Hi Phil,
On Wed, Sep 23, 2020 at 12:53:39AM +0200, Phil Sutter wrote:
> Insert extensions into pending lists in ordered fashion: Group by
> extension name (and, for matches, family) and order groups by descending
> revision number.
>
> This allows to simplify the later full registration considerably. Since
> that involves kernel compatibility checks, the extra cycles here pay off
> eventually.
>
> Signed-off-by: Phil Sutter <phil@xxxxxx>
> ---
> libxtables/xtables.c | 64 +++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 58 insertions(+), 6 deletions(-)
>
> diff --git a/libxtables/xtables.c b/libxtables/xtables.c
> index 8907ba2069be7..63d0ea5def2d5 100644
> --- a/libxtables/xtables.c
> +++ b/libxtables/xtables.c
> @@ -948,8 +948,14 @@ static void xtables_check_options(const char *name, const struct option *opt)
> }
> }
>
> +static int xtables_match_prefer(const struct xtables_match *a,
> + const struct xtables_match *b);
> +
> void xtables_register_match(struct xtables_match *me)
> {
> + struct xtables_match **pos;
> + bool seen_myself = false;
> +
> if (me->next) {
> fprintf(stderr, "%s: match \"%s\" already registered\n",
> xt_params->program_name, me->name);
> @@ -1001,10 +1007,32 @@ void xtables_register_match(struct xtables_match *me)
> if (me->extra_opts != NULL)
> xtables_check_options(me->name, me->extra_opts);
>
> + /* order into linked list of matches pending full registration */
> + for (pos = &xtables_pending_matches; *pos; pos = &(*pos)->next) {
> + /* NOTE: No extension_cmp() here as we accept all families */
> + if (strcmp(me->name, (*pos)->name) ||
> + me->family != (*pos)->family) {
> + if (seen_myself)
> + break;
> + continue;
> + }
> + seen_myself = true;
> + if (xtables_match_prefer(me, *pos) >= 0)
xtables_match_prefer() evaluates >= 0 if 'me' has higher revision
number than *pos. So list order is: higher revision first.
> + break;
> + }
> + if (!*pos)
> + pos = &xtables_pending_matches;
>
> - /* place on linked list of matches pending full registration */
> - me->next = xtables_pending_matches;
> - xtables_pending_matches = me;
> + me->next = *pos;
This line above is placing 'me' right before the existing match in the list.
> + *pos = me;
This line above only works if *pos is &xtables_pending_matches?
Looking at the in-tree extensions, they are always ordered from lower
to higher (in array definitions).
