support hole punching when _DELETE commands are received... If the

server doesn't support it, EOPNOTSUPP is returned..

ggatessh/ggatessh.c

@@ -387,11 +387,11 @@ req_thread(void *arg __unused)
 			buf = NULL;
 			break;
 
+		case BIO_DELETE:
 		case BIO_FLUSH:
 			greq->r_ggio.gctl_data = NULL;
 			break;
 
-		case BIO_DELETE:
 		default:
 			greq->r_ggio.gctl_error = EOPNOTSUPP;
 			g_gate_ioctl(G_GATE_CMD_DONE, &greq->r_ggio);
@@ -426,6 +426,27 @@ req_thread(void *arg __unused)
 	return (NULL);
 }
 
+static const char *
+sftperrno_str(int err)
+{
+	const char *strs[] = {
+		[0] = "ok",
+		[1] = "eof",
+		[2] = "no such file",
+		[3] = "permission denied",
+		[4] = "failure",
+		[5] = "bad message",
+		[6] = "no connection",
+		[7] = "connection lost",
+		[8] = "op unsupported",
+	};
+
+	if (err < 0 || err >= (int)nitems(strs))
+		return "invalid errno";
+
+	return strs[err];
+}
+
 static int
 process_pending(struct ggs_reqqueue *req_pending,
     struct ggs_sessqueue *sessqueue)
@@ -433,6 +454,7 @@ process_pending(struct ggs_reqqueue *req_pending,
 	struct ggs_req *greq, *greq2;
 	char *errmsg;
 	int rc;
+	int sftperrno;
 	int didwork;
 
 	didwork = 0;
@@ -505,6 +527,38 @@ again:
 			/* NOTREACHABLE */
 			break;
 
+		case BIO_DELETE:
+			g_gate_log(LOG_DEBUG, "sftp_punchhole(%p)", greq);
+			rc = libssh2_sftp_punchhole(greq->r_handle,
+			    greq->r_ggio.gctl_offset, greq->r_ggio.gctl_length);
+
+			didwork = 1;	/* assume this always does work */
+			switch (rc) {
+			case LIBSSH2_ERROR_SFTP_PROTOCOL:
+				greq->r_ggio.gctl_error = EOPNOTSUPP;
+				sftperrno = libssh2_sftp_last_error(
+				    greq->r_session);
+				g_gate_log(LOG_DEBUG, "sftp_punchhole(%p) errno: %s(%d)", greq,
+				    sftperrno_str(sftperrno), sftperrno);
+				goto completeio;
+
+			case LIBSSH2_ERROR_EAGAIN:
+				continue;
+
+			case 0:	/* success */
+				goto completeio;
+
+			default:
+				libssh2_session_last_error(greq->r_ssh_session,
+				    &errmsg, NULL, 0);
+				g_gate_log(LOG_ERR, "sftp_punchhole(%p) ret %d: %s",
+				    greq, rc, errmsg);
+				greq->r_ggio.gctl_error = EIO;
+				goto completeio;
+			}
+			/* NOTREACHABLE */
+			break;
+
 		default:
 			rc = 0;
 			g_gate_log(LOG_ERR, "unhandled op: %d",