[NETFILTER]: ebtables: add --snap-arp option

The attached patch adds --snat-arp support, which makes it possible to
change the source mac address in both the mac header and the arp header
with one rule.

Signed-off-by: Bart De Schuymer <bdschuym@pandora.be>
Signed-off-by: Patrick McHardy <kaber@trash.net>

2 files changed, 27 insertions, 6 deletions

diff --git a/net/bridge/netfilter/ebt_mark.c b/net/bridge/netfilter/ebt_mark.c
index 2458638561cb..62d23c7b25e6 100644
--- a/net/bridge/netfilter/ebt_mark.c
+++ b/net/bridge/netfilter/ebt_mark.c
@@ -33,7 +33,7 @@ static int ebt_target_mark(struct sk_buff **pskb, unsigned int hooknr,
         else
                 (*pskb)->mark ^= info->mark;
 
-        return info->target | -16;
+        return info->target | ~EBT_VERDICT_BITS;
 }
 
 static int ebt_target_mark_check(const char *tablename, unsigned int hookmask,
@@ -44,13 +44,13 @@ static int ebt_target_mark_check(const char *tablename, unsigned int hookmask,
 
         if (datalen != EBT_ALIGN(sizeof(struct ebt_mark_t_info)))
                 return -EINVAL;
-        tmp = info->target | -16;
+        tmp = info->target | ~EBT_VERDICT_BITS;
         if (BASE_CHAIN && tmp == EBT_RETURN)
                 return -EINVAL;
         CLEAR_BASE_CHAIN_BIT;
         if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0)
                 return -EINVAL;
-        tmp = info->target & -16;
+        tmp = info->target & ~EBT_VERDICT_BITS;
         if (tmp != MARK_SET_VALUE && tmp != MARK_OR_VALUE &&
             tmp != MARK_AND_VALUE && tmp != MARK_XOR_VALUE)
                 return -EINVAL;
diff --git a/net/bridge/netfilter/ebt_snat.c b/net/bridge/netfilter/ebt_snat.c
index cbb33e24ca8a..a50722182bfe 100644
--- a/net/bridge/netfilter/ebt_snat.c
+++ b/net/bridge/netfilter/ebt_snat.c
@@ -12,6 +12,8 @@
 #include <linux/netfilter_bridge/ebt_nat.h>
 #include <linux/module.h>
 #include <net/sock.h>
+#include <linux/if_arp.h>
+#include <net/arp.h>
 
 static int ebt_target_snat(struct sk_buff **pskb, unsigned int hooknr,
    const struct net_device *in, const struct net_device *out,
@@ -31,24 +33,43 @@ static int ebt_target_snat(struct sk_buff **pskb, unsigned int hooknr,
                 *pskb = nskb;
         }
         memcpy(eth_hdr(*pskb)->h_source, info->mac, ETH_ALEN);
-        return info->target;
+        if (!(info->target & NAT_ARP_BIT) &&
+            eth_hdr(*pskb)->h_proto == htons(ETH_P_ARP)) {
+                struct arphdr _ah, *ap;
+
+                ap = skb_header_pointer(*pskb, 0, sizeof(_ah), &_ah);
+                if (ap == NULL)
+                        return EBT_DROP;
+                if (ap->ar_hln != ETH_ALEN)
+                        goto out;
+                if (skb_store_bits(*pskb, sizeof(_ah), info->mac,ETH_ALEN))
+                        return EBT_DROP;
+        }
+out:
+        return info->target | ~EBT_VERDICT_BITS;
 }
 
 static int ebt_target_snat_check(const char *tablename, unsigned int hookmask,
    const struct ebt_entry *e, void *data, unsigned int datalen)
 {
         struct ebt_nat_info *info = (struct ebt_nat_info *) data;
+        int tmp;
 
         if (datalen != EBT_ALIGN(sizeof(struct ebt_nat_info)))
                 return -EINVAL;
-        if (BASE_CHAIN && info->target == EBT_RETURN)
+        tmp = info->target | ~EBT_VERDICT_BITS;
+        if (BASE_CHAIN && tmp == EBT_RETURN)
                 return -EINVAL;
         CLEAR_BASE_CHAIN_BIT;
         if (strcmp(tablename, "nat"))
                 return -EINVAL;
         if (hookmask & ~(1 << NF_BR_POST_ROUTING))
                 return -EINVAL;
-        if (INVALID_TARGET)
+
+        if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0)
+                return -EINVAL;
+        tmp = info->target | EBT_VERDICT_BITS;
+        if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT)
                 return -EINVAL;
         return 0;
 }