# lwres_getnameinfo

## 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.