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SubjectRegression in staging:r8712u since 3.4 merge
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

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

commit c8628155ece363487b57d33441ea0359018c0fa7
Author: Eric Dumazet <>
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 <>
Cc: Neal Cardwell <>
Cc: Yuchung Cheng <>
Cc: H.K. Jerry Chu <>
Cc: Tom Herbert <>
Cc: Ilpo Järvinen <>
Acked-by: Neal Cardwell <>
Signed-off-by: David S. Miller <>

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



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