iproxy: Print correct error message when receiving fails

tools/iproxy.c

diff --git a/tools/iproxy.c b/tools/iproxy.c
index 36d4521..2d32275 100644
--- a/tools/iproxy.c
+++ b/tools/iproxy.c
@@ -71,7 +71,7 @@
 				// try again
 				continue;
 			} else {
-				fprintf(stderr, "recv failed: %s\n", strerror(errno));
+				fprintf(stderr, "recv failed: %s\n", strerror(-recv_len));
 				break;
 			}
 		} else {
@@ -124,7 +124,7 @@
 				// try again
 				continue;
 			} else {
-			fprintf(stderr, "recv failed: %s\n", strerror(errno));
+				fprintf(stderr, "recv failed: %s\n", strerror(-recv_len));
 				break;
 			}
 		} else {