From: Ondřej Surý <ondrej@isc.org>
Date: Mon, 25 Apr 2022 12:09:44 +0000 (+0200)
Subject: Set IP(V6)_RECVERR on connect UDP sockets (via libuv)
X-Git-Tag: v9.19.1~51^2~1
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=407b37c3f21f03d8148a652cd026ca6939da3517;p=thirdparty%2Fbind9.git

Set IP(V6)_RECVERR on connect UDP sockets (via libuv)

The connect()ed UDP socket provides feedback on a variety of ICMP
errors (eg port unreachable) which bind can then use to decide what to
do with errors (report them to the client, try again with a different
nameserver etc).  However, Linux's implementation does not report what
it considers "transient" conditions, which is defined as Destination
host Unreachable, Destination network unreachable, Source Route Failed
and Message Too Big.

Explicitly enable IP_RECVERR / IPV6_RECVERR (via libuv uv_udp_bind()
flag) to learn about ICMP destination network/host unreachable.
---

diff --git a/configure.ac b/configure.ac
index 072f535a84d..9b29cb4901d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -562,6 +562,9 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <sys/socket.h>],
 		  [AC_MSG_RESULT([no])
 		   AC_CHECK_DECLS([UV_UDP_RECVMMSG], [], [], [[#include <uv.h>]])])
 
+# libuv recverr support
+AC_CHECK_DECLS([UV_UDP_LINUX_RECVERR], [], [], [[#include <uv.h>]])
+
 # [pairwise: --enable-doh --with-libnghttp2=auto, --enable-doh --with-libnghttp2=yes, --disable-doh]
 AC_ARG_ENABLE([doh],
 	      [AS_HELP_STRING([--disable-doh], [enable DNS over HTTPS, requires libnghttp2 (default=yes)])],
diff --git a/lib/isc/netmgr/udp.c b/lib/isc/netmgr/udp.c
index 4c0848fdeaa..29a603a0dd2 100644
--- a/lib/isc/netmgr/udp.c
+++ b/lib/isc/netmgr/udp.c
@@ -882,6 +882,10 @@ udp_connect_direct(isc_nmsocket_t *sock, isc__nm_uvreq_t *req) {
 		uv_bind_flags |= UV_UDP_IPV6ONLY;
 	}
 
+#if HAVE_DECL_UV_UDP_LINUX_RECVERR
+	uv_bind_flags |= UV_UDP_LINUX_RECVERR;
+#endif
+
 	r = uv_udp_bind(&sock->uv_handle.udp, &sock->iface.type.sa,
 			uv_bind_flags);
 	if (r != 0) {