.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "<netdb.h>" P 2003 POSIX
.\" <netdb.h> 
.SH NAME
netdb.h \- definitions for network database operations
.SH SYNOPSIS
.LP
\fB#include <netdb.h>\fP
.SH DESCRIPTION
.LP
The \fI<netdb.h>\fP header may define the \fBin_port_t\fP type and
the \fBin_addr_t\fP type as described in \fI<netinet/in.h>\fP .
.LP
The \fI<netdb.h>\fP header shall define the \fBhostent\fP structure
that includes at least the following members:
.sp
.RS
.nf

\fBchar   *h_name      \fP Official name of the host. \fB
char  **h_aliases   \fP A pointer to an array of pointers to \fB
                    \fP alternative host names, terminated by a \fB
                    \fP null pointer. \fB
int     h_addrtype  \fP Address type. \fB
int     h_length    \fP The length, in bytes, of the address. \fB
char  **h_addr_list \fP A pointer to an array of pointers to network \fB
                    \fP addresses (in network byte order) for the host, \fB
                    \fP terminated by a null pointer. \fB
\fP
.fi
.RE
.LP
The \fI<netdb.h>\fP header shall define the \fBnetent\fP structure
that includes at least the following members:
.sp
.RS
.nf

\fBchar     *n_name     \fP Official, fully-qualified (including the \fB
                     \fP domain) name of the host. \fB
char    **n_aliases  \fP A pointer to an array of pointers to \fB
                     \fP alternative network names, terminated by a \fB
                     \fP null pointer. \fB
int       n_addrtype \fP The address type of the network. \fB
uint32_t  n_net      \fP The network number, in host byte order. \fB
\fP
.fi
.RE
.LP
The \fBuint32_t\fP type shall be defined as described in \fI<inttypes.h>\fP
\&.
.LP
The \fI<netdb.h>\fP header shall define the \fBprotoent\fP structure
that includes at least the following members:
.sp
.RS
.nf

\fBchar   *p_name    \fP Official name of the protocol. \fB
char  **p_aliases \fP A pointer to an array of pointers to \fB
                  \fP alternative protocol names, terminated by \fB
                  \fP a null pointer. \fB
int     p_proto   \fP The protocol number. \fB
\fP
.fi
.RE
.LP
The \fI<netdb.h>\fP header shall define the \fBservent\fP structure
that includes at least the following members:
.sp
.RS
.nf

\fBchar   *s_name    \fP Official name of the service. \fB
char  **s_aliases \fP A pointer to an array of pointers to \fB
                  \fP alternative service names, terminated by \fB
                  \fP a null pointer. \fB
int     s_port    \fP The port number at which the service \fB
                  \fP resides, in network byte order. \fB
char   *s_proto   \fP The name of the protocol to use when \fB
                  \fP contacting the service. \fB
\fP
.fi
.RE
.LP
The \fI<netdb.h>\fP header shall define the IPPORT_RESERVED macro
with the value of the highest reserved Internet port
number.
.LP
When the \fI<netdb.h>\fP header is included, \fIh_errno\fP shall be
available as a modifiable lvalue of type \fBint\fP. It
is unspecified whether \fIh_errno\fP is a macro or an identifier declared
with external linkage. 
.LP
The \fI<netdb.h>\fP header shall define the following macros for use
as error values for \fIgethostbyaddr\fP() and \fIgethostbyname\fP():
.sp
.RS
.nf

HOST_NOT_FOUND
NO_DATA
NO_RECOVERY
TRY_AGAIN
.fi
.RE
.SS Address Information Structure
.LP
The \fI<netdb.h>\fP header shall define the \fBaddrinfo\fP structure
that includes at least the following members:
.sp
.RS
.nf

\fBint               ai_flags     \fP Input flags. \fB
int               ai_family    \fP Address family of socket. \fB
int               ai_socktype  \fP Socket type. \fB
int               ai_protocol  \fP Protocol of socket. \fB
socklen_t         ai_addrlen   \fP Length of socket address. \fB
struct sockaddr  *ai_addr      \fP Socket address of socket. \fB
char             *ai_canonname \fP Canonical name of service location. \fB
struct addrinfo  *ai_next      \fP Pointer to next in list. \fB
\fP
.fi
.RE
.LP
The \fI<netdb.h>\fP header shall define the following macros that
evaluate to bitwise-distinct integer constants for use
in the \fIflags\fP field of the \fBaddrinfo\fP structure:
.TP 7
AI_PASSIVE
Socket address is intended for \fIbind\fP().
.TP 7
AI_CANONNAME
.sp
Request for canonical name.
.TP 7
AI_NUMERICHOST
.sp
Return numeric host address as name.
.TP 7
AI_NUMERICSERV
.sp
Inhibit service name resolution.
.TP 7
AI_V4MAPPED
If no IPv6 addresses are found, query for IPv4 addresses and return
them to the caller as IPv4-mapped IPv6 addresses.
.TP 7
AI_ALL
Query for both IPv4 and IPv6 addresses.
.TP 7
AI_ADDRCONFIG
.sp
Query for IPv4 addresses only when an IPv4 address is configured;
query for IPv6 addresses only when an IPv6 address is
configured.
.sp
.LP
The \fI<netdb.h>\fP header shall define the following macros that
evaluate to bitwise-distinct integer constants for use
in the \fIflags\fP argument to \fIgetnameinfo\fP():
.TP 7
NI_NOFQDN
Only the nodename portion of the FQDN is returned for local hosts.
.TP 7
NI_NUMERICHOST
.sp
The numeric form of the node's address is returned instead of its
name.
.TP 7
NI_NAMEREQD
Return an error if the node's name cannot be located in the database.
.TP 7
NI_NUMERICSERV
.sp
The numeric form of the service address is returned instead of its
name.
.TP 7
NI_NUMERICSCOPE
.sp
For IPv6 addresses, the numeric form of the scope identifier is returned
instead of its name.
.TP 7
NI_DGRAM
Indicates that the service is a datagram service (SOCK_DGRAM).
.sp
.SS Address Information Errors
.LP
The \fI<netdb.h>\fP header shall define the following macros for use
as error values for \fIgetaddrinfo\fP() and \fIgetnameinfo\fP():
.TP 7
EAI_AGAIN
The name could not be resolved at this time. Future attempts may succeed.
.TP 7
EAI_BADFLAGS
The flags had an invalid value.
.TP 7
EAI_FAIL
A non-recoverable error occurred.
.TP 7
EAI_FAMILY
The address family was not recognized or the address length was invalid
for the specified family.
.TP 7
EAI_MEMORY
There was a memory allocation failure.
.TP 7
EAI_NONAME
The name does not resolve for the supplied parameters. 
.LP
NI_NAMEREQD is set and the host's name cannot be located, or both
\fInodename\fP and \fIservname\fP were null.
.TP 7
EAI_SERVICE
The service passed was not recognized for the specified socket type.
.TP 7
EAI_SOCKTYPE
The intended socket type was not recognized.
.TP 7
EAI_SYSTEM
A system error occurred. The error code can be found in \fIerrno\fP.
.TP 7
EAI_OVERFLOW
.sp
An argument buffer overflowed.
.sp
.LP
The following shall be declared as functions and may also be defined
as macros. Function prototypes shall be provided.
.sp
.RS
.nf

\fBvoid              endhostent(void);
void              endnetent(void);
void              endprotoent(void);
void              endservent(void);
void              freeaddrinfo(struct addrinfo *);
const char       *gai_strerror(int);
int               getaddrinfo(const char *restrict, const char *restrict,
                      const struct addrinfo *restrict,
                      struct addrinfo **restrict);
struct hostent   *gethostbyaddr(const void *, socklen_t, int);
struct hostent   *gethostbyname(const char *);
struct hostent   *gethostent(void);
int               getnameinfo(const struct sockaddr *restrict, socklen_t,
                      char *restrict, socklen_t, char *restrict,
                      socklen_t, int);
struct netent    *getnetbyaddr(uint32_t, int);
struct netent    *getnetbyname(const char *);
struct netent    *getnetent(void);
struct protoent  *getprotobyname(const char *);
struct protoent  *getprotobynumber(int);
struct protoent  *getprotoent(void);
struct servent   *getservbyname(const char *, const char *);
struct servent   *getservbyport(int, const char *);
struct servent   *getservent(void);
void              sethostent(int);
void              setnetent(int);
void              setprotoent(int);
void              setservent(int);
\fP
.fi
.RE
.LP
The type \fBsocklen_t\fP shall be defined through \fBtypedef\fP as
described in \fI<sys/socket.h>\fP.
.LP
Inclusion of the \fI<netdb.h>\fP header may also make visible all
symbols from \fI<netinet/in.h>\fP, \fI<sys/socket.h>\fP, and \fI<inttypes.h>\fP.
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fI<netinet/in.h>\fP , \fI<inttypes.h>\fP , \fI<sys/socket.h>\fP ,
the System Interfaces volume of IEEE\ Std\ 1003.1-2001, \fIbind\fP(),
\fIendhostent\fP(), \fIendnetent\fP(), \fIendprotoent\fP(), \fIendservent\fP(),
\fIgetaddrinfo\fP(), \fIgetnameinfo\fP()
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .