drbd: --dry-run option for drbdsetup net ( drbdadm -- --dry-run connect <res> )

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index ab871e0..b2d347d 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1668,7 +1668,7 @@
 int drbd_send_protocol(struct drbd_conf *mdev)
 {
 	struct p_protocol *p;
-	int size, rv;
+	int size, cf, rv;
 
 	size = sizeof(struct p_protocol);
 
@@ -1685,9 +1685,21 @@
 	p->after_sb_0p   = cpu_to_be32(mdev->net_conf->after_sb_0p);
 	p->after_sb_1p   = cpu_to_be32(mdev->net_conf->after_sb_1p);
 	p->after_sb_2p   = cpu_to_be32(mdev->net_conf->after_sb_2p);
-	p->want_lose     = cpu_to_be32(mdev->net_conf->want_lose);
 	p->two_primaries = cpu_to_be32(mdev->net_conf->two_primaries);
 
+	cf = 0;
+	if (mdev->net_conf->want_lose)
+		cf |= CF_WANT_LOSE;
+	if (mdev->net_conf->dry_run) {
+		if (mdev->agreed_pro_version >= 92)
+			cf |= CF_DRY_RUN;
+		else {
+			dev_err(DEV, "--dry-run is not supported by peer");
+			return 0;
+		}
+	}
+	p->conn_flags    = cpu_to_be32(cf);
+
 	if (mdev->agreed_pro_version >= 87)
 		strcpy(p->integrity_alg, mdev->net_conf->integrity_alg);