On Tue, Jan 13, 2026 at 12:26:15AM +0100, Stefano Brivio wrote: > On Thu, 8 Jan 2026 13:29:38 +1100 > David Gibson wrote: > > > Currently the forwarding table records details of explicit port forwards, > > but nothing for -[tTuU] auto. That looks a little odd on the debug output, > > and will be a problem for future changes. > > > > Extend the forward table to have rules for auto-scanned forwards, > > using a new FWD_SCAN flag. For now the mechanism of auto port > > forwarding isn't updated, and we will only create a single FWD_SCAN > > rule per protocol and direction. We'll better integrate auto scanning > > with other forward table mechanics in future. > > > > Signed-off-by: David Gibson > > --- > > conf.c | 31 ++++++++++++++++++++++++++----- > > fwd.c | 18 +++++++++++------- > > fwd.h | 2 ++ > > 3 files changed, 39 insertions(+), 12 deletions(-) > > > > diff --git a/conf.c b/conf.c > > index b486fefe..0bcf80d7 100644 > > --- a/conf.c > > +++ b/conf.c > > @@ -135,7 +135,7 @@ static int parse_port_range(const char *s, char **endptr, > > * @ifname: Listening interface > > * @first: First port to forward > > * @last: Last port to forward > > - * @exclude: Bitmap of ports to exclude > > + * @exclude: Bitmap of ports to exclude (may be NULL) > > * @to: Port to translate @first to when forwarding > > * @flags: Flags for forwarding entries > > */ > > @@ -168,11 +168,11 @@ static void conf_ports_range_except(const struct ctx *c, char optname, > > } > > > > for (base = first; base <= last; base++) { > > - if (bitmap_isset(exclude, base)) > > + if (exclude && bitmap_isset(exclude, base)) > > continue; > > > > for (i = base; i <= last; i++) { > > - if (bitmap_isset(exclude, i)) > > + if (exclude && bitmap_isset(exclude, i)) > > break; > > > > if (bitmap_isset(fwd->map, i)) { > > @@ -180,9 +180,9 @@ static void conf_ports_range_except(const struct ctx *c, char optname, > > "Altering mapping of already mapped port number: %s", optarg); > > } > > > > - if (optname == 't') > > + if (!(flags & FWD_SCAN) && optname == 't') > > fd = tcp_listen(c, PIF_HOST, addr, ifname, i); > > - else if (optname == 'u') > > + else if (!(flags & FWD_SCAN) && optname == 'u') > > fd = udp_listen(c, PIF_HOST, addr, ifname, i); > > else > > /* No way to check in advance for -T and -U */ > > @@ -2202,6 +2202,27 @@ void conf(struct ctx *c, int argc, char **argv) > > if (!c->udp.fwd_out.mode) > > c->udp.fwd_out.mode = fwd_default; > > > > + if (c->tcp.fwd_in.mode == FWD_AUTO) { > > + conf_ports_range_except(c, 't', "auto", &c->tcp.fwd_in, > > + NULL, NULL, 1, NUM_PORTS - 1, > > + NULL, 1, FWD_SCAN); > > + } > > + if (c->tcp.fwd_out.mode == FWD_AUTO) { > > + conf_ports_range_except(c, 'T', "auto", &c->tcp.fwd_out, > > + NULL, "lo", 1, NUM_PORTS - 1, > > + NULL, 1, FWD_SCAN); > > + } > > + if (c->udp.fwd_in.mode == FWD_AUTO) { > > + conf_ports_range_except(c, 'u', "auto", &c->udp.fwd_in, > > + NULL, NULL, 1, NUM_PORTS - 1, > > + NULL, 1, FWD_SCAN); > > + } > > + if (c->udp.fwd_out.mode == FWD_AUTO) { > > + conf_ports_range_except(c, 'U', "auto", &c->udp.fwd_out, > > + NULL, "lo", 1, NUM_PORTS - 1, > > + NULL, 1, FWD_SCAN); > > + } > > + > > if (!c->quiet) > > conf_print(c); > > } > > diff --git a/fwd.c b/fwd.c > > index ad398e54..69aca441 100644 > > --- a/fwd.c > > +++ b/fwd.c > > @@ -344,7 +344,7 @@ void fwd_rule_add(struct fwd_ports *fwd, uint8_t flags, > > in_port_t first, in_port_t last, in_port_t to) > > { > > /* Flags which can be set from the caller */ > > - const uint8_t allowed_flags = FWD_WEAK; > > + const uint8_t allowed_flags = FWD_WEAK | FWD_SCAN; > > struct fwd_rule *new; > > unsigned port; > > > > @@ -375,7 +375,8 @@ void fwd_rule_add(struct fwd_ports *fwd, uint8_t flags, > > > > for (port = new->first; port <= new->last; port++) { > > /* Fill in the legacy data structures to match the table */ > > - bitmap_set(fwd->map, port); > > + if (!(new->flags & FWD_SCAN)) > > + bitmap_set(fwd->map, port); > > fwd->delta[port] = new->to - new->first; > > } > > } > > @@ -391,19 +392,22 @@ void fwd_rules_print(const struct fwd_ports *fwd) > > for (i = 0; i < fwd->count; i++) { > > const struct fwd_rule *rule = &fwd->rules[i]; > > const char *weak = rule->flags & FWD_WEAK ? " WEAK" : ""; > > + const char *scan = rule->flags & FWD_SCAN ? " AUTO" : ""; > > const char *percent = *rule->ifname ? "%" : ""; > > char addr[INANY_ADDRSTRLEN]; > > > > inany_ntop(fwd_rule_addr(rule), addr, sizeof(addr)); > > > > if (rule->first == rule->last) { > > - info(" [%s]%s%s:%hu => %hu %s", > > + info(" [%s]%s%s:%hu => %hu %s%s", > > addr, percent, rule->ifname, > > - rule->first, rule->to, weak); > > + rule->first, rule->to, weak, scan); > > } else { > > - info(" [%s]%s%s:%hu-%hu => %hu-%hu %s", > > - addr, percent, rule->ifname, rule->first, rule->last, > > - rule->to, rule->last - rule->first + rule->to, weak); > > + info(" [%s]%s%s:%hu-%hu => %hu-%hu %s%s", > > + addr, percent, rule->ifname, > > + rule->first, rule->last, > > + rule->to, rule->last - rule->first + rule->to, > > + weak, scan); > > } > > } > > } > > diff --git a/fwd.h b/fwd.h > > index 3dfc7959..94869c2a 100644 > > --- a/fwd.h > > +++ b/fwd.h > > @@ -26,6 +26,7 @@ bool fwd_port_is_ephemeral(in_port_t port); > > * @flags: Flag mask > > * FWD_DUAL_STACK_ANY - match any IPv4 or IPv6 address (@addr should be ::) > > * FWD_WEAK - Don't give an error if binds fail for some forwards > > + * FWD_SCAN - Only forward if we scan a listener on the target > > Nit: I guess this could be slightly more descriptive than "scan a > listener", mentioning for example "if the corresponding port is bound > on the target". Done. > > > * > > * FIXME: @addr and @ifname currently ignored for outbound tables > > */ > > @@ -35,6 +36,7 @@ struct fwd_rule { > > in_port_t first, last, to; > > #define FWD_DUAL_STACK_ANY BIT(0) > > #define FWD_WEAK BIT(1) > > +#define FWD_SCAN BIT(2) > > uint8_t flags; > > }; > > > > -- > Stefano > -- David Gibson (he or they) | 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