4 * Copyright (c) 2018 Cisco and/or its affiliates.
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at:
9 * http://www.apache.org/licenses/LICENSE-2.0
11 * Unless required by applicable law or aipiped to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
19 #include <vnet/adj/adj_midchain.h>
20 #include <vnet/ipip/ipip.h>
21 #include <vnet/vnet.h>
22 #include <vnet/adj/adj_nbr.h>
23 #include <vnet/adj/adj_midchain.h>
24 #include <vnet/fib/ip4_fib.h>
25 #include <vnet/fib/ip6_fib.h>
26 #include <vnet/ip/format.h>
27 #include <vnet/ipip/ipip.h>
28 #include <vnet/nhrp/nhrp.h>
29 #include <vnet/tunnel/tunnel_dp.h>
31 ipip_main_t ipip_main;
33 /* Packet trace structure */
43 format_ipip_tx_trace (u8 * s, va_list * args)
45 CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
46 CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
47 ipip_tx_trace_t *t = va_arg (*args, ipip_tx_trace_t *);
50 format (s, "IPIP: tunnel %d len %d src %U dst %U", t->tunnel_id,
51 t->length, format_ip46_address, &t->src, IP46_TYPE_ANY,
52 format_ip46_address, &t->dst, IP46_TYPE_ANY);
57 ipip_build_rewrite (vnet_main_t * vnm, u32 sw_if_index,
58 vnet_link_t link_type, const void *dst_address)
60 const ip46_address_t *dst;
67 t = ipip_tunnel_db_find_by_sw_if_index (sw_if_index);
75 case IPIP_TRANSPORT_IP4:
76 vec_validate (rewrite, sizeof (*ip4) - 1);
77 ip4 = (ip4_header_t *) rewrite;
78 ip4->ip_version_and_header_length = 0x45;
80 /* fixup ip4 header length, protocol and checksum after-the-fact */
81 ip4->src_address.as_u32 = t->tunnel_src.ip4.as_u32;
82 ip4->dst_address.as_u32 = dst->ip4.as_u32;
83 if (!(t->flags & TUNNEL_ENCAP_DECAP_FLAG_ENCAP_COPY_DSCP))
84 ip4_header_set_dscp (ip4, t->dscp);
85 if (t->flags & TUNNEL_ENCAP_DECAP_FLAG_ENCAP_SET_DF)
86 ip4_header_set_df (ip4);
87 ip4->checksum = ip4_header_checksum (ip4);
92 ip4->protocol = IP_PROTOCOL_IPV6;
95 ip4->protocol = IP_PROTOCOL_IP_IN_IP;
102 case IPIP_TRANSPORT_IP6:
103 vec_validate (rewrite, sizeof (*ip6) - 1);
104 ip6 = (ip6_header_t *) rewrite;
105 ip6->ip_version_traffic_class_and_flow_label =
106 clib_host_to_net_u32 (6 << 28);
108 /* fixup ip6 header length and protocol after-the-fact */
109 ip6->src_address.as_u64[0] = t->tunnel_src.ip6.as_u64[0];
110 ip6->src_address.as_u64[1] = t->tunnel_src.ip6.as_u64[1];
111 ip6->dst_address.as_u64[0] = dst->ip6.as_u64[0];
112 ip6->dst_address.as_u64[1] = dst->ip6.as_u64[1];
113 if (!(t->flags & TUNNEL_ENCAP_DECAP_FLAG_ENCAP_COPY_DSCP))
114 ip6_set_dscp_network_order (ip6, t->dscp);
119 ip6->protocol = IP_PROTOCOL_IPV6;
122 ip6->protocol = IP_PROTOCOL_IP_IN_IP;
133 ipip64_fixup (vlib_main_t * vm, const ip_adjacency_t * adj, vlib_buffer_t * b,
136 tunnel_encap_decap_flags_t flags;
139 flags = pointer_to_uword (data);
141 ip4 = vlib_buffer_get_current (b);
142 ip4->length = clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b));
143 tunnel_encap_fixup_6o4 (flags, ((ip6_header_t *) (ip4 + 1)), ip4);
145 ip4->checksum = ip4_header_checksum (ip4);
149 ipip44_fixup (vlib_main_t * vm, const ip_adjacency_t * adj, vlib_buffer_t * b,
152 tunnel_encap_decap_flags_t flags;
155 flags = pointer_to_uword (data);
157 ip4 = vlib_buffer_get_current (b);
158 ip4->length = clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b));
159 tunnel_encap_fixup_4o4 (flags, ip4 + 1, ip4);
161 ip4->checksum = ip4_header_checksum (ip4);
165 ipip46_fixup (vlib_main_t * vm, const ip_adjacency_t * adj, vlib_buffer_t * b,
168 tunnel_encap_decap_flags_t flags;
171 flags = pointer_to_uword (data);
173 /* Must set locally originated otherwise we're not allowed to
174 fragment the packet later */
175 b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
177 ip6 = vlib_buffer_get_current (b);
178 ip6->payload_length =
179 clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b) -
181 tunnel_encap_fixup_4o6 (flags, ((ip4_header_t *) (ip6 + 1)), ip6);
185 ipip66_fixup (vlib_main_t * vm,
186 const ip_adjacency_t * adj, vlib_buffer_t * b, const void *data)
188 tunnel_encap_decap_flags_t flags;
191 flags = pointer_to_uword (data);
193 /* Must set locally originated otherwise we're not allowed to
194 fragment the packet later */
195 b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
197 ip6 = vlib_buffer_get_current (b);
198 ip6->payload_length =
199 clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b) -
201 tunnel_encap_fixup_6o6 (flags, ip6 + 1, ip6);
205 ipip_tunnel_stack (adj_index_t ai)
212 sw_if_index = adj->rewrite_header.sw_if_index;
214 t = ipip_tunnel_db_find_by_sw_if_index (sw_if_index);
218 if ((vnet_hw_interface_get_flags (vnet_get_main (), t->hw_if_index) &
219 VNET_HW_INTERFACE_FLAG_LINK_UP) == 0)
221 adj_midchain_delegate_unstack (ai);
227 .fp_len = t->transport == IPIP_TRANSPORT_IP6 ? 128 : 32,
228 .fp_proto = (t->transport == IPIP_TRANSPORT_IP6 ?
231 .fp_addr = t->tunnel_dst
235 adj_midchain_delegate_stack (ai, t->fib_index, &dst);
240 ipip_adj_walk_cb (adj_index_t ai, void *ctx)
242 ipip_tunnel_stack (ai);
244 return (ADJ_WALK_RC_CONTINUE);
248 ipip_tunnel_restack (ipip_tunnel_t * gt)
250 fib_protocol_t proto;
253 * walk all the adjacencies on th IPIP interface and restack them
255 FOR_EACH_FIB_IP_PROTOCOL (proto)
257 adj_nbr_walk (gt->sw_if_index, proto, ipip_adj_walk_cb, NULL);
261 static adj_midchain_fixup_t
262 ipip_get_fixup (const ipip_tunnel_t * t, vnet_link_t lt)
264 if (t->transport == IPIP_TRANSPORT_IP6 && lt == VNET_LINK_IP6)
265 return (ipip66_fixup);
266 if (t->transport == IPIP_TRANSPORT_IP6 && lt == VNET_LINK_IP4)
267 return (ipip46_fixup);
268 if (t->transport == IPIP_TRANSPORT_IP4 && lt == VNET_LINK_IP6)
269 return (ipip64_fixup);
270 if (t->transport == IPIP_TRANSPORT_IP4 && lt == VNET_LINK_IP4)
271 return (ipip44_fixup);
274 return (ipip44_fixup);
278 ipip_update_adj (vnet_main_t * vnm, u32 sw_if_index, adj_index_t ai)
283 t = ipip_tunnel_db_find_by_sw_if_index (sw_if_index);
287 af = ADJ_FLAG_MIDCHAIN_IP_STACK;
288 if (VNET_LINK_ETHERNET == adj_get_link_type (ai))
289 af |= ADJ_FLAG_MIDCHAIN_NO_COUNT;
291 adj_nbr_midchain_update_rewrite
292 (ai, ipip_get_fixup (t, adj_get_link_type (ai)),
293 uword_to_pointer (t->flags, void *), af,
294 ipip_build_rewrite (vnm, sw_if_index,
295 adj_get_link_type (ai), &t->tunnel_dst));
296 ipip_tunnel_stack (ai);
299 typedef struct mipip_walk_ctx_t_
301 const ipip_tunnel_t *t;
302 const nhrp_entry_t *ne;
306 mipip_mk_complete_walk (adj_index_t ai, void *data)
308 mipip_walk_ctx_t *ctx = data;
310 adj_nbr_midchain_update_rewrite
311 (ai, ipip_get_fixup (ctx->t, adj_get_link_type (ai)),
312 uword_to_pointer (ctx->t->flags, void *),
313 ADJ_FLAG_MIDCHAIN_IP_STACK, ipip_build_rewrite (vnet_get_main (),
315 adj_get_link_type (ai),
317 (ctx->ne)->fp_addr));
319 nhrp_entry_adj_stack (ctx->ne, ai);
321 return (ADJ_WALK_RC_CONTINUE);
325 mipip_mk_incomplete_walk (adj_index_t ai, void *data)
327 ipip_tunnel_t *t = data;
329 adj_nbr_midchain_update_rewrite
330 (ai, ipip_get_fixup (t, adj_get_link_type (ai)),
331 NULL, ADJ_FLAG_NONE, NULL);
333 adj_midchain_delegate_unstack (ai);
335 return (ADJ_WALK_RC_CONTINUE);
339 mipip_update_adj (vnet_main_t * vnm, u32 sw_if_index, adj_index_t ai)
341 ipip_main_t *gm = &ipip_main;
348 ti = gm->tunnel_index_by_sw_if_index[sw_if_index];
349 t = pool_elt_at_index (gm->tunnels, ti);
351 ne = nhrp_entry_find (sw_if_index, &adj->sub_type.nbr.next_hop);
355 // no NHRP entry to provide the next-hop
356 adj_nbr_midchain_update_rewrite
357 (ai, ipip_get_fixup (t, adj_get_link_type (ai)),
358 uword_to_pointer (t->flags, void *), ADJ_FLAG_NONE, NULL);
362 mipip_walk_ctx_t ctx = {
366 adj_nbr_walk_nh (sw_if_index,
368 &adj->sub_type.nbr.next_hop, mipip_mk_complete_walk, &ctx);
372 format_ipip_tunnel_name (u8 * s, va_list * args)
374 u32 dev_instance = va_arg (*args, u32);
375 ipip_main_t *gm = &ipip_main;
378 if (dev_instance >= vec_len (gm->tunnels))
379 return format (s, "<improperly-referenced>");
381 t = pool_elt_at_index (gm->tunnels, dev_instance);
382 return format (s, "ipip%d", t->user_instance);
386 format_ipip_device (u8 * s, va_list * args)
388 u32 dev_instance = va_arg (*args, u32);
389 CLIB_UNUSED (int verbose) = va_arg (*args, int);
391 s = format (s, "IPIP tunnel: id %d\n", dev_instance);
395 static clib_error_t *
396 ipip_interface_admin_up_down (vnet_main_t * vnm, u32 hw_if_index, u32 flags)
398 vnet_hw_interface_t *hi;
401 hi = vnet_get_hw_interface (vnm, hw_if_index);
403 t = ipip_tunnel_db_find_by_sw_if_index (hi->sw_if_index);
407 if (flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP)
408 vnet_hw_interface_set_flags (vnm, hw_if_index,
409 VNET_HW_INTERFACE_FLAG_LINK_UP);
411 vnet_hw_interface_set_flags (vnm, hw_if_index, 0 /* down */ );
413 ipip_tunnel_restack (t);
415 return /* no error */ 0;
419 ipip_tunnel_desc (u32 sw_if_index,
420 ip46_address_t * src, ip46_address_t * dst, u8 * is_l2)
424 t = ipip_tunnel_db_find_by_sw_if_index (sw_if_index);
428 *src = t->tunnel_src;
429 *dst = t->tunnel_dst;
436 VNET_DEVICE_CLASS(ipip_device_class) = {
437 .name = "IPIP tunnel device",
438 .format_device_name = format_ipip_tunnel_name,
439 .format_device = format_ipip_device,
440 .format_tx_trace = format_ipip_tx_trace,
441 .admin_up_down_function = ipip_interface_admin_up_down,
442 .ip_tun_desc = ipip_tunnel_desc,
448 VNET_HW_INTERFACE_CLASS(ipip_hw_interface_class) = {
450 //.format_header = format_ipip_header_with_length,
451 //.unformat_header = unformat_ipip_header,
452 .build_rewrite = ipip_build_rewrite,
453 .update_adjacency = ipip_update_adj,
454 .flags = VNET_HW_INTERFACE_CLASS_FLAG_P2P,
457 VNET_HW_INTERFACE_CLASS(mipip_hw_interface_class) = {
459 //.format_header = format_ipip_header_with_length,
460 //.unformat_header = unformat_ipip_header,
461 .build_rewrite = ipip_build_rewrite,
462 .update_adjacency = mipip_update_adj,
463 .flags = VNET_HW_INTERFACE_CLASS_FLAG_NBMA,
468 ipip_tunnel_db_find (const ipip_tunnel_key_t * key)
470 ipip_main_t *gm = &ipip_main;
473 p = hash_get_mem (gm->tunnel_by_key, key);
476 return (pool_elt_at_index (gm->tunnels, p[0]));
480 ipip_tunnel_db_find_by_sw_if_index (u32 sw_if_index)
482 ipip_main_t *gm = &ipip_main;
483 if (vec_len (gm->tunnel_index_by_sw_if_index) <= sw_if_index)
485 u32 ti = gm->tunnel_index_by_sw_if_index[sw_if_index];
488 return pool_elt_at_index (gm->tunnels, ti);
492 ipip_tunnel_db_add (ipip_tunnel_t * t, const ipip_tunnel_key_t * key)
494 ipip_main_t *gm = &ipip_main;
496 hash_set_mem_alloc (&gm->tunnel_by_key, key, t->dev_instance);
500 ipip_tunnel_db_remove (ipip_tunnel_t * t, const ipip_tunnel_key_t * key)
502 ipip_main_t *gm = &ipip_main;
504 hash_unset_mem_free (&gm->tunnel_by_key, key);
508 ipip_mk_key_i (ipip_transport_t transport,
510 const ip46_address_t * src,
511 const ip46_address_t * dst,
512 u32 fib_index, ipip_tunnel_key_t * key)
514 key->transport = transport;
518 key->fib_index = fib_index;
523 ipip_mk_key (const ipip_tunnel_t * t, ipip_tunnel_key_t * key)
525 ipip_mk_key_i (t->transport, t->mode,
526 &t->tunnel_src, &t->tunnel_dst, t->fib_index, key);
530 ipip_nhrp_mk_key (const ipip_tunnel_t * t,
531 const nhrp_entry_t * ne, ipip_tunnel_key_t * key)
533 const fib_prefix_t *nh;
535 nh = nhrp_entry_get_nh (ne);
537 /* construct the key using mode P2P so it can be found in the DP */
538 ipip_mk_key_i (t->transport, IPIP_MODE_P2P,
539 &t->tunnel_src, &nh->fp_addr,
540 nhrp_entry_get_fib_index (ne), key);
544 ipip_nhrp_entry_added (const nhrp_entry_t * ne)
546 ipip_main_t *gm = &ipip_main;
547 const ip46_address_t *nh;
548 ipip_tunnel_key_t key;
553 sw_if_index = nhrp_entry_get_sw_if_index (ne);
554 if (vec_len (gm->tunnel_index_by_sw_if_index) < sw_if_index)
557 t_idx = gm->tunnel_index_by_sw_if_index[sw_if_index];
559 if (INDEX_INVALID == t_idx)
562 t = pool_elt_at_index (gm->tunnels, t_idx);
564 ipip_nhrp_mk_key (t, ne, &key);
565 ipip_tunnel_db_add (t, &key);
567 // update the rewrites for each of the adjacencies for this next-hop
568 mipip_walk_ctx_t ctx = {
572 nh = nhrp_entry_get_peer (ne);
573 adj_nbr_walk_nh (nhrp_entry_get_sw_if_index (ne),
574 (ip46_address_is_ip4 (nh) ?
576 FIB_PROTOCOL_IP6), nh, mipip_mk_complete_walk, &ctx);
580 ipip_nhrp_entry_deleted (const nhrp_entry_t * ne)
582 ipip_main_t *gm = &ipip_main;
583 const ip46_address_t *nh;
584 ipip_tunnel_key_t key;
589 sw_if_index = nhrp_entry_get_sw_if_index (ne);
590 if (vec_len (gm->tunnel_index_by_sw_if_index) < sw_if_index)
593 t_idx = gm->tunnel_index_by_sw_if_index[sw_if_index];
595 if (INDEX_INVALID == t_idx)
598 t = pool_elt_at_index (gm->tunnels, t_idx);
600 ipip_nhrp_mk_key (t, ne, &key);
601 ipip_tunnel_db_remove (t, &key);
603 nh = nhrp_entry_get_peer (ne);
605 /* make all the adjacencies incomplete */
606 adj_nbr_walk_nh (nhrp_entry_get_sw_if_index (ne),
607 (ip46_address_is_ip4 (nh) ?
609 FIB_PROTOCOL_IP6), nh, mipip_mk_incomplete_walk, t);
613 ipip_tunnel_delete_nhrp_walk (index_t nei, void *ctx)
615 ipip_tunnel_t *t = ctx;
616 ipip_tunnel_key_t key;
618 ipip_nhrp_mk_key (t, nhrp_entry_get (nei), &key);
619 ipip_tunnel_db_remove (t, &key);
621 return (WALK_CONTINUE);
625 ipip_tunnel_add_nhrp_walk (index_t nei, void *ctx)
627 ipip_tunnel_t *t = ctx;
628 ipip_tunnel_key_t key;
630 ipip_nhrp_mk_key (t, nhrp_entry_get (nei), &key);
631 ipip_tunnel_db_add (t, &key);
633 return (WALK_CONTINUE);
637 ipip_add_tunnel (ipip_transport_t transport,
638 u32 instance, ip46_address_t * src, ip46_address_t * dst,
639 u32 fib_index, tunnel_encap_decap_flags_t flags,
640 ip_dscp_t dscp, tunnel_mode_t tmode, u32 * sw_if_indexp)
642 ipip_main_t *gm = &ipip_main;
643 vnet_main_t *vnm = gm->vnet_main;
644 ip4_main_t *im4 = &ip4_main;
645 ip6_main_t *im6 = &ip6_main;
647 vnet_hw_interface_t *hi;
648 u32 hw_if_index, sw_if_index;
649 ipip_tunnel_key_t key;
652 if (tmode == TUNNEL_MODE_MP && !ip46_address_is_zero (dst))
653 return (VNET_API_ERROR_INVALID_DST_ADDRESS);
655 mode = (tmode == TUNNEL_MODE_P2P ? IPIP_MODE_P2P : IPIP_MODE_P2MP);
656 ipip_mk_key_i (transport, mode, src, dst, fib_index, &key);
658 t = ipip_tunnel_db_find (&key);
662 sw_if_indexp[0] = t->sw_if_index;
663 return VNET_API_ERROR_IF_ALREADY_EXISTS;
666 pool_get_aligned (gm->tunnels, t, CLIB_CACHE_LINE_BYTES);
667 clib_memset (t, 0, sizeof (*t));
669 /* Reconcile the real dev_instance and a possible requested instance */
670 u32 t_idx = t - gm->tunnels; /* tunnel index (or instance) */
671 u32 u_idx = instance; /* user specified instance */
674 if (hash_get (gm->instance_used, u_idx))
676 pool_put (gm->tunnels, t);
677 return VNET_API_ERROR_INSTANCE_IN_USE;
679 hash_set (gm->instance_used, u_idx, 1);
681 t->dev_instance = t_idx; /* actual */
682 t->user_instance = u_idx; /* name */
684 hw_if_index = vnet_register_interface (vnm, ipip_device_class.index, t_idx,
685 (mode == IPIP_MODE_P2P ?
686 ipip_hw_interface_class.index :
687 mipip_hw_interface_class.index),
690 hi = vnet_get_hw_interface (vnm, hw_if_index);
691 sw_if_index = hi->sw_if_index;
694 t->hw_if_index = hw_if_index;
695 t->fib_index = fib_index;
696 t->sw_if_index = sw_if_index;
699 t->transport = transport;
701 vec_validate_init_empty (gm->tunnel_index_by_sw_if_index, sw_if_index, ~0);
702 gm->tunnel_index_by_sw_if_index[sw_if_index] = t_idx;
704 if (t->transport == IPIP_TRANSPORT_IP4)
706 vec_validate (im4->fib_index_by_sw_if_index, sw_if_index);
707 hi->min_packet_bytes = 64 + sizeof (ip4_header_t);
711 vec_validate (im6->fib_index_by_sw_if_index, sw_if_index);
712 hi->min_packet_bytes = 64 + sizeof (ip6_header_t);
715 /* Standard default ipip MTU. */
716 vnet_sw_interface_set_mtu (vnm, sw_if_index, 9000);
718 t->tunnel_src = *src;
719 t->tunnel_dst = *dst;
721 ipip_tunnel_db_add (t, &key);
723 if (t->mode == IPIP_MODE_P2MP)
724 nhrp_walk_itf (t->sw_if_index, ipip_tunnel_add_nhrp_walk, t);
727 *sw_if_indexp = sw_if_index;
729 if (t->transport == IPIP_TRANSPORT_IP6 && !gm->ip6_protocol_registered)
731 ip6_register_protocol (IP_PROTOCOL_IP_IN_IP, ipip6_input_node.index);
732 ip6_register_protocol (IP_PROTOCOL_IPV6, ipip6_input_node.index);
733 gm->ip6_protocol_registered = true;
735 else if (t->transport == IPIP_TRANSPORT_IP4 && !gm->ip4_protocol_registered)
737 ip4_register_protocol (IP_PROTOCOL_IP_IN_IP, ipip4_input_node.index);
738 ip4_register_protocol (IP_PROTOCOL_IPV6, ipip4_input_node.index);
739 gm->ip4_protocol_registered = true;
745 ipip_del_tunnel (u32 sw_if_index)
747 ipip_main_t *gm = &ipip_main;
748 vnet_main_t *vnm = gm->vnet_main;
750 ipip_tunnel_key_t key;
752 t = ipip_tunnel_db_find_by_sw_if_index (sw_if_index);
754 return VNET_API_ERROR_NO_SUCH_ENTRY;
756 if (t->mode == IPIP_MODE_P2MP)
757 nhrp_walk_itf (t->sw_if_index, ipip_tunnel_delete_nhrp_walk, t);
759 vnet_sw_interface_set_flags (vnm, sw_if_index, 0 /* down */ );
760 gm->tunnel_index_by_sw_if_index[sw_if_index] = ~0;
761 vnet_delete_hw_interface (vnm, t->hw_if_index);
762 hash_unset (gm->instance_used, t->user_instance);
764 ipip_mk_key (t, &key);
765 ipip_tunnel_db_remove (t, &key);
766 pool_put (gm->tunnels, t);
771 const static nhrp_vft_t ipip_nhrp_vft = {
772 .nv_added = ipip_nhrp_entry_added,
773 .nv_deleted = ipip_nhrp_entry_deleted,
776 static clib_error_t *
777 ipip_init (vlib_main_t * vm)
779 ipip_main_t *gm = &ipip_main;
781 clib_memset (gm, 0, sizeof (gm[0]));
783 gm->vnet_main = vnet_get_main ();
785 hash_create_mem (0, sizeof (ipip_tunnel_key_t), sizeof (uword));
787 nhrp_register (&ipip_nhrp_vft);
792 VLIB_INIT_FUNCTION (ipip_init);
795 * fd.io coding-style-patch-verification: ON
798 * eval: (c-set-style "gnu")