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Give no answer, not NOTIMPL, for unsupported DNS query types

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According to reports, most programs degrade somewhat gracefully on
getting no answer for an MX or a CERT for www.example.com, but many
flip out completely on a NOTIMPL error.

Also, treat a QTYPE_ALL query as just asking for an A record.

The real fix here is to implement proposal 219 or something like it.

Fixes bug 10268; bugfix on 0.2.0.1-alpha.

Based on a patch from "epoch".
This commit is contained in:
Nick Mathewson 2014-04-07 22:03:19 -04:00
parent bc0882c868
commit 6d0991ea08
2 changed files with 25 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
changes/bug10268 Normal file
View File

@ -0,0 +1,6 @@
o Minor bugfixes:
- When receing a DNS query for an unsupported type, reply with
no answer rather than with a NOTIMPL error. This behavior isn't
correct either, but it will break fewer client programs, we hope.
Fixes bug 10268; bugfix on 0.2.0.1-alpha. Original patch
from "epoch".

29
src/or/dnsserv.c
View File

@ -35,7 +35,7 @@ evdns_server_callback(struct evdns_server_request *req, void *data_)
entry_connection_t *entry_conn;
edge_connection_t *conn;
int i = 0;
struct evdns_server_question *q = NULL;
struct evdns_server_question *q = NULL, *supported_q = NULL;
struct sockaddr_storage addr;
struct sockaddr *sa;
int addrlen;
@ -87,31 +87,37 @@ evdns_server_callback(struct evdns_server_request *req, void *data_)
for (i = 0; i < req->nquestions; ++i) {
if (req->questions[i]->dns_question_class != EVDNS_CLASS_INET)
continue;
if (! q)
q = req->questions[i];
switch (req->questions[i]->type) {
case EVDNS_TYPE_A:
case EVDNS_TYPE_AAAA:
case EVDNS_TYPE_PTR:
q = req->questions[i];
/* We always pick the first one of these questions, if there is
one. */
if (! supported_q)
supported_q = q;
break;
default:
break;
}
}
if (supported_q)
q = supported_q;
if (!q) {
log_info(LD_APP, "None of the questions we got were ones we're willing "
"to support. Sending NOTIMPL.");
evdns_server_request_respond(req, DNS_ERR_NOTIMPL);
return;
}
if (q->type != EVDNS_TYPE_A && q->type != EVDNS_TYPE_AAAA) {
tor_assert(q->type == EVDNS_TYPE_PTR);
}
/* Make sure the name isn't too long: This should be impossible, I think. */
if (err == DNS_ERR_NONE && strlen(q->name) > MAX_SOCKS_ADDR_LEN-1)
err = DNS_ERR_FORMAT;
if (err != DNS_ERR_NONE) {
/* We got an error? Then send back an answer immediately; we're done. */
if (err != DNS_ERR_NONE || !supported_q) {
/* We got an error? There's no question we're willing to answer? Then
* send back an answer immediately; we're done. */
evdns_server_request_respond(req, err);
return;
}
@ -126,12 +132,15 @@ evdns_server_callback(struct evdns_server_request *req, void *data_)
TO_CONN(conn)->port = port;
TO_CONN(conn)->address = tor_dup_addr(&tor_addr);
if (q->type == EVDNS_TYPE_A || q->type == EVDNS_TYPE_AAAA)
if (q->type == EVDNS_TYPE_A || q->type == EVDNS_TYPE_AAAA ||
q->type == EVDNS_QTYPE_ALL) {
entry_conn->socks_request->command = SOCKS_COMMAND_RESOLVE;
else
} else {
tor_assert(q->type == EVDNS_TYPE_PTR);
entry_conn->socks_request->command = SOCKS_COMMAND_RESOLVE_PTR;
}
if (q->type == EVDNS_TYPE_A) {
if (q->type == EVDNS_TYPE_A || q->type == EVDNS_QTYPE_ALL) {
entry_conn->ipv4_traffic_ok = 1;
entry_conn->ipv6_traffic_ok = 0;
entry_conn->prefer_ipv6_traffic = 0;