.\" $NetBSD: getipnodebyname.3,v 1.1.1.2 2012/09/09 16:07:43 christos Exp $ .\" .\" Copyright (C) 2009 Internet Systems Consortium, Inc. ("ISC") .\" .\" Permission to use, copy, modify, and/or distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH .\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY .\" AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, .\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM .\" LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE .\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR .\" PERFORMANCE OF THIS SOFTWARE. .\" .\" Id: getipnodebyname.3,v 1.3 2009/01/22 23:49:23 tbox Exp .\" .Dd September 17, 1999 .Dt GETIPNODEBYNAME @LIB_NETWORK_EXT_U@ .Os BSD 4 .Sh NAME .Nm getipnodebyname , .Nm getipnodebyaddr .Nd get network host entry .br .Nm freehostent .Nd free network host entry .Sh SYNOPSIS .Fd #include .Pp .Ft struct hostent * .Fn getipnodebyname "const char *name" "int af" "int flags" "int *error" .Ft struct hostent * .Fn getipnodebyaddr "const void *addr" "size_t len" "int af" "int *error" .Ft void .Fn freehostent "struct hostent *he" .Sh DESCRIPTION .Fn Getipnodebyname , and .Fn getipnodebyaddr each return a pointer to a .Ft hostent structure (see below) describing an internet host referenced by name or by address, as the function names indicate. This structure contains either the information obtained from the name server, or broken-out fields from a line in .Pa /etc/hosts . If the local name server is not running, these routines do a lookup in .Pa /etc/hosts . .Bd -literal -offset indent struct hostent { char *h_name; /* official name of host */ char **h_aliases; /* alias list */ int h_addrtype; /* host address type */ int h_length; /* length of address */ char **h_addr_list; /* list of addresses from name server */ }; #define h_addr h_addr_list[0] /* address, for backward compatibility */ .Ed .Pp The members of this structure are: .Bl -tag -width "h_addr_list" .It h_name Official name of the host. .It h_aliases A zero-terminated array of alternate names for the host. .It h_addrtype The type of address being returned. .It h_length The length, in bytes, of the address. .It h_addr_list A zero-terminated array of network addresses for the host. Host addresses are returned in network byte order. .It h_addr The first address in .Li h_addr_list ; this is for backward compatibility. .El .Pp This structure should be freed after use by calling .Fn freehostent . .Pp When using the nameserver, .Fn getiphostbyaddr will search for the named host in each parent domain given in the .Dq Li search directive of .Xr resolv.conf @FORMAT_EXT@ unless the name contains a dot .Pq Dq \&. . If the name contains no dot, and if the environment variable .Ev HOSTALIASES contains the name of an alias file, the alias file will first be searched for an alias matching the input name. See .Xr hostname @DESC_EXT@ for the domain search procedure and the alias file format. .Pp .Fn Getiphostbyaddr can be told to look for IPv4 addresses, IPv6 addresses or both IPv4 and IPv6. If IPv4 addresses only are to be looked up then .Fa af should be set to .Dv AF_INET , otherwise it should be set to .Dv AF_INET6 . .Pp There are three flags that can be set .Bl -tag -width "AI_ADDRCONFIG" .It Dv AI_V4MAPPED Return IPv4 addresses if no IPv6 addresses are found. This flag is ignored unless .Fa af is .Dv AF_INET6 . .It Dv AI_ALL Return IPv4 addresses as well IPv6 addresses if .Dv AI_V4MAPPED is set. This flag is ignored unless .Fa af is .Dv AF_INET6 . .It Dv AI_ADDRCONFIG Only return addresses of a given type if the system has an active interface with that type. .El .Pp Also .Dv AI_DEFAULT is defined to be .Dv (AI_V4MAPPED|AI_ADDRCONFIG) . .Pp .Fn Getipnodebyaddr will lookup IPv4 mapped and compatible addresses in the IPv4 name space and IPv6 name space .Pp .Fn Freehostent frees the hostent structure allocated be .Fn getipnodebyname and .Fn getipnodebyaddr . The structures returned by .Fn gethostbyname , .Fn gethostbyname2 , .Fn gethostbyaddr and .Fn gethostent should not be passed to .Fn freehostent as they are pointers to static areas. .Sh ENVIRONMENT .Bl -tag -width "HOSTALIASES " -compact .It Ev HOSTALIASES Name of file containing .Pq Ar host alias , full hostname pairs. .El .Sh FILES .Bl -tag -width "HOSTALIASES " -compact .It Pa /etc/hosts See .Xr hosts @FORMAT_EXT@ . .El .Sh DIAGNOSTICS .Pp Error return status from .Fn getipnodebyname and .Fn getipnodebyaddr is indicated by return of a null pointer. In this case .Ft error may then be checked to see whether this is a temporary failure or an invalid or unknown host. .Ft errno can have the following values: .Bl -tag -width "HOST_NOT_FOUND " -offset indent .It Dv NETDB_INTERNAL This indicates an internal error in the library, unrelated to the network or name service. .Ft errno will be valid in this case; see .Xr perror @SYSCALL_EXT@ . .It Dv HOST_NOT_FOUND No such host is known. .It Dv TRY_AGAIN This is usually a temporary error and means that the local server did not receive a response from an authoritative server. A retry at some later time may succeed. .It Dv NO_RECOVERY Some unexpected server failure was encountered. This is a non-recoverable error, as one might expect. .It Dv NO_ADDRESS The requested name is valid but does not have an IP address; this is not a temporary error. This means that the name is known to the name server but there is no address associated with this name. Another type of request to the name server using this domain name will result in an answer; for example, a mail-forwarder may be registered for this domain. .El .Sh SEE ALSO .Xr hosts @FORMAT_EXT@ , .Xr hostname @DESC_EXT@ , .Xr resolver @LIB_NETWORK_EXT@ , .Xr resolver @FORMAT_EXT@ , .Xr gethostbyname @LIB_NETWORK_EXT@ , .Xr RFC2553 .