static int nbd_opt_go(QIOChannel *ioc, const char *wantname, NBDExportInfo *info, Error **errp) { nbd_opt_reply reply; uint32_t len = strlen(wantname); uint16_t type; int error; char *buf; /* The protocol requires that the server send NBD_INFO_EXPORT with * a non-zero flags (at least NBD_FLAG_HAS_FLAGS must be set); so * flags still 0 is a witness of a broken server. */ info->flags = 0; trace_nbd_opt_go_start(wantname); buf = g_malloc(4 + len + 2 + 1); stl_be_p(buf, len); memcpy(buf + 4, wantname, len); /* No requests, live with whatever server sends */ stw_be_p(buf + 4 + len, 0); if (nbd_send_option_request(ioc, NBD_OPT_GO, len + 6, buf, errp) < 0) { return -1; } while (1) { if (nbd_receive_option_reply(ioc, NBD_OPT_GO, &reply, errp) < 0) { return -1; } error = nbd_handle_reply_err(ioc, &reply, errp); if (error <= 0) { return error; } len = reply.length; if (reply.type == NBD_REP_ACK) { /* Server is done sending info and moved into transmission phase, but make sure it sent flags */ if (len) { error_setg(errp, "server sent invalid NBD_REP_ACK"); nbd_send_opt_abort(ioc); return -1; } if (!info->flags) { error_setg(errp, "broken server omitted NBD_INFO_EXPORT"); nbd_send_opt_abort(ioc); return -1; } trace_nbd_opt_go_success(); return 1; } if (reply.type != NBD_REP_INFO) { error_setg(errp, "unexpected reply type %" PRIx32 ", expected %x", reply.type, NBD_REP_INFO); nbd_send_opt_abort(ioc); return -1; } if (len < sizeof(type)) { error_setg(errp, "NBD_REP_INFO length %" PRIu32 " is too short", len); nbd_send_opt_abort(ioc); return -1; } if (nbd_read(ioc, &type, sizeof(type), errp) < 0) { error_prepend(errp, "failed to read info type"); nbd_send_opt_abort(ioc); return -1; } len -= sizeof(type); be16_to_cpus(&type); switch (type) { case NBD_INFO_EXPORT: if (len != sizeof(info->size) + sizeof(info->flags)) { error_setg(errp, "remaining export info len %" PRIu32 " is unexpected size", len); nbd_send_opt_abort(ioc); return -1; } if (nbd_read(ioc, &info->size, sizeof(info->size), errp) < 0) { error_prepend(errp, "failed to read info size"); nbd_send_opt_abort(ioc); return -1; } be64_to_cpus(&info->size); if (nbd_read(ioc, &info->flags, sizeof(info->flags), errp) < 0) { error_prepend(errp, "failed to read info flags"); nbd_send_opt_abort(ioc); return -1; } be16_to_cpus(&info->flags); trace_nbd_receive_negotiate_size_flags(info->size, info->flags); break; default: trace_nbd_opt_go_info_unknown(type, nbd_info_lookup(type)); if (nbd_drop(ioc, len, errp) < 0) { error_prepend(errp, "Failed to read info payload"); nbd_send_opt_abort(ioc); return -1; } break; } } }