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Cancelation of TCP queries while they were still connecting was broken, and

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would cause seg faults.

Do not update the RTT if a query is being canceled due to internal failures.

Some servers generate badly formatted responses when they get an EDNS
query.  We were marking these servers as bad, but a more practical
solution is to retry without EDNS.  If a message fails to parse due to
DNS_R_FORMERR or DNS_R_UNEXPECTEDEND, and we were using EDNS, we now
retry the query without EDNS.

Add a "default" case to the message parsing error switch.  This prevents bad
things from happening if message parsing fails in a nontypical way.
This commit is contained in:
Bob Halley 1999-11-30 20:57:05 +00:00
parent d4539375e2
commit e7cdf5a35c
1 changed files with 147 additions and 48 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

195
lib/dns/resolver.c
View file

@ -106,6 +106,7 @@ typedef struct query {
dns_rdata_any_tsig_t *tsig;
dns_tsigkey_t *tsigkey;
unsigned int options;
unsigned int attributes;
unsigned char data[512];
} resquery_t;
@ -113,6 +114,14 @@ typedef struct query {
#define VALID_QUERY(query) ((query) != NULL && \
(query)->magic == QUERY_MAGIC)
#define RESQUERY_ATTR_CONNECTING 0x01
#define RESQUERY_ATTR_CANCELED 0x02
#define RESQUERY_CONNECTING(q) (((q)->attributes & \
RESQUERY_ATTR_CONNECTING) != 0)
#define RESQUERY_CANCELED(q) (((q)->attributes & \
RESQUERY_ATTR_CANCELED) != 0)
typedef enum {
fetchstate_init = 0, /* Start event has not run yet. */
fetchstate_active,
@ -260,58 +269,94 @@ fctx_stoptimer(fetchctx_t *fctx) {
}
}
static inline void
resquery_destroy(resquery_t **queryp) {
resquery_t *query;
REQUIRE(queryp != NULL);
query = *queryp;
REQUIRE(!ISC_LINK_LINKED(query, link));
query->magic = 0;
isc_mem_put(query->fctx->res->mctx, query, sizeof *query);
*queryp = NULL;
}
static void
fctx_cancelquery(resquery_t **queryp, dns_dispatchevent_t **deventp,
isc_time_t *finish)
isc_time_t *finish, isc_boolean_t no_response)
{
fetchctx_t *fctx;
resquery_t *query;
unsigned int rtt;
unsigned int factor;
isc_socket_t *socket;
query = *queryp;
fctx = query->fctx;
FCTXTRACE("cancelquery");
REQUIRE(!RESQUERY_CANCELED(query));
query->attributes |= RESQUERY_ATTR_CANCELED;
/*
* XXXRTH We don't want to set RTT in some cases (e.g. canceled due
* to client disinterest). Also, deal with dropped UDP datagram
* case. Don't improve RTT if this wasn't a measured time.
* Should we update the RTT?
*/
if (finish != NULL) {
rtt = (unsigned int)isc_time_microdiff(finish, &query->start);
factor = DNS_ADB_RTTADJDEFAULT;
} else {
/*
* We don't have an RTT for this query. Maybe the packet
* was lost, or maybe this server is very slow. We don't
* know. Increase the RTT.
*/
rtt = query->addrinfo->srtt + (100000 * fctx->restarts);
if (rtt > 10000000)
rtt = 10000000;
/*
* Replace the current RTT with our value.
*/
factor = DNS_ADB_RTTADJREPLACE;
if (finish != NULL || no_response) {
if (finish != NULL) {
/*
* We have both the start and finish times for this
* packet, so we can compute a real RTT.
*/
rtt = (unsigned int)isc_time_microdiff(finish,
&query->start);
factor = DNS_ADB_RTTADJDEFAULT;
} else {
/*
* We don't have an RTT for this query. Maybe the
* packet was lost, or maybe this server is very
* slow. We don't know. Increase the RTT.
*/
INSIST(no_response);
rtt = query->addrinfo->srtt +
(100000 * fctx->restarts);
if (rtt > 10000000)
rtt = 10000000;
/*
* Replace the current RTT with our value.
*/
factor = DNS_ADB_RTTADJREPLACE;
}
dns_adb_adjustsrtt(fctx->res->view->adb, query->addrinfo, rtt,
factor);
}
dns_adb_adjustsrtt(fctx->res->view->adb, query->addrinfo, rtt, factor);
if (query->dispentry != NULL)
dns_dispatch_removeresponse(query->dispatch, &query->dispentry,
deventp);
ISC_LIST_UNLINK(fctx->queries, query, link);
query->magic = 0;
if (query->tsig != NULL)
dns_rdata_freestruct(query->tsig);
if (RESQUERY_CONNECTING(query)) {
/*
* Cancel the connect.
*/
socket = dns_dispatch_getsocket(query->dispatch);
isc_socket_cancel(socket, NULL, ISC_SOCKCANCEL_CONNECT);
}
dns_dispatch_detach(&query->dispatch);
isc_mem_put(fctx->res->mctx, query, sizeof *query);
*queryp = NULL;
if (!RESQUERY_CONNECTING(query)) {
/*
* It's safe to destroy the query now.
*/
resquery_destroy(&query);
}
}
static void
fctx_cancelqueries(fetchctx_t *fctx) {
fctx_cancelqueries(fetchctx_t *fctx, isc_boolean_t no_response) {
resquery_t *query, *next_query;
FCTXTRACE("cancelqueries");
@ -320,7 +365,7 @@ fctx_cancelqueries(fetchctx_t *fctx) {
query != NULL;
query = next_query) {
next_query = ISC_LIST_NEXT(query, link);
fctx_cancelquery(&query, NULL, NULL);
fctx_cancelquery(&query, NULL, NULL, no_response);
}
}
@ -343,7 +388,7 @@ fctx_cleanupfinds(fetchctx_t *fctx) {
static inline void
fctx_stopeverything(fetchctx_t *fctx) {
FCTXTRACE("stopeverything");
fctx_cancelqueries(fctx);
fctx_cancelqueries(fctx, ISC_FALSE);
fctx_cleanupfinds(fctx);
fctx_stoptimer(fctx);
}
@ -411,7 +456,7 @@ resquery_senddone(isc_task_t *task, isc_event_t *event) {
(void)task;
if (sevent->result != ISC_R_SUCCESS)
fctx_cancelquery(&query, NULL, NULL);
fctx_cancelquery(&query, NULL, NULL, ISC_FALSE);
isc_event_free(&event);
}
@ -490,6 +535,7 @@ fctx_query(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo,
goto stop_timer;
}
query->options = options;
query->attributes = 0;
/*
* Note that the caller MUST guarantee that 'addrinfo' will remain
* valid until this query is canceled.
@ -561,6 +607,7 @@ fctx_query(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo,
task, resquery_connected, query);
if (result != ISC_R_SUCCESS)
goto cleanup_dispatch;
query->attributes |= RESQUERY_ATTR_CONNECTING;
QTRACE("connecting via TCP");
} else {
result = resquery_send(query);
@ -568,6 +615,8 @@ fctx_query(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo,
goto cleanup_dispatch;
}
ISC_LIST_APPEND(fctx->queries, query, link);
return (ISC_R_SUCCESS);
cleanup_dispatch:
@ -745,12 +794,6 @@ resquery_send(resquery_t *query) {
goto cleanup_message;
QTRACE("sent");
/*
* Finally, we've got everything going! XXXRTH move to
* fctx_query()!
*/
ISC_LIST_APPEND(fctx->queries, query, link);
return (ISC_R_SUCCESS);
cleanup_message:
@ -779,6 +822,7 @@ resquery_connected(isc_task_t *task, isc_event_t *event) {
isc_result_t result;
REQUIRE(event->type == ISC_SOCKEVENT_CONNECT);
REQUIRE(VALID_QUERY(query));
QTRACE("connected");
@ -792,12 +836,26 @@ resquery_connected(isc_task_t *task, isc_event_t *event) {
* up doing extra work!
*/
if (sevent->result == ISC_R_SUCCESS) {
result = resquery_send(query);
if (result != ISC_R_SUCCESS)
fctx_cancelquery(&query, NULL, NULL);
} else
fctx_cancelquery(&query, NULL, NULL);
query->attributes &= ~RESQUERY_ATTR_CONNECTING;
if (RESQUERY_CANCELED(query)) {
/*
* This query was canceled while the connect() was in
* progress.
*/
resquery_destroy(&query);
} else {
if (sevent->result == ISC_R_SUCCESS) {
/*
* We are connected. Send the query.
*/
result = resquery_send(query);
if (result != ISC_R_SUCCESS)
fctx_cancelquery(&query, NULL, NULL,
ISC_FALSE);
} else
fctx_cancelquery(&query, NULL, NULL, ISC_FALSE);
}
isc_event_free(&event);
}
@ -1095,7 +1153,7 @@ fctx_try(fetchctx_t *fctx) {
/*
* We have no more addresses. Start over.
*/
fctx_cancelqueries(fctx);
fctx_cancelqueries(fctx, ISC_TRUE);
fctx_cleanupfinds(fctx);
result = fctx_getaddresses(fctx);
if (result == DNS_R_WAIT) {
@ -2648,8 +2706,27 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
* server and we don't want to retry using
* TCP.
*/
broken_server = ISC_TRUE;
keep_trying = ISC_TRUE;
if ((query->options & DNS_FETCHOPT_NOEDNS0)
== 0) {
/*
* The problem might be that they
* don't understand EDNS0. Turn it
* off and try again.
*/
options |= DNS_FETCHOPT_NOEDNS0;
resend = ISC_TRUE;
/*
* Remember that they don't like EDNS0.
*/
dns_adb_changeflags(
fctx->res->view->adb,
query->addrinfo,
DNS_FETCHOPT_NOEDNS0,
DNS_FETCHOPT_NOEDNS0);
} else {
broken_server = ISC_TRUE;
keep_trying = ISC_TRUE;
}
goto done;
}
/*
@ -2659,12 +2736,34 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
truncated = ISC_TRUE;
break;
case DNS_R_FORMERR:
broken_server = ISC_TRUE;
keep_trying = ISC_TRUE;
if ((query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
/*
* The problem might be that they
* don't understand EDNS0. Turn it
* off and try again.
*/
options |= DNS_FETCHOPT_NOEDNS0;
resend = ISC_TRUE;
/*
* Remember that they don't like EDNS0.
*/
dns_adb_changeflags(fctx->res->view->adb,
query->addrinfo,
DNS_FETCHOPT_NOEDNS0,
DNS_FETCHOPT_NOEDNS0);
} else {
broken_server = ISC_TRUE;
keep_trying = ISC_TRUE;
}
goto done;
case DNS_R_MOREDATA:
result = DNS_R_NOTIMPLEMENTED;
goto done;
default:
/*
* Something bad has happened.
*/
goto done;
}
}
@ -2831,7 +2930,7 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
/*
* Cancel the query.
*/
fctx_cancelquery(&query, &devent, finish);
fctx_cancelquery(&query, &devent, finish, ISC_FALSE);
if (keep_trying) {
if (result == DNS_R_FORMERR)
@ -2894,7 +2993,7 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
fctx_done(fctx, DNS_R_SERVFAIL);
return;
}
fctx_cancelqueries(fctx);
fctx_cancelqueries(fctx, ISC_TRUE);
fctx_cleanupfinds(fctx);
}
/*
@ -2914,7 +3013,7 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
* All has gone well so far, but we are waiting for the
* DNSSEC validator to validate the answer.
*/
fctx_cancelqueries(fctx);
fctx_cancelqueries(fctx, ISC_TRUE);
result = fctx_stopidletimer(fctx);
if (result != ISC_R_SUCCESS)
fctx_done(fctx, result);