Граф коммитов

3 Коммитов

Автор SHA1 Сообщение Дата
David Howells bbb4c4323a dns: Allow the dns resolver to retrieve a server set
Allow the DNS resolver to retrieve a set of servers and their associated
addresses, ports, preference and weight ratings.

In terms of communication with userspace, "srv=1" is added to the callout
string (the '1' indicating the maximum data version supported by the
kernel) to ask the userspace side for this.

If the userspace side doesn't recognise it, it will ignore the option and
return the usual text address list.

If the userspace side does recognise it, it will return some binary data
that begins with a zero byte that would cause the string parsers to give an
error.  The second byte contains the version of the data in the blob (this
may be between 1 and the version specified in the callout data).  The
remainder of the payload is version-specific.

In version 1, the payload looks like (note that this is packed):

	u8	Non-string marker (ie. 0)
	u8	Content (0 => Server list)
	u8	Version (ie. 1)
	u8	Source (eg. DNS_RECORD_FROM_DNS_SRV)
	u8	Status (eg. DNS_LOOKUP_GOOD)
	u8	Number of servers
	foreach-server {
		u16	Name length (LE)
		u16	Priority (as per SRV record) (LE)
		u16	Weight (as per SRV record) (LE)
		u16	Port (LE)
		u8	Source (eg. DNS_RECORD_FROM_NSS)
		u8	Status (eg. DNS_LOOKUP_GOT_NOT_FOUND)
		u8	Protocol (eg. DNS_SERVER_PROTOCOL_UDP)
		u8	Number of addresses
		char[]	Name (not NUL-terminated)
		foreach-address {
			u8		Family (AF_INET{,6})
			union {
				u8[4]	ipv4_addr
				u8[16]	ipv6_addr
			}
		}
	}

This can then be used to fetch a whole cell's VL-server configuration for
AFS, for example.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-10-04 09:40:52 -07:00
Aya Mahfouz 451c2b5caf net: dns_resolver: convert time_t to time64_t
Changes the definition of the pointer _expiry from time_t to
time64_t. This is to handle the Y2038 problem where time_t
will overflow in the year 2038. The change is safe because
the kernel subsystems that call dns_query pass NULL.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Aya Mahfouz <mahfouz.saif.elyazal@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-11-18 16:27:46 -05:00
Wang Lei 1a4240f476 DNS: Separate out CIFS DNS Resolver code
Separate out the DNS resolver key type from the CIFS filesystem into its own
module so that it can be made available for general use, including the AFS
filesystem module.

This facility makes it possible for the kernel to upcall to userspace to have
it issue DNS requests, package up the replies and present them to the kernel
in a useful form.  The kernel is then able to cache the DNS replies as keys
can be retained in keyrings.

Resolver keys are of type "dns_resolver" and have a case-insensitive
description that is of the form "[<type>:]<domain_name>".  The optional <type>
indicates the particular DNS lookup and packaging that's required.  The
<domain_name> is the query to be made.

If <type> isn't given, a basic hostname to IP address lookup is made, and the
result is stored in the key in the form of a printable string consisting of a
comma-separated list of IPv4 and IPv6 addresses.

This key type is supported by userspace helpers driven from /sbin/request-key
and configured through /etc/request-key.conf.  The cifs.upcall utility is
invoked for UNC path server name to IP address resolution.

The CIFS functionality is encapsulated by the dns_resolve_unc_to_ip() function,
which is used to resolve a UNC path to an IP address for CIFS filesystem.  This
part remains in the CIFS module for now.

See the added Documentation/networking/dns_resolver.txt for more information.

Signed-off-by: Wang Lei <wang840925@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
2010-08-05 17:17:51 +00:00