[libvirt] [PATCH] log: actually do substring matches with fnmatch

[Daniel P. Berrangé]

On Wed, May 16, 2018 at 11:59:31AM +0200, Erik Skultety wrote:
> On Mon, May 14, 2018 at 02:53:49PM +0100, Daniel P. Berrangé wrote:
> > Historically we matched log filters with strstr(), and when switching to
> > fnmatch in cbb0fd3cfdc287f6f4653ef1f04a7cfb2ea51b27, it was stated that
> > we would continue to match substrings, with "foo" being equivalent to
> > "*foo*". Unfortuntely I forget to provide the code to actually make that
> > happen. This fixes it to prepend and append "*" if not already present in
> > the user's pattern.
> >
> > Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
> > ---
> >  src/util/virlog.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/util/virlog.c b/src/util/virlog.c
> > index be9fc0cf78..d548010b10 100644
> > --- a/src/util/virlog.c
> > +++ b/src/util/virlog.c
> > @@ -1409,6 +1409,8 @@ virLogFilterNew(const char *match,
> >  {
> >      virLogFilterPtr ret = NULL;
> >      char *mdup = NULL;
> > +    size_t mlen = strlen(match);
> > +    size_t off = 0;
> >
> >      virCheckFlags(VIR_LOG_STACK_TRACE, NULL);
> >
> > @@ -1418,9 +1420,19 @@ virLogFilterNew(const char *match,
> >          return NULL;
> >      }
> >
> > -    if (VIR_STRDUP_QUIET(mdup, match) < 0)
> > +    if (VIR_ALLOC_N_QUIET(mdup, mlen + 3) < 0)
> >          return NULL;
> >
> 
> At first glance it's not very clear why we need the hunk below, so I'd add a
> comment stating that we treat a match 'foo' to be equal to '*foo*' for the
> purposes of fnmatch() use.
> 
> Also, now that I see commit 8ccee910f5, I know we say
> we treat the match always as substring, but I'd go even further and enhance the
> sentence in that config (could be a separate patch) that not just 'foo', but
> also '*foo' and 'foo*' are in fact equal to '*foo*' for that matter. But this
> config change is not a deal-breaker to me.
> 
> > +    if (match[0] != '*') {
> > +        mdup[off++] = '*';
> > +    }
> 
> ^Braces around a single line body...
> 
> > +    memcpy(mdup + off, match, mlen + 1);
> 
> Why do you copy the null byte too? 'mlen' should suffice.

Oh true, I forgot that.

> 
> > +    off += mlen;
> > +    if (match[mlen - 1] != '*') {
> > +        mdup[off++] = '*';
> > +        mdup[off++] = '\0';
> 
> You won't need ^this extra null byte assignment, because we always use calloc
> to allocate a block.

Yep.

> > +    }
> > +
> >      if (VIR_ALLOC_QUIET(ret) < 0) {
> >          VIR_FREE(mdup);
> >          return NULL;
> 
> With the nit-picks fixed and a commentary added right before the hunk this
> patch adds:
> Reviewed-by: Erik Skultety <eskultet at redhat.com>

Thanks, will do.

Regards,
Daniel
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