lwres_getnameinfo man page
lwres_getnameinfo — lightweight resolver socket address structure to hostname and service name
int lwres_getnameinfo(const struct sockaddr *sa, size_t salen, char *host, size_t hostlen, char *serv, size_t servlen, int flags);
This function is equivalent to the getnameinfo(3) function defined in RFC2133. lwres_getnameinfo() returns the hostname for the struct sockaddrsa 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:
A fully qualified domain name is not required for local hosts. The local part of the fully qualified domain name is returned instead.
Return the address in numeric form, as if calling inet_ntop(), instead of a host name.
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.
The service name is returned as a digit string representing the port number.
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.
lwres_getnameinfo() returns 0 on success or a non-zero error code if an error occurs.
RFC2133(), getservbyport(3), lwres(3), lwres_getnameinfo(3), lwres_getnamebyaddr(3). lwres_net_ntop(3).
RFC2133 fails to define what the nonzero return values of getnameinfo(3) are.
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