Re: [PATCH 4/4] netconsole: implement extended console support

Tejun Heo
2015-05-11T20:37:52Z

Hello,

On Mon, May 11, 2015 at 01:23:39PM -0400, David Miller wrote:
> From: Tejun Heo <tj@kernel.org>
> Date: Mon, 11 May 2015 12:41:34 -0400
>
> > + /* need to insert extra header fields, detect header and body */
> > + header = msg;
> > + body = memchr(msg, ';', msg_len);
> > + if (WARN_ON_ONCE(!body))
> > + return;
> > +
> > + header_len = body - header;
> > + body_len = msg_len - header_len - 1;
> > + body++;
> > +
> > + /*
> > + * Transfer multiple chunks with the following extra header.
> > + * "ncfrag=<byte-offset>/<total-bytes>"
> > + */
> > + memcpy(buf, header, header_len);
> > +
> > + while (offset < body_len) {
> > + int this_header = header_len;
> > + int this_chunk;
> > +
> > + this_header += scnprintf(buf + this_header,
> > + sizeof(buf) - this_header,
> > + ",ncfrag=%d/%d;", offset, body_len);
> > +
>
> Hmmm, do you intend ncfrag= to be amongst the other metadata in the first
> fragment? The way I read the code above it's going to be:
>
> <level>,<sequnum>,<timestamp>,<contflag>;,ncfrag=x/y;
>
> If you intend to keep all the metadata, including the ncfrag bit,
> together, you probably need to clip off the initial semicolon, so
> that it looks like:
>
> <level>,<sequnum>,<timestamp>,<contflag>,ncfrag=x/y;

The current code does produce the latter outcome.

header = msg;
body = memchr(msg, ';', msg_len);
if (WARN_ON_ONCE(!body))
return;

header_len = body - header;
body_len = msg_len - header_len - 1;
body++;

@body points to ';' after memchr(), so @header_len doesn't include
';'. @body is incremented after calculating @header_len.

Thanks.

--
tejun