[OpenWrt-Devel] [PATCH firewall] zones: add zone identifying local traffic in raw OUTPUT chain

[Hans Dedecker]

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 <alin.nastac at gmail.com>
Signed-off-by: Hans Dedecker <dedeckeh at gmail.com>
---
 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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