linux/net/bridge
Vlad Yasevich 0d5501c1c8 net: Always untag vlan-tagged traffic on input.
Currently the functionality to untag traffic on input resides
as part of the vlan module and is build only when VLAN support
is enabled in the kernel.  When VLAN is disabled, the function
vlan_untag() turns into a stub and doesn't really untag the
packets.  This seems to create an interesting interaction
between VMs supporting checksum offloading and some network drivers.

There are some drivers that do not allow the user to change
tx-vlan-offload feature of the driver.  These drivers also seem
to assume that any VLAN-tagged traffic they transmit will
have the vlan information in the vlan_tci and not in the vlan
header already in the skb.  When transmitting skbs that already
have tagged data with partial checksum set, the checksum doesn't
appear to be updated correctly by the card thus resulting in a
failure to establish TCP connections.

The following is a packet trace taken on the receiver where a
sender is a VM with a VLAN configued.  The host VM is running on
doest not have VLAN support and the outging interface on the
host is tg3:
10:12:43.503055 52:54:00:ae:42:3f > 28:d2:44:7d:c2:de, ethertype 802.1Q
(0x8100), length 78: vlan 100, p 0, ethertype IPv4, (tos 0x0, ttl 64, id 27243,
offset 0, flags [DF], proto TCP (6), length 60)
    10.0.100.1.58545 > 10.0.100.10.ircu-2: Flags [S], cksum 0xdc39 (incorrect
-> 0x48d9), seq 1069378582, win 29200, options [mss 1460,sackOK,TS val
4294837885 ecr 0,nop,wscale 7], length 0
10:12:44.505556 52:54:00:ae:42:3f > 28:d2:44:7d:c2:de, ethertype 802.1Q
(0x8100), length 78: vlan 100, p 0, ethertype IPv4, (tos 0x0, ttl 64, id 27244,
offset 0, flags [DF], proto TCP (6), length 60)
    10.0.100.1.58545 > 10.0.100.10.ircu-2: Flags [S], cksum 0xdc39 (incorrect
-> 0x44ee), seq 1069378582, win 29200, options [mss 1460,sackOK,TS val
4294838888 ecr 0,nop,wscale 7], length 0

This connection finally times out.

I've only access to the TG3 hardware in this configuration thus have
only tested this with TG3 driver.  There are a lot of other drivers
that do not permit user changes to vlan acceleration features, and
I don't know if they all suffere from a similar issue.

The patch attempt to fix this another way.  It moves the vlan header
stipping code out of the vlan module and always builds it into the
kernel network core.  This way, even if vlan is not supported on
a virtualizatoin host, the virtual machines running on top of such
host will still work with VLANs enabled.

CC: Patrick McHardy <kaber@trash.net>
CC: Nithin Nayak Sujir <nsujir@broadcom.com>
CC: Michael Chan <mchan@broadcom.com>
CC: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
Acked-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-08-11 12:16:51 -07:00
..
netfilter netfilter: don't use mutex_lock_interruptible() 2014-08-08 16:47:23 +02:00
Kconfig bridge: Add vlan filtering infrastructure 2013-02-13 19:41:46 -05:00
Makefile netfilter: bridge: fix Kconfig unmet dependencies 2014-05-26 00:42:30 -04:00
br.c bridge: make br_device_notifier static 2014-05-22 15:33:47 -04:00
br_device.c bridge: Prepare for forwarding another bridge group addresses 2014-06-11 15:22:53 -07:00
br_fdb.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-08-05 18:46:26 -07:00
br_forward.c bridge: use is_skb_forwardable in forward path 2014-03-31 16:04:04 -04:00
br_if.c net: set name_assign_type in alloc_netdev() 2014-07-15 16:12:48 -07:00
br_input.c bridge: Prepare for forwarding another bridge group addresses 2014-06-11 15:22:53 -07:00
br_ioctl.c bridge: add space before '(/{', after ',', etc. 2013-12-19 19:27:26 -05:00
br_mdb.c bridge: rename struct bridge_mcast_query/querier 2014-06-10 23:50:46 -07:00
br_multicast.c list: fix order of arguments for hlist_add_after(_rcu) 2014-08-06 18:01:24 -07:00
br_netfilter.c vlan: rename __vlan_find_dev_deep() to __vlan_find_dev_deep_rcu() 2014-05-12 14:39:13 -04:00
br_netlink.c bridge: remove a useless comment 2014-08-04 12:46:51 -07:00
br_private.h bridge: fdb dumping takes a filter device 2014-07-10 12:37:33 -07:00
br_private_stp.h net: 8021q/bluetooth/bridge/can/ceph: Remove extern from function prototypes 2013-10-19 19:12:11 -04:00
br_stp.c bridge: Clamp forward_delay when enabling STP 2013-09-12 23:32:14 -04:00
br_stp_bpdu.c br: fix use of ->rx_handler_data in code executed on non-rx_handler path 2013-12-06 15:41:40 -05:00
br_stp_if.c bridge: Change local fdb entries whenever mac address of bridge device changes 2014-02-10 14:34:33 -08:00
br_stp_timer.c bridge: add space before '(/{', after ',', etc. 2013-12-19 19:27:26 -05:00
br_sysfs_br.c bridge: Support 802.1ad vlan filtering 2014-06-11 15:22:53 -07:00
br_sysfs_if.c bridge: Keep track of ports capable of automatic discovery. 2014-05-16 17:06:33 -04:00
br_vlan.c net: Always untag vlan-tagged traffic on input. 2014-08-11 12:16:51 -07:00