- For #1301: configure cant find SSL_is_quic in OpenSSL 3.5.1.

configure

@@ -22560,6 +22560,10 @@ then :
 fi
 
 
+    # these check_funcs need -lssl
+    BAKLIBS="$LIBS"
+    LIBS="-lssl $LIBS"
+
   for ac_func in SSL_is_quic
 do :
   ac_fn_c_check_func "$LINENO" "SSL_is_quic" "ac_cv_func_SSL_is_quic"
@@ -22572,6 +22576,8 @@ else $as_nop
 fi
 
 done
+    LIBS="$BAKLIBS"
+
     ac_fn_c_check_type "$LINENO" "struct ngtcp2_version_cid" "ac_cv_type_struct_ngtcp2_version_cid" "$ac_includes_default
     #include <ngtcp2/ngtcp2.h>
 

configure.ac

@@ -1626,7 +1626,13 @@ if test x_$withval = x_yes -o x_$withval != x_no; then
 	])
     ])
     AC_CHECK_FUNCS([ngtcp2_crypto_encrypt_cb ngtcp2_ccerr_default ngtcp2_conn_in_closing_period ngtcp2_conn_in_draining_period ngtcp2_conn_get_max_local_streams_uni ngtcp2_crypto_quictls_from_ossl_encryption_level ngtcp2_crypto_quictls_configure_server_context ngtcp2_crypto_quictls_configure_client_context ngtcp2_crypto_quictls_init ngtcp2_conn_get_num_scid ngtcp2_conn_tls_early_data_rejected ngtcp2_conn_encode_0rtt_transport_params])
+
+    # these check_funcs need -lssl
+    BAKLIBS="$LIBS"
+    LIBS="-lssl $LIBS"
     AC_CHECK_FUNCS([SSL_is_quic], [], [AC_MSG_ERROR([No QUIC support detected in OpenSSL. Need OpenSSL version with QUIC support to enable DNS over QUIC with libngtcp2.])])
+    LIBS="$BAKLIBS"
+
     AC_CHECK_TYPES([struct ngtcp2_version_cid, ngtcp2_encryption_level],,,[AC_INCLUDES_DEFAULT
     #include <ngtcp2/ngtcp2.h>
     ])

doc/Changelog

@@ -1,5 +1,6 @@
 11 July 2025: Wouter
 	- Fix detection of SSL_CTX_set_tmp_ecdh function.
+	- For #1301: configure cant find SSL_is_quic in OpenSSL 3.5.1.
 
 8 July 2025: Wouter
 	- Fix to improve dnstap discovery on Fedora.