getaddrinfo.3n (2010 09)

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getaddrinfo(3N) getaddrinfo(3N)

NAME

getaddrinfo(), getnameinfo(), freeaddrinfo(), gai_strerror() - get hostname and address entry

SYNOPSIS

#include <sys/socket.h>

#include <netdb.h>

int getaddrinfo(const char *hostname, const char *servname,

const struct addrinfo *hints, struct addrinfo **res);

int getnameinfo(const struct sockaddr *sa, size_t salen,

char *host, size_t hostlen,

char *serv, size_t servlen, int flags);

_XOPEN_SOURCE_EXTENDED

int getnameinfo(const struct sockaddr *sa, socklen_t salen,

char *host, socklen_t hostlen,

char *serv, socklen_t servlen, int flags);

void freeaddrinfo(struct addrinfo *ai);

char *gai_strerror(int encode);

_XOPEN_SOURCE_EXTENDED

const char *gai_strerror(int encode);

DESCRIPTION

getaddrinfo()

Hostname-to-address translation is done in a protocol-independent fashion using the

getaddrinfo()

function.

The

getaddrinfo() function returns an integer. The input arguments hostname and servname are

pointers to null-terminated strings or NULL. One or both of these two arguments must be a non-NULL

pointer.

In the normal client scenario, both hostname and servname are speciﬁed. The non-NULL hostname

string can be either a hostname or a numeric host address string (a dotted-decimal IPv4 address or a hex-

adecimal IPv6 address). The non-NULL servname string can be either a service name or a decimal port

number. However, in the server scenario, only servname is speciﬁed.

The third input argument is a pointer to the structure of type

addrinfo deﬁned as follows in

<netdb.h>:

struct addrinfo {

int ai_flags;

int ai_family;

int ai_socktype;

int ai_protocol;

size_t ai_addrlen;

char *ai_canonname;

struct sockaddr *ai_addr;

struct addrinfo *ai_next;

};

The members of this structure are:

ai_flags The ﬂag used to set the socket address structure for an IPv4 address or an IPv6

address.

If the

AI_PASSIVE bit is set, then the returned socket address structure from

the getaddrinfo() function will be used as an argument to the bind()

function call. When this bit is set and the hostname argument to the getad-

drinfo() function is a NULL pointer, then the IP address portion of the

socket address structure will be set to INADDR_ANY for an IPv4 address or

IN6ADDR_ANY_INIT for an IPv6 address.

If the

AI_PASSIVE is not set, then the returned socket address structure will

be used as an argument to the connect(), sendto(),orsendmsg() func-

tions. In this case, if the hostname argument is a NULL pointer, then the IP

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (6 pages)

PAGE 1
getaddrinfo(3N) getaddrinfo(3N) NAME getaddrinfo(), getnameinfo(), freeaddrinfo(), gai_strerror() - get hostname and address entry SYNOPSIS #include #include
PAGE 2
getaddrinfo(3N) getaddrinfo(3N) address portion of the socket address will be set to loopback address. If the AI_CANONNAME bit is set, then upon successful return, getaddrinfo() will return the ai_canonname member of the first addrinfo structure, which is a NULL terminated string containing the canonical name of the specified host. If an AI_V4MAPPED flag is specified with an ai_family value of AF_INET6, getaddrinfo() returns IPv4-mapped IPv6 addresses when it does not find any matching IPv6 addresses.
PAGE 3
getaddrinfo(3N) getaddrinfo(3N) EAI_FAIL Non-recoverable failure in name resolution. EAI_OVERFLOW Argument buffer overflow EAI_FAMILY ai_family not supported. EAI_MEMORY Memory allocation failure. EAI_NODATA No address associated with hostname . EAI_NONAME No hostname nor servname provided, or not known. EAI_SERVICE The servname is not supported for ai_socktype. EAI_SOCKTYPE ai_socktype not supported. EAI_SYSTEM System error returned in errno.
PAGE 4
getaddrinfo(3N) getaddrinfo(3N) The function returns the hostname associated with the IP address in the buffer pointed to by the host argument. The caller provides the size of this buffer via the hostlen argument. The service name associated with the port number is returned in the buffer pointed to by serv, and the servlen argument gives the length of this buffer. The caller specifies not to return either string by providing zero values for the hostlen or servlen arguments.
PAGE 5
getaddrinfo(3N) getaddrinfo(3N) is used for name/address resolution, the method used by the functions getnameinfo() and getad- drinfo() to search an address is listed below: getnameinfo() Sequentially searches the /etc/hosts file until an address matching the src parameter is found or until the end of file is encountered.
PAGE 6
(Notes) A (Notes) gA 6 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010