xtables RAWNAT patch to allow easy round-robin of udp/tcp data between multiple local processes

patch-xt_RAWNAT.diff

--- /home/build/aur/xtables-addons/orig-src/src/xtables-addons-1.46/extensions/xt_RAWNAT.c      2012-08-23 16:54:21.000000000 +0300
+++ /home/build/aur/xtables-addons/src/xtables-addons-1.46/extensions/xt_RAWNAT.c       2012-11-30 18:13:18.000000000 +0200
@@ -154,7 +154,30 @@
        __be32 new_addr;
 
        iph = ip_hdr(*pskb);
-       new_addr = remask(iph->daddr, info->addr.ip, info->mask);
+   if(info->mask < 32) {
+      void *transport_hdr = (void *)iph + ip_hdrlen(*pskb);
+      struct tcphdr *tcph;
+      struct udphdr *udph;
+      register __u32 hash_val = iph->saddr;
+ 
+      switch (iph->protocol) {
+         case IPPROTO_TCP:
+            tcph = transport_hdr;
+            hash_val ^= tcph->source << 16;
+            break;
+         case IPPROTO_UDP:
+         case IPPROTO_UDPLITE:
+            udph = transport_hdr;
+            hash_val ^= udph->source << 16;
+            break;
+      }
+      hash_val ^= (hash_val << 16);
+      hash_val ^= (hash_val << 8);
+
+      new_addr = remask(hash_val , info->addr.ip, info->mask);
+   } else {
+      new_addr = remask(iph->saddr, info->addr.ip, info->mask);
+   }
        if (iph->daddr == new_addr)
                return XT_CONTINUE;