On 2/17/25 1:28 PM, Tom Talpey wrote:
On 2/17/2025 4:18 PM, Steve French wrote:
On Mon, Feb 17, 2025 at 3:08 PM Tom Talpey <tom@xxxxxxxxxx> wrote:
On 2/17/2025 1:27 PM, Steve French wrote:
Noticed this old bug today when cleaning up emails.
When the user specifies a srcaddr on mount, the DNS resolution of the
host name should only look for the same type of address (ie IPv4 if
srcaddr is IPv4, IPv6 if IPv6) right?
Any thoughts on how this was handled in other protocols?
What is this "srcaddr" witchcraft that thou dost utter? :)
The original patch which added it was this, and apparently is needed in some
cases where the subnet the request comes from is restricted:
commit 3eb9a8893a76cf1cda3b41c3212eb2cfe83eae0e
Author: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Date: Wed Sep 1 17:06:02 2010 -0700
cifs: Allow binding to local IP address.
When using multi-homed machines, it's nice to be able to specify
the local IP to use for outbound connections. This patch gives
cifs the ability to bind to a particular IP address.
Usage: mount -t cifs -o srcaddr=192.168.1.50,user=foo, ...
Usage: mount -t cifs -o srcaddr=2002::100:1,user=foo, ...
Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
Acked-by: Dr. David Holder <david.holder@xxxxxxxxxxx>
Signed-off-by: Ben Greear <greearb@xxxxxxxxxxxxxxx>
I still think this is a hack, and unlikely to work reliably.
Except for that DNS issue, it works as intended as far as I can tell, and someone that doesn't want
the behaviour can just not use it.
I guess we never run CIFS in mixed ipv4/6 environment with DNS.
There isn't such an option in mount.nfs that I'm aware of.
And, it isn't documented in mount.cifs either.
NFS man page does show "clientaddr=" mount option,
and it is necessary apparently in some cases (e.g.
https://forum.proxmox.com/threads/nfs-mounts-using-wrong-source-ip-interface.70754/)
The NFSv4.0 clientaddr is totally different, that protocol requires
the client to inform the server which address to establish a
callback channel to. This horribly broken protocol architecture
was corrected in NFSv4.1.
NFS requires a small pile of patches to have a similar behaviour...they are in
our kernel (github.com greearb) in case anyone wants them, but were never accepted upstream.
Thanks,
Ben
Tom.
It seems like a hack on top of a hack to match the DNS result
to the type of the specified srcaddr. If the server supports
both IP versions and the DNS record exposes them, won't the
same issue occur on "normal" mounts?
I would not see this playing nicely with multichannel, btw.
Or RDMA. Probably other scenarios.
Tom.
https://bugzilla.kernel.org/show_bug.cgi?id=218523
--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc http://www.candelatech.com
