ntpd: add comment about mode6, no code changes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/networking/ntpd.c b/networking/ntpd.c
index 465c74d6c..48dc1c379 100644
--- a/networking/ntpd.c
+++ b/networking/ntpd.c
@@ -2238,6 +2238,13 @@ recv_and_process_client_pkt(void /*int fd*/)
         from = xzalloc(to->len);
 
         size = recv_from_to(G_listen_fd, &msg, sizeof(msg), MSG_DONTWAIT, from, &to->u.sa, to->len);
+
+        /* "ntpq -p" (4.2.8p13) sends a 12-byte NTPv2 request:
+         * m_status is 0x16: leap:0 version:2 mode:6(reserved1)
+         *  https://docs.ntpsec.org/latest/mode6.html
+         * We don't support this.
+         */
+
 #if ENABLE_FEATURE_NTP_AUTH
         if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE_MD5_AUTH && size != NTP_MSGSIZE_SHA1_AUTH)
 #else