[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>
diff --git a/include/linux/netfilter_bridge/ebt_nat.h b/include/linux/netfilter_bridge/ebt_nat.h
index 26fd90d..435b886 100644
--- a/include/linux/netfilter_bridge/ebt_nat.h
+++ b/include/linux/netfilter_bridge/ebt_nat.h
@@ -1,6 +1,7 @@
#ifndef __LINUX_BRIDGE_EBT_NAT_H
#define __LINUX_BRIDGE_EBT_NAT_H
+#define NAT_ARP_BIT (0x00000010)
struct ebt_nat_info
{
unsigned char mac[ETH_ALEN];
diff --git a/include/linux/netfilter_bridge/ebtables.h b/include/linux/netfilter_bridge/ebtables.h
index e6ea70d..8777526 100644
--- a/include/linux/netfilter_bridge/ebtables.h
+++ b/include/linux/netfilter_bridge/ebtables.h
@@ -26,6 +26,10 @@
#define EBT_CONTINUE -3
#define EBT_RETURN -4
#define NUM_STANDARD_TARGETS 4
+/* ebtables target modules store the verdict inside an int. We can
+ * reclaim a part of this int for backwards compatible extensions.
+ * The 4 lsb are more than enough to store the verdict. */
+#define EBT_VERDICT_BITS 0x0000000F
struct ebt_counter
{
diff --git a/net/bridge/netfilter/ebt_mark.c b/net/bridge/netfilter/ebt_mark.c
index 2458638..62d23c7 100644
--- a/net/bridge/netfilter/ebt_mark.c
+++ b/net/bridge/netfilter/ebt_mark.c
@@ -33,7 +33,7 @@
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 @@
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 cbb33e2..a507221 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 @@
*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;
}