commit 5fb355a7c9a1fdd5842c4b9dbd5e48ba6b767921
Author: Toke Høiland-Jørgensen <toke@redhat.com>
Date:   Wed Feb 10 16:59:08 2021 +0100

    xdp-filter: Check whether we have already been loaded
    
    Now that we can attach multiple programs to an interface, xdp-filter will
    happily load itself multiple times on the same interface. Fix that by
    checking if it's already loaded before attempting a new load.
    
    Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>

diff --git a/xdp-filter/xdp-filter.c b/xdp-filter/xdp-filter.c
index 08cfd722e169..895dbd5750b2 100644
--- a/xdp-filter/xdp-filter.c
+++ b/xdp-filter/xdp-filter.c
@@ -268,6 +268,13 @@ int do_load(const void *cfg, const char *pin_root_path)
 	}
 	features |= opt->policy_mode;
 
+	err = get_pinned_program(&opt->iface, pin_root_path, NULL, &p);
+	if (!err) {
+		pr_warn("xdp-filter is already loaded on %s\n", opt->iface.ifname);
+		xdp_program__close(p);
+		return EXIT_FAILURE;
+	}
+
 	print_flags(featbuf, sizeof(featbuf), print_features, features);
 	pr_debug("Looking for eBPF program with features %s\n", featbuf);