Re: [PATCH][SMB3] 3 small multichannel client patches

[Steve French <smfrench@gmail.com>]

added RB tag and added cc:stable to those two as well

On Sat, May 8, 2021 at 10:20 AM Tom Talpey <tom@talpey.com> wrote:
>
> LGTM
>
> Reviewed-By: Tom Talpey <tom@talpey.com>
>
> On 5/8/2021 11:10 AM, Steve French wrote:
> > 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