2 * esp_decrypt.c : IPSec ESP Decrypt node using DPDK Cryptodev
4 * Copyright (c) 2017 Intel 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 opy of the License at:
9 * http://www.apache.org/licenses/LICENSE-2.0
11 * Unless required by applicable law or agreed 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.
18 #include <vnet/vnet.h>
19 #include <vnet/api_errno.h>
20 #include <vnet/ip/ip.h>
22 #include <vnet/ipsec/ipsec.h>
23 #include <vnet/ipsec/esp.h>
24 #include <dpdk/buffer.h>
25 #include <dpdk/ipsec/ipsec.h>
26 #include <dpdk/device/dpdk.h>
27 #include <dpdk/device/dpdk_priv.h>
29 #define foreach_esp_decrypt_next \
30 _(DROP, "error-drop") \
31 _(IP4_INPUT, "ip4-input-no-checksum") \
32 _(IP6_INPUT, "ip6-input")
34 #define _(v, s) ESP_DECRYPT_NEXT_##v,
37 foreach_esp_decrypt_next
42 #define foreach_esp_decrypt_error \
43 _(RX_PKTS, "ESP pkts received") \
44 _(DECRYPTION_FAILED, "ESP decryption failed") \
45 _(REPLAY, "SA replayed packet") \
46 _(NOT_IP, "Not IP packet (dropped)") \
47 _(ENQ_FAIL, "Enqueue failed (buffer full)") \
48 _(DISCARD, "Not enough crypto operations, discarding frame") \
49 _(BAD_LEN, "Invalid ciphertext length") \
50 _(SESSION, "Failed to get crypto session") \
51 _(NOSUP, "Cipher/Auth not supported")
56 #define _(sym,str) ESP_DECRYPT_ERROR_##sym,
57 foreach_esp_decrypt_error
60 } esp_decrypt_error_t;
62 static char *esp_decrypt_error_strings[] = {
63 #define _(sym,string) string,
64 foreach_esp_decrypt_error
68 extern vlib_node_registration_t dpdk_esp4_decrypt_node;
69 extern vlib_node_registration_t dpdk_esp6_decrypt_node;
73 ipsec_crypto_alg_t crypto_alg;
74 ipsec_integ_alg_t integ_alg;
76 } esp_decrypt_trace_t;
78 /* packet trace format function */
80 format_esp_decrypt_trace (u8 * s, va_list * args)
82 CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
83 CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
84 esp_decrypt_trace_t *t = va_arg (*args, esp_decrypt_trace_t *);
85 u32 indent = format_get_indent (s);
87 s = format (s, "cipher %U auth %U\n",
88 format_ipsec_crypto_alg, t->crypto_alg,
89 format_ipsec_integ_alg, t->integ_alg);
90 s = format (s, "%U%U",
91 format_white_space, indent, format_esp_header, t->packet_data);
96 dpdk_esp_decrypt_inline (vlib_main_t * vm,
97 vlib_node_runtime_t * node,
98 vlib_frame_t * from_frame, int is_ip6)
100 u32 n_left_from, *from, *to_next, next_index, thread_index;
101 ipsec_main_t *im = &ipsec_main;
102 u32 thread_idx = vlib_get_thread_index ();
103 dpdk_crypto_main_t *dcm = &dpdk_crypto_main;
104 crypto_resource_t *res = 0;
106 crypto_alg_t *cipher_alg = 0, *auth_alg = 0;
107 struct rte_cryptodev_sym_session *session = 0;
108 u32 ret, last_sa_index = ~0;
109 u8 numa = rte_socket_id ();
111 crypto_worker_main_t *cwm =
112 vec_elt_at_index (dcm->workers_main, thread_idx);
113 struct rte_crypto_op **ops = cwm->ops;
115 from = vlib_frame_vector_args (from_frame);
116 n_left_from = from_frame->n_vectors;
117 thread_index = vm->thread_index;
119 ret = crypto_alloc_ops (numa, ops, n_left_from);
123 vlib_node_increment_counter (vm, dpdk_esp6_decrypt_node.index,
124 ESP_DECRYPT_ERROR_DISCARD, 1);
126 vlib_node_increment_counter (vm, dpdk_esp4_decrypt_node.index,
127 ESP_DECRYPT_ERROR_DISCARD, 1);
128 /* Discard whole frame */
132 next_index = ESP_DECRYPT_NEXT_DROP;
134 while (n_left_from > 0)
138 vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
140 while (n_left_from > 0 && n_left_to_next > 0)
143 u32 bi0, sa_index0, iv_size;
147 struct rte_mbuf *mb0;
148 struct rte_crypto_op *op;
155 b0 = vlib_get_buffer (vm, bi0);
156 mb0 = rte_mbuf_from_vlib_buffer (b0);
157 esp0 = vlib_buffer_get_current (b0);
160 CLIB_PREFETCH (esp0, sizeof (esp0[0]) + 16, LOAD);
162 CLIB_PREFETCH (mb0, CLIB_CACHE_LINE_BYTES, STORE);
166 ASSERT (op->status == RTE_CRYPTO_OP_STATUS_NOT_PROCESSED);
168 dpdk_op_priv_t *priv = crypto_op_get_priv (op);
169 /* store bi in op private */
174 sizeof (op[0]) + sizeof (op[0].sym[0]) + sizeof (priv[0]);
175 CLIB_PREFETCH (op, op_len, STORE);
177 sa_index0 = vnet_buffer (b0)->ipsec.sad_index;
178 vlib_prefetch_combined_counter (&ipsec_sa_counters,
179 thread_index, sa_index0);
181 if (sa_index0 != last_sa_index)
183 sa0 = pool_elt_at_index (im->sad, sa_index0);
186 vec_elt_at_index (dcm->cipher_algs, sa0->crypto_alg);
187 auth_alg = vec_elt_at_index (dcm->auth_algs, sa0->integ_alg);
189 is_aead = (cipher_alg->type == RTE_CRYPTO_SYM_XFORM_AEAD);
191 auth_alg = cipher_alg;
193 res_idx = get_resource (cwm, sa0);
195 if (PREDICT_FALSE (res_idx == (u16) ~ 0))
197 clib_warning ("unsupported SA by thread index %u",
200 vlib_node_increment_counter (vm,
201 dpdk_esp6_decrypt_node.index,
202 ESP_DECRYPT_ERROR_NOSUP, 1);
204 vlib_node_increment_counter (vm,
205 dpdk_esp4_decrypt_node.index,
206 ESP_DECRYPT_ERROR_NOSUP, 1);
212 res = vec_elt_at_index (dcm->resource, res_idx);
214 error = crypto_get_session (&session, sa_index0, res, cwm, 0);
215 if (PREDICT_FALSE (error || !session))
217 clib_warning ("failed to get crypto session");
219 vlib_node_increment_counter (vm,
220 dpdk_esp6_decrypt_node.index,
221 ESP_DECRYPT_ERROR_SESSION,
224 vlib_node_increment_counter (vm,
225 dpdk_esp4_decrypt_node.index,
226 ESP_DECRYPT_ERROR_SESSION,
234 last_sa_index = sa_index0;
237 /* anti-replay check */
238 if (ipsec_sa_anti_replay_check
239 (sa0, clib_host_to_net_u32 (esp0->seq)))
241 clib_warning ("failed anti-replay check");
243 vlib_node_increment_counter (vm,
244 dpdk_esp6_decrypt_node.index,
245 ESP_DECRYPT_ERROR_REPLAY, 1);
247 vlib_node_increment_counter (vm,
248 dpdk_esp4_decrypt_node.index,
249 ESP_DECRYPT_ERROR_REPLAY, 1);
257 priv->next = DPDK_CRYPTO_INPUT_NEXT_DECRYPT6_POST;
259 priv->next = DPDK_CRYPTO_INPUT_NEXT_DECRYPT4_POST;
261 /* FIXME multi-seg */
262 vlib_increment_combined_counter
263 (&ipsec_sa_counters, thread_index, sa_index0,
264 1, b0->current_length);
266 res->ops[res->n_ops] = op;
267 res->bi[res->n_ops] = bi0;
270 /* Convert vlib buffer to mbuf */
271 mb0->data_len = b0->current_length;
272 mb0->pkt_len = b0->current_length;
273 mb0->data_off = RTE_PKTMBUF_HEADROOM + b0->current_data;
275 trunc_size = auth_alg->trunc_size;
276 iv_size = cipher_alg->iv_len;
278 /* Outer IP header has already been stripped */
280 b0->current_length - sizeof (esp_header_t) - iv_size - trunc_size;
282 ASSERT (payload_len >= 4);
284 if (payload_len & (cipher_alg->boundary - 1))
286 clib_warning ("payload %u not multiple of %d\n",
287 payload_len, cipher_alg->boundary);
289 vlib_node_increment_counter (vm, dpdk_esp6_decrypt_node.index,
290 ESP_DECRYPT_ERROR_BAD_LEN, 1);
292 vlib_node_increment_counter (vm, dpdk_esp4_decrypt_node.index,
293 ESP_DECRYPT_ERROR_BAD_LEN, 1);
301 u32 cipher_off, cipher_len;
305 u8 *iv = (u8 *) (esp0 + 1);
307 dpdk_gcm_cnt_blk *icb = &priv->cb;
309 cipher_off = sizeof (esp_header_t) + iv_size;
310 cipher_len = payload_len;
312 u8 *digest = vlib_buffer_get_tail (b0) - trunc_size;
314 mb0->buf_physaddr + digest - ((u8 *) mb0->buf_addr);
316 if (!is_aead && cipher_alg->alg == RTE_CRYPTO_CIPHER_AES_CBC)
317 clib_memcpy_fast (icb, iv, 16);
320 u32 *_iv = (u32 *) iv;
322 crypto_set_icb (icb, sa0->salt, _iv[0], _iv[1]);
328 u32 *_aad = (u32 *) aad;
329 clib_memcpy_fast (aad, esp0, 8);
331 /* _aad[3] should always be 0 */
332 if (PREDICT_FALSE (ipsec_sa_is_set_USE_ESN (sa0)))
333 _aad[2] = clib_host_to_net_u32 (sa0->seq_hi);
339 auth_len = sizeof (esp_header_t) + iv_size + payload_len;
341 if (ipsec_sa_is_set_USE_ESN (sa0))
343 clib_memcpy_fast (priv->icv, digest, trunc_size);
344 u32 *_digest = (u32 *) digest;
345 _digest[0] = clib_host_to_net_u32 (sa0->seq_hi);
346 auth_len += sizeof (sa0->seq_hi);
350 op->phys_addr + (uintptr_t) priv->icv - (uintptr_t) op;
354 crypto_op_setup (is_aead, mb0, op, session, cipher_off, cipher_len,
355 0, auth_len, aad, digest, digest_paddr);
357 if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
359 esp_decrypt_trace_t *tr =
360 vlib_add_trace (vm, node, b0, sizeof (*tr));
361 tr->crypto_alg = sa0->crypto_alg;
362 tr->integ_alg = sa0->integ_alg;
363 clib_memcpy_fast (tr->packet_data, vlib_buffer_get_current (b0),
364 sizeof (esp_header_t));
367 vlib_put_next_frame (vm, node, next_index, n_left_to_next);
372 vlib_node_increment_counter (vm, dpdk_esp6_decrypt_node.index,
373 ESP_DECRYPT_ERROR_RX_PKTS,
374 from_frame->n_vectors);
376 crypto_enqueue_ops (vm, cwm, dpdk_esp6_decrypt_node.index,
377 ESP_DECRYPT_ERROR_ENQ_FAIL, numa, 0 /* encrypt */ );
381 vlib_node_increment_counter (vm, dpdk_esp4_decrypt_node.index,
382 ESP_DECRYPT_ERROR_RX_PKTS,
383 from_frame->n_vectors);
385 crypto_enqueue_ops (vm, cwm, dpdk_esp4_decrypt_node.index,
386 ESP_DECRYPT_ERROR_ENQ_FAIL, numa, 0 /* encrypt */ );
389 crypto_free_ops (numa, ops, cwm->ops + from_frame->n_vectors - ops);
391 return from_frame->n_vectors;
394 VLIB_NODE_FN (dpdk_esp4_decrypt_node) (vlib_main_t * vm,
395 vlib_node_runtime_t * node,
396 vlib_frame_t * from_frame)
398 return dpdk_esp_decrypt_inline (vm, node, from_frame, 0 /*is_ip6 */ );
402 VLIB_REGISTER_NODE (dpdk_esp4_decrypt_node) = {
403 .name = "dpdk-esp4-decrypt",
404 .vector_size = sizeof (u32),
405 .format_trace = format_esp_decrypt_trace,
406 .type = VLIB_NODE_TYPE_INTERNAL,
408 .n_errors = ARRAY_LEN(esp_decrypt_error_strings),
409 .error_strings = esp_decrypt_error_strings,
411 .n_next_nodes = ESP_DECRYPT_N_NEXT,
413 #define _(s,n) [ESP_DECRYPT_NEXT_##s] = n,
414 foreach_esp_decrypt_next
420 VLIB_NODE_FN (dpdk_esp6_decrypt_node) (vlib_main_t * vm,
421 vlib_node_runtime_t * node,
422 vlib_frame_t * from_frame)
424 return dpdk_esp_decrypt_inline (vm, node, from_frame, 1 /*is_ip6 */ );
428 VLIB_REGISTER_NODE (dpdk_esp6_decrypt_node) = {
429 .name = "dpdk-esp6-decrypt",
430 .vector_size = sizeof (u32),
431 .format_trace = format_esp_decrypt_trace,
432 .type = VLIB_NODE_TYPE_INTERNAL,
434 .n_errors = ARRAY_LEN(esp_decrypt_error_strings),
435 .error_strings = esp_decrypt_error_strings,
437 .n_next_nodes = ESP_DECRYPT_N_NEXT,
439 #define _(s,n) [ESP_DECRYPT_NEXT_##s] = n,
440 foreach_esp_decrypt_next
450 #define foreach_esp_decrypt_post_error \
451 _(PKTS, "ESP post pkts")
455 #define _(sym,str) ESP_DECRYPT_POST_ERROR_##sym,
456 foreach_esp_decrypt_post_error
458 ESP_DECRYPT_POST_N_ERROR,
459 } esp_decrypt_post_error_t;
461 static char *esp_decrypt_post_error_strings[] = {
462 #define _(sym,string) string,
463 foreach_esp_decrypt_post_error
467 extern vlib_node_registration_t dpdk_esp4_decrypt_post_node;
468 extern vlib_node_registration_t dpdk_esp6_decrypt_post_node;
471 format_esp_decrypt_post_trace (u8 * s, va_list * args)
473 CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
474 CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
475 esp_decrypt_trace_t *t = va_arg (*args, esp_decrypt_trace_t *);
476 u32 indent = format_get_indent (s);
478 s = format (s, "cipher %U auth %U\n",
479 format_ipsec_crypto_alg, t->crypto_alg,
480 format_ipsec_integ_alg, t->integ_alg);
482 ip4_header_t *ih4 = (ip4_header_t *) t->packet_data;
483 if ((ih4->ip_version_and_header_length & 0xF0) == 0x60)
485 format (s, "%U%U", format_white_space, indent, format_ip6_header, ih4);
488 format (s, "%U%U", format_white_space, indent, format_ip4_header, ih4);
494 dpdk_esp_decrypt_post_inline (vlib_main_t * vm,
495 vlib_node_runtime_t * node,
496 vlib_frame_t * from_frame, int is_ip6)
498 u32 n_left_from, *from, *to_next = 0, next_index;
501 ipsec_main_t *im = &ipsec_main;
502 dpdk_crypto_main_t *dcm = &dpdk_crypto_main;
504 from = vlib_frame_vector_args (from_frame);
505 n_left_from = from_frame->n_vectors;
507 next_index = node->cached_next_index;
509 while (n_left_from > 0)
513 vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
515 while (n_left_from > 0 && n_left_to_next > 0)
518 u32 bi0, iv_size, next0;
519 vlib_buffer_t *b0 = 0;
520 ip4_header_t *ih4 = 0, *oh4 = 0;
521 ip6_header_t *ih6 = 0, *oh6 = 0;
522 crypto_alg_t *cipher_alg, *auth_alg;
524 u8 trunc_size, is_aead;
525 u16 udp_encap_adv = 0;
527 next0 = ESP_DECRYPT_NEXT_DROP;
534 b0 = vlib_get_buffer (vm, bi0);
535 esp0 = vlib_buffer_get_current (b0);
537 sa_index0 = vnet_buffer (b0)->ipsec.sad_index;
538 sa0 = pool_elt_at_index (im->sad, sa_index0);
543 cipher_alg = vec_elt_at_index (dcm->cipher_algs, sa0->crypto_alg);
544 auth_alg = vec_elt_at_index (dcm->auth_algs, sa0->integ_alg);
545 is_aead = cipher_alg->type == RTE_CRYPTO_SYM_XFORM_AEAD;
547 auth_alg = cipher_alg;
549 trunc_size = auth_alg->trunc_size;
551 iv_size = cipher_alg->iv_len;
553 ipsec_sa_anti_replay_advance (sa0,
554 clib_host_to_net_u32 (esp0->seq));
556 /* if UDP encapsulation is used adjust the address of the IP header */
557 if (ipsec_sa_is_set_UDP_ENCAP (sa0)
558 && (b0->flags & VNET_BUFFER_F_IS_IP4))
560 udp_encap_adv = sizeof (udp_header_t);
563 if (b0->flags & VNET_BUFFER_F_IS_IP4)
564 ih4 = (ip4_header_t *)
565 ((u8 *) esp0 - udp_encap_adv - sizeof (ip4_header_t));
567 ih4 = (ip4_header_t *) ((u8 *) esp0 - sizeof (ip6_header_t));
569 vlib_buffer_advance (b0, sizeof (esp_header_t) + iv_size);
571 b0->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID;
572 f0 = (esp_footer_t *) (vlib_buffer_get_tail (b0) - trunc_size - 2);
573 b0->current_length -= (f0->pad_length + trunc_size + 2);
576 const u8 *padding = vlib_buffer_get_tail (b0);
577 if (PREDICT_FALSE (memcmp (padding, pad_data, f0->pad_length)))
579 clib_warning ("bad padding");
580 vlib_node_increment_counter (vm, dpdk_esp_decrypt_node.index,
581 ESP_DECRYPT_ERROR_DECRYPTION_FAILED,
586 if (ipsec_sa_is_set_IS_TUNNEL (sa0))
588 if (f0->next_header == IP_PROTOCOL_IP_IN_IP)
589 next0 = ESP_DECRYPT_NEXT_IP4_INPUT;
590 else if (f0->next_header == IP_PROTOCOL_IPV6)
591 next0 = ESP_DECRYPT_NEXT_IP6_INPUT;
594 clib_warning ("next header: 0x%x", f0->next_header);
596 vlib_node_increment_counter (vm,
597 dpdk_esp6_decrypt_node.index,
598 ESP_DECRYPT_ERROR_DECRYPTION_FAILED,
601 vlib_node_increment_counter (vm,
602 dpdk_esp4_decrypt_node.index,
603 ESP_DECRYPT_ERROR_DECRYPTION_FAILED,
608 else /* transport mode */
610 if ((ih4->ip_version_and_header_length & 0xF0) == 0x40)
612 u16 ih4_len = ip4_header_bytes (ih4);
613 vlib_buffer_advance (b0, -ih4_len - udp_encap_adv);
614 next0 = ESP_DECRYPT_NEXT_IP4_INPUT;
615 if (!ipsec_sa_is_set_UDP_ENCAP (sa0))
617 oh4 = vlib_buffer_get_current (b0);
618 memmove (oh4, ih4, ih4_len);
619 oh4->protocol = f0->next_header;
620 oh4->length = clib_host_to_net_u16 (b0->current_length);
621 oh4->checksum = ip4_header_checksum (oh4);
624 else if ((ih4->ip_version_and_header_length & 0xF0) == 0x60)
626 ih6 = (ip6_header_t *) ih4;
627 vlib_buffer_advance (b0, -sizeof (ip6_header_t));
628 oh6 = vlib_buffer_get_current (b0);
629 memmove (oh6, ih6, sizeof (ip6_header_t));
631 next0 = ESP_DECRYPT_NEXT_IP6_INPUT;
632 oh6->protocol = f0->next_header;
633 u16 len = b0->current_length - sizeof (ip6_header_t);
634 oh6->payload_length = clib_host_to_net_u16 (len);
638 clib_warning ("next header: 0x%x", f0->next_header);
640 vlib_node_increment_counter (vm,
641 dpdk_esp6_decrypt_node.index,
642 ESP_DECRYPT_ERROR_DECRYPTION_FAILED,
645 vlib_node_increment_counter (vm,
646 dpdk_esp4_decrypt_node.index,
647 ESP_DECRYPT_ERROR_DECRYPTION_FAILED,
653 vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
656 if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
658 esp_decrypt_trace_t *tr =
659 vlib_add_trace (vm, node, b0, sizeof (*tr));
660 tr->crypto_alg = sa0->crypto_alg;
661 tr->integ_alg = sa0->integ_alg;
662 ih4 = vlib_buffer_get_current (b0);
663 clib_memcpy_fast (tr->packet_data, ih4, sizeof (ip6_header_t));
666 vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
667 to_next, n_left_to_next, bi0,
670 vlib_put_next_frame (vm, node, next_index, n_left_to_next);
674 vlib_node_increment_counter (vm, dpdk_esp6_decrypt_post_node.index,
675 ESP_DECRYPT_POST_ERROR_PKTS,
676 from_frame->n_vectors);
678 vlib_node_increment_counter (vm, dpdk_esp4_decrypt_post_node.index,
679 ESP_DECRYPT_POST_ERROR_PKTS,
680 from_frame->n_vectors);
682 return from_frame->n_vectors;
685 VLIB_NODE_FN (dpdk_esp4_decrypt_post_node) (vlib_main_t * vm,
686 vlib_node_runtime_t * node,
687 vlib_frame_t * from_frame)
689 return dpdk_esp_decrypt_post_inline (vm, node, from_frame, 0 /*is_ip6 */ );
693 VLIB_REGISTER_NODE (dpdk_esp4_decrypt_post_node) = {
694 .name = "dpdk-esp4-decrypt-post",
695 .vector_size = sizeof (u32),
696 .format_trace = format_esp_decrypt_post_trace,
697 .type = VLIB_NODE_TYPE_INTERNAL,
699 .n_errors = ARRAY_LEN(esp_decrypt_post_error_strings),
700 .error_strings = esp_decrypt_post_error_strings,
702 .n_next_nodes = ESP_DECRYPT_N_NEXT,
704 #define _(s,n) [ESP_DECRYPT_NEXT_##s] = n,
705 foreach_esp_decrypt_next
711 VLIB_NODE_FN (dpdk_esp6_decrypt_post_node) (vlib_main_t * vm,
712 vlib_node_runtime_t * node,
713 vlib_frame_t * from_frame)
715 return dpdk_esp_decrypt_post_inline (vm, node, from_frame, 0 /*is_ip6 */ );
719 VLIB_REGISTER_NODE (dpdk_esp6_decrypt_post_node) = {
720 .name = "dpdk-esp6-decrypt-post",
721 .vector_size = sizeof (u32),
722 .format_trace = format_esp_decrypt_post_trace,
723 .type = VLIB_NODE_TYPE_INTERNAL,
725 .n_errors = ARRAY_LEN(esp_decrypt_post_error_strings),
726 .error_strings = esp_decrypt_post_error_strings,
728 .n_next_nodes = ESP_DECRYPT_N_NEXT,
730 #define _(s,n) [ESP_DECRYPT_NEXT_##s] = n,
731 foreach_esp_decrypt_next
738 * fd.io coding-style-patch-verification: ON
741 * eval: (c-set-style "gnu")