Re: [PATCH] cifs: On cifs_reconnect, resolve the hostname again.

[Paulo Alcantara <pc@cjr.nz>]

Shyam Prasad N <nspmangalore@gmail.com> writes:

> Please consider the attached patch for performing the DNS query again
> on reconnect.
> This is important when connecting to Azure file shares. The UNC
> generally contains the server name as a FQDN, and the IP address which
> the name resolves to can change over time.
>
> After our last conversation about this, I discovered that for the
> non-DFS scenario, we never do DNS resolutions in cifs.ko, since
> mount.cifs already resolves the name and passes the "addr=" arg during
> mount.

Yeah, this should happen for both cases.  Good catch!

> I noticed that you had a patch for this long back. But I don't see
> that call happening in the latest code. Any idea why that was done?

I don't know.  Maybe some other patch broke it.

We should probably mark it for stable as well.

> From 289f7f0fa229ea181094821c309a2ba9358791a3 Mon Sep 17 00:00:00 2001
> From: Shyam Prasad N <sprasad@microsoft.com>
> Date: Wed, 31 Mar 2021 14:35:24 +0000
> Subject: [PATCH] cifs: On cifs_reconnect, resolve the hostname again.
>
> On cifs_reconnect, make sure that DNS resolution happens again.
> It could be the cause of connection to go dead in the first place.
>
> Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
> ---
>  fs/cifs/connect.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)

This patch breaks when CONFIG_CIFS_DFS_UPCALL isn't set.

Please declare reconn_set_ipaddr_from_hostname() outside the "#ifdef
CONFIG_CIFS_DFS_UPCALL" in connect.c.

Otherwise,

Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>