Regression in staging:r8712u since 3.4 merge

[Larry Finger]

Since kernel 3.4, driver r8712u has yielded intermittent errors when connected 
to a secure connection. With Firefox, the message is "Secure Connection Failed: 
SSL received a record with an incorrect Message Authentication Code (Error code: 
ssl_error_bad_mac_read)". A retry may work eventually, When using wget with an 
https URL, the error message is "SSL3_GET_RECORD: decryption failed or bad 
record mac".

This regression is the basis for https://bugzilla.kernel.org/show_bug.cgi?id=45071.

Although intermittent, I managed to bisect the problem. The bad commit is

==========================================================================
commit c8628155ece363487b57d33441ea0359018c0fa7
Author: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Date:   Sun Mar 18 11:07:47 2012 +0000

    tcp: reduce out_of_order memory use

    With increasing receive window sizes, but speed of light not improved
    that much, out of order queue can contain a huge number of skbs, waiting
    to be moved to receive_queue when missing packets can fill the holes.

    Some devices happen to use fat skbs (truesize of 4096 + sizeof(struct
    sk_buff)) to store regular (MTU <= 1500) frames. This makes highly
    probable sk_rmem_alloc hits sk_rcvbuf limit, which can be 4Mbytes in
    many cases.

    When limit is hit, tcp stack calls tcp_collapse_ofo_queue(), a true
    latency killer and cpu cache blower.

    Doing the coalescing attempt each time we add a frame in ofo queue
    permits to keep memory use tight and in many cases avoid the
    tcp_collapse() thing later.

    Tested on various wireless setups (b43, ath9k, ...) known to use big skb
    truesize, this patch removed the "packets collapsed in receive queue due
    to low socket buffer" I had before.

    This also reduced average memory used by tcp sockets.

    With help from Neal Cardwell.

    Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
    Cc: Neal Cardwell <ncardwell@xxxxxxxxxx>
    Cc: Yuchung Cheng <ycheng@xxxxxxxxxx>
    Cc: H.K. Jerry Chu <hkchu@xxxxxxxxxx>
    Cc: Tom Herbert <therbert@xxxxxxxxxx>
    Cc: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxx>
    Acked-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
============================================================================

As every other network driver is OK with this patch, I know the problem is in 
r8712u. Do you have any thoughts on what it might be doing wrong to cause this 
problem?

Thanks,

Larry

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