From 8b9021bf3403ce74f1b20266053352687f685c5c Mon Sep 17 00:00:00 2001
From: Miroslav Lichvar <mlichvar@redhat.com>
Date: Thu, 24 May 2018 15:17:53 +0200
Subject: [PATCH] ntp: allow online/offline state to be selected by
 connectability

Allow SRC_MAYBE_ONLINE to be specified for new NTP sources and
connectivity setting to select between SRC_ONLINE and SRC_OFFLINE
according to the result of the connect() system call, i.e. check whether
the client has a route to send its requests.
---
 ntp_core.c  |  7 ++++++-
 ntp_io.c    | 17 +++++++++++++++++
 ntp_io.h    |  3 +++
 srcparams.h |  1 +
 4 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/ntp_core.c b/ntp_core.c
index 45956e7..c9d0969 100644
--- a/ntp_core.c
+++ b/ntp_core.c
@@ -603,7 +603,9 @@ NCR_GetInstance(NTP_Remote_Address *remote_addr, NTP_Source_Type type, SourcePar
   result->rx_timeout_id = 0;
   result->tx_timeout_id = 0;
   result->tx_suspended = 1;
-  result->opmode = params->connectivity == SRC_ONLINE ? MD_ONLINE : MD_OFFLINE;
+  result->opmode = params->connectivity == SRC_ONLINE ||
+                   (params->connectivity == SRC_MAYBE_ONLINE &&
+                    NIO_IsServerConnectable(remote_addr)) ? MD_ONLINE : MD_OFFLINE;
   result->local_poll = result->minpoll;
   result->poll_score = 0.0;
   zero_local_timestamp(&result->local_tx);
@@ -2281,6 +2283,9 @@ NCR_SetConnectivity(NCR_Instance inst, SRC_Connectivity connectivity)
 
   s = UTI_IPToString(&inst->remote_addr.ip_addr);
 
+  if (connectivity == SRC_MAYBE_ONLINE)
+    connectivity = NIO_IsServerConnectable(&inst->remote_addr) ? SRC_ONLINE : SRC_OFFLINE;
+
   switch (connectivity) {
     case SRC_ONLINE:
       switch (inst->opmode) {
diff --git a/ntp_io.c b/ntp_io.c
index 3a3398a..8df093e 100644
--- a/ntp_io.c
+++ b/ntp_io.c
@@ -574,6 +574,23 @@ NIO_IsServerSocket(int sock_fd)
 
 /* ================================================== */
 
+int
+NIO_IsServerConnectable(NTP_Remote_Address *remote_addr)
+{
+  int sock_fd, r;
+
+  sock_fd = prepare_separate_client_socket(remote_addr->ip_addr.family);
+  if (sock_fd == INVALID_SOCK_FD)
+    return 0;
+
+  r = connect_socket(sock_fd, remote_addr);
+  close_socket(sock_fd);
+
+  return r;
+}
+
+/* ================================================== */
+
 static void
 process_message(struct msghdr *hdr, int length, int sock_fd)
 {
diff --git a/ntp_io.h b/ntp_io.h
index 1bdcf12..628f736 100644
--- a/ntp_io.h
+++ b/ntp_io.h
@@ -53,6 +53,9 @@ extern void NIO_CloseServerSocket(int sock_fd);
 /* Function to check if socket is a server socket */
 extern int NIO_IsServerSocket(int sock_fd);
 
+/* Function to check if client packets can be sent to a server */
+extern int NIO_IsServerConnectable(NTP_Remote_Address *remote_addr);
+
 /* Function to transmit a packet */
 extern int NIO_SendPacket(NTP_Packet *packet, NTP_Remote_Address *remote_addr,
                           NTP_Local_Address *local_addr, int length, int process_tx);
diff --git a/srcparams.h b/srcparams.h
index 48fa19c..e11edc6 100644
--- a/srcparams.h
+++ b/srcparams.h
@@ -32,6 +32,7 @@
 typedef enum {
   SRC_OFFLINE,
   SRC_ONLINE,
+  SRC_MAYBE_ONLINE,
 } SRC_Connectivity;
 
 typedef struct {