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net: cdc_ncm: use sane defaults for rx/tx buffers 

Lots of devices request much larger buffers than reasonable. This
cause real problems for users of hosts with limited resources.

Reducing the default buffer size to 16kB for such devices is
a reasonable trade-off between allowing them to aggregate traffic
and avoiding memory exhaustion on resource restrained hosts.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Bjørn Mork 2014-05-16 21:48:26 +02:00 committed by David S. Miller
parent beeecd42c3
commit 50f1cb1cc8
2 changed files with 14 additions and 2 deletions
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12
drivers/net/usb/cdc_ncm.c
View File

@ -492,10 +492,18 @@ static void cdc_ncm_fix_modulus(struct usbnet *dev)
static int cdc_ncm_setup(struct usbnet *dev)
{
struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
u32 def_rx, def_tx;
/* be conservative when selecting intial buffer size to
* increase the number of hosts this will work for
*/
def_rx = min_t(u32, CDC_NCM_NTB_DEF_SIZE_RX,
le32_to_cpu(ctx->ncm_parm.dwNtbInMaxSize));
def_tx = min_t(u32, CDC_NCM_NTB_DEF_SIZE_TX,
le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize));
/* clamp rx_max and tx_max and inform device */
cdc_ncm_update_rxtx_max(dev, le32_to_cpu(ctx->ncm_parm.dwNtbInMaxSize),
le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize));
cdc_ncm_update_rxtx_max(dev, def_rx, def_tx);
/* sanitize the modulus and remainder values */
cdc_ncm_fix_modulus(dev);

4
include/linux/usb/cdc_ncm.h
View File

@ -52,6 +52,10 @@
#define CDC_NCM_NTB_MAX_SIZE_TX 32768 /* bytes */
#define CDC_NCM_NTB_MAX_SIZE_RX 32768 /* bytes */
/* Initial NTB length */
#define CDC_NCM_NTB_DEF_SIZE_TX 16384 /* bytes */
#define CDC_NCM_NTB_DEF_SIZE_RX 16384 /* bytes */
/* Minimum value for MaxDatagramSize, ch. 6.2.9 */
#define CDC_NCM_MIN_DATAGRAM_SIZE 1514 /* bytes */