From 1294de8e360c29e038fdc6d8d23c435c802ea491 Mon Sep 17 00:00:00 2001
From: Aram Sargsyan <aram@isc.org>
Date: Fri, 1 Apr 2022 13:12:40 +0000
Subject: [PATCH] Fix dig hanging issue in cases when the lookup's next query
 can't start

In recv_done(), when dig decides to start the lookup's next query in
the line using `start_udp()` or `start_tcp()`, and for some reason,
no queries get started, dig doesn't cancel the lookup.

This can occur, for example, when there are two queries in the lookup,
one with a regular IP address, and another with a IPv4 mapped IPv6
address. When the regular IP address fails to serve the query, its
`recv_done()` callback starts the next query in the line (in this
case the one with a mapped IP address), but because `dig` doesn't
connect to such IP addresses, and there are no other queries in the
list, no new queries are being started, and the lookup keeps hanging.

After calling `start_udp()` or `start_tcp()` in `recv_done()`, check
if there are no pending/working queries then cancel the lookup instead
of only detaching from the current query.

(cherry picked from commit 7e2f50c36958f8c98d54e6d131f088a4837ce269)
---
 bin/dig/dighost.c                 | 15 +++++++++++++++
 bin/tests/system/digdelv/tests.sh | 10 ++++++++++
 2 files changed, 25 insertions(+)

diff --git a/bin/dig/dighost.c b/bin/dig/dighost.c
index 2556f25ac8..627ad61b5b 100644
--- a/bin/dig/dighost.c
+++ b/bin/dig/dighost.c
@@ -3691,6 +3691,9 @@ recv_done(isc_nmhandle_t *handle, isc_result_t eresult, isc_region_t *region,
 				      l->retries);
 				start_udp(newq);
 			}
+			if (check_if_queries_done(l, query)) {
+				goto cancel_lookup;
+			}
 
 			goto detach_query;
 		} else if (l->retries > 1 && l->tcp_mode) {
@@ -3727,6 +3730,10 @@ recv_done(isc_nmhandle_t *handle, isc_result_t eresult, isc_region_t *region,
 						start_udp(next);
 					}
 				}
+				if (check_if_queries_done(l, query)) {
+					goto cancel_lookup;
+				}
+
 				goto detach_query;
 			}
 
@@ -3768,6 +3775,10 @@ recv_done(isc_nmhandle_t *handle, isc_result_t eresult, isc_region_t *region,
 					start_udp(next);
 				}
 			}
+			if (check_if_queries_done(l, query)) {
+				goto cancel_lookup;
+			}
+
 			goto detach_query;
 		}
 
@@ -4044,6 +4055,10 @@ recv_done(isc_nmhandle_t *handle, isc_result_t eresult, isc_region_t *region,
 						 ? "SERVFAIL reply"
 						 : "recursion not available",
 					 query->servname);
+			if (check_if_queries_done(l, query)) {
+				goto cancel_lookup;
+			}
+
 			goto detach_query;
 		}
 	}
diff --git a/bin/tests/system/digdelv/tests.sh b/bin/tests/system/digdelv/tests.sh
index 2e735c66ea..05ee710522 100644
--- a/bin/tests/system/digdelv/tests.sh
+++ b/bin/tests/system/digdelv/tests.sh
@@ -1071,6 +1071,16 @@ if [ -x "$DIG" ] ; then
   grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
   if [ $ret -ne 0 ]; then echo_i "failed"; fi
   status=$((status+ret))
+
+  # See [GL #3248] for more information
+  n=$((n+1))
+  echo_i "check that dig correctly refuses to use a server with a IPv4 mapped IPv6 address after failing with a regular IP address ($n)"
+  ret=0
+  dig_with_opts @10.53.0.8 @::ffff:10.53.0.8 a.example > dig.out.test$n 2>&1 || ret=1
+  grep -F ";; Skipping mapped address" dig.out.test$n > /dev/null || ret=1
+  grep -F ";; No acceptable nameservers" dig.out.test$n > /dev/null || ret=1
+  if [ $ret -ne 0 ]; then echo_i "failed"; fi
+  status=$((status+ret))
 else
   echo_i "$DIG is needed, so skipping these dig tests"
 fi