netdb.c File Reference

API functions for name resolving.

#include "lwip/netdb.h"
#include "lwip/err.h"
#include "lwip/mem.h"
#include "lwip/memp.h"
#include "lwip/ip_addr.h"
#include "lwip/api.h"
#include "lwip/dns.h"
#include <string.h>
#include <stdlib.h>

Data Structures
struct	gethostbyname_r_helper
	helper struct for gethostbyname_r to access the char* buffer More...

Macros
#define	HOSTENT_STORAGE   static
	define "hostent" variables storage More...
#define	LWIP_DNS_API_HOSTENT_STORAGE   0
	define "hostent" variables storage: 0 if we use a static (but unprotected) set of variables for lwip_gethostbyname, 1 if we use a local storage More...

Functions
void	lwip_freeaddrinfo (struct addrinfo *ai)
	Frees one or more addrinfo structures returned by getaddrinfo(), along with any additional storage associated with those structures. More...
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. More...
struct hostent *	lwip_gethostbyname (const char *name)
	Returns an entry containing addresses of address family AF_INET for the host with name name. More...
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. More...

Variables
int	h_errno
	h_errno is exported in netdb.h for access by applications. More...

#define HOSTENT_STORAGE   static

define "hostent" variables storage

Referenced by lwip_gethostbyname().

#define LWIP_DNS_API_HOSTENT_STORAGE   0

define "hostent" variables storage: 0 if we use a static (but unprotected) set of variables for lwip_gethostbyname, 1 if we use a local storage

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

References addrinfo::ai_next, memp_free(), next, and NULL.

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

References AF_INET, AF_UNSPEC, addrinfo::ai_addr, addrinfo::ai_addrlen, addrinfo::ai_canonname, addrinfo::ai_family, addrinfo::ai_protocol, addrinfo::ai_socktype, EAI_FAIL, EAI_FAMILY, EAI_MEMORY, EAI_NONAME, EAI_SERVICE, ERR_OK, htons, inet_addr_from_ipaddr, ip_addr_set_loopback, LWIP_ASSERT, memp_malloc(), netconn_gethostbyname(), NETDB_ELEM_SIZE, NULL, sockaddr_in::sin_addr, sockaddr_in::sin_family, sockaddr_in::sin_len, and sockaddr_in::sin_port.

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

References AF_INET, DNS_DEBUG, ERR_OK, hostent::h_addr_list, hostent::h_addrtype, hostent::h_aliases, h_errno, hostent::h_length, hostent::h_name, HOST_NOT_FOUND, HOSTENT_STORAGE, ip_ntoa, LWIP_DEBUGF, netconn_gethostbyname(), and NULL.

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

References gethostbyname_r_helper::addr, gethostbyname_r_helper::addr_list, AF_INET, gethostbyname_r_helper::aliases, DNS_DEBUG, EINVAL, ERANGE, ERR_OK, h, hostent::h_addr_list, hostent::h_addrtype, hostent::h_aliases, hostent::h_length, hostent::h_name, HOST_NOT_FOUND, LWIP_DEBUGF, LWIP_MEM_ALIGN, MEM_ALIGNMENT, netconn_gethostbyname(), and NULL.

int h_errno

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

Referenced by lwip_gethostbyname().