Have you tested this in a real world scenario?
I attempted to use a linux bridge to bridge a few vlans and found that
it didn't work as expected. At first I thought it was a performance
problem relating to the linux bridge code because it was dropping
packets, but I believe the problem is inherent in using a bridge in a
vlan environment.
The problem lies in the fact that the switch connected to the bridge
(which has the vlans tagged) gets confused as to which port that
particular mac address is out of. Take the following scenario: (based on
my understanding of how things should work)
1. Computer a on vlan 6 wants to send out a packet to computer b on vlan 7.
2. Computer a sends out an arp request for computer b. (core switch
records computer A as being on port A14)
3. The arp request reaches the linux bridge, which doesn't know computer
b yet, so it send out an arp request on all other vlans its bridging.
(core switch records computer A as being on port A1 because it saw a
packet from that mac on port A1)
4. Computer b responds to the arp request. (core switch records computer
b as being on port A10)
5. bridge forwards the arp response out A10 to computer a (core switch
records computer b as being on A10)
As you can see, the core switch (and I've seen this happen on our HP
5300 switch) gets confused as to which port to send out unicast packets
-- hence sometimes when it _thinks_ it sent out a packet to the
computer, the computer didn't actually receive it and the packet needs
to be resent multiple times until the mac cache times out on the core
switch. Under other circumstances, the switch doesn't seem to get
confused, so it appears to be flaky, not completely broken.
Is there something I could have done differently which would have
avoided that problem? Does this patch somehow address that problem? Is
my HP switch just inept and do most switches keep a mac-port table per
vlan? (I doubt this, because the SNMP mib doesn't allow that to be
represented.)
Ethan Sommer
UNIX Systems Administrator
Gustavus Adolphus College
David Kimdon wrote:
> Hi,
>
> The attached patches enables the bridge to filter and forward packets
> according to their IEEE 802.1q headers. The goals behind this change
> include :
>
> - Enable running STP on 802.1q tagged networks. STP packets
> must be untagged. It isn't obvious how else to enable STP
> with the current bridge and vlan code.
> - Add native support for an untagged vlan. Currently an untagged
> vlan can be implimented using ebtables or similar.
> - On devices bridging a large number of interfaces across various
> vlans this significantly simplifies configuration and, depending on
> configuration, can improve performance.
>
> Comments appreciated,
>
> David
>
> From: Simon Barber <simon at devicescape.com>
>
> Signed-off-by: Simon Barber <simon at devicescape.com>
> Signed-off-by: David Kimdon <david.kimdon at devicescape.com>
>
> Index: wireless-dev/include/linux/if_bridge.h
> ===================================================================
> --- wireless-dev.orig/include/linux/if_bridge.h
> +++ wireless-dev/include/linux/if_bridge.h
> @@ -44,6 +44,10 @@
> #define BRCTL_SET_PORT_PRIORITY 16
> #define BRCTL_SET_PATH_COST 17
> #define BRCTL_GET_FDB_ENTRIES 18
> +#define BRCTL_SET_PORT_UNTAGGED_VLAN 19
> +#define BRCTL_ADD_PORT_VLAN 20
> +#define BRCTL_DEL_PORT_VLAN 21
> +#define BRCTL_GET_PORT_VLAN_INFO 22
>
> #define BR_STATE_DISABLED 0
> #define BR_STATE_LISTENING 1
> @@ -91,6 +95,12 @@ struct __port_info
> __u32 hold_timer_value;
> };
>
> +struct __vlan_info
> +{
> + __u32 untagged;
> + __u8 filter[4096/8];
> +};
> +
> struct __fdb_entry
> {
> __u8 mac_addr[6];
> Index: wireless-dev/include/linux/skbuff.h
> ===================================================================
> --- wireless-dev.orig/include/linux/skbuff.h
> +++ wireless-dev/include/linux/skbuff.h
> @@ -296,6 +296,9 @@ struct sk_buff {
> #endif
> __u32 nfmark;
> #endif /* CONFIG_NETFILTER */
> +#ifdef CONFIG_BRIDGE_VLAN
> + unsigned int vlan;
> +#endif
> #ifdef CONFIG_NET_SCHED
> __u16 tc_index; /* traffic control index */
> #ifdef CONFIG_NET_CLS_ACT
> Index: wireless-dev/net/bridge/br_forward.c
> ===================================================================
> --- wireless-dev.orig/net/bridge/br_forward.c
> +++ wireless-dev/net/bridge/br_forward.c
> @@ -24,7 +24,16 @@
> static inline int should_deliver(const struct net_bridge_port *p,
> const struct sk_buff *skb)
> {
> - return (skb->dev != p->dev && p->state == BR_STATE_FORWARDING);
> + if (skb->dev == p->dev ||
> + p->state != BR_STATE_FORWARDING)
> + return 0;
> +
> +#ifdef CONFIG_BRIDGE_VLAN
> + if (skb->vlan && br_vlan_filter(skb, &p->vlan))
> + return 0;
> +#endif
> +
> + return 1;
> }
>
> static inline unsigned packet_length(const struct sk_buff *skb)
> @@ -47,6 +56,10 @@ int br_dev_queue_push_xmit(struct sk_buf
> {
> skb_push(skb, ETH_HLEN);
>
> + if (br_vlan_output_frame(&skb,
> + skb->dev->br_port->vlan.untagged))
> + return 0;
> +
> dev_queue_xmit(skb);
> }
> }
> Index: wireless-dev/net/bridge/br_if.c
> ===================================================================
> --- wireless-dev.orig/net/bridge/br_if.c
> +++ wireless-dev/net/bridge/br_if.c
> @@ -227,6 +227,7 @@ static struct net_device *new_bridge_dev
> INIT_LIST_HEAD(&br->age_list);
>
> br_stp_timer_init(br);
> + br_vlan_init(&br->vlan);
>
> return dev;
> }
> @@ -278,6 +279,7 @@ static struct net_bridge_port *new_nbp(s
> p->state = BR_STATE_DISABLED;
> INIT_WORK(&p->carrier_check, port_carrier_check, dev);
> br_stp_port_timer_init(p);
> + br_vlan_init(&p->vlan);
>
> kobject_init(&p->kobj);
> kobject_set_name(&p->kobj, SYSFS_BRIDGE_PORT_ATTR);
> Index: wireless-dev/net/bridge/br_input.c
> ===================================================================
> --- wireless-dev.orig/net/bridge/br_input.c
> +++ wireless-dev/net/bridge/br_input.c
> @@ -26,12 +26,20 @@ static void br_pass_frame_up(struct net_
> {
> struct net_device *indev;
>
> + if (br_vlan_filter(skb, &br->vlan)) {
> + kfree_skb(skb);
> + return;
> + }
> +
> br->statistics.rx_packets++;
> br->statistics.rx_bytes += skb->len;
>
> indev = skb->dev;
> skb->dev = br->dev;
>
> + if (br_vlan_output_frame(&skb, br->vlan.untagged))
> + return;
> +
> NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
> netif_receive_skb);
> }
> @@ -136,6 +144,10 @@ int br_handle_frame(struct net_bridge_po
> }
>
> if (p->state == BR_STATE_FORWARDING || p->state == BR_STATE_LEARNING) {
> + if (br_vlan_input_frame(skb, &p->vlan)) {
> + return 1;
> + }
> +
> if (br_should_route_hook) {
> if (br_should_route_hook(pskb))
> return 0;
> Index: wireless-dev/net/bridge/br_ioctl.c
> ===================================================================
> --- wireless-dev.orig/net/bridge/br_ioctl.c
> +++ wireless-dev/net/bridge/br_ioctl.c
> @@ -302,6 +302,18 @@ static int old_dev_ioctl(struct net_devi
> case BRCTL_GET_FDB_ENTRIES:
> return get_fdb_entries(br, (void __user *)args[1],
> args[2], args[3]);
> +
> +#ifdef CONFIG_BRIDGE_VLAN
> + case BRCTL_SET_PORT_UNTAGGED_VLAN:
> + return br_vlan_set_untagged(br, args[1], args[2]);
> +
> + case BRCTL_ADD_PORT_VLAN:
> + case BRCTL_DEL_PORT_VLAN:
> + return br_vlan_set_filter(br, args[0], args[1], args[2]);
> +
> + case BRCTL_GET_PORT_VLAN_INFO:
> + return br_vlan_get_info(br, (void *)args[1], args[2]);
> +#endif
> }
>
> return -EOPNOTSUPP;
> Index: wireless-dev/net/bridge/br_private.h
> ===================================================================
> --- wireless-dev.orig/net/bridge/br_private.h
> +++ wireless-dev/net/bridge/br_private.h
> @@ -59,6 +59,14 @@ struct net_bridge_fdb_entry
> unsigned char is_static;
> };
>
> +#ifdef CONFIG_BRIDGE_VLAN
> +struct net_bridge_port_vlan
> +{
> + int untagged;
> + u8 filter[4096/8];
> +};
> +#endif
> +
> struct net_bridge_port
> {
> struct net_bridge *br;
> @@ -84,6 +92,9 @@ struct net_bridge_port
> struct kobject kobj;
> struct work_struct carrier_check;
> struct rcu_head rcu;
> +#ifdef CONFIG_BRIDGE_VLAN
> + struct net_bridge_port_vlan vlan;
> +#endif
> };
>
> struct net_bridge
> @@ -96,6 +107,9 @@ struct net_bridge
> struct hlist_head hash[BR_HASH_SIZE];
> struct list_head age_list;
> unsigned long feature_mask;
> +#ifdef CONFIG_BRIDGE_VLAN
> + struct net_bridge_port_vlan vlan;
> +#endif
>
> /* STP */
> bridge_id designated_root;
> @@ -258,4 +272,32 @@ extern void br_sysfs_delbr(struct net_de
> #define br_sysfs_delbr(dev) do { } while(0)
> #endif /* CONFIG_SYSFS */
>
> +#ifdef CONFIG_BRIDGE_VLAN
> +#include <linux/if_vlan.h>
> +
> +static inline int br_vlan_filter(const struct sk_buff *skb,
> + const struct net_bridge_port_vlan *vlan)
> +{
> + return !(vlan->filter[skb->vlan / 8] & (1 << (skb->vlan & 7)));
> +}
> +
> +/* br_vlan.c */
> +extern int br_vlan_input_frame(struct sk_buff *skb,
> + struct net_bridge_port_vlan *vlan);
> +extern int br_vlan_output_frame(struct sk_buff **pskb, unsigned int untagged);
> +extern void br_vlan_init(struct net_bridge_port_vlan *vlan);
> +extern int br_vlan_set_untagged(struct net_bridge *br,
> + unsigned int port, unsigned int vid);
> +extern int br_vlan_set_filter(struct net_bridge *br,
> + unsigned int cmd,
> + unsigned int port, unsigned int vid);
> +extern int br_vlan_get_info(struct net_bridge *br,
> + void *user_mem, unsigned long port);
> +#else
> +
> +#define br_vlan_filter(skb, vlan) (0)
> +#define br_vlan_input_frame(skb, vlan) (0)
> +#define br_vlan_output_frame(pskb, untagged) (0)
> +#define br_vlan_init(vlan) do { } while(0)
> +#endif /* CONFIG_BRIDGE_VLAN */
> #endif
> Index: wireless-dev/net/bridge/br_vlan.c
> ===================================================================
> --- /dev/null
> +++ wireless-dev/net/bridge/br_vlan.c
> @@ -0,0 +1,203 @@
> +/*
> + * VLAN support
> + * Linux ethernet bridge
> + *
> + * Authors:
> + * Simon Barber <simon at devicescape.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/netdevice.h>
> +#include <linux/inetdevice.h>
> +#include <linux/skbuff.h>
> +#include <linux/if_bridge.h>
> +#include <linux/netfilter_bridge.h>
> +#include <asm/uaccess.h>
> +#include "br_private.h"
> +
> +int br_vlan_input_frame(struct sk_buff *skb, struct net_bridge_port_vlan *vlan)
> +{
> + if (skb->protocol != htons(ETH_P_8021Q)) {
> + skb->vlan = vlan->untagged;
> + } else {
> + struct vlan_ethhdr *vhdr = (struct vlan_ethhdr *)(skb->mac.raw);
> + unsigned short vlan_TCI = ntohs(vhdr->h_vlan_TCI);
> + unsigned short vid = (vlan_TCI & VLAN_VID_MASK);
> +
> + skb->vlan = vid ? vid : vlan->untagged;
> + }
> +
> + if (skb->vlan == 0)
> + goto err;
> +
> + if (br_vlan_filter(skb, vlan))
> + goto err;
> +
> + return 0;
> +
> +err:
> + kfree_skb(skb);
> + return 1;
> +}
> +
> +int br_vlan_output_frame(struct sk_buff **pskb, unsigned int untagged)
> +{
> + struct sk_buff *skb = *pskb;
> +
> + if (skb->vlan == 0) /* don't touch the frame */
> + return 0;
> +
> + if (skb->vlan == untagged) {
> + /* frame should be untagged */
> + if (eth_hdr(skb)->h_proto == htons(ETH_P_8021Q)) {
> + /* remove VLAN tag */
> + if (skb_cloned(skb) || skb_shared(skb)) {
> + struct sk_buff *new_skb;
> +
> + new_skb = skb_copy(skb, GFP_ATOMIC);
> + kfree_skb(skb);
> + if (!new_skb)
> + return 1;
> + *pskb = skb = new_skb;
> + }
> +
> + skb->mac.raw += VLAN_HLEN;
> + memmove(skb->mac.raw, skb->data, ETH_ALEN * 2);
> + skb_pull(skb, VLAN_HLEN);
> + }
> + } else {
> + /* frame should be tagged */
> + if (eth_hdr(skb)->h_proto != htons(ETH_P_8021Q)) {
> + /* add VLAN tag */
> + struct vlan_ethhdr *vhdr;
> + if (skb_cloned(skb) || skb_shared(skb)) {
> + struct sk_buff *new_skb;
> +
> + new_skb = skb_copy(skb, GFP_ATOMIC);
> + kfree_skb(skb);
> + if (!new_skb)
> + return 1;
> + *pskb = skb = new_skb;
> + }
> +
> + if (skb_headroom(skb) < VLAN_HLEN) {
> + if (pskb_expand_head(skb, VLAN_HLEN, 0,
> + GFP_ATOMIC)) {
> + kfree_skb(skb);
> + return 1;
> + }
> + }
> +
> + skb_push(skb, VLAN_HLEN);
> +
> + skb->mac.raw -= VLAN_HLEN;
> + memmove(skb->mac.raw, skb->mac.raw + VLAN_HLEN,
> + ETH_ALEN * 2);
> + vhdr = (struct vlan_ethhdr *)skb->mac.raw;
> + vhdr->h_vlan_proto = htons(ETH_P_8021Q);
> + vhdr->h_vlan_TCI = htons(skb->vlan);
> + } else {
> + /* ensure VID is correct */
> + struct vlan_ethhdr *vhdr =
> + (struct vlan_ethhdr *)skb->mac.raw;
> + vhdr->h_vlan_TCI = (vhdr->h_vlan_TCI & htons(~VLAN_VID_MASK)) |
> + htons(skb->vlan);
> + }
> + // TODO: set priority in tag correctly
> + }
> +
> + return 0;
> +}
> +
> +void br_vlan_init(struct net_bridge_port_vlan *vlan)
> +{
> + vlan->untagged = 1;
> + vlan->filter[0] = 1 << 1;
> +}
> +
> +/* ioctl functions */
> +int br_vlan_set_untagged(struct net_bridge *br,
> + unsigned int port, unsigned int vid)
> +{
> + struct net_bridge_port_vlan *vlan;
> +
> + if (vid > 4094)
> + return -EINVAL;
> +
> + if (port) {
> + struct net_bridge_port *p = br_get_port(br, port);
> +
> + if (p == NULL)
> + return -EINVAL;
> + vlan = &p->vlan;
> + } else {
> + vlan = &br->vlan;
> + }
> +
> + vlan->untagged = vid;
> +
> + return 0;
> +}
> +
> +int br_vlan_set_filter(struct net_bridge *br,
> + unsigned int cmd, unsigned int port, unsigned int vid)
> +{
> + struct net_bridge_port_vlan *vlan;
> + int add = (cmd == BRCTL_ADD_PORT_VLAN);
> +
> + if (vid > 4094)
> + return -EINVAL;
> +
> + if (port) {
> + struct net_bridge_port *p = br_get_port(br, port);
> +
> + if (p == NULL)
> + return -EINVAL;
> + vlan = &p->vlan;
> + } else {
> + vlan = &br->vlan;
> + }
> +
> + if (vid == 0) {
> + /* special case - add/del for all vlans */
> + memset(vlan->filter, add ? 255 : 0, 4096 / 8);
> + if (add) {
> + vlan->filter[4095 / 8] &= ~(1 << (4095 & 7));
> + }
> + } else if (add)
> + vlan->filter[vid / 8] |= 1 << (vid & 7);
> + else
> + vlan->filter[vid / 8] &= ~(1 << (vid & 7));
> +
> + return 0;
> +}
> +
> +int br_vlan_get_info(struct net_bridge *br, void *user_mem, unsigned long port)
> +{
> + struct net_bridge_port_vlan *vlan;
> + struct __vlan_info v;
> +
> + if (port) {
> + struct net_bridge_port *p = br_get_port(br, port);
> +
> + if (p == NULL)
> + return -EINVAL;
> + vlan = &p->vlan;
> + } else {
> + vlan = &br->vlan;
> + }
> +
> + memset(&v, 0, sizeof(v));
> + v.untagged = vlan->untagged;
> + memcpy(v.filter, vlan->filter, 4096 / 8);
> +
> + if (copy_to_user((void __user *)user_mem, &v, sizeof(v)))
> + return -EFAULT;
> +
> + return 0;
> +}
> Index: wireless-dev/net/bridge/Makefile
> ===================================================================
> --- wireless-dev.orig/net/bridge/Makefile
> +++ wireless-dev/net/bridge/Makefile
> @@ -12,4 +12,6 @@ bridge-$(CONFIG_SYSFS) += br_sysfs_if.o
>
> bridge-$(CONFIG_BRIDGE_NETFILTER) += br_netfilter.o
>
> +bridge-$(CONFIG_BRIDGE_VLAN) += br_vlan.o
> +
> obj-$(CONFIG_BRIDGE_NF_EBTABLES) += netfilter/
> Index: wireless-dev/net/core/skbuff.c
> ===================================================================
> --- wireless-dev.orig/net/core/skbuff.c
> +++ wireless-dev/net/core/skbuff.c
> @@ -486,6 +486,9 @@ struct sk_buff *skb_clone(struct sk_buff
> nf_bridge_get(skb->nf_bridge);
> #endif
> #endif /*CONFIG_NETFILTER*/
> +#ifdef CONFIG_BRIDGE_VLAN
> + C(vlan);
> +#endif
> #ifdef CONFIG_NET_SCHED
> C(tc_index);
> #ifdef CONFIG_NET_CLS_ACT
> @@ -550,6 +553,9 @@ static void copy_skb_header(struct sk_bu
> nf_bridge_get(old->nf_bridge);
> #endif
> #endif
> +#ifdef CONFIG_BRIDGE_VLAN
> + new->vlan = old->vlan;
> +#endif
> #ifdef CONFIG_NET_SCHED
> #ifdef CONFIG_NET_CLS_ACT
> new->tc_verd = old->tc_verd;
> Index: wireless-dev/net/bridge/Kconfig
> ===================================================================
> --- wireless-dev.orig/net/bridge/Kconfig
> +++ wireless-dev/net/bridge/Kconfig
> @@ -30,3 +30,13 @@ config BRIDGE
> will be called bridge.
>
> If unsure, say N.
> +
> +config BRIDGE_VLAN
> + bool "802.1Q bridge support"
> + depends on BRIDGE
> + ---help---
> + If you say Y here, then your bridge will be able to filter and
> + forward packets according to their IEEE 802.1Q headers.
> +
> + If unsure, say N.
> +
> Index: wireless-dev/net/bridge/br_device.c
> ===================================================================
> --- wireless-dev.orig/net/bridge/br_device.c
> +++ wireless-dev/net/bridge/br_device.c
> @@ -34,6 +34,9 @@ int br_dev_xmit(struct sk_buff *skb, str
> const unsigned char *dest = skb->data;
> struct net_bridge_fdb_entry *dst;
>
> + if (br_vlan_input_frame(skb, &br->vlan))
> + return 0;
> +
> br->statistics.tx_packets++;
> br->statistics.tx_bytes += skb->len;
>
> _______________________________________________
> Bridge mailing list
> Bridge at lists.osdl.org
> https://lists.osdl.org/mailman/listinfo/bridge
>
>
>
--
Ethan Sommer
UNIX Systems Administrator
Gustavus Adolphus College
507-933-7042
sommere at gac.edu
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