ethtool: fix missing NLM_F_MULTI flag when dumping

When dumping the ethtool information from all the interfaces, the
netlink reply should contain the NLM_F_MULTI flag. This flag allows
userspace tools to identify that multiple messages are expected.

Link: https://bugzilla.redhat.com/1953847
Fixes: 365f9ae4 ("ethtool: fix genlmsg_put() failure handling in ethnl_default_dumpit()")
Signed-off-by: NFernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ethtool/netlink.c

@@ -387,7 +387,8 @@ static int ethnl_default_dump_one(struct sk_buff *skb, struct net_device *dev,
 	int ret;
 
 	ehdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
-			   &ethtool_genl_family, 0, ctx->ops->reply_cmd);
+			   &ethtool_genl_family, NLM_F_MULTI,
+			   ctx->ops->reply_cmd);
 	if (!ehdr)
 		return -EMSGSIZE;