samples/bpf: fix XDP_FLAGS_SKB_MODE detach for xdp_tx_iptunnel

The xdp_tx_iptunnel program can be terminated in two ways, after
N-seconds or via Ctrl-C SIGINT.  The SIGINT code path does not
handle detatching the correct XDP program, in-case the program
was attached with XDP_FLAGS_SKB_MODE.

Fix this by storing the XDP flags as a global variable, which is
available for the SIGINT handler function.

Fixes: 3993f2cb ("samples/bpf: Add support for SKB_MODE to xdp1 and xdp_tx_iptunnel")
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Reviewed-by: NAndy Gospodarek <andy@greyhouse.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

samples/bpf/xdp_tx_iptunnel_user.c

@@ -25,11 +25,12 @@
 #define STATS_INTERVAL_S 2U
 
 static int ifindex = -1;
+static __u32 xdp_flags = 0;
 
 static void int_exit(int sig)
 {
 	if (ifindex > -1)
-		set_link_xdp_fd(ifindex, -1, 0);
+		set_link_xdp_fd(ifindex, -1, xdp_flags);
 	exit(0);
 }
 
@@ -142,7 +143,6 @@ int main(int argc, char **argv)
 	struct iptnl_info tnl = {};
 	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
 	struct vip vip = {};
-	__u32 xdp_flags = 0;
 	char filename[256];
 	int opt;
 	int i;