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[dns] Add support for resolving IPv6 addresses via AAAA records
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Our policy is to prefer IPv6 addreses to IPv4 addresses, but to
request IPv6 addresses only if we have an IPv6 address for the name
server itself.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
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@mcb30
mcb30 committed Dec 5, 2013
1 parent 60c4e62 commit 6248894
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Showing 4 changed files with 112 additions and 36 deletions.
4 changes: 2 additions & 2 deletions src/include/ipxe/dhcpv6.h
View file
Expand Up @@ -147,10 +147,10 @@ struct dhcpv6_user_class_option {
#define DHCPV6_USER_CLASS 15

/** DHCPv6 DNS recursive name server option */
#define DHCPV6_DNS_SERVER 23
#define DHCPV6_DNS_SERVERS 23

/** DHCPv6 domain search list option */
#define DHCPV6_DOMAIN_SEARCH 24
#define DHCPV6_DOMAIN_LIST 24

/**
* Any DHCPv6 option
Expand Down
7 changes: 7 additions & 0 deletions src/include/ipxe/dns.h
View file
Expand Up @@ -19,6 +19,7 @@ FILE_LICENCE ( GPL2_OR_LATER );

#define DNS_TYPE_A 1
#define DNS_TYPE_CNAME 5
#define DNS_TYPE_AAAA 28
#define DNS_TYPE_ANY 255

#define DNS_CLASS_IN 1
Expand Down Expand Up @@ -78,6 +79,11 @@ struct dns_rr_info_a {
struct in_addr in_addr;
} __attribute__ (( packed ));

struct dns_rr_info_aaaa {
struct dns_rr_info_common common;
struct in6_addr in6_addr;
} __attribute__ (( packed ));

struct dns_rr_info_cname {
struct dns_rr_info_common common;
char cname[0];
Expand All @@ -86,6 +92,7 @@ struct dns_rr_info_cname {
union dns_rr_info {
struct dns_rr_info_common common;
struct dns_rr_info_a a;
struct dns_rr_info_aaaa aaaa;
struct dns_rr_info_cname cname;
};

Expand Down
2 changes: 1 addition & 1 deletion src/net/udp/dhcpv6.c
View file
Expand Up @@ -362,7 +362,7 @@ static int dhcpv6_register ( struct dhcpv6_option_list *options,

/** Options to be requested */
static uint16_t dhcpv6_requested_options[] = {
htons ( DHCPV6_DNS_SERVER ), htons ( DHCPV6_DOMAIN_SEARCH ),
htons ( DHCPV6_DNS_SERVERS ), htons ( DHCPV6_DOMAIN_LIST ),
};

/**
Expand Down
135 changes: 102 additions & 33 deletions src/net/udp/dns.c
View file
Expand Up @@ -37,6 +37,8 @@ FILE_LICENCE ( GPL2_OR_LATER );
#include <ipxe/tcpip.h>
#include <ipxe/settings.h>
#include <ipxe/features.h>
#include <ipxe/dhcp.h>
#include <ipxe/dhcpv6.h>
#include <ipxe/dns.h>

/** @file
Expand All @@ -56,8 +58,15 @@ FEATURE ( FEATURE_PROTOCOL, "DNS", DHCP_EB_FEATURE_DNS, 1 );
__einfo_uniqify ( EINFO_ENXIO, 0x02, "No DNS servers available" )

/** The DNS server */
static struct sockaddr_tcpip nameserver = {
.st_port = htons ( DNS_PORT ),
static union {
struct sockaddr sa;
struct sockaddr_tcpip st;
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
} nameserver = {
.st = {
.st_port = htons ( DNS_PORT ),
},
};

/** The local domain */
Expand All @@ -75,7 +84,13 @@ struct dns_request {
struct retry_timer timer;

/** Socket address to fill in with resolved address */
struct sockaddr sa;
union {
struct sockaddr sa;
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
} address;
/** Initial query type */
uint16_t qtype;
/** Current query packet */
struct dns_query query;
/** Location of query info structure within current packet
Expand Down Expand Up @@ -104,6 +119,24 @@ static void dns_done ( struct dns_request *dns, int rc ) {
intf_shutdown ( &dns->resolv, rc );
}

/**
* Mark DNS request as resolved and complete
*
* @v dns DNS request
* @v rc Return status code
*/
static void dns_resolved ( struct dns_request *dns ) {

DBGC ( dns, "DNS %p found address %s\n",
dns, sock_ntoa ( &dns->address.sa ) );

/* Return resolved address */
resolv_done ( &dns->resolv, &dns->address.sa );

/* Mark operation as complete */
dns_done ( dns, 0 );
}

/**
* Compare DNS reply name against the query name from the original request
*
Expand Down Expand Up @@ -345,7 +378,6 @@ static int dns_xfer_deliver ( struct dns_request *dns,
struct xfer_metadata *meta __unused ) {
const struct dns_header *reply = iobuf->data;
union dns_rr_info *rr_info;
struct sockaddr_in *sin;
unsigned int qtype = dns->qinfo->qtype;
int rc;

Expand Down Expand Up @@ -383,20 +415,23 @@ static int dns_xfer_deliver ( struct dns_request *dns,
while ( ( rr_info = dns_find_rr ( dns, reply ) ) ) {
switch ( rr_info->common.type ) {

case htons ( DNS_TYPE_A ):
case htons ( DNS_TYPE_AAAA ):

/* Found the target A record */
DBGC ( dns, "DNS %p found address %s\n",
dns, inet_ntoa ( rr_info->a.in_addr ) );
sin = ( struct sockaddr_in * ) &dns->sa;
sin->sin_family = AF_INET;
sin->sin_addr = rr_info->a.in_addr;
/* Found the target AAAA record */
dns->address.sin6.sin6_family = AF_INET6;
memcpy ( &dns->address.sin6.sin6_addr,
&rr_info->aaaa.in6_addr,
sizeof ( dns->address.sin6.sin6_addr ) );
dns_resolved ( dns );
rc = 0;
goto done;

/* Return resolved address */
resolv_done ( &dns->resolv, &dns->sa );
case htons ( DNS_TYPE_A ):

/* Mark operation as complete */
dns_done ( dns, 0 );
/* Found the target A record */
dns->address.sin.sin_family = AF_INET;
dns->address.sin.sin_addr = rr_info->a.in_addr;
dns_resolved ( dns );
rc = 0;
goto done;

Expand All @@ -407,7 +442,7 @@ static int dns_xfer_deliver ( struct dns_request *dns,
dns->qinfo = ( void * ) dns_decompress_name ( reply,
rr_info->cname.cname,
dns->query.payload );
dns->qinfo->qtype = htons ( DNS_TYPE_A );
dns->qinfo->qtype = dns->qtype;
dns->qinfo->qclass = htons ( DNS_CLASS_IN );

/* Terminate the operation if we recurse too far */
Expand All @@ -432,6 +467,16 @@ static int dns_xfer_deliver ( struct dns_request *dns,
*/
switch ( qtype ) {

case htons ( DNS_TYPE_AAAA ):
/* We asked for an AAAA record and got nothing; try
* the A.
*/
DBGC ( dns, "DNS %p found no AAAA record; trying A\n", dns );
dns->qinfo->qtype = htons ( DNS_TYPE_A );
dns_send_packet ( dns );
rc = 0;
goto done;

case htons ( DNS_TYPE_A ):
/* We asked for an A record and got nothing;
* try the CNAME.
Expand All @@ -447,7 +492,7 @@ static int dns_xfer_deliver ( struct dns_request *dns,
* (i.e. if the next A query is already set up), then
* issue it, otherwise abort.
*/
if ( dns->qinfo->qtype == htons ( DNS_TYPE_A ) ) {
if ( dns->qinfo->qtype == dns->qtype ) {
dns_send_packet ( dns );
rc = 0;
goto done;
Expand Down Expand Up @@ -519,7 +564,7 @@ static int dns_resolv ( struct interface *resolv,
int rc;

/* Fail immediately if no DNS servers */
if ( ! nameserver.st_family ) {
if ( ! nameserver.sa.sa_family ) {
DBG ( "DNS not attempting to resolve \"%s\": "
"no DNS servers\n", name );
rc = -ENXIO_NO_NAMESERVER;
Expand All @@ -543,20 +588,32 @@ static int dns_resolv ( struct interface *resolv,
intf_init ( &dns->resolv, &dns_resolv_desc, &dns->refcnt );
intf_init ( &dns->socket, &dns_socket_desc, &dns->refcnt );
timer_init ( &dns->timer, dns_timer_expired, &dns->refcnt );
memcpy ( &dns->sa, sa, sizeof ( dns->sa ) );
memcpy ( &dns->address.sa, sa, sizeof ( dns->address.sa ) );

/* Determine initial query type */
switch ( nameserver.sa.sa_family ) {
case AF_INET:
dns->qtype = htons ( DNS_TYPE_A );
break;
case AF_INET6:
dns->qtype = htons ( DNS_TYPE_AAAA );
break;
default:
rc = -ENOTSUP;
goto err_qtype;
}

/* Create query */
dns->query.dns.flags = htons ( DNS_FLAG_QUERY | DNS_FLAG_OPCODE_QUERY |
DNS_FLAG_RD );
dns->query.dns.qdcount = htons ( 1 );
dns->qinfo = ( void * ) dns_make_name ( fqdn, dns->query.payload );
dns->qinfo->qtype = htons ( DNS_TYPE_A );
dns->qinfo->qtype = dns->qtype;
dns->qinfo->qclass = htons ( DNS_CLASS_IN );

/* Open UDP connection */
if ( ( rc = xfer_open_socket ( &dns->socket, SOCK_DGRAM,
( struct sockaddr * ) &nameserver,
NULL ) ) != 0 ) {
&nameserver.sa, NULL ) ) != 0 ) {
DBGC ( dns, "DNS %p could not open socket: %s\n",
dns, strerror ( rc ) );
goto err_open_socket;
Expand All @@ -572,10 +629,11 @@ static int dns_resolv ( struct interface *resolv,
return 0;

err_open_socket:
err_alloc_dns:
err_qtype:
ref_put ( &dns->refcnt );
err_qualify_name:
err_alloc_dns:
free ( fqdn );
err_qualify_name:
err_no_nameserver:
return rc;
}
Expand All @@ -593,31 +651,42 @@ struct resolver dns_resolver __resolver ( RESOLV_NORMAL ) = {
******************************************************************************
*/

/** DNS server setting */
/** IPv4 DNS server setting */
const struct setting dns_setting __setting ( SETTING_IPv4_EXTRA ) = {
.name = "dns",
.description = "DNS server",
.tag = DHCP_DNS_SERVERS,
.type = &setting_type_ipv4,
};

/** IPv6 DNS server setting */
const struct setting dns6_setting __setting ( SETTING_IPv6_EXTRA ) = {
.name = "dns6",
.description = "DNS server",
.tag = DHCPV6_DNS_SERVERS,
.type = &setting_type_ipv6,
.scope = &ipv6_scope,
};

/**
* Apply DNS settings
*
* @ret rc Return status code
*/
static int apply_dns_settings ( void ) {
struct sockaddr_in *sin_nameserver =
( struct sockaddr_in * ) &nameserver;
int len;

/* Fetch DNS server address */
nameserver.st_family = 0;
if ( ( len = fetch_ipv4_setting ( NULL, &dns_setting,
&sin_nameserver->sin_addr ) ) >= 0 ){
nameserver.st_family = AF_INET;
nameserver.sa.sa_family = 0;
if ( fetch_ipv6_setting ( NULL, &dns6_setting,
&nameserver.sin6.sin6_addr ) >= 0 ) {
nameserver.sin6.sin6_family = AF_INET6;
} else if ( fetch_ipv4_setting ( NULL, &dns_setting,
&nameserver.sin.sin_addr ) >= 0 ) {
nameserver.sin.sin_family = AF_INET;
}
if ( nameserver.sa.sa_family ) {
DBG ( "DNS using nameserver %s\n",
inet_ntoa ( sin_nameserver->sin_addr ) );
sock_ntoa ( &nameserver.sa ) );
}

/* Get local domain DHCP option */
Expand Down

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