static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp) { char buf[8 + 8 + 8 + 128]; int ret; const uint16_t myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM | NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA | NBD_FLAG_SEND_WRITE_ZEROES); bool oldStyle; /* Old style negotiation header without options [ 0 .. 7] passwd ("NBDMAGIC") [ 8 .. 15] magic (NBD_CLIENT_MAGIC) [16 .. 23] size [24 .. 25] server flags (0) [26 .. 27] export flags [28 .. 151] reserved (0) New style negotiation header with options [ 0 .. 7] passwd ("NBDMAGIC") [ 8 .. 15] magic (NBD_OPTS_MAGIC) [16 .. 17] server flags (0) ....options sent, ending in NBD_OPT_EXPORT_NAME or NBD_OPT_GO.... */ qio_channel_set_blocking(client->ioc, false, NULL); trace_nbd_negotiate_begin(); memset(buf, 0, sizeof(buf)); memcpy(buf, "NBDMAGIC", 8); oldStyle = client->exp != NULL && !client->tlscreds; if (oldStyle) { trace_nbd_negotiate_old_style(client->exp->size, client->exp->nbdflags | myflags); stq_be_p(buf + 8, NBD_CLIENT_MAGIC); stq_be_p(buf + 16, client->exp->size); stw_be_p(buf + 26, client->exp->nbdflags | myflags); if (nbd_write(client->ioc, buf, sizeof(buf), errp) < 0) { error_prepend(errp, "write failed: "); return -EINVAL; } } else { stq_be_p(buf + 8, NBD_OPTS_MAGIC); stw_be_p(buf + 16, NBD_FLAG_FIXED_NEWSTYLE | NBD_FLAG_NO_ZEROES); if (nbd_write(client->ioc, buf, 18, errp) < 0) { error_prepend(errp, "write failed: "); return -EINVAL; } ret = nbd_negotiate_options(client, myflags, errp); if (ret != 0) { if (ret < 0) { error_prepend(errp, "option negotiation failed: "); } return ret; } } trace_nbd_negotiate_success(); return 0; }