selftests: net: retry when bind returns EBUSY in xdp_helper

When binding the XDP socket, we may get EBUSY because the deferred
destructor of XDP socket in previous test has not been executed yet. If
that is the case, just sleep and retry some times.

Signed-off-by: Bui Quang Minh <[e-mail]>
Acked-by: Michael S. Tsirkin <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/lib/xdp_helper.c

···
 	struct sockaddr_xdp sxdp = { 0 };
 	int num_desc = NUM_DESC;
 	void *umem_area;
+	int retry = 0;
 	int ifindex;
 	int sock_fd;
 	int queue;
···
 		}
 	}
 
-	if (bind(sock_fd, (struct sockaddr *)&sxdp, sizeof(sxdp)) != 0) {
-		munmap(umem_area, UMEM_SZ);
-		perror("bind failed");
-		close(sock_fd);
-		return 1;
+	while (1) {
+		if (bind(sock_fd, (struct sockaddr *)&sxdp, sizeof(sxdp)) == 0)
+			break;
+
+		if (errno == EBUSY && retry < 3) {
+			retry++;
+			sleep(1);
+			continue;
+		} else {
+			perror("bind failed");
+			munmap(umem_area, UMEM_SZ);
+			close(sock_fd);
+			return 1;
+		}
 	}
 
 	ksft_ready();