Re: [PATCH v3 05/15] flow, tcp, tcp_splice: Uniform debug helpers for new flows

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

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On Wed, Jan 17, 2024 at 08:59:22PM +0100, Stefano Brivio wrote:
> On Thu, 21 Dec 2023 18:02:27 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > When debugging passt/pasta, and the flow table in particular, one of the
> > most obvious things to know is when a new flow is initiated, along with the
> > details of its interface, addresses and ports.  Once we've determined to
> > what interface the flow should be forwarded, it's useful to know the
> > details of how it will appear on that other interface.
> > 
> > To help present that information uniformly, introduce FLOW_NEW_DBG() and
> > FLOW_FWD_DBG() helpers and use them for TCP connections, both "tap" and
> > spliced.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  flow.c       | 40 ++++++++++++++++++++++++++++++++++++++++
> >  flow.h       | 16 ++++++++++++++++
> >  tcp.c        | 11 +++++++++--
> >  tcp_splice.c |  3 ++-
> >  4 files changed, 67 insertions(+), 3 deletions(-)
> > 
> > diff --git a/flow.c b/flow.c
> > index b9c4a18..bc8cfc6 100644
> > --- a/flow.c
> > +++ b/flow.c
> > @@ -9,6 +9,7 @@
> >  #include <unistd.h>
> >  #include <string.h>
> >  #include <errno.h>
> > +#include <arpa/inet.h>
> >  
> >  #include "util.h"
> >  #include "passt.h"
> > @@ -50,6 +51,45 @@ void flow_log_(const struct flow_common *f, int pri, const char *fmt, ...)
> >  	logmsg(pri, "Flow %u (%s): %s", flow_idx(f), FLOW_TYPE(f), msg);
> >  }
> >  
> > +/**
> > + * flow_new_dbg() - Print debug message for new flow
> > + * @f:		Common flow structure
> > + * @side:	Which side initiated the new flow
> > + */
> > +void flow_new_dbg(const struct flow_common *f, unsigned side)
> > +{
> > +	char ebuf[INET6_ADDRSTRLEN], fbuf[INET6_ADDRSTRLEN];
> > +	const struct flowside *fside = &f->side[side];
> > +
> > +	flow_log_(f, LOG_DEBUG, "New %s from %s/%u: [%s]:%hu <-> [%s]:%hu",
> 
> I think we should always print the connection index too (passed from
> the macro, or passing 'conn' as argument here) -- especially if we want
> to correlate this to what flow_fwd_dbg() will print later.

Printing the index is built into flow_log_(), so we're already doing
that.

> It's also useful if anything goes wrong with the flow table itself.
> 
> Sure, address/ports pairs should now be sufficient to uniquely identify
> a flow, and the flow table should be otherwise transparent, but the idea
> behind debugging is that there's a bug somewhere.
> 
> > +		  flow_type_str[f->type], pif_name(fside->pif), side,
> > +		  inet_ntop(AF_INET6, &fside->faddr, fbuf, sizeof(fbuf)),
> > +		  fside->fport,
> > +		  inet_ntop(AF_INET6, &fside->eaddr, ebuf, sizeof(ebuf)),
> > +		  fside->eport);
> > +}
> > +
> > +/**
> > + * flow_fwd_dbg() - Print debug message for newly forwarded flow
> > + * @f:		Common flow structure
> > + * @side:	Which side was the flow forwarded to
> > + */
> > +void flow_fwd_dbg(const struct flow_common *f, unsigned side)
> > +{
> > +	char ebuf[INET6_ADDRSTRLEN], fbuf[INET6_ADDRSTRLEN];
> > +	const struct flowside *fside = &f->side[side];
> > +
> > +	inet_ntop(AF_INET6, &fside->eaddr, ebuf, sizeof(ebuf));
> > +	inet_ntop(AF_INET6, &fside->faddr, fbuf, sizeof(fbuf));
> > +
> > +	flow_log_(f, LOG_DEBUG, "Forwarded to %s/%u: [%s]:%hu <-> [%s]:%hu",
> > +		  pif_name(fside->pif), side,
> > +		  inet_ntop(AF_INET6, &fside->faddr, fbuf, sizeof(fbuf)),
> > +		  fside->fport,
> > +		  inet_ntop(AF_INET6, &fside->eaddr, ebuf, sizeof(ebuf)),
> > +		  fside->eport);
> > +}
> > +
> >  /** flowside_from_sock - Initialize flowside to match an existing socket
> >   * @fside:	flowside to initialize
> >   * @pif:	pif id of this flowside
> > diff --git a/flow.h b/flow.h
> > index 37885b2..e7c4484 100644
> > --- a/flow.h
> > +++ b/flow.h
> > @@ -97,6 +97,22 @@ struct flow_common {
> >  #define FLOW_TABLE_PRESSURE		30	/* % of FLOW_MAX */
> >  #define FLOW_FILE_PRESSURE		30	/* % of c->nofile */
> >  
> > +/** flow_complete - Check if common parts of flow are fully initialized
> > + * @flow:	flow to check
> > + */
> > +static inline bool flow_complete(const struct flow_common *f)
> > +{
> > +	return f->type != FLOW_TYPE_NONE && f->type < FLOW_NUM_TYPES &&
> > +		flowside_complete(&f->side[0]) &&
> > +		flowside_complete(&f->side[1]);
> 
> Preferably align next lines after "return ".

Done.

-- 
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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