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2010-08-11DNS: If the DNS server returns an error, allow that to be cached [ver #2]Wang Lei2-5/+92
If the DNS server returns an error, allow that to be cached in the DNS resolver key in lieu of a value. Userspace passes the desired error number as an option in the payload: "#dnserror=<number>" Userspace must map h_errno from the name resolution routines to an appropriate Linux error before passing it up. Something like the following mapping is recommended: [HOST_NOT_FOUND] = ENODATA, [TRY_AGAIN] = EAGAIN, [NO_RECOVERY] = ECONNREFUSED, [NO_DATA] = ENODATA, in lieu of Linux errors specifically for representing name service errors. The filesystem must map these errors appropropriately before passing them to userspace. AFS is made to map ENODATA and EAGAIN to EDESTADDRREQ for the return to userspace; ECONNREFUSED is allowed to stand as is. The error can be seen in /proc/keys as a negative number after the description of the key. Compare, for example, the following key entries: 2f97238c I--Q-- 1 53s 3f010000 0 0 dns_resol afsdb:grand.centrall.org: -61 338bfbbe I--Q-- 1 59m 3f010000 0 0 dns_resol afsdb:grand.central.org: 37 If the error option is supplied in the payload, the main part of the payload is discarded. The key should have an expiry time set by userspace. 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>
2010-08-06[DNS RESOLVER] Minor typo correctionSteve French1-1/+1
CC: Dave Howells <dhowells@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
2010-08-06DNS: Fixes for the DNS query moduleDavid Howells1-1/+1
Fixes for the DNS query module, including: (1) Use 'negative' instead of '-ve' in the documentation. (2) Mark the kdoc comment with '/**' on dns_query(). Reported-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
2010-08-06cifs: Include linux/err.h for IS_ERR and PTR_ERRStephen Rothwell2-0/+2
Fixes build errors: net/dns_resolver/dns_key.c: In function 'init_dns_resolver': net/dns_resolver/dns_key.c:170: error: implicit declaration of function 'IS_ERR' net/dns_resolver/dns_key.c:171: error: implicit declaration of function 'PTR_ERR' net/dns_resolver/dns_query.c: In function 'dns_query': net/dns_resolver/dns_query.c:126: error: implicit declaration of function 'IS_ERR' net/dns_resolver/dns_query.c:127: error: implicit declaration of function 'PTR_ERR' Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
2010-08-05DNS: Separate out CIFS DNS Resolver codeWang Lei5-0/+447
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>