netdb.h File Reference

#include "lwip/opt.h"
#include "lwip/arch.h"
#include "lwip/inet.h"
#include "lwip/sockets.h"

Macros
#define	EAI_NONAME   200
#define	gethostbyname(name)   lwip_gethostbyname(name)
#define	gethostbyname_r(name, ret, buf, buflen, result, h_errnop)   lwip_gethostbyname_r(name, ret, buf, buflen, result, h_errnop)
#define	freeaddrinfo(addrinfo)   lwip_freeaddrinfo(addrinfo)
#define	getaddrinfo(nodname, servname, hints, res)   lwip_getaddrinfo(nodname, servname, hints, res)

Functions
struct hostent *	lwip_gethostbyname (const char *name)
int	lwip_gethostbyname_r (const char *name, struct hostent *ret, char *buf, size_t buflen, struct hostent **result, int *h_errnop)
void	lwip_freeaddrinfo (struct addrinfo *ai)
int	lwip_getaddrinfo (const char *nodename, const char *servname, const struct addrinfo *hints, struct addrinfo **res)

Variables
int	h_errno

Detailed Description

NETDB API (sockets)

Macro Definition Documentation

EAI_NONAME

#define EAI_NONAME   200

Errors used by the DNS API functions, h_errno can be one of them

Function Documentation

lwip_freeaddrinfo()

void lwip_freeaddrinfo

(

struct addrinfo *

ai

)

Frees one or more addrinfo structures returned by getaddrinfo(), along with any additional storage associated with those structures. If the ai_next field of the structure is not null, the entire list of structures is freed.

Parameters

ai	struct addrinfo to free

lwip_getaddrinfo()

int lwip_getaddrinfo	(	const char *	nodename,
		const char *	servname,
		const struct addrinfo *	hints,
		struct addrinfo **	res
	)

Translates the name of a service location (for example, a host name) and/or a service name and returns a set of socket addresses and associated information to be used in creating a socket with which to address the specified service. Memory for the result is allocated internally and must be freed by calling lwip_freeaddrinfo()!

Due to a limitation in dns_gethostbyname, only the first address of a host is returned. Also, service names are not supported (only port numbers)!

Parameters

nodename	descriptive name or address string of the host (may be NULL -> local address)
servname	port number as string of NULL
hints	structure containing input values that set socktype and protocol
res	pointer to a pointer where to store the result (set to NULL on failure)

Returns

0 on success, non-zero on failure

lwip_gethostbyname()

struct hostent* lwip_gethostbyname

(

const char *

name

)

Returns an entry containing addresses of address family AF_INET for the host with name name. Due to dns_gethostbyname limitations, only one address is returned.

Parameters

name	the hostname to resolve

Returns

an entry containing addresses of address family AF_INET for the host with name name

lwip_gethostbyname_r()

int lwip_gethostbyname_r	(	const char *	name,
		struct hostent *	ret,
		char *	buf,
		size_t	buflen,
		struct hostent **	result,
		int *	h_errnop
	)

Thread-safe variant of lwip_gethostbyname: instead of using a static buffer, this function takes buffer and errno pointers as arguments and uses these for the result.

Parameters

name	the hostname to resolve
ret	pre-allocated struct where to store the result
buf	pre-allocated buffer where to store additional data
buflen	the size of buf
result	pointer to a hostent pointer that is set to ret on success and set to zero on error
h_errnop	pointer to an int where to store errors (instead of modifying the global h_errno)

Returns

0 on success, non-zero on error, additional error information is stored in *h_errnop instead of h_errno to be thread-safe

Variable Documentation

h_errno

int h_errno

h_errno is exported in netdb.h for access by applications.