Re: [PATCH 6/6] flow, tcp: Add logging helpers for connection related messages

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Nov 23, 2023 at 07:58:45AM +0100, Stefano Brivio wrote:
> On Thu, 23 Nov 2023 13:36:29 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Most of the messages logged by the TCP code (be they errors, debug or
> > trace messages) are related to a specific connection / flow.  We're fairly
> > consistent about prefixing these with the type of connection and the
> > connection / flow index.  However there are a few places where we put the
> > index later in the message or omit it entirely.  The template with the
> > prefix is also a little bulky to carry around for every message,
> > particularly for spliced connections.
> > 
> > To help keep this consistent, introduce some helpers to log messages
> > linked to a specific flow.  It takes the flow as a parameter and adds a
> > uniform prefix to each message.  This makes things slightly neater now, but
> > more importantly will help keep formatting consistent as we add more things
> > to the flow table.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  flow.c       | 21 ++++++++++++++
> >  flow.h       | 14 +++++++++
> >  tcp.c        | 81 ++++++++++++++++++++++++----------------------------
> >  tcp_splice.c | 61 +++++++++++++++++----------------------
> >  4 files changed, 99 insertions(+), 78 deletions(-)
> > 
> > diff --git a/flow.c b/flow.c
> > index 0fff119..cb2cf62 100644
> > --- a/flow.c
> > +++ b/flow.c
> > @@ -64,3 +64,24 @@ void flow_table_compact(struct ctx *c, union flow *hole)
> >  
> >  	memset(from, 0, sizeof(*from));
> >  }
> > +
> > +/** flow_log_ - Log flow-related message
> > + * @f:		flow the message is related to
> > + * @pri:	Log priority
> > + * @fmt:	Format string
> > + * @...:	printf-arguments
> > + *
> > + * @fmt must include an initial "%s" to expand to the prefix we generate
> > + * (typically added by the flow_log() macro).
> 
> I don't understand how it does that -- flow_log() seems to just pass
> __VA_ARGS__ through?

Oops, that's a leftover from an earlier version.  I formatting the
prefix first, then adding it to the message, rather than the message
first and adding it to the prefix.  I was attempting to avoid a fixed
size buffer for the message, but it just turned out weird and
troublesome.  Plus vlogmsg() has a fixed sized buffer anyway, so why
bother.

Anyway, I've removed the stale comment.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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