On Sat, May 8, 2021 at 8:29 AM Tom Talpey <tom@talpey.com> wrote:
>
> On 5/7/2021 9:13 PM, Steve French wrote:
> > 1) we were not setting CAP_MULTICHANNEL on negotiate request
>
> > diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> > index e36c2a867783..a8bf43184773 100644
> > --- a/fs/cifs/smb2pdu.c
> > +++ b/fs/cifs/smb2pdu.c
> > @@ -841,6 +841,8 @@ SMB2_negotiate(const unsigned int xid, struct cifs_ses *ses)
> >               req->SecurityMode = 0;
> >
> >       req->Capabilities = cpu_to_le32(server->vals->req_capabilities);
> > +     if (ses->chan_max > 1)
> > +             req->Capabilities |= cpu_to_le32(SMB2_GLOBAL_CAP_MULTI_CHANNEL);
> >
> >       /* ClientGUID must be zero for SMB2.02 dialect */
> >       if (server->vals->protocol_id == SMB20_PROT_ID)
> > @@ -1032,6 +1034,9 @@ int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
> >
> >       pneg_inbuf->Capabilities =
> >                       cpu_to_le32(server->vals->req_capabilities);
> > +     if (tcon->ses->chan_max > 1)
> > +             pneg_inbuf->Capabilities |= cpu_to_le32(SMB2_GLOBAL_CAP_MULTI_CHANNEL);
> > +
>
> This doesn't look quite right, and it can lead to failed negotiate by
> setting CAP_MULTI_CHANNEL when the server didn't actually send the bit.
> Have you tested this with servers that don't do multichannel?

Yes.   Validate negotiate ioctl request is supposed to validate what
the client sent not what the server responded, so according to
MS-SMB2, I must send in the ioctl what I sent before on negprot
request

Section 3.2.5.5 says for validate negotiate "Capabilities is set to
Connection.ClientCapabilities."  where
"Connection.ClientCapabilities: The capabilities sent by the client in
the SMB2 NEGOTIATE Request"   (not what the server responded with,
what the ClientCapabilities were sent)

I tested it with two cases that don't support multichannel: Samba, and
also an azure server target where multichannel was disabled.


>
> > 2) we were ignoring whether the server set CAP_NEGOTIATE in the response
>
> Is this "CAP_NEGOTIATE" a typo? I think you mean CAP_MULTI_CHANNEL.

Yes - typo

>
> > diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
> > index 63d517b9f2ff..a391ca3166f3 100644
> > --- a/fs/cifs/sess.c
> > +++ b/fs/cifs/sess.c
> > @@ -97,6 +97,12 @@ int cifs_try_adding_channels(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses)
> >               return 0;
> >       }
> >
> > +     if ((ses->server->capabilities & SMB2_GLOBAL_CAP_MULTI_CHANNEL) == false) {
>
> This compares a bit to a boolean. "false" should be "0"?

I changed it to the more common style  if (!(ses->...capabilities & SMB@....))
>
> > +             cifs_dbg(VFS, "server does not support CAP_MULTI_CHANNEL, multichannel disabled\n");
>
> The wording could be clearer. Technically speaking, the server does not
> support _multichannel_, which it indicated by not setting CAP_MULTI_CHANNEL.
> Also, wouldn't it be more useful to add the servername to this message?
>         "server %s does not support multichannel, using single channel"
> or similar.

Good idea

> > 3) we were silently ignoring multichannel when "max_channels" was > 1
> > but the user forgot to include "multichannel" in mount line.
>
>  > diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
>  > index 3bcf881c3ae9..8f7af6fcdc76 100644
>  > --- a/fs/cifs/fs_context.c
>  > +++ b/fs/cifs/fs_context.c
>  > @@ -1021,6 +1021,9 @@ static int smb3_fs_context_parse_param(struct
> fs_context *fc,
>  >                      goto cifs_parse_mount_err;
>  >              }
>  >              ctx->max_channels = result.uint_32;
>  > +            /* If more than one channel requested ... they want multichan */
>  > +            if ((ctx->multichannel == false) && (result.uint_32 > 1))
>  > +                    ctx->multichannel = true;
>
> Wouldn't this be clearer and simpler as just "if (result.uint32 > 1)" ?

made that change

Updated two of the patches as described above - attached.
-- 
Thanks,

Steve