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netdb: Extend dns_query so that it can handle multiple nameserver addresses

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This commit is contained in:
Gregory Nutt 2016-01-14 14:18:19 -06:00
parent 9097425203
commit 1a8531c951
1 changed files with 243 additions and 130 deletions
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373
libc/netdb/lib_dnsquery.c
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@ -1,5 +1,5 @@
/****************************************************************************
* libc/netdb/lib_dnsclient.c
* libc/netdb/lib_dnsquery.c
* DNS host name to IP address resolver.
*
* The uIP DNS resolver functions are used to lookup a hostname and
@ -73,6 +73,15 @@
* Private Types
****************************************************************************/
struct dns_query_s
{
int sd; /* DNS server socket */
int result; /* Explanation of the failure */
FAR const char *hostname; /* Hostname to lookup */
FAR struct sockaddr *addr; /* Location to return host address */
FAR socklen_t *addrlen; /* Length of the address */
};
/****************************************************************************
* Private Data
****************************************************************************/
@ -398,6 +407,215 @@ static int dns_recv_response(int sd, FAR struct sockaddr *addr,
return -EADDRNOTAVAIL;
}
/****************************************************************************
* Name: dns_query_callback
*
* Description:
* Using the DNS information and this DNS server address, look up the the
* hostname.
*
* Input Parameters:
* arg - Query arguements
* addr - DNS name server address
* addrlen - Length of the DNS name server address.
*
* Returned Value:
* Returns one (1) if the query was successful. Zero is returned in all
* other cases. The result field of the query structure is set to a
* negated errno value indicate the reason for the last failure (only).
*
****************************************************************************/
static int dns_query_callback(FAR void *arg, FAR struct sockaddr *addr,
FAR socklen_t addrlen)
{
FAR struct dns_query_s *query = (FAR struct dns_query_s *)arg;
int retries;
int ret;
/* Loop while receive timeout errors occur and there are remaining retries */
for (retries = 0; retries < 3; retries++)
{
#ifdef CONFIG_NET_IPv4
/* Is this an IPv4 address? */
if (addr->sa_family == AF_INET)
{
/* Yes.. verify the address size */
if (addrlen < sizeof(struct sockaddr_in))
{
/* Return zero to skip this address and try the next
* namserver address in resolv.conf.
*/
ndbg("ERROR: Invalid IPv4 address size: %d\n", addrlen);
query->result = -EINVAL;
return 0;
}
/* Send the IPv4 query */
ret = dns_send_query(query->sd, query->hostname,
(FAR union dns_server_u *)addr,
DNS_RECTYPE_A);
if (ret < 0)
{
/* Return zero to skip this address and try the next
* namserver address in resolv.conf.
*/
ndbg("ERROR: IPv4 dns_send_query failed: %d\n", ret);
query->result = ret;
return 0;
}
/* Obtain the IPv4 response */
ret = dns_recv_response(query->sd, query->addr, query->addrlen);
if (ret >= 0)
{
/* IPv4 response received successfully */
#if CONFIG_NETDB_DNSCLIENT_ENTRIES > 0
/* Save the answer in the DNS cache */
dns_save_answer(query->hostname, query->addr, *query->addrlen);
#endif
/* Return 1 to indicate to (1) stop the traversal, and (2)
* indicate that the address was found.
*/
return 1;
}
/* Handle errors */
ndbg("ERROR: IPv4 dns_recv_response failed: %d\n", ret);
if (ret != -EADDRNOTAVAIL)
{
/* The IPv4 address is not available. Return zero to
* continue the tranversal with the next nameserver
* address in resolv.conf.
*/
query->result = -EADDRNOTAVAIL;
return 0;
}
else if (ret != -EAGAIN)
{
/* Some failure other than receive timeout occurred. Return
* zero to skip this address and try the next namserver
* address in resolv.conf.
*/
query->result = ret;
return 0;
}
}
else
#endif /* CONFIG_NET_IPv4 */
#ifdef CONFIG_NET_IPv6
/* Is this an IPv4 address? */
if (query->addr.sa_family == AF_INET6)
{
/* Yes.. verify the address size */
if (addrlen < sizeof(struct sockaddr_in6))
{
/* Return zero to skip this address and try the next
* namserver address in resolv.conf.
*/
ndbg("ERROR: Invalid IPv6 address size: %d\n", addrlen);
query->result = -EINVAL;
return 0;
}
/* Send the IPv6 query */
ret = dns_send_query(query->sd, query->hostname,
(FAR union dns_server_u *)addr,
DNS_RECTYPE_AAAA);
if (ret < 0)
{
/* Return zero to skip this address and try the next
* namserver address in resolv.conf.
*/
ndbg("ERROR: IPv6 dns_send_query failed: %d\n", ret);
query->result = ret;
return 0;
}
/* Obtain the IPv6 response */
ret = dns_recv_response(query->sd, query->addr, query->addrlen);
if (ret >= 0)
{
/* IPv6 response received successfully */
#if CONFIG_NETDB_DNSCLIENT_ENTRIES > 0
/* Save the answer in the DNS cache */
dns_save_answer(query->hostname, query->addr, *query->addrlen);
#endif
/* Return 1 to indicate to (1) stop the traversal, and (2)
* indicate that the address was found.
*/
return 1;
}
/* Handle errors */
ndbg("ERROR: IPv6 dns_recv_response failed: %d\n", ret);
if (ret != -EADDRNOTAVAIL)
{
/* The IPv6 address is not available. Return zero to
* continue the tranversal with the next nameserver
* address in resolv.conf.
*/
query->result = -EADDRNOTAVAIL;
return 0;
}
else if (ret != -EAGAIN)
{
/* Some failure other than receive timeout occurred. Return
* zero to skip this address and try the next namserver
* address in resolv.conf.
*/
query->result = ret;
return 0;
}
}
else
#endif
{
/* Unsupported address family. Return zero to continue the
* tranversal with the next nameserver address in resolv.conf.
*/
return 0;
}
}
/* We tried three times and could not communicate with this nameserver.
* Perhaps it is down? Return zero to continue with the next address
* in the resolv.conf file.
*/
query->result = -ETIMEDOUT;
return 0;
}
/****************************************************************************
* Public Functions
****************************************************************************/
@ -426,140 +644,35 @@ static int dns_recv_response(int sd, FAR struct sockaddr *addr,
int dns_query(int sd, FAR const char *hostname, FAR struct sockaddr *addr,
FAR socklen_t *addrlen)
{
#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
int noipv4 = false;
int noipv6 = false;
#endif
int retries;
FAR struct dns_query_s query;
int ret;
/* Loop while receive timeout errors occur and there are remaining retries */
/* Set up the query info structure */
for (retries = 0; retries < 3; retries++)
query.sd = sd;
query.result = OK;
query.hostname = hostname;
query.addr = addr;
query.addrlen = addrlen;
/* Perform the query. dns_foreach_nameserver() will return:
*
* 1 - The query was successful.
* 0 - Look up failed
* <0 - Some other failure (?, shouldn't happen)
*/
ret = dns_foreach_nameserver(dns_query_callback, &query);
if (ret > 0)
{
#ifdef CONFIG_NET_IPv4
#ifdef CONFIG_NET_IPv6
/* If we know that the IPv4 address is not available, then don't try
* again.
*/
/* The lookup was successful */
if (!noipv4)
#endif
{
/* Send the IPv4 query */
ret = dns_send_query(sd, hostname, &g_dns_server, DNS_RECTYPE_A);
if (ret < 0)
{
ndbg("ERROR: IPv4 dns_send_query failed: %d\n", ret);
return ret;
}
/* Obtain the IPv4 response */
ret = dns_recv_response(sd, addr, addrlen);
if (ret >= 0)
{
/* IPv4 response received successfully */
#if CONFIG_NETDB_DNSCLIENT_ENTRIES > 0
/* Save the answer in the DNS cache */
dns_save_answer(hostname, addr, *addrlen);
#endif
return OK;
}
/* Handle errors */
ndbg("ERROR: IPv4 dns_recv_response failed: %d\n", ret);
#ifdef CONFIG_NET_IPv6
if (ret != -EADDRNOTAVAIL)
{
/* The IPv4 address is not available. */
noipv4 = true;
if (noipv6)
{
/* Neither address is available */
return ret;
}
}
else
#endif
if (ret != -EAGAIN)
{
/* Some failure other than receive timeout occurred */
return ret;
}
}
#endif
#ifdef CONFIG_NET_IPv6
#ifdef CONFIG_NET_IPv4
/* If we know that the IPv4 address is not available, then don't try
* again.
*/
if (!noipv6)
#endif
{
/* Send the IPv6 query */
ret = dns_send_query(sd, hostname, &g_dns_server,
DNS_RECTYPE_AAAA);
if (ret < 0)
{
ndbg("ERROR: IPv6 dns_send_query failed: %d\n", ret);
return ret;
}
/* Obtain the IPv6 response */
ret = dns_recv_response(sd, addr, addrlen);
if (ret >= 0)
{
/* IPv6 response received successfully */
#if CONFIG_NETDB_DNSCLIENT_ENTRIES > 0
/* Save the answer in the DNS cache */
dns_save_answer(hostname, addr, *addrlen);
#endif
return OK;
}
/* Handle errors */
ndbg("ERROR: IPv6 dns_recv_response failed: %d\n", ret);
#ifdef CONFIG_NET_IPv4
if (ret != -EADDRNOTAVAIL)
{
/* The IPv6 address is not available. */
noipv6 = true;
if (noipv4)
{
/* Neither address is available */
return ret;
}
}
else
#endif
if (ret != -EAGAIN)
{
/* Some failure other than receive timeout occurred */
return ret;
}
}
#endif
ret = OK;
}
else if (ret == 0)
{
ret = query.result;
}
return -ETIMEDOUT;
return ret;
}