NAME¶

lwres_getaddrinfo, lwres_freeaddrinfo - socket address structure to host and service name

SYNOPSIS¶

#include <lwres/netdb.h>

int lwres_getaddrinfo(const char *hostname, const char *servname, const struct addrinfo *hints, struct addrinfo **res);

void lwres_freeaddrinfo(struct addrinfo *ai);

If the operating system does not provide a struct addrinfo, the following structure is used:

struct  addrinfo {


        int             ai_flags;       /* AI_PASSIVE, AI_CANONNAME */


        int             ai_family;      /* PF_xxx */


        int             ai_socktype;    /* SOCK_xxx */


        int             ai_protocol;    /* 0 or IPPROTO_xxx for IPv4 and IPv6 */


        size_t          ai_addrlen;     /* length of ai_addr */


        char            *ai_canonname;  /* canonical name for hostname */


        struct sockaddr *ai_addr;       /* binary address */


        struct addrinfo *ai_next;       /* next structure in linked list */
};

DESCRIPTION¶

lwres_getaddrinfo() is used to get a list of IP addresses and port numbers for host hostname and service servname. The function is the lightweight resolver's implementation of getaddrinfo() as defined in RFC2133. hostname and servname are pointers to null-terminated strings or NULL. hostname is either a host name or a numeric host address string: a dotted decimal IPv4 address or an IPv6 address. servname is either a decimal port number or a service name as listed in /etc/services.

hints is an optional pointer to a struct addrinfo. This structure can be used to provide hints concerning the type of socket that the caller supports or wishes to use. The caller can supply the following structure elements in *hints:

ai_family

ai_socktype

ai_protocol

ai_flags

All other elements of the struct addrinfo passed via hints must be zero.

A hints of NULL is treated as if the caller provided a struct addrinfo initialized to zero with ai_familyset to PF_UNSPEC.

After a successful call to lwres_getaddrinfo(), *res is a pointer to a linked list of one or more addrinfo structures. Each struct addrinfo in this list cn be processed by following the ai_next pointer, until a NULL pointer is encountered. The three members ai_family, ai_socktype, and ai_protocol in each returned addrinfo structure contain the corresponding arguments for a call to socket(2). For each addrinfo structure in the list, the ai_addr member points to a filled-in socket address structure of length ai_addrlen.

All of the information returned by lwres_getaddrinfo() is dynamically allocated: the addrinfo structures, and the socket address structures and canonical host name strings pointed to by the addrinfostructures. Memory allocated for the dynamically allocated structures created by a successful call to lwres_getaddrinfo() is released by lwres_freeaddrinfo(). ai is a pointer to a struct addrinfo created by a call to lwres_getaddrinfo().

RETURN VALUES¶

lwres_getaddrinfo() returns zero on success or one of the error codes listed in gai_strerror(3) if an error occurs. If both hostname and servname are NULL lwres_getaddrinfo() returns EAI_NONAME.

SEE ALSO¶

lwres(3), lwres_getaddrinfo(3), lwres_freeaddrinfo(3), lwres_gai_strerror(3), RFC2133(), getservbyname(3), bind(2), connect(2), sendto(2), sendmsg(2), socket(2).

AUTHOR¶

Internet Systems Consortium, Inc.

COPYRIGHT¶

Copyright © 2000, 2001, 2003-2005, 2007, 2014-2016, 2018-2021 Internet Systems Consortium, Inc. ("ISC")