+ /* esp_footer_t */
+ CLIB_PREFETCH (data + pd[1].current_length - pd[1].icv_sz - 2,
+ CLIB_CACHE_LINE_BYTES, LOAD);
+
+ /* packet headers */
+ CLIB_PREFETCH (data - CLIB_CACHE_LINE_BYTES,
+ CLIB_CACHE_LINE_BYTES * 2, LOAD);
+ }
+
+ if (next[0] < ESP_DECRYPT_N_NEXT)
+ goto trace;
+
+ sa0 = vec_elt_at_index (im->sad, pd->sa_index);
+
+ /*
+ * redo the anti-reply check
+ * in this frame say we have sequence numbers, s, s+1, s+1, s+1
+ * and s and s+1 are in the window. When we did the anti-replay
+ * check above we did so against the state of the window (W),
+ * after packet s-1. So each of the packets in the sequence will be
+ * accepted.
+ * This time s will be cheked against Ws-1, s+1 chceked against Ws
+ * (i.e. the window state is updated/advnaced)
+ * so this time the successive s+! packet will be dropped.
+ * This is a consequence of batching the decrypts. If the
+ * check-dcrypt-advance process was done for each packet it would
+ * be fine. But we batch the decrypts because it's much more efficient
+ * to do so in SW and if we offload to HW and the process is async.
+ *
+ * You're probably thinking, but this means an attacker can send the
+ * above sequence and cause VPP to perform decrpyts that will fail,
+ * and that's true. But if the attacker can determine s (a valid
+ * sequence number in the window) which is non-trivial, it can generate
+ * a sequence s, s+1, s+2, s+3, ... s+n and nothing will prevent any
+ * implementation, sequential or batching, from decrypting these.
+ */
+ if (ipsec_sa_anti_replay_check (sa0, pd->seq))
+ {
+ b[0]->error = node->errors[ESP_DECRYPT_ERROR_REPLAY];
+ next[0] = ESP_DECRYPT_NEXT_DROP;
+ goto trace;
+ }
+
+ ipsec_sa_anti_replay_advance (sa0, pd->seq);
+
+ u8 pad_length = 0, next_header = 0;
+ u16 icv_sz = pd->icv_removed ? 0 : pd->icv_sz;
+
+ if (pd->free_buffer_index)
+ vlib_buffer_free_one (vm, pd->free_buffer_index);
+
+ if (pd->lb->current_length < sizeof (esp_footer_t) + icv_sz)
+ {
+ /* esp footer is either splitted in two buffers or in the before
+ * last buffer */
+
+ vlib_buffer_t *before_last = b[0], *bp = b[0];
+ while (bp->flags & VLIB_BUFFER_NEXT_PRESENT)
+ {
+ before_last = bp;
+ bp = vlib_get_buffer (vm, bp->next_buffer);
+ }
+ u8 *bt = vlib_buffer_get_tail (before_last);
+
+ if (pd->lb->current_length == icv_sz)
+ {
+ esp_footer_t *f = (esp_footer_t *) (bt - sizeof (*f));
+ pad_length = f->pad_length;
+ next_header = f->next_header;
+ }
+ else
+ {
+ pad_length = (bt - 1)[0];
+ next_header = ((u8 *) vlib_buffer_get_current (pd->lb))[0];
+ }
+ }
+ else
+ {
+ esp_footer_t *f =
+ (esp_footer_t *) (pd->lb->data + pd->lb->current_data +
+ pd->lb->current_length - sizeof (esp_footer_t) -
+ icv_sz);
+ pad_length = f->pad_length;
+ next_header = f->next_header;
+ }
+
+ u16 adv = pd->iv_sz + esp_sz;
+ u16 tail = sizeof (esp_footer_t) + pad_length + icv_sz;
+ u16 tail_orig = sizeof (esp_footer_t) + pad_length + pd->icv_sz;
+ b[0]->flags &= ~VLIB_BUFFER_TOTAL_LENGTH_VALID;
+
+ if ((pd->flags & tun_flags) == 0 && !is_tun) /* transport mode */
+ {
+ u8 udp_sz = (is_ip6 == 0 && pd->flags & IPSEC_SA_FLAG_UDP_ENCAP) ?
+ sizeof (udp_header_t) : 0;
+ u16 ip_hdr_sz = pd->hdr_sz - udp_sz;
+ u8 *old_ip = b[0]->data + pd->current_data - ip_hdr_sz - udp_sz;
+ u8 *ip = old_ip + adv + udp_sz;
+
+ if (is_ip6 && ip_hdr_sz > 64)
+ memmove (ip, old_ip, ip_hdr_sz);
+ else
+ clib_memcpy_le64 (ip, old_ip, ip_hdr_sz);
+
+ b[0]->current_data = pd->current_data + adv - ip_hdr_sz;
+ b[0]->current_length = pd->current_length + ip_hdr_sz - adv;
+ esp_remove_tail (vm, b[0], pd->lb, tail);
+
+ if (is_ip6)
+ {
+ ip6_header_t *ip6 = (ip6_header_t *) ip;
+ u16 len = clib_net_to_host_u16 (ip6->payload_length);
+ len -= adv + tail_orig;
+ ip6->payload_length = clib_host_to_net_u16 (len);
+ ip6->protocol = next_header;
+ next[0] = ESP_DECRYPT_NEXT_IP6_INPUT;
+ }
+ else
+ {
+ ip4_header_t *ip4 = (ip4_header_t *) ip;
+ ip_csum_t sum = ip4->checksum;
+ u16 len = clib_net_to_host_u16 (ip4->length);
+ len = clib_host_to_net_u16 (len - adv - tail_orig - udp_sz);
+ sum = ip_csum_update (sum, ip4->protocol, next_header,
+ ip4_header_t, protocol);
+ sum = ip_csum_update (sum, ip4->length, len,
+ ip4_header_t, length);
+ ip4->checksum = ip_csum_fold (sum);
+ ip4->protocol = next_header;
+ ip4->length = len;
+ next[0] = ESP_DECRYPT_NEXT_IP4_INPUT;
+ }
+ }
+ else
+ {
+ if (PREDICT_TRUE (next_header == IP_PROTOCOL_IP_IN_IP))
+ {
+ next[0] = ESP_DECRYPT_NEXT_IP4_INPUT;
+ b[0]->current_data = pd->current_data + adv;
+ b[0]->current_length = pd->current_length - adv;
+ esp_remove_tail (vm, b[0], pd->lb, tail);
+ }
+ else if (next_header == IP_PROTOCOL_IPV6)
+ {
+ next[0] = ESP_DECRYPT_NEXT_IP6_INPUT;
+ b[0]->current_data = pd->current_data + adv;
+ b[0]->current_length = pd->current_length - adv;
+ esp_remove_tail (vm, b[0], pd->lb, tail);
+ }
+ else
+ {
+ if (is_tun && next_header == IP_PROTOCOL_GRE)