bpf: Fix tcp_clamp_kern.c sample program

The program was returning -1 in some cases which is not allowed
by the verifier any longer.

Fixes: 390ee7e29fc8 ("bpf: enforce return code for cgroup-bpf programs")
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

samples/bpf/tcp_clamp_kern.c

@@ -41,8 +41,10 @@ int bpf_clamp(struct bpf_sock_ops *skops)
 	/* For testing purposes, only execute rest of BPF program
 	 * if neither port numberis 55601
 	 */
-	if (bpf_ntohl(skops->remote_port) != 55601 && skops->local_port != 55601)
-		return -1;
+	if (bpf_ntohl(skops->remote_port) != 55601 && skops->local_port != 55601) {
+		skops->reply = -1;
+		return 0;
+	}
 
 	op = (int) skops->op;
 
@@ -66,9 +68,9 @@ int bpf_clamp(struct bpf_sock_ops *skops)
 			/* Set sndbuf and rcvbuf of active connections */
 			rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF,
 					    &bufsize, sizeof(bufsize));
-			rv = rv*100 + bpf_setsockopt(skops, SOL_SOCKET,
-						      SO_RCVBUF, &bufsize,
-						      sizeof(bufsize));
+			rv += bpf_setsockopt(skops, SOL_SOCKET,
+					     SO_RCVBUF, &bufsize,
+					     sizeof(bufsize));
 			break;
 		case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
 			rv = bpf_setsockopt(skops, SOL_TCP,
@@ -80,12 +82,12 @@ int bpf_clamp(struct bpf_sock_ops *skops)
 			rv = bpf_setsockopt(skops, SOL_TCP,
 					    TCP_BPF_SNDCWND_CLAMP,
 					    &clamp, sizeof(clamp));
-			rv = rv*100 + bpf_setsockopt(skops, SOL_SOCKET,
-						      SO_SNDBUF, &bufsize,
-						      sizeof(bufsize));
-			rv = rv*100 + bpf_setsockopt(skops, SOL_SOCKET,
-						      SO_RCVBUF, &bufsize,
-						      sizeof(bufsize));
+			rv += bpf_setsockopt(skops, SOL_SOCKET,
+					     SO_SNDBUF, &bufsize,
+					     sizeof(bufsize));
+			rv += bpf_setsockopt(skops, SOL_SOCKET,
+					     SO_RCVBUF, &bufsize,
+					     sizeof(bufsize));
 			break;
 		default:
 			rv = -1;