1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
|
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
.TH "<netdb.h>" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" <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 .
|
