Allow --with-bonjour to work with non-macOS implementations of Bonjour.

On macOS the relevant functions require no special library, but elsewhere
we need to pull in libdns_sd.

Back-patch to supported branches.  No docs change since the docs do not
suggest that this is a Mac-only feature.

Luke Lonergan

Discussion: https://postgr.es/m/2D8331C5-D64F-44C1-8717-63EDC6EAF7EB@brightforge.com

configure

@@ -11124,6 +11124,64 @@ else
 fi
 
 
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing DNSServiceRefSockFD" >&5
+$as_echo_n "checking for library containing DNSServiceRefSockFD... " >&6; }
+if ${ac_cv_search_DNSServiceRefSockFD+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char DNSServiceRefSockFD ();
+int
+main ()
+{
+return DNSServiceRefSockFD ();
+  ;
+  return 0;
+}
+_ACEOF
+for ac_lib in '' dns_sd; do
+  if test -z "$ac_lib"; then
+    ac_res="none required"
+  else
+    ac_res=-l$ac_lib
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+  fi
+  if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_search_DNSServiceRefSockFD=$ac_res
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext
+  if ${ac_cv_search_DNSServiceRefSockFD+:} false; then :
+  break
+fi
+done
+if ${ac_cv_search_DNSServiceRefSockFD+:} false; then :
+
+else
+  ac_cv_search_DNSServiceRefSockFD=no
+fi
+rm conftest.$ac_ext
+LIBS=$ac_func_search_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_DNSServiceRefSockFD" >&5
+$as_echo "$ac_cv_search_DNSServiceRefSockFD" >&6; }
+ac_res=$ac_cv_search_DNSServiceRefSockFD
+if test "$ac_res" != no; then :
+  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+
+else
+  as_fn_error $? "could not find function 'DNSServiceRefSockFD' required for Bonjour" "$LINENO" 5
+fi
+
 fi
 
 # for contrib/uuid-ossp

configure.in

@@ -1061,8 +1061,8 @@ if test "$with_openssl" = yes ; then
      AC_CHECK_LIB(crypto, CRYPTO_new_ex_data, [], [AC_MSG_ERROR([library 'crypto' is required for OpenSSL])])
      AC_CHECK_LIB(ssl,    SSL_new, [], [AC_MSG_ERROR([library 'ssl' is required for OpenSSL])])
   else
-     AC_SEARCH_LIBS(CRYPTO_new_ex_data, eay32 crypto, [], [AC_MSG_ERROR([library 'eay32' or 'crypto' is required for OpenSSL])])
-     AC_SEARCH_LIBS(SSL_new, ssleay32 ssl, [], [AC_MSG_ERROR([library 'ssleay32' or 'ssl' is required for OpenSSL])])
+     AC_SEARCH_LIBS(CRYPTO_new_ex_data, [eay32 crypto], [], [AC_MSG_ERROR([library 'eay32' or 'crypto' is required for OpenSSL])])
+     AC_SEARCH_LIBS(SSL_new, [ssleay32 ssl], [], [AC_MSG_ERROR([library 'ssleay32' or 'ssl' is required for OpenSSL])])
   fi
   AC_CHECK_FUNCS([SSL_get_current_compression])
   # Functions introduced in OpenSSL 1.1.0. We used to check for
@@ -1262,6 +1262,8 @@ fi
 
 if test "$with_bonjour" = yes ; then
   AC_CHECK_HEADER(dns_sd.h, [], [AC_MSG_ERROR([header file <dns_sd.h> is required for Bonjour])])
+  AC_SEARCH_LIBS(DNSServiceRefSockFD, dns_sd, [],
+    [AC_MSG_ERROR([could not find function 'DNSServiceRefSockFD' required for Bonjour])])
 fi
 
 # for contrib/uuid-ossp