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lwres_getnameinfo(3) [centos man page]

LWRES_GETNAMEINFO(3)						       BIND9						      LWRES_GETNAMEINFO(3)

NAME
lwres_getnameinfo - lightweight resolver socket address structure to hostname and service name SYNOPSIS
#include <lwres/netdb.h> int lwres_getnameinfo(const struct sockaddr *sa, size_t salen, char *host, size_t hostlen, char *serv, size_t servlen, int flags); DESCRIPTION
This function is equivalent to the getnameinfo(3) function defined in RFC2133. lwres_getnameinfo() returns the hostname for the struct sockaddr sa which is salen bytes long. The hostname is of length hostlen and is returned via *host. The maximum length of the hostname is 1025 bytes: NI_MAXHOST. The name of the service associated with the port number in sa is returned in *serv. It is servlen bytes long. The maximum length of the service name is NI_MAXSERV - 32 bytes. The flags argument sets the following bits: NI_NOFQDN A fully qualified domain name is not required for local hosts. The local part of the fully qualified domain name is returned instead. NI_NUMERICHOST Return the address in numeric form, as if calling inet_ntop(), instead of a host name. NI_NAMEREQD A name is required. If the hostname cannot be found in the DNS and this flag is set, a non-zero error code is returned. If the hostname is not found and the flag is not set, the address is returned in numeric form. NI_NUMERICSERV The service name is returned as a digit string representing the port number. NI_DGRAM Specifies that the service being looked up is a datagram service, and causes getservbyport() to be called with a second argument of "udp" instead of its default of "tcp". This is required for the few ports (512-514) that have different services for UDP and TCP. RETURN VALUES
lwres_getnameinfo() returns 0 on success or a non-zero error code if an error occurs. SEE ALSO
RFC2133(), getservbyport(3), lwres(3), lwres_getnameinfo(3), lwres_getnamebyaddr(3). lwres_net_ntop(3). BUGS
RFC2133 fails to define what the nonzero return values of getnameinfo(3) are. COPYRIGHT
Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC") Copyright (C) 2000, 2001 Internet Software Consortium. BIND9 Jun 30, 2000 LWRES_GETNAMEINFO(3)

Check Out this Related Man Page

getnameinfo(3)						     Library Functions Manual						    getnameinfo(3)

NAME
getnameinfo - Get a node name and service name for an address and port number LIBRARY
Standard C Library (libc.so, libc.a) SYNOPSIS
#include <netdb.h> int getnameinfo( const struct sockaddr *sa, socklen_t salen, char *node, size_t *nodelen, char *serv, size_t servlen, int flags); PARAMETERS
Points either to a sockaddr_in structure (for IPv4) or to a sockaddr_in6 structure (for IPv6) that holds the IP address and port number. Specifies the length of either the sockaddr_in structure or the sockaddr_in6 structure. Points to a buffer in which to receive the null- terminated network node name or alias corresponding to the address contained in sa. A NULL pointer instructs the routine not to return a node name. Both node and serv cannot be zero. Specifies the length of the node buffer. A value of zero instructs the routine not to return a node name. Points to a buffer in which to receive the null-terminated network service name associated with the port number con- tained in sa. A NULL pointer instructs the routine not to return a service name. Both node and serv cannot be zero. Specifies the length of the serv buffer. A value of zero instructs the routine not to return a service name. Specifies changes to the routine's default actions. By default, the routine searches for the fully-qualified domain name of the node in the hosts database and returns it. See the "Flag Bits" section for additional flags. DESCRIPTION
The getnameinfo() routine looks up an IP address and port number in a sockaddr structure specified by sa and returns node name and service name text strings in the buffers pointed to by the host and serv parameters, respectively. If the node's name is not found, the routine returns the numeric form of the node's address, regardless of the value of the flags parame- ter. If the service's name is not found, the routine returns the numeric form of the service's address (port number) regardless of the value of the flag parameter. The application must provide buffers large enough to hold the fully-qualified domain name and the service name, including the terminating null characters. To assist in initializing the buffers, the following constants are defined in <netdb.h>: #define NI_MAXHOST 1025 #define NI_MAXSERV 32 Flag Bits The flag bits and their meanings, if set, are as follows: Specifies that the service is a datagram service (SOCK_DGRAM). The default is to assume a stream service (SOCK_STREAM). This is required for the few ports (512-514) that have different services for UDP and TCP. Returns an error if the host's name cannot be located in the hosts database. Searches the hosts database and returns the node name portion of the fully-qualified domain name for local hosts. Returns the numeric form of the host's address instead of its name. No host name resolution is performed. Returns the numeric form (port number) of the service address instead of its name. No service name resolution is performed. The two NI_NUMERIC* flags are required to support the -n flag that many commands provide. All flags are defined in <netdb.h> header file. RETURN VALUES
Upon successful completion, the getnameinfo() function returns 0 (zero). Upon failure, it returns a non-zero value. ERRORS
If the getnameinfo() function fails, it returns one of the following values: The nodename parameter could not be resolved this time. Try the request again. The value of the flags parameter is invalid. A non-recoverable error occurred. The address family (ai_family in the hints structure) was not recognized, or the address length was invalid. A memory allocation failure occurred. Name does not resolve to supplied parameters. The NI_NAMEREQD flag was set and the node's name was not found. You did not pass either the nodename or servname parameter. You must pass at least one. A system error occurred; errno is set to the error value. FILES
The Internet network hostname database. Each record in the file occupies a single line and has three fields consisting of the host address, official hostname, and aliases. The resolver configuration file. The database service selection configuration file. RELATED INFORMATION
Functions: getaddrinfo(3), getservbyname(3), gethostbyport(3), inet_ntop(3), socket(3). Files: hostname(5), resolv.conf(4), svc.conf(4). Networks: bind_intro(7), nis_intro(7). delim off getnameinfo(3)

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