Skip to content

Commit

Permalink
netfilter: bridge-netfilter: simplify IP DNAT
Browse files Browse the repository at this point in the history 
Remove br_netfilter.c::br_nf_local_out(). The function
br_nf_local_out() was needed because the PF_BRIDGE::LOCAL_OUT hook
could be called when IP DNAT happens on to-be-bridged traffic. The
new scheme eliminates this mess.

Signed-off-by: Bart De Schuymer <bdschuym@pandora.be>
Signed-off-by: Patrick McHardy <kaber@trash.net>
  • Loading branch information
Bart De Schuymer authored and Patrick McHardy committed Apr 15, 2010
1 parent 9c6eb28 commit ea2d9b4
Show file tree
Hide file tree
Showing 3 changed files with 40 additions and 100 deletions.
17 changes: 14 additions & 3 deletions include/linux/netfilter_bridge.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -41,9 +41,8 @@ enum nf_br_hook_priorities {

#define BRNF_PKT_TYPE 0x01
#define BRNF_BRIDGED_DNAT 0x02
#define BRNF_DONT_TAKE_PARENT 0x04
#define BRNF_BRIDGED 0x08
#define BRNF_NF_BRIDGE_PREROUTING 0x10
#define BRNF_BRIDGED 0x04
#define BRNF_NF_BRIDGE_PREROUTING 0x08


/* Only used in br_forward.c */
Expand All @@ -68,6 +67,18 @@ static inline unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
}
}

extern int br_handle_frame_finish(struct sk_buff *skb);
/* Only used in br_device.c */
static inline int br_nf_pre_routing_finish_bridge_slow(struct sk_buff *skb)
{
struct nf_bridge_info *nf_bridge = skb->nf_bridge;

skb_pull(skb, ETH_HLEN);
nf_bridge->mask ^= BRNF_BRIDGED_DNAT;
skb->dev = nf_bridge->physindev;
return br_handle_frame_finish(skb);
}

/* This is called by the IP fragmenting code and it ensures there is
* enough room for the encapsulating header (if there is one). */
static inline unsigned int nf_bridge_pad(const struct sk_buff *skb)
Expand Down
9 changes: 8 additions & 1 deletion net/bridge/br_device.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>

#include <linux/netfilter_bridge.h>
#include <asm/uaccess.h>
#include "br_private.h"

Expand All @@ -28,6 +28,13 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
struct net_bridge_mdb_entry *mdst;
struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);

#ifdef CONFIG_BRIDGE_NETFILTER
if (skb->nf_bridge && (skb->nf_bridge->mask & BRNF_BRIDGED_DNAT)) {
br_nf_pre_routing_finish_bridge_slow(skb);
return NETDEV_TX_OK;
}
#endif

brstats->tx_packets++;
brstats->tx_bytes += skb->len;

Expand Down
114 changes: 18 additions & 96 deletions net/bridge/br_netfilter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -246,8 +246,7 @@ static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb)
}

/* This requires some explaining. If DNAT has taken place,
* we will need to fix up the destination Ethernet address,
* and this is a tricky process.
* we will need to fix up the destination Ethernet address.
*
* There are two cases to consider:
* 1. The packet was DNAT'ed to a device in the same bridge
Expand All @@ -261,52 +260,38 @@ static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb)
* call ip_route_input() and to look at skb->dst->dev, which is
* changed to the destination device if ip_route_input() succeeds.
*
* Let us first consider the case that ip_route_input() succeeds:
*
* If skb->dst->dev equals the logical bridge device the packet
* came in on, we can consider this bridging. The packet is passed
* through the neighbour output function to build a new destination
* MAC address, which will make the packet enter br_nf_local_out()
* not much later. In that function it is assured that the iptables
* FORWARD chain is traversed for the packet.
* Let's first consider the case that ip_route_input() succeeds:
*
* If the output device equals the logical bridge device the packet
* came in on, we can consider this bridging. The corresponding MAC
* address will be obtained in br_nf_pre_routing_finish_bridge.
* Otherwise, the packet is considered to be routed and we just
* change the destination MAC address so that the packet will
* later be passed up to the IP stack to be routed. For a redirected
* packet, ip_route_input() will give back the localhost as output device,
* which differs from the bridge device.
*
* Let us now consider the case that ip_route_input() fails:
* Let's now consider the case that ip_route_input() fails:
*
* This can be because the destination address is martian, in which case
* the packet will be dropped.
* After a "echo '0' > /proc/sys/net/ipv4/ip_forward" ip_route_input()
* will fail, while __ip_route_output_key() will return success. The source
* address for __ip_route_output_key() is set to zero, so __ip_route_output_key
* If IP forwarding is disabled, ip_route_input() will fail, while
* ip_route_output_key() can return success. The source
* address for ip_route_output_key() is set to zero, so ip_route_output_key()
* thinks we're handling a locally generated packet and won't care
* if IP forwarding is allowed. We send a warning message to the users's
* log telling her to put IP forwarding on.
*
* ip_route_input() will also fail if there is no route available.
* In that case we just drop the packet.
*
* --Lennert, 20020411
* --Bart, 20020416 (updated)
* --Bart, 20021007 (updated)
* --Bart, 20062711 (updated) */
* if IP forwarding is enabled. If the output device equals the logical bridge
* device, we proceed as if ip_route_input() succeeded. If it differs from the
* logical bridge port or if ip_route_output_key() fails we drop the packet.
*/

static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb)
{
if (skb->pkt_type == PACKET_OTHERHOST) {
skb->pkt_type = PACKET_HOST;
skb->nf_bridge->mask |= BRNF_PKT_TYPE;
}
skb->nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;

skb->dev = bridge_parent(skb->dev);
if (skb->dev) {
struct dst_entry *dst = skb_dst(skb);

nf_bridge_pull_encap_header(skb);
skb->nf_bridge->mask |= BRNF_BRIDGED_DNAT;

if (dst->hh)
return neigh_hh_output(dst->hh, skb);
Expand Down Expand Up @@ -368,9 +353,6 @@ static int br_nf_pre_routing_finish(struct sk_buff *skb)
} else {
if (skb_dst(skb)->dev == dev) {
bridged_dnat:
/* Tell br_nf_local_out this is a
* bridged frame */
nf_bridge->mask |= BRNF_BRIDGED_DNAT;
skb->dev = nf_bridge->physindev;
nf_bridge_push_encap_header(skb);
NF_HOOK_THRESH(NFPROTO_BRIDGE,
Expand Down Expand Up @@ -721,54 +703,6 @@ static unsigned int br_nf_forward_arp(unsigned int hook, struct sk_buff *skb,
return NF_STOLEN;
}

/* PF_BRIDGE/LOCAL_OUT ***********************************************
*
* This function sees both locally originated IP packets and forwarded
* IP packets (in both cases the destination device is a bridge
* device). It also sees bridged-and-DNAT'ed packets.
*
* If (nf_bridge->mask & BRNF_BRIDGED_DNAT) then the packet is bridged
* and we fake the PF_BRIDGE/FORWARD hook. The function br_nf_forward()
* will then fake the PF_INET/FORWARD hook. br_nf_local_out() has priority
* NF_BR_PRI_FIRST, so no relevant PF_BRIDGE/INPUT functions have been nor
* will be executed.
*/
static unsigned int br_nf_local_out(unsigned int hook, struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
struct net_device *realindev;
struct nf_bridge_info *nf_bridge;

if (!skb->nf_bridge)
return NF_ACCEPT;

/* Need exclusive nf_bridge_info since we might have multiple
* different physoutdevs. */
if (!nf_bridge_unshare(skb))
return NF_DROP;

nf_bridge = skb->nf_bridge;
if (!(nf_bridge->mask & BRNF_BRIDGED_DNAT))
return NF_ACCEPT;

/* Bridged, take PF_BRIDGE/FORWARD.
* (see big note in front of br_nf_pre_routing_finish) */
nf_bridge->physoutdev = skb->dev;
realindev = nf_bridge->physindev;

if (nf_bridge->mask & BRNF_PKT_TYPE) {
skb->pkt_type = PACKET_OTHERHOST;
nf_bridge->mask ^= BRNF_PKT_TYPE;
}
nf_bridge_push_encap_header(skb);

NF_HOOK(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, realindev, skb->dev,
br_forward_finish);
return NF_STOLEN;
}

#if defined(CONFIG_NF_CONNTRACK_IPV4) || defined(CONFIG_NF_CONNTRACK_IPV4_MODULE)
static int br_nf_dev_queue_xmit(struct sk_buff *skb)
{
Expand Down Expand Up @@ -797,10 +731,7 @@ static unsigned int br_nf_post_routing(unsigned int hook, struct sk_buff *skb,
struct net_device *realoutdev = bridge_parent(skb->dev);
u_int8_t pf;

if (!nf_bridge)
return NF_ACCEPT;

if (!(nf_bridge->mask & (BRNF_BRIDGED | BRNF_BRIDGED_DNAT)))
if (!nf_bridge || !(nf_bridge->mask & BRNF_BRIDGED))
return NF_ACCEPT;

if (!realoutdev)
Expand Down Expand Up @@ -847,10 +778,8 @@ static unsigned int ip_sabotage_in(unsigned int hook, struct sk_buff *skb,
return NF_ACCEPT;
}

/* For br_nf_local_out we need (prio = NF_BR_PRI_FIRST), to insure that innocent
* PF_BRIDGE/NF_BR_LOCAL_OUT functions don't get bridged traffic as input.
* For br_nf_post_routing, we need (prio = NF_BR_PRI_LAST), because
* ip_refrag() can return NF_STOLEN. */
/* For br_nf_post_routing, we need (prio = NF_BR_PRI_LAST), because
* br_dev_queue_push_xmit is called afterwards */
static struct nf_hook_ops br_nf_ops[] __read_mostly = {
{
.hook = br_nf_pre_routing,
Expand Down Expand Up @@ -880,13 +809,6 @@ static struct nf_hook_ops br_nf_ops[] __read_mostly = {
.hooknum = NF_BR_FORWARD,
.priority = NF_BR_PRI_BRNF,
},
{
.hook = br_nf_local_out,
.owner = THIS_MODULE,
.pf = PF_BRIDGE,
.hooknum = NF_BR_LOCAL_OUT,
.priority = NF_BR_PRI_FIRST,
},
{
.hook = br_nf_post_routing,
.owner = THIS_MODULE,
Expand Down

0 comments on commit ea2d9b4

Please sign in to comment.