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[master] Prevent dig INSIST failures and hangs in some failure modes

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4756.	[bug]		Interrupting dig could lead to an INSIST failure after
			certain errors were encountered while querying a host
			whose name resolved to more than one address.  Change
			4537 increased the odds of triggering this issue by
			causing dig to hang indefinitely when certain error
			paths were evaluated.  dig now also retries TCP queries
			(once) if the server gracefully closes the connection
			before sending a response. [RT #42832, #45159]
This commit is contained in:
Michał Kępień 2017-10-05 09:42:31 +02:00
parent d7ee3ed488
commit 14afc8425b
3 changed files with 34 additions and 3 deletions
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9
CHANGES
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@ -1,3 +1,12 @@
4756. [bug] Interrupting dig could lead to an INSIST failure after
certain errors were encountered while querying a host
whose name resolved to more than one address. Change
4537 increased the odds of triggering this issue by
causing dig to hang indefinitely when certain error
paths were evaluated. dig now also retries TCP queries
(once) if the server gracefully closes the connection
before sending a response. [RT #42832, #45159]
4755. [cleanup] Silence unnecessary log message when NZF file doesn't
exist. [RT #46186]

27
bin/dig/dighost.c
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@ -646,6 +646,7 @@ make_empty_lookup(void) {
looknew->mapped = ISC_TRUE;
looknew->dscp = -1;
looknew->rrcomments = 0;
looknew->eoferr = 0;
dns_fixedname_init(&looknew->fdomain);
ISC_LINK_INIT(looknew, link);
ISC_LIST_INIT(looknew->q);
@ -737,6 +738,7 @@ clone_lookup(dig_lookup_t *lookold, isc_boolean_t servers) {
looknew->done_as_is = lookold->done_as_is;
looknew->dscp = lookold->dscp;
looknew->rrcomments = lookold->rrcomments;
looknew->eoferr = lookold->eoferr;
if (lookold->ecs_addr != NULL) {
size_t len = sizeof(isc_sockaddr_t);
@ -2775,9 +2777,12 @@ send_udp(dig_query_t *query) {
next = ISC_LIST_NEXT(query, link);
l = query->lookup;
clear_query(query);
if (next == NULL)
if (next == NULL) {
printf(";; No acceptable nameservers\n");
check_next_lookup(l);
check_next_lookup(l);
} else {
send_udp(next);
}
return;
}
@ -2909,7 +2914,7 @@ tcp_length_done(isc_task_t *task, isc_event_t *event) {
isc_buffer_t *b = NULL;
isc_result_t result;
dig_query_t *query = NULL;
dig_lookup_t *l;
dig_lookup_t *l, *n;
isc_uint16_t length;
REQUIRE(event->ev_type == ISC_SOCKEVENT_RECVDONE);
@ -2944,13 +2949,20 @@ tcp_length_done(isc_task_t *task, isc_event_t *event) {
sizeof(sockstr));
printf(";; communications error to %s: %s\n",
sockstr, isc_result_totext(sevent->result));
if (keep != NULL)
isc_socket_detach(&keep);
l = query->lookup;
isc_socket_detach(&query->sock);
sockcount--;
debug("sockcount=%d", sockcount);
INSIST(sockcount >= 0);
if (sevent->result == ISC_R_EOF && l->eoferr == 0U) {
n = requeue_lookup(l, ISC_TRUE);
n->eoferr++;
}
isc_event_free(&event);
clear_query(query);
cancel_lookup(l);
check_next_lookup(l);
UNLOCK_LOOKUP;
return;
@ -3443,13 +3455,20 @@ recv_done(isc_task_t *task, isc_event_t *event) {
} else {
printf(";; communications error: %s\n",
isc_result_totext(sevent->result));
if (keep != NULL)
isc_socket_detach(&keep);
isc_socket_detach(&query->sock);
sockcount--;
debug("sockcount=%d", sockcount);
INSIST(sockcount >= 0);
}
if (sevent->result == ISC_R_EOF && l->eoferr == 0U) {
n = requeue_lookup(l, ISC_TRUE);
n->eoferr++;
}
isc_event_free(&event);
clear_query(query);
cancel_lookup(l);
check_next_lookup(l);
UNLOCK_LOOKUP;
return;
@ -3511,6 +3530,7 @@ recv_done(isc_task_t *task, isc_event_t *event) {
if (fail) {
isc_event_free(&event);
clear_query(query);
cancel_lookup(l);
check_next_lookup(l);
UNLOCK_LOOKUP;
return;
@ -3614,6 +3634,7 @@ recv_done(isc_task_t *task, isc_event_t *event) {
if (l->tcp_mode) {
isc_event_free(&event);
clear_query(query);
cancel_lookup(l);
check_next_lookup(l);
UNLOCK_LOOKUP;
return;

1
bin/dig/include/dig/dig.h
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@ -168,6 +168,7 @@ struct dig_lookup {
unsigned int ednsflags;
dns_opcode_t opcode;
int rrcomments;
unsigned int eoferr;
};
/*% The dig_query structure */