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IPv6-on-windows: find DNS servers correctly

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1 parent d60f07d commit 6518b56a5e2bc9e39d720f17fa7dd322a28dc33c David Stuart committed with bagder May 17, 2011
Showing with 197 additions and 62 deletions.
  1. +181 −58 ares_init.c
  2. +10 −0 ares_library_init.c
  3. +2 −0 ares_library_init.h
  4. +1 −1 ares_private.h
  5. +2 −2 ares_process.c
  6. +1 −1 ares_send.c
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239 ares_init.c
@@ -69,6 +69,7 @@
#include "ares_nowarn.h"
#include "ares_platform.h"
#include "ares_private.h"
+#include "inet_ntop.h"
#ifdef ANDROID
#include <sys/system_properties.h>
@@ -595,73 +596,195 @@ static int get_res_interfaces_nt(HKEY hKey, const char *subkey, char **obuf)
return 0;
}
+/**
+ * The desired output for this method is that we set "ret_buf" to
+ * something like:
+ *
+ * 192.168.0.1,dns01.my.domain,fe80::200:f8ff:fe21:67cf
+ *
+ * The only ordering requirement is that primary servers are listed
+ * before secondary. There is no requirement that IPv4 addresses should
+ * necessarily be before IPv6.
+ *
+ * Note that ret_size should ideally be big enough to hold around
+ * 2-3 IPv4 and 2-3 IPv6 addresses.
+ *
+ * Finally, we need to return the total number of DNS servers located.
+ */
static int get_iphlpapi_dns_info (char *ret_buf, size_t ret_size)
{
- FIXED_INFO *fi, *newfi;
- DWORD size = sizeof (*fi);
- IP_ADDR_STRING *ipAddr;
- int i, count = 0;
- int debug = 0;
- size_t ip_size = sizeof("255.255.255.255,")-1;
- size_t left = ret_size;
- char *ret = ret_buf;
- HRESULT res;
-
- fi = malloc(size);
- if (!fi)
- return 0;
-
- res = (*ares_fpGetNetworkParams) (fi, &size);
- if ((res != ERROR_BUFFER_OVERFLOW) && (res != ERROR_SUCCESS))
- goto quit;
-
- newfi = realloc(fi, size);
- if (!newfi)
- goto quit;
-
- fi = newfi;
- res = (*ares_fpGetNetworkParams) (fi, &size);
- if (res != ERROR_SUCCESS)
- goto quit;
-
- if (debug)
+ const size_t ipv4_size = INET_ADDRSTRLEN + 1; /* +1 for ',' at end */
+ const size_t ipv6_size = INET6_ADDRSTRLEN + 12; /* +12 for "%0123456789," at end */
+ size_t left = ret_size;
+ char *ret = ret_buf;
+ int count = 0;
+
+ /* Use the GetAdaptersAddresses method if it's available, otherwise
+ fall back to GetNetworkParams. */
+ if (ares_fpGetAdaptersAddresses != ZERO_NULL)
{
- printf ("Host Name: %s\n", fi->HostName);
- printf ("Domain Name: %s\n", fi->DomainName);
- printf ("DNS Servers:\n"
- " %s (primary)\n", fi->DnsServerList.IpAddress.String);
+ const ULONG working_buf_size = 15000;
+ IP_ADAPTER_ADDRESSES *pFirstEntry = NULL;
+ IP_ADAPTER_ADDRESSES *pEntry = NULL;
+ ULONG bufSize = 0;
+ ULONG result = 0;
+
+ /* According to MSDN, the recommended way to do this is to use a temporary
+ buffer of 15K, to "dramatically reduce the chance that the GetAdaptersAddresses
+ method returns ERROR_BUFFER_OVERFLOW" */
+ pFirstEntry = ( IP_ADAPTER_ADDRESSES * ) malloc( working_buf_size );
+ bufSize = working_buf_size;
+ if( !pFirstEntry )
+ return 0;
+
+ /* Call the method one time */
+ result = ( *ares_fpGetAdaptersAddresses )( AF_UNSPEC, 0, 0, pFirstEntry, &bufSize );
+ if( result == ERROR_BUFFER_OVERFLOW )
+ {
+ /* Reallocate, bufSize should now be set to the required size */
+ pFirstEntry = ( IP_ADAPTER_ADDRESSES * ) realloc( pFirstEntry, bufSize );
+ if( !pFirstEntry )
+ return 0;
+
+ /* Call the method a second time */
+ result = ( *ares_fpGetAdaptersAddresses )( AF_UNSPEC, 0, 0, pFirstEntry, &bufSize );
+ if( result == ERROR_BUFFER_OVERFLOW )
+ {
+ /* Reallocate, bufSize should now be set to the required size */
+ pFirstEntry = ( IP_ADAPTER_ADDRESSES * ) realloc( pFirstEntry, bufSize );
+ if( !pFirstEntry )
+ return 0;
+
+ /* Call the method a third time. The maximum number of times we're going to do
+ this is 3. Three shall be the number thou shalt count, and the number of the
+ counting shall be three. Five is right out. */
+ result = ( *ares_fpGetAdaptersAddresses )( AF_UNSPEC, 0, 0, pFirstEntry, &bufSize );
+ }
+ }
+
+ /* Check the current result for failure */
+ if( result != ERROR_SUCCESS )
+ {
+ free( pFirstEntry );
+ return 0;
+ }
+
+ /* process the results */
+ for( pEntry = pFirstEntry ; pEntry != NULL ; pEntry = pEntry->Next )
+ {
+ IP_ADAPTER_DNS_SERVER_ADDRESS* pDNSAddr = pEntry->FirstDnsServerAddress;
+ for( ; pDNSAddr != NULL ; pDNSAddr = pDNSAddr->Next )
+ {
+ struct sockaddr *pGenericAddr = pDNSAddr->Address.lpSockaddr;
+ int stringlen = 0;
+
+ if( pGenericAddr->sa_family == AF_INET && left > ipv4_size )
+ {
+ /* Handle the v4 case */
+ struct sockaddr_in *pIPv4Addr = ( struct sockaddr_in * ) pGenericAddr;
+ ares_inet_ntop( AF_INET, &pIPv4Addr->sin_addr, ret, ipv4_size - 1 ); /* -1 for comma */
+
+ /* Append a comma to the end, THEN NULL. Should be OK because we
+ already tested the size at the top of the if statement. */
+ stringlen = strlen( ret );
+ ret[ stringlen ] = ',';
+ ret[ stringlen + 1 ] = '\0';
+ ret += stringlen + 1;
+ left -= ret - ret_buf;
+ ++count;
+ }
+ else if( pGenericAddr->sa_family == AF_INET6 && left > ipv6_size )
+ {
+ /* Handle the v6 case */
+ struct sockaddr_in6 *pIPv6Addr = ( struct sockaddr_in6 * ) pGenericAddr;
+ ares_inet_ntop( AF_INET6, &pIPv6Addr->sin6_addr, ret, ipv6_size - 1 ); /* -1 for comma */
+
+ /* Append a comma to the end, THEN NULL. Should be OK because we
+ already tested the size at the top of the if statement. */
+ stringlen = strlen( ret );
+ ret[ stringlen ] = ',';
+ ret[ stringlen + 1 ] = '\0';
+ ret += stringlen + 1;
+ left -= ret - ret_buf;
+ ++count;
+
+ /* NB on Windows this also returns stuff in the fec0::/10 range,
+ seems to be hard-coded somehow. Do we need to ignore them? */
+ }
+ }
+ }
+
+ if( pFirstEntry )
+ free( pFirstEntry );
+ if (ret > ret_buf)
+ ret[-1] = '\0';
+ return count;
}
- if (strlen(fi->DnsServerList.IpAddress.String) > 0 &&
- inet_addr(fi->DnsServerList.IpAddress.String) != INADDR_NONE &&
- left > ip_size)
+ else
{
- ret += sprintf (ret, "%s,", fi->DnsServerList.IpAddress.String);
- left -= ret - ret_buf;
- count++;
- }
+ FIXED_INFO *fi, *newfi;
+ DWORD size = sizeof (*fi);
+ IP_ADDR_STRING *ipAddr;
+ int i;
+ int debug = 0;
+ HRESULT res;
+
+ fi = malloc(size);
+ if (!fi)
+ return 0;
+
+ res = (*ares_fpGetNetworkParams) (fi, &size);
+ if ((res != ERROR_BUFFER_OVERFLOW) && (res != ERROR_SUCCESS))
+ goto quit;
+
+ newfi = realloc(fi, size);
+ if (!newfi)
+ goto quit;
+
+ fi = newfi;
+ res = (*ares_fpGetNetworkParams) (fi, &size);
+ if (res != ERROR_SUCCESS)
+ goto quit;
- for (i = 0, ipAddr = fi->DnsServerList.Next; ipAddr && left > ip_size;
- ipAddr = ipAddr->Next, i++)
- {
- if (inet_addr(ipAddr->IpAddress.String) != INADDR_NONE)
+ if (debug)
{
- ret += sprintf (ret, "%s,", ipAddr->IpAddress.String);
- left -= ret - ret_buf;
- count++;
+ printf ("Host Name: %s\n", fi->HostName);
+ printf ("Domain Name: %s\n", fi->DomainName);
+ printf ("DNS Servers:\n"
+ " %s (primary)\n", fi->DnsServerList.IpAddress.String);
+ }
+ if (strlen(fi->DnsServerList.IpAddress.String) > 0 &&
+ inet_addr(fi->DnsServerList.IpAddress.String) != INADDR_NONE &&
+ left > ipv4_size)
+ {
+ ret += sprintf (ret, "%s,", fi->DnsServerList.IpAddress.String);
+ left -= ret - ret_buf;
+ ++count;
+ }
+
+ for (i = 0, ipAddr = fi->DnsServerList.Next; ipAddr && left > ipv4_size;
+ ipAddr = ipAddr->Next, i++)
+ {
+ if (inet_addr(ipAddr->IpAddress.String) != INADDR_NONE)
+ {
+ ret += sprintf (ret, "%s,", ipAddr->IpAddress.String);
+ left -= ret - ret_buf;
+ ++count;
+ }
+ if (debug)
+ printf (" %s (secondary %d)\n", ipAddr->IpAddress.String, i+1);
}
- if (debug)
- printf (" %s (secondary %d)\n", ipAddr->IpAddress.String, i+1);
- }
quit:
- if (fi)
- free(fi);
-
- if (debug && left <= ip_size)
- printf ("Too many nameservers. Truncating to %d addressess", count);
- if (ret > ret_buf)
- ret[-1] = '\0';
- return count;
+ if (fi)
+ free(fi);
+
+ if (debug && left <= ipv4_size)
+ printf ("Too many nameservers. Truncating to %d addressess", count);
+ if (ret > ret_buf)
+ ret[-1] = '\0';
+ return count;
+ }
}
#endif
@@ -704,7 +827,7 @@ DhcpNameServer
DWORD data_type;
DWORD bytes;
DWORD result;
- char buf[256];
+ char buf[512];
win_platform platform;
if (channel->nservers > -1) /* don't override ARES_OPT_SERVER */
View
10 ares_library_init.c
@@ -26,6 +26,7 @@
#ifdef USE_WINSOCK
fpGetNetworkParams_t ares_fpGetNetworkParams = ZERO_NULL;
fpSystemFunction036_t ares_fpSystemFunction036 = ZERO_NULL;
+fpGetAdaptersAddresses_t ares_fpGetAdaptersAddresses = ZERO_NULL;
#endif
/* library-private global vars with source visibility restricted to this file */
@@ -56,6 +57,15 @@ static int ares_win32_init(void)
return ARES_EADDRGETNETWORKPARAMS;
}
+ ares_fpGetAdaptersAddresses = (fpGetAdaptersAddresses_t)
+ GetProcAddress(hnd_iphlpapi, "GetAdaptersAddresses");
+ if (!ares_fpGetAdaptersAddresses)
+ {
+ /* This can happen on clients before WinXP, I don't
+ think it should be an error, unless we don't want to
+ support Windows 2000 anymore */
+ }
+
/*
* When advapi32.dll is unavailable or advapi32.dll has no SystemFunction036,
* also known as RtlGenRandom, which is the case for Windows versions prior
View
2 ares_library_init.h
@@ -26,12 +26,14 @@
typedef DWORD (WINAPI *fpGetNetworkParams_t) (FIXED_INFO*, DWORD*);
typedef BOOLEAN (APIENTRY *fpSystemFunction036_t) (void*, ULONG);
+typedef ULONG (WINAPI *fpGetAdaptersAddresses_t) ( ULONG, ULONG, void*, IP_ADAPTER_ADDRESSES*, ULONG* );
/* Forward-declaration of variables defined in ares_library_init.c */
/* that are global and unique instances for whole c-ares library. */
extern fpGetNetworkParams_t ares_fpGetNetworkParams;
extern fpSystemFunction036_t ares_fpSystemFunction036;
+extern fpGetAdaptersAddresses_t ares_fpGetAdaptersAddresses;
#endif /* USE_WINSOCK */
View
2 ares_private.h
@@ -203,7 +203,7 @@ struct query {
void *arg;
/* Query status */
- int try; /* Number of times we tried this query already. */
+ int try_count; /* Number of times we tried this query already. */
int server; /* Server this query has last been sent to. */
struct query_server_info *server_info; /* per-server state */
int using_tcp;
View
4 ares_process.c
@@ -684,7 +684,7 @@ static void next_server(ares_channel channel, struct query *query,
* servers to try. In total, we need to do channel->nservers * channel->tries
* attempts. Use query->try to remember how many times we already attempted
* this query. Use modular arithmetic to find the next server to try. */
- while (++(query->try) < (channel->nservers * channel->tries))
+ while (++(query->try_count) < (channel->nservers * channel->tries))
{
struct server_state *server;
@@ -789,7 +789,7 @@ void ares__send_query(ares_channel channel, struct query *query,
return;
}
}
- timeplus = channel->timeout << (query->try / channel->nservers);
+ timeplus = channel->timeout << (query->try_count / channel->nservers);
timeplus = (timeplus * (9 + (rand () & 7))) / 16;
query->timeout = *now;
ares__timeadd(&query->timeout,
View
2 ares_send.c
@@ -96,7 +96,7 @@ void ares_send(ares_channel channel, const unsigned char *qbuf, int qlen,
query->arg = arg;
/* Initialize query status. */
- query->try = 0;
+ query->try_count = 0;
/* Choose the server to send the query to. If rotation is enabled, keep track
* of the next server we want to use. */

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