Re: [PATCH] NFS4: fix referrals with IPv6 mounts

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On Apr 20, 2012, at 4:13 PM, Myklebust, Trond wrote:

> On Fri, 2012-04-20 at 19:57 +0000, Adamson, Dros wrote:
>> On Apr 20, 2012, at 3:45 PM, Jim Rees wrote:
>> 
>>> Weston Andros Adamson wrote:
>>> 
>>> nfs4_path() was parsing the path component by splitting on the first colon.
>>> This is wrong when an IPv6 address is used to mount a server.
>>> 
>>> For example, having mounted 'fc00::10:/export', nfs4_path() returned
>>> ':10:/export'.  This causes referrals (using IPv4 or IPv6 addresses) to fail
>>> in nfs4_validate_fspath().
>>> 
>>> Parsing the path component by using the *last* colon works with
>>> IPv6 as well as IPv4 addrs.
>>> 
>>> What if your mount is:
>>> 
>>> server.edu:/export/:I-like-colons:
>>> 
>>> It seems to me something has to give.  Either we require v6 addresses be
>>> enclosed in [], export dirs start with "/", or exports have no ":".
>> 
>> 
>> Yeah, you're right.
>> 
>> Although IPv6 addrs must be enclosed in [] to work with mount, it's always displayed in the kernel without the [].
>> 
>> I suppose the correct fix is to always display IPv6 addresses enclosed in [], which might touch a *lot* of places.
>> 
>> Thoughts?  I'll wait for others to chime in before I go fixing this. I have a set of nfsd and mountd patches that deal with similar issues on the server side.  I'll clean those up and submit them before getting back to this.
> 
> We do know which part is the hostname, and which is the pathname. If you
> look at "try_location()", you'll see that the hostname is stored in
> location->servers, and is then copied into this empty buffer.
> 
> If you want to test if that is an IPv6 address so that you can enclose
> it in [], then that should be fairly easy to do right there…

Right, we have separate hostname and pathname for each fs_location4, but I'm talking about the return value of nfs_path() which is used to determine the server-side path on an arbitrary dentry on the *current* mountpoint (not the referral server).
The path part of nfs_path() is then compared against the fs_path of the nfs4_fs_locations struct (this is all in nfs4_validate_fspath).

Having nfs_path return [] wrapped IPv6 addresses basically means changing the devname to that format (d_fsdata is used by nfs_path()).  I'm concerned about changing the format of devname - its used all over the place.

So the options are:
 1) change the format of devname
 2) change how nfs4_validate_fspath gets the server-side path component of the current mount (don't use nfs_path())

I'll try option 1 and see what breaks.

-dros

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