Add zone chains identifying local generated traffic; either by configuring
a loopback device or as subnet a loopback address; in the raw OUTPUT chain
as local generated traffic is passing this chain.
This allows helpers to be used for local generated traffic.

Signed-off-by: Alin Nastac <[email protected]>
Signed-off-by: Hans Dedecker <[email protected]>
---
 zones.c | 49 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 45 insertions(+), 4 deletions(-)

diff --git a/zones.c b/zones.c
index 505ab20..9ac6551 100644
--- a/zones.c
+++ b/zones.c
@@ -16,6 +16,9 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <net/if.h>
+#include <sys/ioctl.h>
+
 #include "zones.h"
 #include "ubus.h"
 #include "helpers.h"
@@ -98,6 +101,39 @@ const struct fw3_option fw3_zone_opts[] = {
        { }
 };
 
+static bool
+check_loopback_addr(struct fw3_address *addr)
+{
+       if (addr->family == FW3_FAMILY_V4 &&
+           (ntohl(addr->address.v4.s_addr) >> IN_CLASSA_NSHIFT) == 
IN_LOOPBACKNET)
+               return true;
+
+       if (addr->family == FW3_FAMILY_V6 && !addr->range &&
+           fw3_netmask2bitlen(FW3_FAMILY_V6, &addr->mask.v6) == 128 &&
+           IN6_IS_ADDR_LOOPBACK(&addr->address.v6))
+               return true;
+
+       return false;
+}
+
+static bool
+check_loopback_dev(const char *name)
+{
+       struct ifreq ifr;
+       int s = socket(AF_LOCAL, SOCK_DGRAM, 0);
+       bool rv = false;
+
+       memset(&ifr, 0, sizeof(ifr));
+       strncpy(ifr.ifr_name, name, sizeof(ifr.ifr_name) - 1);
+
+       if (s < 0 || ioctl(s, SIOCGIFFLAGS, &ifr) < 0)
+               goto out;
+
+       if (ifr.ifr_flags & IFF_LOOPBACK)
+               rv = true;
+out:
+       return rv;
+}
 
 static void
 check_policy(struct uci_element *e, enum fw3_flag *pol, enum fw3_flag def,
@@ -557,22 +593,27 @@ print_interface_rule(struct fw3_ipt_handle *handle, 
struct fw3_state *state,
        }
        else if (handle->table == FW3_TABLE_RAW)
        {
+               bool loopback_dev = (dev != NULL && !dev->any &&
+                                    !dev->invert && 
check_loopback_dev(dev->name));
+               char *chain = loopback_dev || (sub != NULL && !sub->invert && 
check_loopback_addr(sub)) ?
+                             "OUTPUT" : "PREROUTING";
+
                if (has(zone->flags, handle->family, FW3_FLAG_HELPER))
                {
-                       r = fw3_ipt_rule_create(handle, NULL, dev, NULL, sub, 
NULL);
+                       r = fw3_ipt_rule_create(handle, NULL, loopback_dev ? 
NULL : dev, NULL, sub, NULL);
                        fw3_ipt_rule_comment(r, "%s CT helper assignment", 
zone->name);
                        fw3_ipt_rule_target(r, "zone_%s_helper", zone->name);
                        fw3_ipt_rule_extra(r, zone->extra_src);
-                       fw3_ipt_rule_replace(r, "PREROUTING");
+                       fw3_ipt_rule_replace(r, chain);
                }
 
                if (has(zone->flags, handle->family, FW3_FLAG_NOTRACK))
                {
-                       r = fw3_ipt_rule_create(handle, NULL, dev, NULL, sub, 
NULL);
+                       r = fw3_ipt_rule_create(handle, NULL, loopback_dev ? 
NULL : dev, NULL, sub, NULL);
                        fw3_ipt_rule_comment(r, "%s CT bypass", zone->name);
                        fw3_ipt_rule_target(r, "zone_%s_notrack", zone->name);
                        fw3_ipt_rule_extra(r, zone->extra_src);
-                       fw3_ipt_rule_replace(r, "PREROUTING");
+                       fw3_ipt_rule_replace(r, chain);
                }
        }
 }
-- 
2.19.1


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