4.3BSD-Reno/share/man/cat3/resolver.0
RESOLVER(3) 1990 RESOLVER(3)
NNAAMMEE
res_query, res_search, res_mkquery, res_send, res_init,
dn_comp, dn_expand - resolver routines
SSYYNNOOPPSSIISS
##iinncclluuddee <<ssyyss//ttyyppeess..hh>>
##iinncclluuddee <<nneettiinneett//iinn..hh>>
##iinncclluuddee <<aarrppaa//nnaammeesseerr..hh>>
##iinncclluuddee <<rreessoollvv..hh>>
rreess__qquueerryy((ddnnaammee,, ccllaassss,, ttyyppee,, aannsswweerr,, aannsslleenn))
cchhaarr **ddnnaammee;;
iinntt ccllaassss,, ttyyppee;;
uu__cchhaarr **aannsswweerr;;
iinntt aannsslleenn;;
rreess__sseeaarrcchh((ddnnaammee,, ccllaassss,, ttyyppee,, aannsswweerr,, aannsslleenn))
cchhaarr **ddnnaammee;;
iinntt ccllaassss,, ttyyppee;;
uu__cchhaarr **aannsswweerr;;
iinntt aannsslleenn;;
rreess__mmkkqquueerryy((oopp,, ddnnaammee,, ccllaassss,, ttyyppee,, ddaattaa,, ddaattaalleenn,, nneewwrrrr,,
bbuuff,, bbuufflleenn))
iinntt oopp;;
cchhaarr **ddnnaammee;;
iinntt ccllaassss,, ttyyppee;;
cchhaarr **ddaattaa;;
iinntt ddaattaalleenn;;
ssttrruucctt rrrreecc **nneewwrrrr;;
cchhaarr **bbuuff;;
iinntt bbuufflleenn;;
rreess__sseenndd((mmssgg,, mmssgglleenn,, aannsswweerr,, aannsslleenn))
cchhaarr **mmssgg;;
iinntt mmssgglleenn;;
cchhaarr **aannsswweerr;;
iinntt aannsslleenn;;
rreess__iinniitt(())
ddnn__ccoommpp((eexxpp__ddnn,, ccoommpp__ddnn,, lleennggtthh,, ddnnppttrrss,, llaassttddnnppttrr))
cchhaarr **eexxpp__ddnn,, **ccoommpp__ddnn;;
iinntt lleennggtthh;;
cchhaarr ****ddnnppttrrss,, ****llaassttddnnppttrr;;
ddnn__eexxppaanndd((mmssgg,, eeoommoorriigg,, ccoommpp__ddnn,, eexxpp__ddnn,, lleennggtthh))
cchhaarr **mmssgg,, **eeoommoorriigg,, **ccoommpp__ddnn,, eexxpp__ddnn;;
iinntt lleennggtthh;;
DDEESSCCRRIIPPTTIIOONN
These routines are used for making, sending and interpreting
Printed 7/27/90 June 1
RESOLVER(3) 1990 RESOLVER(3)
query and reply messages with Internet domain name servers.
Global configuration and state information that is used by
the resolver routines is kept in the structure __r_e_s. Most
of the values have reasonable defaults and can be ignored.
Options stored in __r_e_s._o_p_t_i_o_n_s are defined in _r_e_s_o_l_v._h and
are as follows. Options are stored as a simple bit mask
containing the bitwise ``or'' of the options enabled.
RES_INIT
True if the initial name server address and default
domain name are initialized (i.e., _r_e_s__i_n_i_t has been
called).
RES_DEBUG
Print debugging messages.
RES_AAONLY
Accept authoritative answers only. With this option,
_r_e_s__s_e_n_d should continue until it finds an authorita-
tive answer or finds an error. Currently this is not
implemented.
RES_USEVC
Use TCP connections for queries instead of UDP
datagrams.
RES_STAYOPEN
Used with RES_USEVC to keep the TCP connection open
between queries. This is useful only in programs that
regularly do many queries. UDP should be the normal
mode used.
RES_IGNTC
Unused currently (ignore truncation errors, i.e., don't
retry with TCP).
RES_RECURSE
Set the recursion-desired bit in queries. This is the
default. (_r_e_s__s_e_n_d does not do iterative queries and
expects the name server to handle recursion.)
RES_DEFNAMES
If set, _r_e_s__s_e_a_r_c_h will append the default domain name
to single-component names (those that do not contain a
dot). This option is enabled by default.
RES_DNSRCH
If this option is set, _r_e_s__s_e_a_r_c_h will search for host
names in the current domain and in parent domains; see
_h_o_s_t_n_a_m_e(7). This is used by the standard host lookup
routine _g_e_t_h_o_s_t_b_y_n_a_m_e(3). This option is enabled by
Printed 7/27/90 June 2
RESOLVER(3) 1990 RESOLVER(3)
default.
The _r_e_s__i_n_i_t routine reads the configuration file (if any;
see _r_e_s_o_l_v_e_r(5)) to get the default domain name, search list
and the Internet address of the local name server(s). If no
server is configured, the host running the resolver is
tried. The current domain name is defined by the hostname
if not specified in the configuration file; it can be over-
ridden by the environment variable LOCALDOMAIN. Initializa-
tion normally occurs on the first call to one of the follow-
ing routines.
The _r_e_s__q_u_e_r_y function provides an interface to the server
query mechanism. It constructs a query, sends it to the
local server, awaits a response, and makes preliminary
checks on the reply. The query requests information of the
specified _t_y_p_e and _c_l_a_s_s for the specified fully-qualified
domain name _d_n_a_m_e . The reply message is left in the _a_n_s_w_e_r
buffer with length _a_n_s_l_e_n supplied by the caller.
The _r_e_s__s_e_a_r_c_h routine makes a query and awaits a response
like _r_e_s__q_u_e_r_y, but in addition, it implements the default
and search rules controlled by the RES_DEFNAMES and
RES_DNSRCH options. It returns the first successful reply.
The remaining routines are lower-level routines used by
_r_e_s__q_u_e_r_y. The _r_e_s__m_k_q_u_e_r_y function constructs a standard
query message and places it in _b_u_f. It returns the size of
the query, or -1 if the query is larger than _b_u_f_l_e_n. The
query type _o_p is usually QUERY, but can be any of the query
types defined in <_a_r_p_a/_n_a_m_e_s_e_r._h>. The domain name for the
query is given by _d_n_a_m_e. _N_e_w_r_r is currently unused but is
intended for making update messages.
The _r_e_s__s_e_n_d routine sends a pre-formatted query and returns
an answer. It will call _r_e_s__i_n_i_t if RES_INIT is not set,
send the query to the local name server, and handle timeouts
and retries. The length of the reply message is returned,
or -1 if there were errors.
The _d_n__c_o_m_p function compresses the domain name _e_x_p__d_n and
stores it in _c_o_m_p__d_n. The size of the compressed name is
returned or -1 if there were errors. The size of the array
pointed to by _c_o_m_p__d_n is given by _l_e_n_g_t_h. The compression
uses an array of pointers _d_n_p_t_r_s to previously-compressed
names in the current message. The first pointer points to
to the beginning of the message and the list ends with NULL.
The limit to the array is specified by _l_a_s_t_d_n_p_t_r. A side
effect of _d_n__c_o_m_p is to update the list of pointers for
labels inserted into the message as the name is compressed.
If _d_n_p_t_r is NULL, names are not compressed. If _l_a_s_t_d_n_p_t_r is
NULL, the list of labels is not updated.
Printed 7/27/90 June 3
RESOLVER(3) 1990 RESOLVER(3)
The _d_n__e_x_p_a_n_d entry expands the compressed domain name
_c_o_m_p__d_n to a full domain name The compressed name is con-
tained in a query or reply message; _m_s_g is a pointer to the
beginning of the message. The uncompressed name is placed
in the buffer indicated by _e_x_p__d_n which is of size _l_e_n_g_t_h.
The size of compressed name is returned or -1 if there was
an error.
FFIILLEESS
/etc/resolv.conf see resolver(5)
SSEEEE AALLSSOO
gethostbyname(3), named(8), resolver(5), hostname(7),
RFC1032, RFC1033, RFC1034, RFC1035, RFC974,
SMM:11 Name Server Operations Guide for BIND
Printed 7/27/90 June 4