target/linux/brcm2708/patches-4.19/950-0127-net-lan78xx-Disable-TCP-Segmentation-Offload-TSO.patch

   1 From 59555269e09f06ae0ded9007c4aa02fa55ce71ca Mon Sep 17 00:00:00 2001
   2 From: Dave Stevenson <dave.stevenson@raspberrypi.org>
   3 Date: Wed, 13 Jun 2018 15:21:10 +0100
   4 Subject: [PATCH] net: lan78xx: Disable TCP Segmentation Offload (TSO)
   5
   6 TSO seems to be having issues when packets are dropped and the
   7 remote end uses Selective Acknowledge (SACK) to denote that
   8 data is missing. The missing data is never resent, so the
   9 connection eventually stalls.
  10
  11 There is a module parameter of enable_tso added to allow
  12 further debugging without forcing a rebuild of the kernel.
  13
  14 https://github.com/raspberrypi/linux/issues/2449
  15 https://github.com/raspberrypi/linux/issues/2482
  16
  17 Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
  18 ---
  19  drivers/net/usb/lan78xx.c | 19 +++++++++++++++++--
  20  1 file changed, 17 insertions(+), 2 deletions(-)
  21
  22 --- a/drivers/net/usb/lan78xx.c
  23 +++ b/drivers/net/usb/lan78xx.c
  24 @@ -439,6 +439,15 @@ static int msg_level = -1;
  25  module_param(msg_level, int, 0);
  26  MODULE_PARM_DESC(msg_level, "Override default message level");
  27
  28 +/* TSO seems to be having some issue with Selective Acknowledge (SACK) that
  29 + * results in lost data never being retransmitted.
  30 + * Disable it by default now, but adds a module parameter to enable it for
  31 + * debug purposes (the full cause is not currently understood).
  32 + */
  33 +static bool enable_tso;
  34 +module_param(enable_tso, bool, 0644);
  35 +MODULE_PARM_DESC(enable_tso, "Enables TCP segmentation offload");
  36 +
  37  static int lan78xx_read_reg(struct lan78xx_net *dev, u32 index, u32 *data)
  38  {
  39         u32 *buf = kmalloc(sizeof(u32), GFP_KERNEL);
  40 @@ -3009,8 +3018,14 @@ static int lan78xx_bind(struct lan78xx_n
  41         if (DEFAULT_RX_CSUM_ENABLE)
  42                 dev->net->features |= NETIF_F_RXCSUM;
  43
  44 -       if (DEFAULT_TSO_CSUM_ENABLE)
  45 -               dev->net->features |= NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_SG;
  46 +       if (DEFAULT_TSO_CSUM_ENABLE) {
  47 +               dev->net->features |= NETIF_F_SG;
  48 +               /* Use module parameter to control TCP segmentation offload as
  49 +                * it appears to cause issues.
  50 +                */
  51 +               if (enable_tso)
  52 +                       dev->net->features |= NETIF_F_TSO | NETIF_F_TSO6;
  53 +       }
  54
  55         if (DEFAULT_VLAN_RX_OFFLOAD)
  56                 dev->net->features |= NETIF_F_HW_VLAN_CTAG_RX;