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msgencode.c

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/*
 * util/data/msgencode.c - Encode DNS messages, queries and replies.
 *
 * Copyright (c) 2007, NLnet Labs. All rights reserved.
 *
 * This software is open source.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * 
 * 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.
 * 
 * Neither the name of the NLNET LABS nor the names of its contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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 REGENTS 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.
 */

/**
 * \file
 *
 * This file contains a routines to encode DNS messages.
 */

#include "config.h"
#include "util/data/msgencode.h"
#include "util/data/msgreply.h"
#include "util/data/msgparse.h"
#include "util/data/dname.h"
#include "util/log.h"
#include "util/regional.h"
#include "util/net_help.h"

/** return code that means the function ran out of memory. negative so it does
 * not conflict with DNS rcodes. */
00053 #define RETVAL_OUTMEM   -2
/** return code that means the data did not fit (completely) in the packet */
00055 #define RETVAL_TRUNC    -4
/** return code that means all is peachy keen. Equal to DNS rcode NOERROR */
00057 #define RETVAL_OK 0

/**
 * Data structure to help domain name compression in outgoing messages.
 * A tree of dnames and their offsets in the packet is kept.
 * It is kept sorted, not canonical, but by label at least, so that after
 * a lookup of a name you know its closest match, and the parent from that
 * closest match. These are possible compression targets.
 *
 * It is a binary tree, not a rbtree or balanced tree, as the effort
 * of keeping it balanced probably outweighs usefulness (given typical
 * DNS packet size).
 */
00070 struct compress_tree_node {
      /** left node in tree, all smaller to this */
00072       struct compress_tree_node* left;
      /** right node in tree, all larger than this */
00074       struct compress_tree_node* right;

      /** the parent node - not for tree, but zone parent. One less label */
00077       struct compress_tree_node* parent;
      /** the domain name for this node. Pointer to uncompressed memory. */
00079       uint8_t* dname;
      /** number of labels in domain name, kept to help compare func. */
00081       int labs;
      /** offset in packet that points to this dname */
00083       size_t offset;
};

/**
 * Find domain name in tree, returns exact and closest match.
 * @param tree: root of tree.
 * @param dname: pointer to uncompressed dname.
 * @param labs: number of labels in domain name.
 * @param match: closest or exact match.
 *    guaranteed to be smaller or equal to the sought dname.
 *    can be null if the tree is empty.
 * @param matchlabels: number of labels that match with closest match.
 *    can be zero is there is no match.
 * @param insertpt: insert location for dname, if not found.
 * @return: 0 if no exact match.
 */
static int
00100 compress_tree_search(struct compress_tree_node** tree, uint8_t* dname,
      int labs, struct compress_tree_node** match, int* matchlabels,
      struct compress_tree_node*** insertpt)
{
      int c, n, closen=0;
      struct compress_tree_node* p = *tree;
      struct compress_tree_node* close = 0;
      struct compress_tree_node** prev = tree;
      while(p) {
            if((c = dname_lab_cmp(dname, labs, p->dname, p->labs, &n)) 
                  == 0) {
                  *matchlabels = n;
                  *match = p;
                  return 1;
            }
            if(c<0) {
                  prev = &p->left;
                  p = p->left;
            } else      {
                  closen = n;
                  close = p; /* p->dname is smaller than dname */
                  prev = &p->right;
                  p = p->right;
            }
      }
      *insertpt = prev;
      *matchlabels = closen;
      *match = close;
      return 0;
}

/**
 * Lookup a domain name in compression tree.
 * @param tree: root of tree (not the node with '.').
 * @param dname: pointer to uncompressed dname.
 * @param labs: number of labels in domain name.
 * @param insertpt: insert location for dname, if not found.
 * @return: 0 if not found or compress treenode with best compression.
 */
static struct compress_tree_node*
00140 compress_tree_lookup(struct compress_tree_node** tree, uint8_t* dname,
      int labs, struct compress_tree_node*** insertpt)
{
      struct compress_tree_node* p;
      int m;
      if(labs <= 1)
            return 0; /* do not compress root node */
      if(compress_tree_search(tree, dname, labs, &p, &m, insertpt)) {
            /* exact match */
            return p;
      }
      /* return some ancestor of p that compresses well. */
      if(m>1) {
            /* www.example.com. (labs=4) matched foo.example.com.(labs=4)
             * then matchcount = 3. need to go up. */
            while(p && p->labs > m)
                  p = p->parent;
            return p;
      }
      return 0;
}

/**
 * Create node for domain name compression tree.
 * @param dname: pointer to uncompressed dname (stored in tree).
 * @param labs: number of labels in dname.
 * @param offset: offset into packet for dname.
 * @param region: how to allocate memory for new node.
 * @return new node or 0 on malloc failure.
 */
static struct compress_tree_node*
00171 compress_tree_newnode(uint8_t* dname, int labs, size_t offset, 
      struct regional* region)
{
      struct compress_tree_node* n = (struct compress_tree_node*)
            regional_alloc(region, sizeof(struct compress_tree_node));
      if(!n) return 0;
      n->left = 0;
      n->right = 0;
      n->parent = 0;
      n->dname = dname;
      n->labs = labs;
      n->offset = offset;
      return n;
}

/**
 * Store domain name and ancestors into compression tree.
 * @param dname: pointer to uncompressed dname (stored in tree).
 * @param labs: number of labels in dname.
 * @param offset: offset into packet for dname.
 * @param region: how to allocate memory for new node.
 * @param closest: match from previous lookup, used to compress dname.
 *    may be NULL if no previous match.
 *    if the tree has an ancestor of dname already, this must be it.
 * @param insertpt: where to insert the dname in tree. 
 * @return: 0 on memory error.
 */
static int
00199 compress_tree_store(uint8_t* dname, int labs, size_t offset, 
      struct regional* region, struct compress_tree_node* closest, 
      struct compress_tree_node** insertpt)
{
      uint8_t lablen;
      struct compress_tree_node* newnode;
      struct compress_tree_node* prevnode = NULL;
      int uplabs = labs-1; /* does not store root in tree */
      if(closest) uplabs = labs - closest->labs;
      log_assert(uplabs >= 0);
      /* algorithms builds up a vine of dname-labels to hang into tree */
      while(uplabs--) {
            if(offset > PTR_MAX_OFFSET) {
                  /* insertion failed, drop vine */
                  return 1; /* compression pointer no longer useful */
            }
            if(!(newnode = compress_tree_newnode(dname, labs, offset, 
                  region))) {
                  /* insertion failed, drop vine */
                  return 0;
            }

            if(prevnode) {
                  /* chain nodes together, last one has one label more,
                   * so is larger than newnode, thus goes right. */
                  newnode->right = prevnode;
                  prevnode->parent = newnode;
            }

            /* next label */
            lablen = *dname++;
            dname += lablen;
            offset += lablen+1;
            prevnode = newnode;
            labs--;
      }
      /* if we have a vine, hang the vine into the tree */
      if(prevnode) {
            *insertpt = prevnode;
            prevnode->parent = closest;
      }
      return 1;
}

/** compress a domain name */
static int
00245 write_compressed_dname(ldns_buffer* pkt, uint8_t* dname, int labs,
      struct compress_tree_node* p)
{
      /* compress it */
      int labcopy = labs - p->labs;
      uint8_t lablen;
      uint16_t ptr;

      if(labs == 1) {
            /* write root label */
            if(ldns_buffer_remaining(pkt) < 1)
                  return 0;
            ldns_buffer_write_u8(pkt, 0);
            return 1;
      }

      /* copy the first couple of labels */
      while(labcopy--) {
            lablen = *dname++;
            if(ldns_buffer_remaining(pkt) < (size_t)lablen+1)
                  return 0;
            ldns_buffer_write_u8(pkt, lablen);
            ldns_buffer_write(pkt, dname, lablen);
            dname += lablen;
      }
      /* insert compression ptr */
      if(ldns_buffer_remaining(pkt) < 2)
            return 0;
      ptr = PTR_CREATE(p->offset);
      ldns_buffer_write_u16(pkt, ptr);
      return 1;
}

/** compress owner name of RR, return RETVAL_OUTMEM RETVAL_TRUNC */
static int
00280 compress_owner(struct ub_packed_rrset_key* key, ldns_buffer* pkt, 
      struct regional* region, struct compress_tree_node** tree, 
      size_t owner_pos, uint16_t* owner_ptr, int owner_labs)
{
      struct compress_tree_node* p;
      struct compress_tree_node** insertpt;
      if(!*owner_ptr) {
            /* compress first time dname */
            if((p = compress_tree_lookup(tree, key->rk.dname, 
                  owner_labs, &insertpt))) {
                  if(p->labs == owner_labs) 
                        /* avoid ptr chains, since some software is
                         * not capable of decoding ptr after a ptr. */
                        *owner_ptr = htons(PTR_CREATE(p->offset));
                  if(!write_compressed_dname(pkt, key->rk.dname, 
                        owner_labs, p))
                        return RETVAL_TRUNC;
                  /* check if typeclass+4 ttl + rdatalen is available */
                  if(ldns_buffer_remaining(pkt) < 4+4+2)
                        return RETVAL_TRUNC;
            } else {
                  /* no compress */
                  if(ldns_buffer_remaining(pkt) < key->rk.dname_len+4+4+2)
                        return RETVAL_TRUNC;
                  ldns_buffer_write(pkt, key->rk.dname, 
                        key->rk.dname_len);
                  if(owner_pos <= PTR_MAX_OFFSET)
                        *owner_ptr = htons(PTR_CREATE(owner_pos));
            }
            if(!compress_tree_store(key->rk.dname, owner_labs, 
                  owner_pos, region, p, insertpt))
                  return RETVAL_OUTMEM;
      } else {
            /* always compress 2nd-further RRs in RRset */
            if(owner_labs == 1) {
                  if(ldns_buffer_remaining(pkt) < 1+4+4+2) 
                        return RETVAL_TRUNC;
                  ldns_buffer_write_u8(pkt, 0);
            } else {
                  if(ldns_buffer_remaining(pkt) < 2+4+4+2) 
                        return RETVAL_TRUNC;
                  ldns_buffer_write(pkt, owner_ptr, 2);
            }
      }
      return RETVAL_OK;
}

/** compress any domain name to the packet, return RETVAL_* */
static int
00329 compress_any_dname(uint8_t* dname, ldns_buffer* pkt, int labs, 
      struct regional* region, struct compress_tree_node** tree)
{
      struct compress_tree_node* p;
      struct compress_tree_node** insertpt;
      size_t pos = ldns_buffer_position(pkt);
      if((p = compress_tree_lookup(tree, dname, labs, &insertpt))) {
            if(!write_compressed_dname(pkt, dname, labs, p))
                  return RETVAL_TRUNC;
      } else {
            if(!dname_buffer_write(pkt, dname))
                  return RETVAL_TRUNC;
      }
      if(!compress_tree_store(dname, labs, pos, region, p, insertpt))
            return RETVAL_OUTMEM;
      return RETVAL_OK;
}

/** return true if type needs domain name compression in rdata */
static const ldns_rr_descriptor*
00349 type_rdata_compressable(struct ub_packed_rrset_key* key)
{
      uint16_t t = ntohs(key->rk.type);
      if(ldns_rr_descript(t) && 
            ldns_rr_descript(t)->_compress == LDNS_RR_COMPRESS)
            return ldns_rr_descript(t);
      return 0;
}

/** compress domain names in rdata, return RETVAL_* */
static int
00360 compress_rdata(ldns_buffer* pkt, uint8_t* rdata, size_t todolen, 
      struct regional* region, struct compress_tree_node** tree, 
      const ldns_rr_descriptor* desc)
{
      int labs, r, rdf = 0;
      size_t dname_len, len, pos = ldns_buffer_position(pkt);
      uint8_t count = desc->_dname_count;

      ldns_buffer_skip(pkt, 2); /* rdata len fill in later */
      /* space for rdatalen checked for already */
      rdata += 2;
      todolen -= 2;
      while(todolen > 0 && count) {
            switch(desc->_wireformat[rdf]) {
            case LDNS_RDF_TYPE_DNAME:
                  labs = dname_count_size_labels(rdata, &dname_len);
                  if((r=compress_any_dname(rdata, pkt, labs, region, 
                        tree)) != RETVAL_OK)
                        return r;
                  rdata += dname_len;
                  todolen -= dname_len;
                  count--;
                  len = 0;
                  break;
            case LDNS_RDF_TYPE_STR:
                  len = *rdata + 1;
                  break;
            default:
                  len = get_rdf_size(desc->_wireformat[rdf]);
            }
            if(len) {
                  /* copy over */
                  if(ldns_buffer_remaining(pkt) < len)
                        return RETVAL_TRUNC;
                  ldns_buffer_write(pkt, rdata, len);
                  todolen -= len;
                  rdata += len;
            }
            rdf++;
      }
      /* copy remainder */
      if(todolen > 0) {
            if(ldns_buffer_remaining(pkt) < todolen)
                  return RETVAL_TRUNC;
            ldns_buffer_write(pkt, rdata, todolen);
      }

      /* set rdata len */
      ldns_buffer_write_u16_at(pkt, pos, ldns_buffer_position(pkt)-pos-2);
      return RETVAL_OK;
}

/** Returns true if RR type should be included */
static int
00414 rrset_belongs_in_reply(ldns_pkt_section s, uint16_t rrtype, uint16_t qtype, 
      int dnssec)
{
      if(dnssec)
            return 1;
      /* skip non DNSSEC types, except if directly queried for */
      if(s == LDNS_SECTION_ANSWER) {
            if(qtype == LDNS_RR_TYPE_ANY || qtype == rrtype)
                  return 1;
      }
      /* check DNSSEC-ness */
      switch(rrtype) {
            case LDNS_RR_TYPE_SIG:
            case LDNS_RR_TYPE_KEY:
            case LDNS_RR_TYPE_NXT:
            case LDNS_RR_TYPE_DS:
            case LDNS_RR_TYPE_RRSIG:
            case LDNS_RR_TYPE_NSEC:
            case LDNS_RR_TYPE_DNSKEY:
            case LDNS_RR_TYPE_NSEC3:
            case LDNS_RR_TYPE_NSEC3PARAMS:
                  return 0;
      }
      return 1;
}

/** store rrset in buffer in wireformat, return RETVAL_* */
static int
00442 packed_rrset_encode(struct ub_packed_rrset_key* key, ldns_buffer* pkt, 
      uint16_t* num_rrs, uint32_t timenow, struct regional* region,
      int do_data, int do_sig, struct compress_tree_node** tree,
      ldns_pkt_section s, uint16_t qtype, int dnssec)
{
      size_t i, owner_pos;
      int r, owner_labs;
      uint16_t owner_ptr = 0;
      struct packed_rrset_data* data = (struct packed_rrset_data*)
            key->entry.data;
      
      /* does this RR type belong in the answer? */
      if(!rrset_belongs_in_reply(s, ntohs(key->rk.type), qtype, dnssec))
            return RETVAL_OK;

      owner_labs = dname_count_labels(key->rk.dname);
      owner_pos = ldns_buffer_position(pkt);

      if(do_data) {
            const ldns_rr_descriptor* c = type_rdata_compressable(key);
            for(i=0; i<data->count; i++) {
                  if((r=compress_owner(key, pkt, region, tree, 
                        owner_pos, &owner_ptr, owner_labs))
                        != RETVAL_OK)
                        return r;
                  ldns_buffer_write(pkt, &key->rk.type, 2);
                  ldns_buffer_write(pkt, &key->rk.rrset_class, 2);
                  ldns_buffer_write_u32(pkt, data->rr_ttl[i]-timenow);
                  if(c) {
                        if((r=compress_rdata(pkt, data->rr_data[i],
                              data->rr_len[i], region, tree, c))
                              != RETVAL_OK)
                              return r;
                  } else {
                        if(ldns_buffer_remaining(pkt) < data->rr_len[i])
                              return RETVAL_TRUNC;
                        ldns_buffer_write(pkt, data->rr_data[i], 
                              data->rr_len[i]);
                  }
            }
      }
      /* insert rrsigs */
      if(do_sig && dnssec) {
            size_t total = data->count+data->rrsig_count;
            for(i=data->count; i<total; i++) {
                  if(owner_ptr && owner_labs != 1) {
                        if(ldns_buffer_remaining(pkt) <
                              2+4+4+data->rr_len[i]) 
                              return RETVAL_TRUNC;
                        ldns_buffer_write(pkt, &owner_ptr, 2);
                  } else {
                        if((r=compress_any_dname(key->rk.dname, 
                              pkt, owner_labs, region, tree))
                              != RETVAL_OK)
                              return r;
                        if(ldns_buffer_remaining(pkt) < 
                              4+4+data->rr_len[i])
                              return RETVAL_TRUNC;
                  }
                  ldns_buffer_write_u16(pkt, LDNS_RR_TYPE_RRSIG);
                  ldns_buffer_write(pkt, &key->rk.rrset_class, 2);
                  ldns_buffer_write_u32(pkt, data->rr_ttl[i]-timenow);
                  /* rrsig rdata cannot be compressed, perform 100+ byte
                   * memcopy. */
                  ldns_buffer_write(pkt, data->rr_data[i],
                        data->rr_len[i]);
            }
      }
      /* change rrnum only after we are sure it fits */
      if(do_data)
            *num_rrs += data->count;
      if(do_sig && dnssec)
            *num_rrs += data->rrsig_count;

      return RETVAL_OK;
}

/** store msg section in wireformat buffer, return RETVAL_* */
static int
00521 insert_section(struct reply_info* rep, size_t num_rrsets, uint16_t* num_rrs,
      ldns_buffer* pkt, size_t rrsets_before, uint32_t timenow, 
      struct regional* region, struct compress_tree_node** tree,
      ldns_pkt_section s, uint16_t qtype, int dnssec)
{
      int r;
      size_t i, setstart;
      *num_rrs = 0;
      if(s != LDNS_SECTION_ADDITIONAL) {
            if(s == LDNS_SECTION_ANSWER && qtype == LDNS_RR_TYPE_ANY)
                  dnssec = 1; /* include all types in ANY answer */
            for(i=0; i<num_rrsets; i++) {
                  setstart = ldns_buffer_position(pkt);
                  if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i], 
                        pkt, num_rrs, timenow, region, 1, 1, tree,
                        s, qtype, dnssec))
                        != RETVAL_OK) {
                        /* Bad, but if due to size must set TC bit */
                        /* trim off the rrset neatly. */
                        ldns_buffer_set_position(pkt, setstart);
                        return r;
                  }
            }
      } else {
            for(i=0; i<num_rrsets; i++) {
                  setstart = ldns_buffer_position(pkt);
                  if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i], 
                        pkt, num_rrs, timenow, region, 1, 0, tree,
                        s, qtype, dnssec))
                        != RETVAL_OK) {
                        ldns_buffer_set_position(pkt, setstart);
                        return r;
                  }
            }
            if(dnssec)
              for(i=0; i<num_rrsets; i++) {
                  setstart = ldns_buffer_position(pkt);
                  if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i], 
                        pkt, num_rrs, timenow, region, 0, 1, tree,
                        s, qtype, dnssec))
                        != RETVAL_OK) {
                        ldns_buffer_set_position(pkt, setstart);
                        return r;
                  }
              }
      }
      return RETVAL_OK;
}

/** store query section in wireformat buffer, return RETVAL */
static int
00572 insert_query(struct query_info* qinfo, struct compress_tree_node** tree, 
      ldns_buffer* buffer, struct regional* region)
{
      if(ldns_buffer_remaining(buffer) < 
            qinfo->qname_len+sizeof(uint16_t)*2)
            return RETVAL_TRUNC; /* buffer too small */
      /* the query is the first name inserted into the tree */
      if(!compress_tree_store(qinfo->qname, 
            dname_count_labels(qinfo->qname), 
            ldns_buffer_position(buffer), region, NULL, tree))
            return RETVAL_OUTMEM;
      ldns_buffer_write(buffer, qinfo->qname, qinfo->qname_len);
      ldns_buffer_write_u16(buffer, qinfo->qtype);
      ldns_buffer_write_u16(buffer, qinfo->qclass);
      return RETVAL_OK;
}

int 
00590 reply_info_encode(struct query_info* qinfo, struct reply_info* rep, 
      uint16_t id, uint16_t flags, ldns_buffer* buffer, uint32_t timenow, 
      struct regional* region, uint16_t udpsize, int dnssec)
{
      uint16_t ancount=0, nscount=0, arcount=0;
      struct compress_tree_node* tree = 0;
      int r;

      ldns_buffer_clear(buffer);
      if(udpsize < ldns_buffer_limit(buffer))
            ldns_buffer_set_limit(buffer, udpsize);
      if(ldns_buffer_remaining(buffer) < LDNS_HEADER_SIZE)
            return 0;

      ldns_buffer_write(buffer, &id, sizeof(uint16_t));
      ldns_buffer_write_u16(buffer, flags);
      ldns_buffer_write_u16(buffer, rep->qdcount);
      /* set an, ns, ar counts to zero in case of small packets */
      ldns_buffer_write(buffer, "\000\000\000\000\000\000", 6);

      /* insert query section */
      if(rep->qdcount) {
            if((r=insert_query(qinfo, &tree, buffer, region)) != 
                  RETVAL_OK) {
                  if(r == RETVAL_TRUNC) {
                        /* create truncated message */
                        ldns_buffer_write_u16_at(buffer, 4, 0);
                        LDNS_TC_SET(ldns_buffer_begin(buffer));
                        ldns_buffer_flip(buffer);
                        return 1;
                  }
                  return 0;
            }
      }

      /* insert answer section */
      if((r=insert_section(rep, rep->an_numrrsets, &ancount, buffer, 
            0, timenow, region, &tree, LDNS_SECTION_ANSWER, qinfo->qtype, 
            dnssec)) != RETVAL_OK) {
            if(r == RETVAL_TRUNC) {
                  /* create truncated message */
                  ldns_buffer_write_u16_at(buffer, 6, ancount);
                  LDNS_TC_SET(ldns_buffer_begin(buffer));
                  ldns_buffer_flip(buffer);
                  return 1;
            }
            return 0;
      }
      ldns_buffer_write_u16_at(buffer, 6, ancount);

      /* insert auth section */
      if((r=insert_section(rep, rep->ns_numrrsets, &nscount, buffer, 
            rep->an_numrrsets, timenow, region, &tree,
            LDNS_SECTION_AUTHORITY, qinfo->qtype, dnssec)) != RETVAL_OK) {
            if(r == RETVAL_TRUNC) {
                  /* create truncated message */
                  ldns_buffer_write_u16_at(buffer, 8, nscount);
                  LDNS_TC_SET(ldns_buffer_begin(buffer));
                  ldns_buffer_flip(buffer);
                  return 1;
            }
            return 0;
      }
      ldns_buffer_write_u16_at(buffer, 8, nscount);

      /* insert add section */
      if((r=insert_section(rep, rep->ar_numrrsets, &arcount, buffer, 
            rep->an_numrrsets + rep->ns_numrrsets, timenow, region, 
            &tree, LDNS_SECTION_ADDITIONAL, qinfo->qtype, 
            dnssec)) != RETVAL_OK) {
            if(r == RETVAL_TRUNC) {
                  /* no need to set TC bit, this is the additional */
                  ldns_buffer_write_u16_at(buffer, 10, arcount);
                  ldns_buffer_flip(buffer);
                  return 1;
            }
            return 0;
      }
      ldns_buffer_write_u16_at(buffer, 10, arcount);
      ldns_buffer_flip(buffer);
      return 1;
}

uint16_t
00674 calc_edns_field_size(struct edns_data* edns)
{
      if(!edns || !edns->edns_present) 
            return 0;
      /* domain root '.' + type + class + ttl + rdatalen(=0) */
      return 1 + 2 + 2 + 4 + 2;
}

void
00683 attach_edns_record(ldns_buffer* pkt, struct edns_data* edns)
{
      size_t len;
      if(!edns || !edns->edns_present)
            return;
      /* inc additional count */
      ldns_buffer_write_u16_at(pkt, 10,
            ldns_buffer_read_u16_at(pkt, 10) + 1);
      len = ldns_buffer_limit(pkt);
      ldns_buffer_clear(pkt);
      ldns_buffer_set_position(pkt, len);
      /* write EDNS record */
      ldns_buffer_write_u8(pkt, 0); /* '.' label */
      ldns_buffer_write_u16(pkt, LDNS_RR_TYPE_OPT); /* type */
      ldns_buffer_write_u16(pkt, edns->udp_size); /* class */
      ldns_buffer_write_u8(pkt, edns->ext_rcode); /* ttl */
      ldns_buffer_write_u8(pkt, edns->edns_version);
      ldns_buffer_write_u16(pkt, edns->bits);
      ldns_buffer_write_u16(pkt, 0); /* rdatalen */
      ldns_buffer_flip(pkt);
}

int 
00706 reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep, 
      uint16_t id, uint16_t qflags, ldns_buffer* pkt, uint32_t timenow,
      int cached, struct regional* region, uint16_t udpsize, 
      struct edns_data* edns, int dnssec, int secure)
{
      uint16_t flags;
      int attach_edns = 1;

      if(!cached) {
            /* original flags, copy RD and CD bits from query. */
            flags = rep->flags | (qflags & (BIT_RD|BIT_CD)); 
      } else {
            /* remove AA bit, copy RD and CD bits from query. */
            flags = (rep->flags & ~BIT_AA) | (qflags & (BIT_RD|BIT_CD)); 
      }
      if(secure && (dnssec || (qflags&BIT_AD)))
            flags |= BIT_AD;
      log_assert(flags & BIT_QR); /* QR bit must be on in our replies */
      if(udpsize < LDNS_HEADER_SIZE)
            return 0;
      if(udpsize < LDNS_HEADER_SIZE + calc_edns_field_size(edns)) {
            /* packet too small to contain edns, omit it. */
            attach_edns = 0;
      } else {
            /* reserve space for edns record */
            udpsize -= calc_edns_field_size(edns);
      }

      if(!reply_info_encode(qinf, rep, id, flags, pkt, timenow, region,
            udpsize, dnssec)) {
            log_err("reply encode: out of memory");
            return 0;
      }
      if(attach_edns)
            attach_edns_record(pkt, edns);
      return 1;
}

void 
00745 qinfo_query_encode(ldns_buffer* pkt, struct query_info* qinfo)
{
      uint16_t flags = 0; /* QUERY, NOERROR */
      ldns_buffer_clear(pkt);
      log_assert(ldns_buffer_remaining(pkt) >= 12+255+4/*max query*/);
      ldns_buffer_skip(pkt, 2); /* id done later */
      ldns_buffer_write_u16(pkt, flags);
      ldns_buffer_write_u16(pkt, 1); /* query count */
      ldns_buffer_write(pkt, "\000\000\000\000\000\000", 6); /* counts */
      ldns_buffer_write(pkt, qinfo->qname, qinfo->qname_len);
      ldns_buffer_write_u16(pkt, qinfo->qtype);
      ldns_buffer_write_u16(pkt, qinfo->qclass);
      ldns_buffer_flip(pkt);
}

void 
00761 error_encode(ldns_buffer* buf, int r, struct query_info* qinfo,
      uint16_t qid, uint16_t qflags, struct edns_data* edns)
{
      uint16_t flags;

      ldns_buffer_clear(buf);
      ldns_buffer_write(buf, &qid, sizeof(uint16_t));
      flags = (uint16_t)(BIT_QR | BIT_RA | r); /* QR and retcode*/
      flags |= (qflags & (BIT_RD|BIT_CD)); /* copy RD and CD bit */
      ldns_buffer_write_u16(buf, flags);
      if(qinfo) flags = 1;
      else  flags = 0;
      ldns_buffer_write_u16(buf, flags);
      flags = 0;
      ldns_buffer_write(buf, &flags, sizeof(uint16_t));
      ldns_buffer_write(buf, &flags, sizeof(uint16_t));
      ldns_buffer_write(buf, &flags, sizeof(uint16_t));
      if(qinfo) {
            ldns_buffer_write(buf, qinfo->qname, qinfo->qname_len);
            ldns_buffer_write_u16(buf, qinfo->qtype);
            ldns_buffer_write_u16(buf, qinfo->qclass);
      }
      ldns_buffer_flip(buf);
      if(edns) {
            struct edns_data es = *edns;
            es.edns_version = EDNS_ADVERTISED_VERSION;
            es.udp_size = EDNS_ADVERTISED_SIZE;
            es.ext_rcode = 0;
            es.bits &= EDNS_DO;
            if(ldns_buffer_limit(buf) + calc_edns_field_size(&es) >
                  edns->udp_size)
                  return;
            attach_edns_record(buf, &es);
      }
}

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