msgencode.c File Reference

This file contains a routines to encode DNS messages. More...

#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"
#include "sldns/sbuffer.h"
#include "services/localzone.h"
#include <sys/time.h>

Data Structures
struct	compress_tree_node
	Data structure to help domain name compression in outgoing messages. More...

Macros
#define	RETVAL_OUTMEM   -2
	return code that means the function ran out of memory.
#define	RETVAL_TRUNC   -4
	return code that means the data did not fit (completely) in the packet
#define	RETVAL_OK   0
	return code that means all is peachy keen.
#define	MAX_COMPRESSION_PER_MESSAGE   120
	Max compressions we are willing to perform; more than that will result in semi-compressed messages, or truncated even on TCP for huge messages, to avoid locking the CPU for long.

Functions
static int	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)
	Find domain name in tree, returns exact and closest match.
static struct compress_tree_node *	compress_tree_lookup (struct compress_tree_node **tree, uint8_t *dname, int labs, struct compress_tree_node ***insertpt)
	Lookup a domain name in compression tree.
static struct compress_tree_node *	compress_tree_newnode (uint8_t *dname, int labs, size_t offset, struct regional *region)
	Create node for domain name compression tree.
static int	compress_tree_store (uint8_t *dname, int labs, size_t offset, struct regional *region, struct compress_tree_node *closest, struct compress_tree_node **insertpt)
	Store domain name and ancestors into compression tree.
static int	write_compressed_dname (sldns_buffer *pkt, uint8_t *dname, int labs, struct compress_tree_node *p)
	compress a domain name
static int	compress_owner (struct ub_packed_rrset_key *key, sldns_buffer *pkt, struct regional *region, struct compress_tree_node **tree, size_t owner_pos, uint16_t *owner_ptr, int owner_labs, size_t *compress_count)
	compress owner name of RR, return RETVAL_OUTMEM RETVAL_TRUNC
static int	compress_any_dname (uint8_t *dname, sldns_buffer *pkt, int labs, struct regional *region, struct compress_tree_node **tree, size_t *compress_count)
	compress any domain name to the packet, return RETVAL_*
static const sldns_rr_descriptor *	type_rdata_compressible (struct ub_packed_rrset_key *key)
	return true if type needs domain name compression in rdata
static int	compress_rdata (sldns_buffer *pkt, uint8_t *rdata, size_t todolen, struct regional *region, struct compress_tree_node **tree, const sldns_rr_descriptor *desc, size_t *compress_count)
	compress domain names in rdata, return RETVAL_*
static int	rrset_belongs_in_reply (sldns_pkt_section s, uint16_t rrtype, uint16_t qtype, int dnssec)
	Returns true if RR type should be included.
static int	packed_rrset_encode (struct ub_packed_rrset_key *key, sldns_buffer *pkt, uint16_t *num_rrs, time_t timenow, struct regional *region, int do_data, int do_sig, struct compress_tree_node **tree, sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset, size_t *compress_count)
	store rrset in buffer in wireformat, return RETVAL_*
static int	insert_section (struct reply_info *rep, size_t num_rrsets, uint16_t *num_rrs, sldns_buffer *pkt, size_t rrsets_before, time_t timenow, struct regional *region, struct compress_tree_node **tree, sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset, size_t *compress_count)
	store msg section in wireformat buffer, return RETVAL_*
static int	insert_query (struct query_info *qinfo, struct compress_tree_node **tree, sldns_buffer *buffer, struct regional *region)
	store query section in wireformat buffer, return RETVAL
static int	positive_answer (struct reply_info *rep, uint16_t qtype)
static int	negative_answer (struct reply_info *rep)
int	reply_info_encode (struct query_info *qinfo, struct reply_info *rep, uint16_t id, uint16_t flags, sldns_buffer *buffer, time_t timenow, struct regional *region, uint16_t udpsize, int dnssec, int minimise)
	Regenerate the wireformat from the stored msg reply.
uint16_t	calc_edns_field_size (struct edns_data *edns)
	Estimate size of EDNS record in packet.
uint16_t	calc_edns_option_size (struct edns_data *edns, uint16_t code)
	Calculate the size of a specific EDNS option in packet.
uint16_t	calc_ede_option_size (struct edns_data *edns, uint16_t *txt_size)
	Calculate the size of the EDE option(s) in packet.
static void	ede_trim_text (struct edns_option **list)
static void	attach_edns_record_max_msg_sz (sldns_buffer *pkt, struct edns_data *edns, uint16_t max_msg_sz)
void	attach_edns_record (sldns_buffer *pkt, struct edns_data *edns)
	Attach EDNS record to buffer.
int	reply_info_answer_encode (struct query_info *qinf, struct reply_info *rep, uint16_t id, uint16_t qflags, sldns_buffer *pkt, time_t timenow, int cached, struct regional *region, uint16_t udpsize, struct edns_data *edns, int dnssec, int secure)
	Generate answer from reply_info.
void	qinfo_query_encode (sldns_buffer *pkt, struct query_info *qinfo)
	Encode query packet.
void	extended_error_encode (sldns_buffer *buf, uint16_t rcode, struct query_info *qinfo, uint16_t qid, uint16_t qflags, uint16_t xflags, struct edns_data *edns)
	Encode an extended error.
void	error_encode (sldns_buffer *buf, int r, struct query_info *qinfo, uint16_t qid, uint16_t qflags, struct edns_data *edns)
	Encode an error.

Detailed Description

This file contains a routines to encode DNS messages.

Macro Definition Documentation

RETVAL_OUTMEM

#define RETVAL_OUTMEM   -2

return code that means the function ran out of memory.

negative so it does not conflict with DNS rcodes.

RETVAL_OK

#define RETVAL_OK   0

return code that means all is peachy keen.

Equal to DNS rcode NOERROR

Function Documentation

compress_tree_search()

static int 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  )

static

Find domain name in tree, returns exact and closest match.

Parameters

tree	root of tree.
dname	pointer to uncompressed dname.
labs	number of labels in domain name.
match	closest or exact match. guaranteed to be smaller or equal to the sought dname. can be null if the tree is empty.
matchlabels	number of labels that match with closest match. can be zero is there is no match.
insertpt	insert location for dname, if not found.

Returns

: 0 if no exact match.

References compress_tree_node::dname, dname_lab_cmp(), compress_tree_node::labs, compress_tree_node::left, match(), and compress_tree_node::right.

Referenced by compress_tree_lookup().

compress_tree_lookup()

static struct compress_tree_node * compress_tree_lookup ( struct compress_tree_node **  tree, uint8_t *  dname, int  labs, struct compress_tree_node ***  insertpt  )

static

Lookup a domain name in compression tree.

Parameters

tree	root of tree (not the node with '.').
dname	pointer to uncompressed dname.
labs	number of labels in domain name.
insertpt	insert location for dname, if not found.

Returns

: 0 if not found or compress treenode with best compression.

References compress_tree_search(), compress_tree_node::dname, compress_tree_node::labs, and compress_tree_node::parent.

Referenced by compress_any_dname(), and compress_owner().

compress_tree_newnode()

static struct compress_tree_node * compress_tree_newnode ( uint8_t *  dname, int  labs, size_t  offset, struct regional *  region  )

static

Create node for domain name compression tree.

Parameters

dname	pointer to uncompressed dname (stored in tree).
labs	number of labels in dname.
offset	offset into packet for dname.
region	how to allocate memory for new node.

Returns

new node or 0 on malloc failure.

References compress_tree_node::dname, compress_tree_node::labs, compress_tree_node::left, compress_tree_node::offset, compress_tree_node::parent, regional_alloc(), and compress_tree_node::right.

Referenced by compress_tree_store().

compress_tree_store()

static int compress_tree_store ( uint8_t *  dname, int  labs, size_t  offset, struct regional *  region, struct compress_tree_node *  closest, struct compress_tree_node **  insertpt  )

static

Store domain name and ancestors into compression tree.

Parameters

dname	pointer to uncompressed dname (stored in tree).
labs	number of labels in dname.
offset	offset into packet for dname.
region	how to allocate memory for new node.
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.
insertpt	where to insert the dname in tree.

Returns

: 0 on memory error.

References compress_tree_newnode(), compress_tree_node::dname, compress_tree_node::labs, log_assert, compress_tree_node::offset, compress_tree_node::parent, PTR_MAX_OFFSET, and compress_tree_node::right.

Referenced by compress_any_dname(), compress_owner(), and insert_query().

packed_rrset_encode()

static int packed_rrset_encode ( struct ub_packed_rrset_key *  key, sldns_buffer *  pkt, uint16_t *  num_rrs, time_t  timenow, struct regional *  region, int  do_data, int  do_sig, struct compress_tree_node **  tree, sldns_pkt_section  s, uint16_t  qtype, int  dnssec, size_t  rr_offset, size_t *  compress_count  )

static

store rrset in buffer in wireformat, return RETVAL_*

Determine relative time adjustment for TTL values. For an rrset with a fixed TTL, use the rrset's TTL as given.

References compress_any_dname(), compress_owner(), compress_rdata(), packed_rrset_data::count, lruhash_entry::data, packed_rrset_key::dname, dname_count_labels(), ub_packed_rrset_key::entry, packed_rrset_key::flags, LDNS_RR_TYPE_RRSIG, PACKED_RRSET_FIXEDTTL, RETVAL_OK, RETVAL_TRUNC, ub_packed_rrset_key::rk, packed_rrset_data::rr_data, packed_rrset_data::rr_len, packed_rrset_data::rr_ttl, rrset_belongs_in_reply(), packed_rrset_key::rrset_class, packed_rrset_data::rrsig_count, SERVE_EXPIRED, SERVE_EXPIRED_REPLY_TTL, SERVE_ORIGINAL_TTL, sldns_buffer_position(), sldns_buffer_remaining(), sldns_buffer_write(), sldns_buffer_write_u16(), sldns_buffer_write_u32(), packed_rrset_data::ttl_add, packed_rrset_key::type, and type_rdata_compressible().

Referenced by insert_section().

reply_info_encode()

int reply_info_encode	(	struct query_info *	qinfo,
		struct reply_info *	rep,
		uint16_t	id,
		uint16_t	flags,
		struct sldns_buffer *	buffer,
		time_t	timenow,
		struct regional *	region,
		uint16_t	udpsize,
		int	dnssec,
		int	minimise
	)

Regenerate the wireformat from the stored msg reply.

If the buffer is too small then the message is truncated at a whole rrset and the TC bit set, or whole rrsets are left out of the additional and the TC bit is not set.

Parameters

qinfo	query info to store.
rep	reply to store.
id	id value to store, network order.
flags	flags value to store, host order.
buffer	buffer to store the packet into.
timenow	time now, to adjust ttl values.
region	to store temporary data in.
udpsize	size of the answer, 512, from EDNS, or 64k for TCP.
dnssec	if 0 DNSSEC records are omitted from the answer.
minimise	if true, the answer is a minimal response, with authority and additional removed if possible.

Returns

: nonzero is success, or 0 on error: malloc failure (no log_err has been done).

References reply_info::an_numrrsets, reply_info::ar_numrrsets, BIT_AA, reply_info::flags, insert_query(), insert_section(), query_info::local_alias, reply_info::ns_numrrsets, reply_info::qdcount, query_info::qtype, RETVAL_OK, RETVAL_TRUNC, local_rrset::rrset, reply_info::rrset_count, RRSET_ROUNDROBIN, reply_info::rrsets, sldns_buffer_begin(), sldns_buffer_clear(), sldns_buffer_flip(), sldns_buffer_limit(), sldns_buffer_remaining(), sldns_buffer_set_limit(), sldns_buffer_write(), sldns_buffer_write_u16(), and sldns_buffer_write_u16_at().

Referenced by log_dns_msg(), perf_encode(), reply_info_answer_encode(), and testpkt().

calc_edns_field_size()

uint16_t calc_edns_field_size

(

struct edns_data *

edns

)

Estimate size of EDNS record in packet.

EDNS record will be no larger.

Parameters

edns	edns data or NULL.

Returns

octets to reserve for EDNS.

References edns_data::edns_present, edns_option::next, edns_option::opt_len, edns_data::opt_list_inplace_cb_out, and edns_data::opt_list_out.

Referenced by chaos_replystr(), extended_error_encode(), reply_info_answer_encode(), testpkt(), and write_q().

calc_edns_option_size()

uint16_t calc_edns_option_size	(	struct edns_data *	edns,
		uint16_t	code
	)

Calculate the size of a specific EDNS option in packet.

Parameters

edns	edns data or NULL.
code	the opt code to get the size of.

Returns

octets the option will take up.

References edns_data::edns_present, edns_option::next, edns_option::opt_code, edns_option::opt_len, edns_data::opt_list_inplace_cb_out, and edns_data::opt_list_out.

calc_ede_option_size()

uint16_t calc_ede_option_size	(	struct edns_data *	edns,
		uint16_t *	txt_size
	)

Calculate the size of the EDE option(s) in packet.

Also calculate separately the size of the EXTRA-TEXT field(s) in case we can trim them to fit. In this case include any LDNS_EDE_OTHER options in their entirety since they are useless without extra text.

Parameters

edns	edns data or NULL.
txt_size	the size of the EXTRA-TEXT field(s); this includes LDNS_EDE_OTHER in their entirety since they are useless without extra text.

Returns

octets the option will take up.

References edns_data::edns_present, edns_option::next, edns_option::opt_code, edns_option::opt_data, edns_option::opt_len, edns_data::opt_list_inplace_cb_out, and edns_data::opt_list_out.

Referenced by reply_info_answer_encode().

attach_edns_record()

void attach_edns_record	(	struct sldns_buffer *	pkt,
		struct edns_data *	edns
	)

Attach EDNS record to buffer.

Buffer has complete packet. There must be enough room left for the EDNS record.

Parameters

pkt	packet added to.
edns	if NULL or present=0, nothing is added to the packet.

References edns_data::edns_present, and edns_data::udp_size.

Referenced by chaos_replystr(), extended_error_encode(), perf_encode(), qlist_parse_line(), serviced_encode(), testpkt(), and write_q().

reply_info_answer_encode()

int reply_info_answer_encode	(	struct query_info *	qinf,
		struct reply_info *	rep,
		uint16_t	id,
		uint16_t	qflags,
		struct sldns_buffer *	dest,
		time_t	timenow,
		int	cached,
		struct regional *	region,
		uint16_t	udpsize,
		struct edns_data *	edns,
		int	dnssec,
		int	secure
	)

Generate answer from reply_info.

Parameters

qinf	query information that provides query section in packet.
rep	reply to fill in.
id	id word from the query.
qflags	flags word from the query.
dest	buffer to put message into; will truncate if it does not fit.
timenow	time to subtract.
cached	set true if a cached reply (so no AA bit). set false for the first reply.
region	where to allocate temp variables (for compression).
udpsize	size of the answer, 512, from EDNS, or 64k for TCP.
edns	EDNS data included in the answer, NULL for none. or if edns_present = 0, it is not included.
dnssec	if 0 DNSSEC records are omitted from the answer.
secure	if 1, the AD bit is set in the reply.

Returns

: 0 on error (server failure).

References reply_info::authoritative, BIT_AA, BIT_AD, BIT_CD, BIT_QR, BIT_RD, calc_ede_option_size(), calc_edns_field_size(), edns_opt_list_remove(), edns_data::edns_present, reply_info::flags, FLAGS_GET_RCODE, query_info::local_alias, log_assert, log_err(), MINIMAL_RESPONSES, edns_data::opt_list_inplace_cb_out, edns_data::opt_list_out, reply_info_encode(), sldns_buffer_capacity(), and sldns_buffer_limit().

Referenced by answer_from_cache(), answer_norec_from_cache(), auth_answer_encode(), local_encode(), mesh_do_callback(), mesh_send_reply(), and rpz_local_encode().

qinfo_query_encode()

void qinfo_query_encode	(	struct sldns_buffer *	pkt,
		struct query_info *	qinfo
	)

Encode query packet.

Assumes the buffer is large enough.

Parameters

pkt	where to store the packet.
qinfo	query info.

References packed_rrset_key::dname, packed_rrset_key::dname_len, query_info::local_alias, log_assert, query_info::qclass, query_info::qname, query_info::qname_len, query_info::qtype, ub_packed_rrset_key::rk, local_rrset::rrset, sldns_buffer_clear(), sldns_buffer_flip(), sldns_buffer_remaining(), sldns_buffer_skip(), sldns_buffer_write(), and sldns_buffer_write_u16().

Referenced by qlist_parse_line(), write_q(), xfr_create_ixfr_packet(), and xfr_create_soa_probe_packet().

extended_error_encode()

void extended_error_encode	(	struct sldns_buffer *	pkt,
		uint16_t	rcode,
		struct query_info *	qinfo,
		uint16_t	qid,
		uint16_t	qflags,
		uint16_t	xflags,
		struct edns_data *	edns
	)

Encode an extended error.

With QR and RA set.

Parameters

pkt	where to store the packet.
rcode	Extended RCODE value to encode.
qinfo	if not NULL, the query is included.
qid	query ID to set in packet. network order.
qflags	original query flags (to copy RD and CD bits). host order.
xflags	extra flags to set (such as for example BIT_AA and/or BIT_TC)
edns	if not NULL, this is the query edns info, and an edns reply is attached. Only attached if EDNS record fits reply. Without edns extended errors (i.e. > 15) will not be conveyed.

References attach_edns_record(), BIT_CD, BIT_QR, BIT_RA, BIT_RD, edns_data::bits, calc_edns_field_size(), packed_rrset_key::dname, packed_rrset_key::dname_len, EDNS_ADVERTISED_SIZE, EDNS_ADVERTISED_VERSION, EDNS_DO, edns_opt_list_remove(), edns_data::edns_version, edns_data::ext_rcode, query_info::local_alias, edns_data::opt_list_inplace_cb_out, edns_data::opt_list_out, query_info::qclass, query_info::qname, query_info::qname_len, query_info::qtype, ub_packed_rrset_key::rk, local_rrset::rrset, sldns_buffer_clear(), sldns_buffer_current(), sldns_buffer_flip(), sldns_buffer_limit(), sldns_buffer_skip(), sldns_buffer_write(), sldns_buffer_write_u16(), and edns_data::udp_size.

Referenced by error_encode(), and worker_handle_request().

error_encode()

void error_encode	(	struct sldns_buffer *	pkt,
		int	r,
		struct query_info *	qinfo,
		uint16_t	qid,
		uint16_t	qflags,
		struct edns_data *	edns
	)

Encode an error.

With QR and RA set.

Parameters

pkt	where to store the packet.
r	RCODE value to encode (may contain extra flags).
qinfo	if not NULL, the query is included.
qid	query ID to set in packet. network order.
qflags	original query flags (to copy RD and CD bits). host order.
edns	if not NULL, this is the query edns info, and an edns reply is attached. Only attached if EDNS record fits reply.

References extended_error_encode().

Referenced by answer_from_cache(), answer_norec_from_cache(), answer_notify(), auth_answer_encode(), auth_error_encode(), libworker_bg_done_cb(), local_encode(), local_error_encode(), mesh_new_client(), mesh_send_reply(), rpz_local_encode(), and worker_handle_request().