text: /* ssl/d1_both.c */
  /*
   * DTLS implementation written by Nagendra Modadugu
   * (nagendra@cs.stanford.edu) for the OpenSSL project 2005.
   */
  /* ====================================================================
   * Copyright (c) 1998-2005 The OpenSSL Project.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. All advertising materials mentioning features or use of this
   *    software must display the following acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
   *
   * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
   *    endorse or promote products derived from this software without
   *    prior written permission. For written permission, please contact
   *    openssl-core@openssl.org.
   *
   * 5. Products derived from this software may not be called "OpenSSL"
   *    nor may "OpenSSL" appear in their names without prior written
   *    permission of the OpenSSL Project.
   *
   * 6. Redistributions of any form whatsoever must retain the following
   *    acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
   *
   * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
   * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   * ====================================================================
   *
   * This product includes cryptographic software written by Eric Young
   * (eay@cryptsoft.com).  This product includes software written by Tim
   * Hudson (tjh@cryptsoft.com).
   *
   */
  /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   * All rights reserved.
   *
   * This package is an SSL implementation written
   * by Eric Young (eay@cryptsoft.com).
   * The implementation was written so as to conform with Netscapes SSL.
   *
   * This library is free for commercial and non-commercial use as long as
   * the following conditions are aheared to.  The following conditions
   * apply to all code found in this distribution, be it the RC4, RSA,
   * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
   * included with this distribution is covered by the same copyright terms
   * except that the holder is Tim Hudson (tjh@cryptsoft.com).
   *
   * Copyright remains Eric Young's, and as such any Copyright notices in
   * the code are not to be removed.
   * If this package is used in a product, Eric Young should be given attribution
   * as the author of the parts of the library used.
   * This can be in the form of a textual message at program startup or
   * in documentation (online or textual) provided with the package.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *    "This product includes cryptographic software written by
   *     Eric Young (eay@cryptsoft.com)"
   *    The word 'cryptographic' can be left out if the rouines from the library
   *    being used are not cryptographic related :-).
   * 4. If you include any Windows specific code (or a derivative thereof) from
   *    the apps directory (application code) you must include an acknowledgement:
   *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
   *
   * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * The licence and distribution terms for any publically available version or
   * derivative of this code cannot be changed.  i.e. this code cannot simply be
   * copied and put under another distribution licence
   * [including the GNU Public Licence.]
   */
  
  #include <limits.h>
  #include <string.h>
  #include <stdio.h>
  #include "ssl_locl.h"
  #include <openssl/buffer.h>
  #include <openssl/rand.h>
  #include <openssl/objects.h>
  #include <openssl/evp.h>
  #include <openssl/x509.h>
  
  #define RSMBLY_BITMASK_SIZE(msg_len) (((msg_len) + 7) / 8)
  
  #define RSMBLY_BITMASK_MARK(bitmask, start, end) { \
                          if ((end) - (start) <= 8) { \
                                  long ii; \
                                  for (ii = (start); ii < (end); ii++) bitmask[((ii) >> 3)] |= (1 << ((ii) & 7)); \
                          } else { \
                                  long ii; \
                                  bitmask[((start) >> 3)] |= bitmask_start_values[((start) & 7)]; \
                                  for (ii = (((start) >> 3) + 1); ii < ((((end) - 1)) >> 3); ii++) bitmask[ii] = 0xff; \
                                  bitmask[(((end) - 1) >> 3)] |= bitmask_end_values[((end) & 7)]; \
                          } }
  
  #define RSMBLY_BITMASK_IS_COMPLETE(bitmask, msg_len, is_complete) { \
                          long ii; \
                          OPENSSL_assert((msg_len) > 0); \
                          is_complete = 1; \
                          if (bitmask[(((msg_len) - 1) >> 3)] != bitmask_end_values[((msg_len) & 7)]) is_complete = 0; \
                          if (is_complete) for (ii = (((msg_len) - 1) >> 3) - 1; ii >= 0 ; ii--) \
                                  if (bitmask[ii] != 0xff) { is_complete = 0; break; } }
  
  #if 0
  # define RSMBLY_BITMASK_PRINT(bitmask, msg_len) { \
                          long ii; \
                          printf("bitmask: "); for (ii = 0; ii < (msg_len); ii++) \
                          printf("%d ", (bitmask[ii >> 3] & (1 << (ii & 7))) >> (ii & 7)); \
                          printf("\n"); }
  #endif
  
  static unsigned char bitmask_start_values[] =
      { 0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80 };
  static unsigned char bitmask_end_values[] =
      { 0xff, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f };
  
  /* XDTLS:  figure out the right values */
  static const unsigned int g_probable_mtu[] = { 1500, 512, 256 };
  
  static void dtls1_fix_message_header(SSL *s, unsigned long frag_off,
                                       unsigned long frag_len);
  static unsigned char *dtls1_write_message_header(SSL *s, unsigned char *p);
  static void dtls1_set_message_header_int(SSL *s, unsigned char mt,
                                           unsigned long len,
                                           unsigned short seq_num,
                                           unsigned long frag_off,
                                           unsigned long frag_len);
  static long dtls1_get_message_fragment(SSL *s, int st1, int stn, long max,
                                         int *ok);
  
  static hm_fragment *dtls1_hm_fragment_new(unsigned long frag_len,
                                            int reassembly)
  {
      hm_fragment *frag = NULL;
      unsigned char *buf = NULL;
      unsigned char *bitmask = NULL;
  
      frag = (hm_fragment *)OPENSSL_malloc(sizeof(hm_fragment));
      if (frag == NULL)
          return NULL;
  
      if (frag_len) {
          buf = (unsigned char *)OPENSSL_malloc(frag_len);
          if (buf == NULL) {
              OPENSSL_free(frag);
              return NULL;
          }
      }
  
      /* zero length fragment gets zero frag->fragment */
      frag->fragment = buf;
  
      /* Initialize reassembly bitmask if necessary */
      if (reassembly) {
          bitmask =
              (unsigned char *)OPENSSL_malloc(RSMBLY_BITMASK_SIZE(frag_len));
          if (bitmask == NULL) {
              if (buf != NULL)
                  OPENSSL_free(buf);
              OPENSSL_free(frag);
              return NULL;
          }
          memset(bitmask, 0, RSMBLY_BITMASK_SIZE(frag_len));
      }
  
      frag->reassembly = bitmask;
  
      return frag;
  }
  
  void dtls1_hm_fragment_free(hm_fragment *frag)
  {
  
      if (frag->msg_header.is_ccs) {
          EVP_CIPHER_CTX_free(frag->msg_header.
                              saved_retransmit_state.enc_write_ctx);
          EVP_MD_CTX_destroy(frag->msg_header.
                             saved_retransmit_state.write_hash);
      }
      if (frag->fragment)
          OPENSSL_free(frag->fragment);
      if (frag->reassembly)
          OPENSSL_free(frag->reassembly);
      OPENSSL_free(frag);
  }
  
  static int dtls1_query_mtu(SSL *s)
  {
      if (s->d1->link_mtu) {
          s->d1->mtu =
              s->d1->link_mtu - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
          s->d1->link_mtu = 0;
      }
  
      /* AHA!  Figure out the MTU, and stick to the right size */
      if (s->d1->mtu < dtls1_min_mtu(s)) {
          if (!(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) {
              s->d1->mtu =
                  BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
  
              /*
               * I've seen the kernel return bogus numbers when it doesn't know
               * (initial write), so just make sure we have a reasonable number
               */
              if (s->d1->mtu < dtls1_min_mtu(s)) {
                  /* Set to min mtu */
                  s->d1->mtu = dtls1_min_mtu(s);
                  BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU,
                           s->d1->mtu, NULL);
              }
          } else
              return 0;
      }
      return 1;
  }
  
  /*
   * send s->init_buf in records of type 'type' (SSL3_RT_HANDSHAKE or
   * SSL3_RT_CHANGE_CIPHER_SPEC)
   */
  int dtls1_do_write(SSL *s, int type)
  {
      int ret;
      unsigned int curr_mtu;
      int retry = 1;
      unsigned int len, frag_off, mac_size, blocksize, used_len;
  
      if (!dtls1_query_mtu(s))
          return -1;
  
      OPENSSL_assert(s->d1->mtu >= dtls1_min_mtu(s)); /* should have something
                                                       * reasonable now */
  
      if (s->init_off == 0 && type == SSL3_RT_HANDSHAKE)
          OPENSSL_assert(s->init_num ==
                         (int)s->d1->w_msg_hdr.msg_len +
                         DTLS1_HM_HEADER_LENGTH);
  
      if (s->write_hash) {
          if (s->enc_write_ctx
              && EVP_CIPHER_CTX_mode(s->enc_write_ctx) == EVP_CIPH_GCM_MODE)
              mac_size = 0;
          else
              mac_size = EVP_MD_CTX_size(s->write_hash);
      } else
          mac_size = 0;
  
      if (s->enc_write_ctx &&
          (EVP_CIPHER_CTX_mode(s->enc_write_ctx) == EVP_CIPH_CBC_MODE))
          blocksize = 2 * EVP_CIPHER_block_size(s->enc_write_ctx->cipher);
      else
          blocksize = 0;
  
      frag_off = 0;
      s->rwstate = SSL_NOTHING;
  
      /* s->init_num shouldn't ever be < 0...but just in case */
      while (s->init_num > 0) {
          if (type == SSL3_RT_HANDSHAKE && s->init_off != 0) {
              /* We must be writing a fragment other than the first one */
  
              if (frag_off > 0) {
                  /* This is the first attempt at writing out this fragment */
  
                  if (s->init_off <= DTLS1_HM_HEADER_LENGTH) {
                      /*
                       * Each fragment that was already sent must at least have
                       * contained the message header plus one other byte.
                       * Therefore |init_off| must have progressed by at least
                       * |DTLS1_HM_HEADER_LENGTH + 1| bytes. If not something went
                       * wrong.
                       */
                      return -1;
                  }
  
                  /*
                   * Adjust |init_off| and |init_num| to allow room for a new
                   * message header for this fragment.
                   */
                  s->init_off -= DTLS1_HM_HEADER_LENGTH;
                  s->init_num += DTLS1_HM_HEADER_LENGTH;
              } else {
                  /*
                   * We must have been called again after a retry so use the
                   * fragment offset from our last attempt. We do not need
                   * to adjust |init_off| and |init_num| as above, because
                   * that should already have been done before the retry.
                   */
                  frag_off = s->d1->w_msg_hdr.frag_off;
              }
          }
  
          used_len = BIO_wpending(SSL_get_wbio(s)) + DTLS1_RT_HEADER_LENGTH
              + mac_size + blocksize;
          if (s->d1->mtu > used_len)
              curr_mtu = s->d1->mtu - used_len;
          else
              curr_mtu = 0;
  
          if (curr_mtu <= DTLS1_HM_HEADER_LENGTH) {
              /*
               * grr.. we could get an error if MTU picked was wrong
               */
              ret = BIO_flush(SSL_get_wbio(s));
              if (ret <= 0) {
                  s->rwstate = SSL_WRITING;
                  return ret;
              }
              used_len = DTLS1_RT_HEADER_LENGTH + mac_size + blocksize;
              if (s->d1->mtu > used_len + DTLS1_HM_HEADER_LENGTH) {
                  curr_mtu = s->d1->mtu - used_len;
              } else {
                  /* Shouldn't happen */
                  return -1;
              }
          }
  
          /*
           * We just checked that s->init_num > 0 so this cast should be safe
           */
          if (((unsigned int)s->init_num) > curr_mtu)
              len = curr_mtu;
          else
              len = s->init_num;
  
          /* Shouldn't ever happen */
          if (len > INT_MAX)
              len = INT_MAX;
  
          /*
           * XDTLS: this function is too long.  split out the CCS part
           */
          if (type == SSL3_RT_HANDSHAKE) {
              if (len < DTLS1_HM_HEADER_LENGTH) {
                  /*
                   * len is so small that we really can't do anything sensible
                   * so fail
                   */
                  return -1;
              }
              dtls1_fix_message_header(s, frag_off,
                                       len - DTLS1_HM_HEADER_LENGTH);
  
              dtls1_write_message_header(s,
                                         (unsigned char *)&s->init_buf->
                                         data[s->init_off]);
          }
  
          ret = dtls1_write_bytes(s, type, &s->init_buf->data[s->init_off],
                                  len);
          if (ret < 0) {
              /*
               * might need to update MTU here, but we don't know which
               * previous packet caused the failure -- so can't really
               * retransmit anything.  continue as if everything is fine and
               * wait for an alert to handle the retransmit
               */
              if (retry && BIO_ctrl(SSL_get_wbio(s),
                                    BIO_CTRL_DGRAM_MTU_EXCEEDED, 0, NULL) > 0) {
                  if (!(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) {
                      if (!dtls1_query_mtu(s))
                          return -1;
                      /* Have one more go */
                      retry = 0;
                  } else
                      return -1;
              } else {
                  return (-1);
              }
          } else {
  
              /*
               * bad if this assert fails, only part of the handshake message
               * got sent.  but why would this happen?
               */
              OPENSSL_assert(len == (unsigned int)ret);
  
              if (type == SSL3_RT_HANDSHAKE && !s->d1->retransmitting) {
                  /*
                   * should not be done for 'Hello Request's, but in that case
                   * we'll ignore the result anyway
                   */
                  unsigned char *p =
                      (unsigned char *)&s->init_buf->data[s->init_off];
                  const struct hm_header_st *msg_hdr = &s->d1->w_msg_hdr;
                  int xlen;
  
                  if (frag_off == 0 && s->version != DTLS1_BAD_VER) {
                      /*
                       * reconstruct message header is if it is being sent in
                       * single fragment
                       */
                      *p++ = msg_hdr->type;
                      l2n3(msg_hdr->msg_len, p);
                      s2n(msg_hdr->seq, p);
                      l2n3(0, p);
                      l2n3(msg_hdr->msg_len, p);
                      p -= DTLS1_HM_HEADER_LENGTH;
                      xlen = ret;
                  } else {
                      p += DTLS1_HM_HEADER_LENGTH;
                      xlen = ret - DTLS1_HM_HEADER_LENGTH;
                  }
  
                  ssl3_finish_mac(s, p, xlen);
              }
  
              if (ret == s->init_num) {
                  if (s->msg_callback)
                      s->msg_callback(1, s->version, type, s->init_buf->data,
                                      (size_t)(s->init_off + s->init_num), s,
                                      s->msg_callback_arg);
  
                  s->init_off = 0; /* done writing this message */
                  s->init_num = 0;
  
                  return (1);
              }
              s->init_off += ret;
              s->init_num -= ret;
              ret -= DTLS1_HM_HEADER_LENGTH;
              frag_off += ret;
  
              /*
               * We save the fragment offset for the next fragment so we have it
               * available in case of an IO retry. We don't know the length of the
               * next fragment yet so just set that to 0 for now. It will be
               * updated again later.
               */
              dtls1_fix_message_header(s, frag_off, 0);
          }
      }
      return (0);
  }
  
  /*
   * Obtain handshake message of message type 'mt' (any if mt == -1), maximum
   * acceptable body length 'max'. Read an entire handshake message.  Handshake
   * messages arrive in fragments.
   */
  long dtls1_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok)
  {
      int i, al;
      struct hm_header_st *msg_hdr;
      unsigned char *p;
      unsigned long msg_len;
  
      /*
       * s3->tmp is used to store messages that are unexpected, caused by the
       * absence of an optional handshake message
       */
      if (s->s3->tmp.reuse_message) {
          s->s3->tmp.reuse_message = 0;
          if ((mt >= 0) && (s->s3->tmp.message_type != mt)) {
              al = SSL_AD_UNEXPECTED_MESSAGE;
              SSLerr(SSL_F_DTLS1_GET_MESSAGE, SSL_R_UNEXPECTED_MESSAGE);
              goto f_err;
          }
          *ok = 1;
          s->init_msg = s->init_buf->data + DTLS1_HM_HEADER_LENGTH;
          s->init_num = (int)s->s3->tmp.message_size;
          return s->init_num;
      }
  
      msg_hdr = &s->d1->r_msg_hdr;
      memset(msg_hdr, 0x00, sizeof(struct hm_header_st));
  
   again:
      i = dtls1_get_message_fragment(s, st1, stn, max, ok);
      if (i == DTLS1_HM_BAD_FRAGMENT || i == DTLS1_HM_FRAGMENT_RETRY) {
          /* bad fragment received */
          goto again;
      } else if (i <= 0 && !*ok) {
          return i;
      }
  
      if (mt >= 0 && s->s3->tmp.message_type != mt) {
          al = SSL_AD_UNEXPECTED_MESSAGE;
          SSLerr(SSL_F_DTLS1_GET_MESSAGE, SSL_R_UNEXPECTED_MESSAGE);
          goto f_err;
      }
  
      p = (unsigned char *)s->init_buf->data;
      msg_len = msg_hdr->msg_len;
  
      /* reconstruct message header */
      *(p++) = msg_hdr->type;
      l2n3(msg_len, p);
      s2n(msg_hdr->seq, p);
      l2n3(0, p);
      l2n3(msg_len, p);
      if (s->version != DTLS1_BAD_VER) {
          p -= DTLS1_HM_HEADER_LENGTH;
          msg_len += DTLS1_HM_HEADER_LENGTH;
      }
  
      ssl3_finish_mac(s, p, msg_len);
      if (s->msg_callback)
          s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE,
                          p, msg_len, s, s->msg_callback_arg);
  
      memset(msg_hdr, 0x00, sizeof(struct hm_header_st));
  
      /* Don't change sequence numbers while listening */
      if (!s->d1->listen)
          s->d1->handshake_read_seq++;
  
      s->init_msg = s->init_buf->data + DTLS1_HM_HEADER_LENGTH;
      return s->init_num;
  
   f_err:
      ssl3_send_alert(s, SSL3_AL_FATAL, al);
      *ok = 0;
      return -1;
  }
  
  static int dtls1_preprocess_fragment(SSL *s, struct hm_header_st *msg_hdr,
                                       int max)
  {
      size_t frag_off, frag_len, msg_len;
  
      msg_len = msg_hdr->msg_len;
      frag_off = msg_hdr->frag_off;
      frag_len = msg_hdr->frag_len;
  
      /* sanity checking */
      if ((frag_off + frag_len) > msg_len) {
          SSLerr(SSL_F_DTLS1_PREPROCESS_FRAGMENT, SSL_R_EXCESSIVE_MESSAGE_SIZE);
          return SSL_AD_ILLEGAL_PARAMETER;
      }
  
      if ((frag_off + frag_len) > (unsigned long)max) {
          SSLerr(SSL_F_DTLS1_PREPROCESS_FRAGMENT, SSL_R_EXCESSIVE_MESSAGE_SIZE);
          return SSL_AD_ILLEGAL_PARAMETER;
      }
  
      if (s->d1->r_msg_hdr.frag_off == 0) { /* first fragment */
          /*
           * msg_len is limited to 2^24, but is effectively checked against max
           * above
           */
          if (!BUF_MEM_grow_clean
              (s->init_buf, msg_len + DTLS1_HM_HEADER_LENGTH)) {
              SSLerr(SSL_F_DTLS1_PREPROCESS_FRAGMENT, ERR_R_BUF_LIB);
              return SSL_AD_INTERNAL_ERROR;
          }
  
          s->s3->tmp.message_size = msg_len;
          s->d1->r_msg_hdr.msg_len = msg_len;
          s->s3->tmp.message_type = msg_hdr->type;
          s->d1->r_msg_hdr.type = msg_hdr->type;
          s->d1->r_msg_hdr.seq = msg_hdr->seq;
      } else if (msg_len != s->d1->r_msg_hdr.msg_len) {
          /*
           * They must be playing with us! BTW, failure to enforce upper limit
           * would open possibility for buffer overrun.
           */
          SSLerr(SSL_F_DTLS1_PREPROCESS_FRAGMENT, SSL_R_EXCESSIVE_MESSAGE_SIZE);
          return SSL_AD_ILLEGAL_PARAMETER;
      }
  
      return 0;                   /* no error */
  }
  
  static int dtls1_retrieve_buffered_fragment(SSL *s, long max, int *ok)
  {
      /*-
       * (0) check whether the desired fragment is available
       * if so:
       * (1) copy over the fragment to s->init_buf->data[]
       * (2) update s->init_num
       */
      pitem *item;
      hm_fragment *frag;
      int al;
  
      *ok = 0;
      item = pqueue_peek(s->d1->buffered_messages);
      if (item == NULL)
          return 0;
  
      frag = (hm_fragment *)item->data;
  
      /* Don't return if reassembly still in progress */
      if (frag->reassembly != NULL)
          return 0;
  
      if (s->d1->handshake_read_seq == frag->msg_header.seq) {
          unsigned long frag_len = frag->msg_header.frag_len;
          pqueue_pop(s->d1->buffered_messages);
  
          al = dtls1_preprocess_fragment(s, &frag->msg_header, max);
  
          if (al == 0) {          /* no alert */
              unsigned char *p =
                  (unsigned char *)s->init_buf->data + DTLS1_HM_HEADER_LENGTH;
              memcpy(&p[frag->msg_header.frag_off], frag->fragment,
                     frag->msg_header.frag_len);
          }
  
          dtls1_hm_fragment_free(frag);
          pitem_free(item);
  
          if (al == 0) {
              *ok = 1;
              return frag_len;
          }
  
          ssl3_send_alert(s, SSL3_AL_FATAL, al);
          s->init_num = 0;
          *ok = 0;
          return -1;
      } else
          return 0;
  }
  
  /*
   * dtls1_max_handshake_message_len returns the maximum number of bytes
   * permitted in a DTLS handshake message for |s|. The minimum is 16KB, but
   * may be greater if the maximum certificate list size requires it.
   */
  static unsigned long dtls1_max_handshake_message_len(const SSL *s)
  {
      unsigned long max_len =
          DTLS1_HM_HEADER_LENGTH + SSL3_RT_MAX_ENCRYPTED_LENGTH;
      if (max_len < (unsigned long)s->max_cert_list)
          return s->max_cert_list;
      return max_len;
  }
  
  static int
  dtls1_reassemble_fragment(SSL *s, const struct hm_header_st *msg_hdr, int *ok)
  {
      hm_fragment *frag = NULL;
      pitem *item = NULL;
      int i = -1, is_complete;
      unsigned char seq64be[8];
      unsigned long frag_len = msg_hdr->frag_len;
  
      if ((msg_hdr->frag_off + frag_len) > msg_hdr->msg_len ||
          msg_hdr->msg_len > dtls1_max_handshake_message_len(s))
          goto err;
  
      if (frag_len == 0)
          return DTLS1_HM_FRAGMENT_RETRY;
  
      /* Try to find item in queue */
      memset(seq64be, 0, sizeof(seq64be));
      seq64be[6] = (unsigned char)(msg_hdr->seq >> 8);
      seq64be[7] = (unsigned char)msg_hdr->seq;
      item = pqueue_find(s->d1->buffered_messages, seq64be);
  
      if (item == NULL) {
          frag = dtls1_hm_fragment_new(msg_hdr->msg_len, 1);
          if (frag == NULL)
              goto err;
          memcpy(&(frag->msg_header), msg_hdr, sizeof(*msg_hdr));
          frag->msg_header.frag_len = frag->msg_header.msg_len;
          frag->msg_header.frag_off = 0;
      } else {
          frag = (hm_fragment *)item->data;
          if (frag->msg_header.msg_len != msg_hdr->msg_len) {
              item = NULL;
              frag = NULL;
              goto err;
          }
      }
  
      /*
       * If message is already reassembled, this must be a retransmit and can
       * be dropped. In this case item != NULL and so frag does not need to be
       * freed.
       */
      if (frag->reassembly == NULL) {
          unsigned char devnull[256];
  
          while (frag_len) {
              i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE,
                                            devnull,
                                            frag_len >
                                            sizeof(devnull) ? sizeof(devnull) :
                                            frag_len, 0);
              if (i <= 0)
                  goto err;
              frag_len -= i;
          }
          return DTLS1_HM_FRAGMENT_RETRY;
      }
  
      /* read the body of the fragment (header has already been read */
      i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE,
                                    frag->fragment + msg_hdr->frag_off,
                                    frag_len, 0);
      if ((unsigned long)i != frag_len)
          i = -1;
      if (i <= 0)
          goto err;
  
      RSMBLY_BITMASK_MARK(frag->reassembly, (long)msg_hdr->frag_off,
                          (long)(msg_hdr->frag_off + frag_len));
  
      RSMBLY_BITMASK_IS_COMPLETE(frag->reassembly, (long)msg_hdr->msg_len,
                                 is_complete);
  
      if (is_complete) {
          OPENSSL_free(frag->reassembly);
          frag->reassembly = NULL;
      }
  
      if (item == NULL) {
          item = pitem_new(seq64be, frag);
          if (item == NULL) {
              i = -1;
              goto err;
          }
  
          item = pqueue_insert(s->d1->buffered_messages, item);
          /*
           * pqueue_insert fails iff a duplicate item is inserted. However,
           * |item| cannot be a duplicate. If it were, |pqueue_find|, above,
           * would have returned it and control would never have reached this
           * branch.
           */
          OPENSSL_assert(item != NULL);
      }
  
      return DTLS1_HM_FRAGMENT_RETRY;
  
   err:
      if (frag != NULL && item == NULL)
          dtls1_hm_fragment_free(frag);
      *ok = 0;
      return i;
  }
  
  static int
  dtls1_process_out_of_seq_message(SSL *s, const struct hm_header_st *msg_hdr,
                                   int *ok)
  {
      int i = -1;
      hm_fragment *frag = NULL;
      pitem *item = NULL;
      unsigned char seq64be[8];
      unsigned long frag_len = msg_hdr->frag_len;
  
      if ((msg_hdr->frag_off + frag_len) > msg_hdr->msg_len)
          goto err;
  
      /* Try to find item in queue, to prevent duplicate entries */
      memset(seq64be, 0, sizeof(seq64be));
      seq64be[6] = (unsigned char)(msg_hdr->seq >> 8);
      seq64be[7] = (unsigned char)msg_hdr->seq;
      item = pqueue_find(s->d1->buffered_messages, seq64be);
  
      /*
       * If we already have an entry and this one is a fragment, don't discard
       * it and rather try to reassemble it.
       */
      if (item != NULL && frag_len != msg_hdr->msg_len)
          item = NULL;
  
      /*
       * Discard the message if sequence number was already there, is too far
       * in the future, already in the queue or if we received a FINISHED
       * before the SERVER_HELLO, which then must be a stale retransmit.
       */
      if (msg_hdr->seq <= s->d1->handshake_read_seq ||
          msg_hdr->seq > s->d1->handshake_read_seq + 10 || item != NULL ||
          (s->d1->handshake_read_seq == 0 && msg_hdr->type == SSL3_MT_FINISHED))
      {
          unsigned char devnull[256];
  
          while (frag_len) {
              i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE,
                                            devnull,
                                            frag_len >
                                            sizeof(devnull) ? sizeof(devnull) :
                                            frag_len, 0);
              if (i <= 0)
                  goto err;
              frag_len -= i;
          }
      } else {
          if (frag_len != msg_hdr->msg_len)
              return dtls1_reassemble_fragment(s, msg_hdr, ok);
  
          if (frag_len > dtls1_max_handshake_message_len(s))
              goto err;
  
          frag = dtls1_hm_fragment_new(frag_len, 0);
          if (frag == NULL)
              goto err;
  
          memcpy(&(frag->msg_header), msg_hdr, sizeof(*msg_hdr));
  
          if (frag_len) {
              /*
               * read the body of the fragment (header has already been read
               */
              i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE,
                                            frag->fragment, frag_len, 0);
              if ((unsigned long)i != frag_len)
                  i = -1;
              if (i <= 0)
                  goto err;
          }
  
          item = pitem_new(seq64be, frag);
          if (item == NULL)
              goto err;
  
          item = pqueue_insert(s->d1->buffered_messages, item);
          /*
           * pqueue_insert fails iff a duplicate item is inserted. However,
           * |item| cannot be a duplicate. If it were, |pqueue_find|, above,
           * would have returned it. Then, either |frag_len| !=
           * |msg_hdr->msg_len| in which case |item| is set to NULL and it will
           * have been processed with |dtls1_reassemble_fragment|, above, or
           * the record will have been discarded.
           */
          OPENSSL_assert(item != NULL);
      }
  
      return DTLS1_HM_FRAGMENT_RETRY;
  
   err:
      if (frag != NULL && item == NULL)
          dtls1_hm_fragment_free(frag);
      *ok = 0;
      return i;
  }
  
  static long
  dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok)
  {
      unsigned char wire[DTLS1_HM_HEADER_LENGTH];
      unsigned long len, frag_off, frag_len;
      int i, al;
      struct hm_header_st msg_hdr;
  
   redo:
      /* see if we have the required fragment already */
      if ((frag_len = dtls1_retrieve_buffered_fragment(s, max, ok)) || *ok) {
          if (*ok)
              s->init_num = frag_len;
          return frag_len;
      }
  
      /* read handshake message header */
      i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE, wire,
                                    DTLS1_HM_HEADER_LENGTH, 0);
      if (i <= 0) {               /* nbio, or an error */
          s->rwstate = SSL_READING;
          *ok = 0;
          return i;
      }
      /* Handshake fails if message header is incomplete */
      if (i != DTLS1_HM_HEADER_LENGTH) {
          al = SSL_AD_UNEXPECTED_MESSAGE;
          SSLerr(SSL_F_DTLS1_GET_MESSAGE_FRAGMENT, SSL_R_UNEXPECTED_MESSAGE);
          goto f_err;
      }
  
      /* parse the message fragment header */
      dtls1_get_message_header(wire, &msg_hdr);
  
      len = msg_hdr.msg_len;
      frag_off = msg_hdr.frag_off;
      frag_len = msg_hdr.frag_len;
  
      /*
       * We must have at least frag_len bytes left in the record to be read.
       * Fragments must not span records.
       */
      if (frag_len > s->s3->rrec.length) {
          al = SSL3_AD_ILLEGAL_PARAMETER;
          SSLerr(SSL_F_DTLS1_GET_MESSAGE_FRAGMENT, SSL_R_BAD_LENGTH);
          goto f_err;
      }
  
      /*
       * if this is a future (or stale) message it gets buffered
       * (or dropped)--no further processing at this time
       * While listening, we accept seq 1 (ClientHello with cookie)
       * although we're still expecting seq 0 (ClientHello)
       */
      if (msg_hdr.seq != s->d1->handshake_read_seq
          && !(s->d1->listen && msg_hdr.seq == 1))
          return dtls1_process_out_of_seq_message(s, &msg_hdr, ok);
  
      if (frag_len && frag_len < len)
          return dtls1_reassemble_fragment(s, &msg_hdr, ok);
  
      if (!s->server && s->d1->r_msg_hdr.frag_off == 0 &&
          wire[0] == SSL3_MT_HELLO_REQUEST) {
          /*
           * The server may always send 'Hello Request' messages -- we are
           * doing a handshake anyway now, so ignore them if their format is
           * correct. Does not count for 'Finished' MAC.
           */
          if (wire[1] == 0 && wire[2] == 0 && wire[3] == 0) {
              if (s->msg_callback)
                  s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE,
                                  wire, DTLS1_HM_HEADER_LENGTH, s,
                                  s->msg_callback_arg);
  
              s->init_num = 0;
              goto redo;
          } else {                /* Incorrectly formated Hello request */
  
              al = SSL_AD_UNEXPECTED_MESSAGE;
              SSLerr(SSL_F_DTLS1_GET_MESSAGE_FRAGMENT,
                     SSL_R_UNEXPECTED_MESSAGE);
              goto f_err;
          }
      }
  
      if ((al = dtls1_preprocess_fragment(s, &msg_hdr, max)))
          goto f_err;
  
      if (frag_len > 0) {
          unsigned char *p =
              (unsigned char *)s->init_buf->data + DTLS1_HM_HEADER_LENGTH;
  
          i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE,
                                        &p[frag_off], frag_len, 0);
  
          /*
           * This shouldn't ever fail due to NBIO because we already checked
           * that we have enough data in the record
           */
          if (i <= 0) {
              s->rwstate = SSL_READING;
              *ok = 0;
              return i;
          }
      } else
          i = 0;
  
      /*
       * XDTLS: an incorrectly formatted fragment should cause the handshake
       * to fail
       */
      if (i != (int)frag_len) {
          al = SSL3_AD_ILLEGAL_PARAMETER;
          SSLerr(SSL_F_DTLS1_GET_MESSAGE_FRAGMENT, SSL3_AD_ILLEGAL_PARAMETER);
          goto f_err;
      }
  
      *ok = 1;
      s->state = stn;
  
      /*
       * Note that s->init_num is *not* used as current offset in
       * s->init_buf->data, but as a counter summing up fragments' lengths: as
       * soon as they sum up to handshake packet length, we assume we have got
       * all the fragments.
       */
      s->init_num = frag_len;
      return frag_len;
  
   f_err:
      ssl3_send_alert(s, SSL3_AL_FATAL, al);
      s->init_num = 0;
  
      *ok = 0;
      return (-1);
  }
  
  /*-
   * for these 2 messages, we need to
   * ssl->enc_read_ctx                    re-init
   * ssl->s3->read_sequence               zero
   * ssl->s3->read_mac_secret             re-init
   * ssl->session->read_sym_enc           assign
   * ssl->session->read_compression       assign
   * ssl->session->read_hash              assign
   */
  int dtls1_send_change_cipher_spec(SSL *s, int a, int b)
  {
      unsigned char *p;
  
      if (s->state == a) {
          p = (unsigned char *)s->init_buf->data;
          *p++ = SSL3_MT_CCS;
          s->d1->handshake_write_seq = s->d1->next_handshake_write_seq;
          s->init_num = DTLS1_CCS_HEADER_LENGTH;
  
          if (s->version == DTLS1_BAD_VER) {
              s->d1->next_handshake_write_seq++;
              s2n(s->d1->handshake_write_seq, p);
              s->init_num += 2;
          }
  
          s->init_off = 0;
  
          dtls1_set_message_header_int(s, SSL3_MT_CCS, 0,
                                       s->d1->handshake_write_seq, 0, 0);
  
          /* buffer the message to handle re-xmits */
          dtls1_buffer_message(s, 1);
  
          s->state = b;
      }
  
      /* SSL3_ST_CW_CHANGE_B */
      return (dtls1_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC));
  }
  
  int dtls1_read_failed(SSL *s, int code)
  {
      if (code > 0) {
          fprintf(stderr, "invalid state reached %s:%d", __FILE__, __LINE__);
          return 1;
      }
  
      if (!dtls1_is_timer_expired(s)) {
          /*
           * not a timeout, none of our business, let higher layers handle
           * this.  in fact it's probably an error
           */
          return code;
      }
  #ifndef OPENSSL_NO_HEARTBEATS
      /* done, no need to send a retransmit */
      if (!SSL_in_init(s) && !s->tlsext_hb_pending)
  #else
      /* done, no need to send a retransmit */
      if (!SSL_in_init(s))
  #endif
      {
          BIO_set_flags(SSL_get_rbio(s), BIO_FLAGS_READ);
          return code;
      }
  #if 0                           /* for now, each alert contains only one
                                   * record number */
      item = pqueue_peek(state->rcvd_records);
      if (item) {
          /* send an alert immediately for all the missing records */
      } else
  #endif
  
  #if 0                           /* no more alert sending, just retransmit the
                                   * last set of messages */
      if (state->timeout.read_timeouts >= DTLS1_TMO_READ_COUNT)
          ssl3_send_alert(s, SSL3_AL_WARNING,
                          DTLS1_AD_MISSING_HANDSHAKE_MESSAGE);
  #endif
  
      return dtls1_handle_timeout(s);
  }
  
  int dtls1_get_queue_priority(unsigned short seq, int is_ccs)
  {
      /*
       * The index of the retransmission queue actually is the message sequence
       * number, since the queue only contains messages of a single handshake.
       * However, the ChangeCipherSpec has no message sequence number and so
       * using only the sequence will result in the CCS and Finished having the
       * same index. To prevent this, the sequence number is multiplied by 2.
       * In case of a CCS 1 is subtracted. This does not only differ CSS and
       * Finished, it also maintains the order of the index (important for
       * priority queues) and fits in the unsigned short variable.
       */
      return seq * 2 - is_ccs;
  }
  
  int dtls1_retransmit_buffered_messages(SSL *s)
  {
      pqueue sent = s->d1->sent_messages;
      piterator iter;
      pitem *item;
      hm_fragment *frag;
      int found = 0;
  
      iter = pqueue_iterator(sent);
  
      for (item = pqueue_next(&iter); item != NULL; item = pqueue_next(&iter)) {
          frag = (hm_fragment *)item->data;
          if (dtls1_retransmit_message(s, (unsigned short)
                                       dtls1_get_queue_priority
                                       (frag->msg_header.seq,
                                        frag->msg_header.is_ccs), 0,
                                       &found) <= 0 && found) {
              fprintf(stderr, "dtls1_retransmit_message() failed\n");
              return -1;
          }
      }
  
      return 1;
  }
  
  int dtls1_buffer_message(SSL *s, int is_ccs)
  {
      pitem *item;
      hm_fragment *frag;
      unsigned char seq64be[8];
  
      /*
       * this function is called immediately after a message has been
       * serialized
       */
      OPENSSL_assert(s->init_off == 0);
  
      frag = dtls1_hm_fragment_new(s->init_num, 0);
      if (!frag)
          return 0;
  
      memcpy(frag->fragment, s->init_buf->data, s->init_num);
  
      if (is_ccs) {
          /* For DTLS1_BAD_VER the header length is non-standard */
          OPENSSL_assert(s->d1->w_msg_hdr.msg_len +
                         ((s->version==DTLS1_BAD_VER)?3:DTLS1_CCS_HEADER_LENGTH)
                         == (unsigned int)s->init_num);
      } else {
          OPENSSL_assert(s->d1->w_msg_hdr.msg_len +
                         DTLS1_HM_HEADER_LENGTH == (unsigned int)s->init_num);
      }
  
      frag->msg_header.msg_len = s->d1->w_msg_hdr.msg_len;
      frag->msg_header.seq = s->d1->w_msg_hdr.seq;
      frag->msg_header.type = s->d1->w_msg_hdr.type;
      frag->msg_header.frag_off = 0;
      frag->msg_header.frag_len = s->d1->w_msg_hdr.msg_len;
      frag->msg_header.is_ccs = is_ccs;
  
      /* save current state */
      frag->msg_header.saved_retransmit_state.enc_write_ctx = s->enc_write_ctx;
      frag->msg_header.saved_retransmit_state.write_hash = s->write_hash;
      frag->msg_header.saved_retransmit_state.compress = s->compress;
      frag->msg_header.saved_retransmit_state.session = s->session;
      frag->msg_header.saved_retransmit_state.epoch = s->d1->w_epoch;
  
      memset(seq64be, 0, sizeof(seq64be));
      seq64be[6] =
          (unsigned
           char)(dtls1_get_queue_priority(frag->msg_header.seq,
                                          frag->msg_header.is_ccs) >> 8);
      seq64be[7] =
          (unsigned
           char)(dtls1_get_queue_priority(frag->msg_header.seq,
                                          frag->msg_header.is_ccs));
  
      item = pitem_new(seq64be, frag);
      if (item == NULL) {
          dtls1_hm_fragment_free(frag);
          return 0;
      }
  #if 0
      fprintf(stderr, "buffered messge: \ttype = %xx\n", msg_buf->type);
      fprintf(stderr, "\t\t\t\t\tlen = %d\n", msg_buf->len);
      fprintf(stderr, "\t\t\t\t\tseq_num = %d\n", msg_buf->seq_num);
  #endif
  
      pqueue_insert(s->d1->sent_messages, item);
      return 1;
  }
  
  int
  dtls1_retransmit_message(SSL *s, unsigned short seq, unsigned long frag_off,
                           int *found)
  {
      int ret;
      /* XDTLS: for now assuming that read/writes are blocking */
      pitem *item;
      hm_fragment *frag;
      unsigned long header_length;
      unsigned char seq64be[8];
      struct dtls1_retransmit_state saved_state;
      unsigned char save_write_sequence[8];
  
      /*-
        OPENSSL_assert(s->init_num == 0);
        OPENSSL_assert(s->init_off == 0);
       */
  
      /* XDTLS:  the requested message ought to be found, otherwise error */
      memset(seq64be, 0, sizeof(seq64be));
      seq64be[6] = (unsigned char)(seq >> 8);
      seq64be[7] = (unsigned char)seq;
  
      item = pqueue_find(s->d1->sent_messages, seq64be);
      if (item == NULL) {
          fprintf(stderr, "retransmit:  message %d non-existant\n", seq);
          *found = 0;
          return 0;
      }
  
      *found = 1;
      frag = (hm_fragment *)item->data;
  
      if (frag->msg_header.is_ccs)
          header_length = DTLS1_CCS_HEADER_LENGTH;
      else
          header_length = DTLS1_HM_HEADER_LENGTH;
  
      memcpy(s->init_buf->data, frag->fragment,
             frag->msg_header.msg_len + header_length);
      s->init_num = frag->msg_header.msg_len + header_length;
  
      dtls1_set_message_header_int(s, frag->msg_header.type,
                                   frag->msg_header.msg_len,
                                   frag->msg_header.seq, 0,
                                   frag->msg_header.frag_len);
  
      /* save current state */
      saved_state.enc_write_ctx = s->enc_write_ctx;
      saved_state.write_hash = s->write_hash;
      saved_state.compress = s->compress;
      saved_state.session = s->session;
      saved_state.epoch = s->d1->w_epoch;
      saved_state.epoch = s->d1->w_epoch;
  
      s->d1->retransmitting = 1;
  
      /* restore state in which the message was originally sent */
      s->enc_write_ctx = frag->msg_header.saved_retransmit_state.enc_write_ctx;
      s->write_hash = frag->msg_header.saved_retransmit_state.write_hash;
      s->compress = frag->msg_header.saved_retransmit_state.compress;
      s->session = frag->msg_header.saved_retransmit_state.session;
      s->d1->w_epoch = frag->msg_header.saved_retransmit_state.epoch;
  
      if (frag->msg_header.saved_retransmit_state.epoch ==
          saved_state.epoch - 1) {
          memcpy(save_write_sequence, s->s3->write_sequence,
                 sizeof(s->s3->write_sequence));
          memcpy(s->s3->write_sequence, s->d1->last_write_sequence,
                 sizeof(s->s3->write_sequence));
      }
  
      ret = dtls1_do_write(s, frag->msg_header.is_ccs ?
                           SSL3_RT_CHANGE_CIPHER_SPEC : SSL3_RT_HANDSHAKE);
  
      /* restore current state */
      s->enc_write_ctx = saved_state.enc_write_ctx;
      s->write_hash = saved_state.write_hash;
      s->compress = saved_state.compress;
      s->session = saved_state.session;
      s->d1->w_epoch = saved_state.epoch;
  
      if (frag->msg_header.saved_retransmit_state.epoch ==
          saved_state.epoch - 1) {
          memcpy(s->d1->last_write_sequence, s->s3->write_sequence,
                 sizeof(s->s3->write_sequence));
          memcpy(s->s3->write_sequence, save_write_sequence,
                 sizeof(s->s3->write_sequence));
      }
  
      s->d1->retransmitting = 0;
  
      (void)BIO_flush(SSL_get_wbio(s));
      return ret;
  }
  
  /* call this function when the buffered messages are no longer needed */
  void dtls1_clear_record_buffer(SSL *s)
  {
      pitem *item;
  
      for (item = pqueue_pop(s->d1->sent_messages);
           item != NULL; item = pqueue_pop(s->d1->sent_messages)) {
          dtls1_hm_fragment_free((hm_fragment *)item->data);
          pitem_free(item);
      }
  }
  
  unsigned char *dtls1_set_message_header(SSL *s, unsigned char *p,
                                          unsigned char mt, unsigned long len,
                                          unsigned long frag_off,
                                          unsigned long frag_len)
  {
      /* Don't change sequence numbers while listening */
      if (frag_off == 0 && !s->d1->listen) {
          s->d1->handshake_write_seq = s->d1->next_handshake_write_seq;
          s->d1->next_handshake_write_seq++;
      }
  
      dtls1_set_message_header_int(s, mt, len, s->d1->handshake_write_seq,
                                   frag_off, frag_len);
  
      return p += DTLS1_HM_HEADER_LENGTH;
  }
  
  /* don't actually do the writing, wait till the MTU has been retrieved */
  static void
  dtls1_set_message_header_int(SSL *s, unsigned char mt,
                               unsigned long len, unsigned short seq_num,
                               unsigned long frag_off, unsigned long frag_len)
  {
      struct hm_header_st *msg_hdr = &s->d1->w_msg_hdr;
  
      msg_hdr->type = mt;
      msg_hdr->msg_len = len;
      msg_hdr->seq = seq_num;
      msg_hdr->frag_off = frag_off;
      msg_hdr->frag_len = frag_len;
  }
  
  static void
  dtls1_fix_message_header(SSL *s, unsigned long frag_off,
                           unsigned long frag_len)
  {
      struct hm_header_st *msg_hdr = &s->d1->w_msg_hdr;
  
      msg_hdr->frag_off = frag_off;
      msg_hdr->frag_len = frag_len;
  }
  
  static unsigned char *dtls1_write_message_header(SSL *s, unsigned char *p)
  {
      struct hm_header_st *msg_hdr = &s->d1->w_msg_hdr;
  
      *p++ = msg_hdr->type;
      l2n3(msg_hdr->msg_len, p);
  
      s2n(msg_hdr->seq, p);
      l2n3(msg_hdr->frag_off, p);
      l2n3(msg_hdr->frag_len, p);
  
      return p;
  }
  
  unsigned int dtls1_link_min_mtu(void)
  {
      return (g_probable_mtu[(sizeof(g_probable_mtu) /
                              sizeof(g_probable_mtu[0])) - 1]);
  }
  
  unsigned int dtls1_min_mtu(SSL *s)
  {
      return dtls1_link_min_mtu() - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
  }
  
  void
  dtls1_get_message_header(unsigned char *data, struct hm_header_st *msg_hdr)
  {
      memset(msg_hdr, 0x00, sizeof(struct hm_header_st));
      msg_hdr->type = *(data++);
      n2l3(data, msg_hdr->msg_len);
  
      n2s(data, msg_hdr->seq);
      n2l3(data, msg_hdr->frag_off);
      n2l3(data, msg_hdr->frag_len);
  }
  
  void dtls1_get_ccs_header(unsigned char *data, struct ccs_header_st *ccs_hdr)
  {
      memset(ccs_hdr, 0x00, sizeof(struct ccs_header_st));
  
      ccs_hdr->type = *(data++);
  }
  
  int dtls1_shutdown(SSL *s)
  {
      int ret;
  #ifndef OPENSSL_NO_SCTP
      BIO *wbio;
  
      wbio = SSL_get_wbio(s);
      if (wbio != NULL && BIO_dgram_is_sctp(wbio) &&
          !(s->shutdown & SSL_SENT_SHUTDOWN)) {
          ret = BIO_dgram_sctp_wait_for_dry(wbio);
          if (ret < 0)
              return -1;
  
          if (ret == 0)
              BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 1,
                       NULL);
      }
  #endif
      ret = ssl3_shutdown(s);
  #ifndef OPENSSL_NO_SCTP
      BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 0, NULL);
  #endif
      return ret;
  }
  
  #ifndef OPENSSL_NO_HEARTBEATS
  int dtls1_process_heartbeat(SSL *s)
  {
      unsigned char *p = &s->s3->rrec.data[0], *pl;
      unsigned short hbtype;
      unsigned int payload;
      unsigned int padding = 16;  /* Use minimum padding */
  
      if (s->msg_callback)
          s->msg_callback(0, s->version, TLS1_RT_HEARTBEAT,
                          &s->s3->rrec.data[0], s->s3->rrec.length,
                          s, s->msg_callback_arg);
  
      /* Read type and payload length first */
      if (1 + 2 + 16 > s->s3->rrec.length)
          return 0;               /* silently discard */
      if (s->s3->rrec.length > SSL3_RT_MAX_PLAIN_LENGTH)
          return 0;               /* silently discard per RFC 6520 sec. 4 */
  
      hbtype = *p++;
      n2s(p, payload);
      if (1 + 2 + payload + 16 > s->s3->rrec.length)
          return 0;               /* silently discard per RFC 6520 sec. 4 */
      pl = p;
  
      if (hbtype == TLS1_HB_REQUEST) {
          unsigned char *buffer, *bp;
          unsigned int write_length = 1 /* heartbeat type */  +
              2 /* heartbeat length */  +
              payload + padding;
          int r;
  
          if (write_length > SSL3_RT_MAX_PLAIN_LENGTH)
              return 0;
  
          /*
           * Allocate memory for the response, size is 1 byte message type,
           * plus 2 bytes payload length, plus payload, plus padding
           */
          buffer = OPENSSL_malloc(write_length);
          bp = buffer;
  
          /* Enter response type, length and copy payload */
          *bp++ = TLS1_HB_RESPONSE;
          s2n(payload, bp);
          memcpy(bp, pl, payload);
          bp += payload;
          /* Random padding */
          if (RAND_pseudo_bytes(bp, padding) < 0) {
              OPENSSL_free(buffer);
              return -1;
          }
  
          r = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buffer, write_length);
  
          if (r >= 0 && s->msg_callback)
              s->msg_callback(1, s->version, TLS1_RT_HEARTBEAT,
                              buffer, write_length, s, s->msg_callback_arg);
  
          OPENSSL_free(buffer);
  
          if (r < 0)
              return r;
      } else if (hbtype == TLS1_HB_RESPONSE) {
          unsigned int seq;
  
          /*
           * We only send sequence numbers (2 bytes unsigned int), and 16
           * random bytes, so we just try to read the sequence number
           */
          n2s(pl, seq);
  
          if (payload == 18 && seq == s->tlsext_hb_seq) {
              dtls1_stop_timer(s);
              s->tlsext_hb_seq++;
              s->tlsext_hb_pending = 0;
          }
      }
  
      return 0;
  }
  
  int dtls1_heartbeat(SSL *s)
  {
      unsigned char *buf, *p;
      int ret = -1;
      unsigned int payload = 18;  /* Sequence number + random bytes */
      unsigned int padding = 16;  /* Use minimum padding */
  
      /* Only send if peer supports and accepts HB requests... */
      if (!(s->tlsext_heartbeat & SSL_TLSEXT_HB_ENABLED) ||
          s->tlsext_heartbeat & SSL_TLSEXT_HB_DONT_SEND_REQUESTS) {
          SSLerr(SSL_F_DTLS1_HEARTBEAT, SSL_R_TLS_HEARTBEAT_PEER_DOESNT_ACCEPT);
          return -1;
      }
  
      /* ...and there is none in flight yet... */
      if (s->tlsext_hb_pending) {
          SSLerr(SSL_F_DTLS1_HEARTBEAT, SSL_R_TLS_HEARTBEAT_PENDING);
          return -1;
      }
  
      /* ...and no handshake in progress. */
      if (SSL_in_init(s) || s->in_handshake) {
          SSLerr(SSL_F_DTLS1_HEARTBEAT, SSL_R_UNEXPECTED_MESSAGE);
          return -1;
      }
  
      /*
       * Check if padding is too long, payload and padding must not exceed 2^14
       * - 3 = 16381 bytes in total.
       */
      OPENSSL_assert(payload + padding <= 16381);
  
      /*-
       * Create HeartBeat message, we just use a sequence number
       * as payload to distuingish different messages and add
       * some random stuff.
       *  - Message Type, 1 byte
       *  - Payload Length, 2 bytes (unsigned int)
       *  - Payload, the sequence number (2 bytes uint)
       *  - Payload, random bytes (16 bytes uint)
       *  - Padding
       */
      buf = OPENSSL_malloc(1 + 2 + payload + padding);
      p = buf;
      /* Message Type */
      *p++ = TLS1_HB_REQUEST;
      /* Payload length (18 bytes here) */
      s2n(payload, p);
      /* Sequence number */
      s2n(s->tlsext_hb_seq, p);
      /* 16 random bytes */
      if (RAND_pseudo_bytes(p, 16) < 0)
          goto err;
      p += 16;
      /* Random padding */
      if (RAND_pseudo_bytes(p, padding) < 0)
          goto err;
  
      ret = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buf, 3 + payload + padding);
      if (ret >= 0) {
          if (s->msg_callback)
              s->msg_callback(1, s->version, TLS1_RT_HEARTBEAT,
                              buf, 3 + payload + padding,
                              s, s->msg_callback_arg);
  
          dtls1_start_timer(s);
          s->tlsext_hb_pending = 1;
      }
  
  err:
      OPENSSL_free(buf);
  
      return ret;
  }
  #endif
  