1LWRES_GETADDRINFO(3) BIND9 LWRES_GETADDRINFO(3)
2
6 lwres_getaddrinfo, lwres_freeaddrinfo - socket address structure to
7 host and service name
8
10 #include <lwres/netdb.h>
11 int lwres_getaddrinfo(const char *hostname, const char *servname,
13 const struct addrinfo *hints,
14 struct addrinfo **res);
15 void lwres_freeaddrinfo(struct addrinfo *ai);
17 If the operating system does not provide a struct addrinfo, the
19 following structure is used:
20 struct addrinfo {
22 int ai_flags; /* AI_PASSIVE, AI_CANONNAME */
23 int ai_family; /* PF_xxx */
24 int ai_socktype; /* SOCK_xxx */
25 int ai_protocol; /* 0 or IPPROTO_xxx for IPv4 and IPv6 */
26 size_t ai_addrlen; /* length of ai_addr */
27 char *ai_canonname; /* canonical name for hostname */
28 struct sockaddr *ai_addr; /* binary address */
29 struct addrinfo *ai_next; /* next structure in linked list */
30 };
31
34 lwres_getaddrinfo() is used to get a list of IP addresses and port
35 numbers for host hostname and service servname. The function is the
36 lightweight resolver's implementation of getaddrinfo() as defined in
37 RFC2133. hostname and servname are pointers to null-terminated strings
38 or NULL. hostname is either a host name or a numeric host address
39 string: a dotted decimal IPv4 address or an IPv6 address. servname is
40 either a decimal port number or a service name as listed in
41 /etc/services.
42 hints is an optional pointer to a struct addrinfo. This structure can
44 be used to provide hints concerning the type of socket that the caller
45 supports or wishes to use. The caller can supply the following
46 structure elements in *hints:
47 ai_family
49 The protocol family that should be used. When ai_family is set to
50 PF_UNSPEC, it means the caller will accept any protocol family
51 supported by the operating system.
52 ai_socktype
54 denotes the type of socket — SOCK_STREAM, SOCK_DGRAM or SOCK_RAW —
55 that is wanted. When ai_socktype is zero the caller will accept any
56 socket type.
57 ai_protocol
59 indicates which transport protocol is wanted: IPPROTO_UDP or
60 IPPROTO_TCP. If ai_protocol is zero the caller will accept any
61 protocol.
62 ai_flags
64 Flag bits. If the AI_CANONNAME bit is set, a successful call to
65 lwres_getaddrinfo() will return a null-terminated string containing
66 the canonical name of the specified hostname in ai_canonname of the
67 first addrinfo structure returned. Setting the AI_PASSIVE bit
68 indicates that the returned socket address structure is intended
69 for used in a call to bind(2). In this case, if the hostname
70 argument is a NULL pointer, then the IP address portion of the
71 socket address structure will be set to INADDR_ANY for an IPv4
72 address or IN6ADDR_ANY_INIT for an IPv6 address.
73 When ai_flags does not set the AI_PASSIVE bit, the returned socket
75 address structure will be ready for use in a call to connect(2) for
76 a connection-oriented protocol or connect(2), sendto(2), or
77 sendmsg(2) if a connectionless protocol was chosen. The IP address
78 portion of the socket address structure will be set to the loopback
79 address if hostname is a NULL pointer and AI_PASSIVE is not set in
80 ai_flags.
81 If ai_flags is set to AI_NUMERICHOST it indicates that hostname
83 should be treated as a numeric string defining an IPv4 or IPv6
84 address and no name resolution should be attempted.
85 All other elements of the struct addrinfo passed via hints must be
87 zero.
88 A hints of NULL is treated as if the caller provided a struct addrinfo
90 initialized to zero with ai_familyset to PF_UNSPEC.
91 After a successful call to lwres_getaddrinfo(), *res is a pointer to a
93 linked list of one or more addrinfo structures. Each struct addrinfo in
94 this list cn be processed by following the ai_next pointer, until a
95 NULL pointer is encountered. The three members ai_family, ai_socktype,
96 and ai_protocol in each returned addrinfo structure contain the
97 corresponding arguments for a call to socket(2). For each addrinfo
98 structure in the list, the ai_addr member points to a filled-in socket
99 address structure of length ai_addrlen.
100 All of the information returned by lwres_getaddrinfo() is dynamically
102 allocated: the addrinfo structures, and the socket address structures
103 and canonical host name strings pointed to by the addrinfostructures.
104 Memory allocated for the dynamically allocated structures created by a
105 successful call to lwres_getaddrinfo() is released by
106 lwres_freeaddrinfo(). ai is a pointer to a struct addrinfo created by
107 a call to lwres_getaddrinfo().
108
110 lwres_getaddrinfo() returns zero on success or one of the error codes
111 listed in gai_strerror(3) if an error occurs. If both hostname and
112 servname are NULLlwres_getaddrinfo() returns EAI_NONAME.
113
115 lwres(3), lwres_getaddrinfo(3), lwres_freeaddrinfo(3),
116 lwres_gai_strerror(3), RFC2133(), getservbyname(3), bind(2),
117 connect(2), sendto(2), sendmsg(2), socket(2).
118
120 Internet Systems Consortium, Inc.
121
123 Copyright © 2000, 2001, 2003-2005, 2007, 2014-2016, 2018-2020 Internet
124 Systems Consortium, Inc. ("ISC")
125ISC 2007-06-18 LWRES_GETADDRINFO(3)