From b34a93b528f08401835259c477ade49730fc1baf Mon Sep 17 00:00:00 2001 From: Dave Stevenson Date: Wed, 13 Jun 2018 15:21:10 +0100 Subject: [PATCH] net: lan78xx: Disable TCP Segmentation Offload (TSO) TSO seems to be having issues when packets are dropped and the remote end uses Selective Acknowledge (SACK) to denote that data is missing. The missing data is never resent, so the connection eventually stalls. There is a module parameter of enable_tso added to allow further debugging without forcing a rebuild of the kernel. https://github.com/raspberrypi/linux/issues/2449 https://github.com/raspberrypi/linux/issues/2482 Signed-off-by: Dave Stevenson --- drivers/net/usb/lan78xx.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) --- a/drivers/net/usb/lan78xx.c +++ b/drivers/net/usb/lan78xx.c @@ -425,6 +425,15 @@ static int msg_level = -1; module_param(msg_level, int, 0); MODULE_PARM_DESC(msg_level, "Override default message level"); +/* TSO seems to be having some issue with Selective Acknowledge (SACK) that + * results in lost data never being retransmitted. + * Disable it by default now, but adds a module parameter to enable it for + * debug purposes (the full cause is not currently understood). + */ +static bool enable_tso; +module_param(enable_tso, bool, 0644); +MODULE_PARM_DESC(enable_tso, "Enables TCP segmentation offload"); + static int lan78xx_read_reg(struct lan78xx_net *dev, u32 index, u32 *data) { u32 *buf = kmalloc(sizeof(u32), GFP_KERNEL); @@ -2925,8 +2934,14 @@ static int lan78xx_bind(struct lan78xx_n if (DEFAULT_RX_CSUM_ENABLE) dev->net->features |= NETIF_F_RXCSUM; - if (DEFAULT_TSO_CSUM_ENABLE) - dev->net->features |= NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_SG; + if (DEFAULT_TSO_CSUM_ENABLE) { + dev->net->features |= NETIF_F_SG; + /* Use module parameter to control TCP segmentation offload as + * it appears to cause issues. + */ + if (enable_tso) + dev->net->features |= NETIF_F_TSO | NETIF_F_TSO6; + } if (DEFAULT_VLAN_RX_OFFLOAD) dev->net->features |= NETIF_F_HW_VLAN_CTAG_RX;