zones: properly handle multiple masq_src / masq_dest negations (FS#248)

Properly implement masquerade exceptions by using -j RETURN rules to jump out
of the postrouting container chain and only emit the permutated -j MASQUERADE
rules for non-negated addresses.

Fixes FD#248.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

diff --git a/zones.c b/zones.c
index 9ae0c75..a95e363 100644 (file)
--- a/zones.c
+++ b/zones.c
@@ -466,11 +466,30 @@ print_interface_rules(struct fw3_ipt_handle *handle, struct fw3_state *state,
        }
 }
 
+static struct fw3_address *
+next_addr(struct fw3_address *addr, struct list_head *list,
+                enum fw3_family family, bool invert)
+{
+       struct list_head *p;
+       struct fw3_address *rv;
+
+       for (p = addr ? addr->list.next : list->next; p != list; p = p->next)
+       {
+               rv = list_entry(p, struct fw3_address, list);
+
+               if (fw3_is_family(rv, family) && rv->invert == invert)
+                       return rv;
+       }
+
+       return NULL;
+}
+
 static void
 print_zone_rule(struct fw3_ipt_handle *handle, struct fw3_state *state,
                 bool reload, struct fw3_zone *zone)
 {
        bool disable_notrack = state->defaults.drop_invalid;
+       bool first_src, first_dest;
        struct fw3_address *msrc;
        struct fw3_address *mdest;
        struct fw3_ipt_rule *r;
@@ -552,17 +571,50 @@ print_zone_rule(struct fw3_ipt_handle *handle, struct fw3_state *state,
        case FW3_TABLE_NAT:
                if (zone->masq && handle->family == FW3_FAMILY_V4)
                {
-                       fw3_foreach(msrc, &zone->masq_src)
-                       fw3_foreach(mdest, &zone->masq_dest)
+                       /* for any negated masq_src ip, emit -s addr -j RETURN rules */
+                       for (msrc = NULL;
+                            (msrc = next_addr(msrc, &zone->masq_src,
+                                              handle->family, true)) != NULL; )
                        {
-                               if (!fw3_is_family(msrc, handle->family) ||
-                                   !fw3_is_family(mdest, handle->family))
-                                       continue;
+                               msrc->invert = false;
+                               r = fw3_ipt_rule_new(handle);
+                               fw3_ipt_rule_src_dest(r, msrc, NULL);
+                               fw3_ipt_rule_target(r, "RETURN");
+                               fw3_ipt_rule_append(r, "zone_%s_postrouting", zone->name);
+                               msrc->invert = true;
+                       }
 
+                       /* for any negated masq_dest ip, emit -d addr -j RETURN rules */
+                       for (mdest = NULL;
+                            (mdest = next_addr(mdest, &zone->masq_dest,
+                                               handle->family, true)) != NULL; )
+                       {
+                               mdest->invert = false;
                                r = fw3_ipt_rule_new(handle);
-                               fw3_ipt_rule_src_dest(r, msrc, mdest);
-                               fw3_ipt_rule_target(r, "MASQUERADE");
+                               fw3_ipt_rule_src_dest(r, NULL, mdest);
+                               fw3_ipt_rule_target(r, "RETURN");
                                fw3_ipt_rule_append(r, "zone_%s_postrouting", zone->name);
+                               mdest->invert = true;
+                       }
+
+                       /* emit masquerading entries for non-negated addresses
+                          and ensure that both src and dest loops run at least once,
+                          even if there are no relevant addresses */
+                       for (first_src = true, msrc = NULL;
+                            (msrc = next_addr(msrc, &zone->masq_src,
+                                                  handle->family, false)) || first_src;
+                            first_src = false)
+                       {
+                               for (first_dest = true, mdest = NULL;
+                                    (mdest = next_addr(mdest, &zone->masq_dest,
+                                                           handle->family, false)) || first_dest;
+                                    first_dest = false)
+                               {
+                                       r = fw3_ipt_rule_new(handle);
+                                       fw3_ipt_rule_src_dest(r, msrc, mdest);
+                                       fw3_ipt_rule_target(r, "MASQUERADE");
+                                       fw3_ipt_rule_append(r, "zone_%s_postrouting", zone->name);
+                               }
                        }
                }
                break;