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author | Stanislaw Gruszka <sgruszka@redhat.com> | 2014-11-11 14:28:47 +0100 |
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committer | Jiri Slaby <jslaby@suse.cz> | 2014-12-06 15:18:25 +0100 |
commit | 8c3b78ffdeff62372503e92c606a262be51fb19a (patch) | |
tree | 1b709bad2c7d9e5c62f625106cf3b8fe2c6d994f | |
parent | 20542e3efc5012451f8e05c17bea46119763fddf (diff) | |
download | lwn-8c3b78ffdeff62372503e92c606a262be51fb19a.tar.gz lwn-8c3b78ffdeff62372503e92c606a262be51fb19a.zip |
rt2x00: do not align payload on modern H/W
commit cfd9167af14eb4ec21517a32911d460083ee3d59 upstream.
RT2800 and newer hardware require padding between header and payload if
header length is not multiple of 4.
For historical reasons we also align payload to to 4 bytes boundary, but
such alignment is not needed on modern H/W.
Patch fixes skb_under_panic problems reported from time to time:
https://bugzilla.kernel.org/show_bug.cgi?id=84911
https://bugzilla.kernel.org/show_bug.cgi?id=72471
http://marc.info/?l=linux-wireless&m=139108549530402&w=2
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1087591
Panic happened because we eat 4 bytes of skb headroom on each
(re)transmission when sending frame without the payload and the header
length not being multiple of 4 (i.e. QoS header has 26 bytes). On such
case because paylad_aling=2 is bigger than header_align=0 we increase
header_align by 4 bytes. To prevent that we could change the check to:
if (payload_length && payload_align > header_align)
header_align += 4;
but not aligning payload at all is more effective and alignment is not
really needed by H/W (that has been tested on OpenWrt project for few
years now).
Reported-and-tested-by: Antti S. Lankila <alankila@bel.fi>
Debugged-by: Antti S. Lankila <alankila@bel.fi>
Reported-by: Henrik Asp <solenskiner@gmail.com>
Originally-From: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
-rw-r--r-- | drivers/net/wireless/rt2x00/rt2x00queue.c | 50 |
1 files changed, 12 insertions, 38 deletions
diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c index 66a2db8c260d..e6182170e791 100644 --- a/drivers/net/wireless/rt2x00/rt2x00queue.c +++ b/drivers/net/wireless/rt2x00/rt2x00queue.c @@ -160,55 +160,29 @@ void rt2x00queue_align_frame(struct sk_buff *skb) skb_trim(skb, frame_length); } -void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int header_length) +/* + * H/W needs L2 padding between the header and the paylod if header size + * is not 4 bytes aligned. + */ +void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int hdr_len) { - unsigned int payload_length = skb->len - header_length; - unsigned int header_align = ALIGN_SIZE(skb, 0); - unsigned int payload_align = ALIGN_SIZE(skb, header_length); - unsigned int l2pad = payload_length ? L2PAD_SIZE(header_length) : 0; + unsigned int l2pad = (skb->len > hdr_len) ? L2PAD_SIZE(hdr_len) : 0; - /* - * Adjust the header alignment if the payload needs to be moved more - * than the header. - */ - if (payload_align > header_align) - header_align += 4; - - /* There is nothing to do if no alignment is needed */ - if (!header_align) + if (!l2pad) return; - /* Reserve the amount of space needed in front of the frame */ - skb_push(skb, header_align); - - /* - * Move the header. - */ - memmove(skb->data, skb->data + header_align, header_length); - - /* Move the payload, if present and if required */ - if (payload_length && payload_align) - memmove(skb->data + header_length + l2pad, - skb->data + header_length + l2pad + payload_align, - payload_length); - - /* Trim the skb to the correct size */ - skb_trim(skb, header_length + l2pad + payload_length); + skb_push(skb, l2pad); + memmove(skb->data, skb->data + l2pad, hdr_len); } -void rt2x00queue_remove_l2pad(struct sk_buff *skb, unsigned int header_length) +void rt2x00queue_remove_l2pad(struct sk_buff *skb, unsigned int hdr_len) { - /* - * L2 padding is only present if the skb contains more than just the - * IEEE 802.11 header. - */ - unsigned int l2pad = (skb->len > header_length) ? - L2PAD_SIZE(header_length) : 0; + unsigned int l2pad = (skb->len > hdr_len) ? L2PAD_SIZE(hdr_len) : 0; if (!l2pad) return; - memmove(skb->data + l2pad, skb->data, header_length); + memmove(skb->data + l2pad, skb->data, hdr_len); skb_pull(skb, l2pad); } |