Tell updown script if DPD cleared connection

We'd like to know if the connection went down because of loss of network
connectivity (DPD) or some other reason. First step, export that data
out of Libreswan.

[TABLET-2117]

programs/pluto/connections.c

@@ -2003,6 +2003,7 @@ struct connection *instantiate(struct connection *c, const ip_address *him,
 	d->newest_isakmp_sa = SOS_NOBODY;
 	d->newest_ipsec_sa = SOS_NOBODY;
 	d->spd.eroute_owner = SOS_NOBODY;
+	d->dpd_killed = FALSE;
 
 	/* reset log file info */
 	d->log_file_name = NULL;
@@ -4201,6 +4202,7 @@ void liveness_action(struct connection *c, enum ike_version ike_version)
 	case DPD_ACTION_CLEAR:
 		libreswan_log("%s action - clearing connection kind %s", ikev,
 				enum_name(&connection_kind_names, c->kind));
+		c->dpd_killed = TRUE;
 		liveness_clear_connection(c, ikev);
 		break;
 

programs/pluto/connections.h

@@ -281,6 +281,7 @@ struct connection {
 	deltatime_t dpd_delay;		/* time between checks */
 	deltatime_t dpd_timeout;	/* time after which we are dead */
 	enum dpd_action dpd_action;	/* what to do when we die */
+	bool dpd_killed;            /* dpd caused connection to end */
 
 	bool nat_keepalive;		/* Send NAT-T Keep-Alives if we are behind NAT */
 	bool initial_contact;		/* Send INITIAL_CONTACT (RFC-2407) payload? */

programs/pluto/kernel.c

@@ -493,6 +493,8 @@ static void jam_common_shell_out(jambuf_t *buf, const struct connection *c,
 
 	jam(buf, "PLUTO_STACK='%s' ", kernel_ops->kern_name);
 
+	jam(buf, "PLUTO_DPD_CLEAR=%i ", (int)c->dpd_killed);
+
 	if (c->metric != 0) {
 		jam(buf, "PLUTO_METRIC=%d ", c->metric);
 	}