bridge: Fix LRO crash with tun

> Kernel BUG at drivers/net/tun.c:444
> invalid opcode: 0000 [1] SMP
> last sysfs file: /class/net/lo/ifindex
> CPU 0
> Modules linked in: tun ipt_MASQUERADE iptable_nat ip_nat xt_state ip_conntrack
> nfnetlink ipt_REJECT xt_tcpudp iptable_filter d
> Pid: 6912, comm: qemu-kvm Tainted: G      2.6.18-128.el5 #1
> RIP: 0010:[<ffffffff886f57b0>]  [<ffffffff886f57b0>]
> :tun:tun_chr_readv+0x2b1/0x3a6
> RSP: 0018:ffff8102202c5e48  EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff8102202c5e98 RCX: 0000000004010000
> RDX: ffff810227063680 RSI: ffff8102202c5e9e RDI: ffff8102202c5e92
> RBP: 0000000000010ff6 R08: 0000000000000000 R09: 0000000000000001
> R10: ffff8102202c5e94 R11: 0000000000000202 R12: ffff8102275357c0
> R13: ffff81022755e500 R14: 0000000000000000 R15: ffff8102202c5ef8
> FS:  00002ae4398db980(0000) GS:ffffffff803ac000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 00002ae4ab514000 CR3: 0000000221344000 CR4: 00000000000026e0
> Process qemu-kvm (pid: 6912, threadinfo ffff8102202c4000, task
> ffff81022e58d820)
> Stack:  00000000498735cb ffff810229d1a3c0 0000000000000000 ffff81022e58d820
>  ffffffff8008a461 ffff81022755e528 ffff81022755e528 ffffffff8009f925
>  000005ea05ea0000 ffff8102209d0000 00001051143e1600 ffffffff8003c00e
> Call Trace:
>  [<ffffffff8008a461>] default_wake_function+0x0/0xe
>  [<ffffffff8009f925>] enqueue_hrtimer+0x55/0x70
>  [<ffffffff8003c00e>] hrtimer_start+0xbc/0xce
>  [<ffffffff886f58bf>] :tun:tun_chr_read+0x1a/0x1f
>  [<ffffffff8000b3f3>] vfs_read+0xcb/0x171
>  [<ffffffff800117d4>] sys_read+0x45/0x6e
>  [<ffffffff8005d116>] system_call+0x7e/0x83
>
>
> Code: 0f 0b 68 40 62 6f 88 c2 bc 01 f6 42 0a 08 74 0c 80 4c 24 41
> RIP  [<ffffffff886f57b0>] :tun:tun_chr_readv+0x2b1/0x3a6
>  RSP <ffff8102202c5e48>
>  <0>Kernel panic - not syncing: Fatal exception

This crashed when an LRO packet generated by bnx2x reached a
tun device through the bridge.  We're supposed to drop it at
the bridge.  However, because the check was placed in br_forward
instead of __br_forward, it's only effective if we are sending
the packet through a single port.

This patch fixes it by moving the check into __br_forward.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>