCHSTATE_NONE:
/* A dispatch in indeterminate state, skip it */
break;
case DNS_DISPATCHSTATE_CONNECTED:
if (ISC_LIST_EMPTY(disp->active)) {
/* Ignore dispatch with no responses */
break;
case DNS_DISPATCHSTATE_CONNECTED:
/* We found a connected dispatch */
dns_dispatch_attach(disp, &disp_connected);
break;
case DNS_DISPATCHSTATE_CONNECTING:
/* We found "a" dispatch, store it for later */
if (disp_fallback == NULL) {
dns_dispatch_attach(disp,
&disp_fallback);
}
break;
case DNS_DISPATCHSTATE_CANCELED:
/*
* We found a canceled dispatch, skip it.
*/
break;
default:
UNREACHABLE();
}
/* We found a connected dispatch */
dns_dispatch_attach(disp, &disp_connected);
break;
case DNS_DISPATCHSTATE_CONNECTING:
if (ISC_LIST_EMPTY(disp->pending)) {
/* Ignore dispatch with no responses */
break;
}
/* We found "a" dispatch, store it for later */
if (disp_fallback == NULL) {
dns_dispatch_attach(disp, &disp_fallback);
}
break;
case DNS_DISPATCHSTATE_CANCELED:
/* A canceled dispatch, skip it. */
break;
default:
UNREACHABLE();
}
UNLOCK(&disp->lock);
@ -1879,7 +1888,10 @@ tcp_connected(isc_nmhandle_t *handle, isc_result_t eresult, void *arg) {
LOCK(&disp->lock);
INSIST(disp->state == DNS_DISPATCHSTATE_CONNECTING);
if (eresult == ISC_R_SUCCESS) {
if (ISC_LIST_EMPTY(disp->pending)) {
/* All responses have been canceled */
disp->state = DNS_DISPATCHSTATE_CANCELED;
} else if (eresult == ISC_R_SUCCESS) {
disp->state = DNS_DISPATCHSTATE_CONNECTED;
tcp_startrecv(handle, disp, resp);
} else {