When fixing the TSO support I noticed we just mask skb->gso_size with the MSSMask value and don't care about the consequences.
That seems... unsagacious.
Instead of masking, WARN and drop the packet if the maximum is exceeded.
And call netif_set_gso_max_size() so it shouldn't happen in the first
place.
Finally, Francois Romieu noticed that we didn't even have the right
value for MSSMask anyway; it should be 0x7ff (11 bits) not 0xfff.
Signed-off-by: David Woodhouse <david.woodho...@intel.com>
---
Nice and simple and obvious, right?
So why does it stop TSO from happening at all?
When I call netif_set_gso_max_size() with a value of 0xaad (2733) or
higher, I see TSO being used (with an MSS of 1214; this is just between
a VM and its host; Legacy IP with an MTU of 1500).
If I set a maximum of 0xaac or lower, TSO never gets used. Am I doing
something wrong? Or is there a problem somewhere else?
drivers/net/ethernet/realtek/8139cp.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/realtek/8139cp.c
b/drivers/net/ethernet/realtek/8139cp.c
index 686334f..ae24d42 100644
--- a/drivers/net/ethernet/realtek/8139cp.c
+++ b/drivers/net/ethernet/realtek/8139cp.c
@@ -175,7 +175,7 @@ enum {
LastFrag = (1 << 28), /* Final segment of a packet */
LargeSend = (1 << 27), /* TCP Large Send Offload (TSO) */
MSSShift = 16, /* MSS value position */
- MSSMask = 0xfff, /* MSS value: 11 bits */
+ MSSMask = 0x7ff, /* MSS value: 11 bits */
TxError = (1 << 23), /* Tx error summary */
RxError = (1 << 20), /* Rx error summary */
IPCS = (1 << 18), /* Calculate IP checksum */
@@ -754,10 +754,16 @@ static netdev_tx_t cp_start_xmit (struct sk_buff *skb,
eor = (entry == (CP_TX_RING_SIZE - 1)) ? RingEnd : 0;
mss = skb_shinfo(skb)->gso_size;
+ if (mss > MSSMask) {
+ WARN_ONCE(1, "Net bug: GSO size %d too large for 8139CP\n",
+ mss);
+ goto out_dma_error;
+ }
+
opts2 = cpu_to_le32(cp_tx_vlan_tag(skb));
opts1 = DescOwn;
if (mss)
- opts1 |= LargeSend | ((mss & MSSMask) << MSSShift);
+ opts1 |= LargeSend | (mss << MSSShift);
else if (skb->ip_summed == CHECKSUM_PARTIAL) {
const struct iphdr *ip = ip_hdr(skb);
if (ip->protocol == IPPROTO_TCP)
@@ -1994,6 +2000,8 @@ static int cp_init_one (struct pci_dev *pdev, const
struct pci_device_id *ent)
dev->vlan_features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO |
NETIF_F_HIGHDMA;
+ netif_set_gso_max_size(dev, MSSMask);
+
rc = register_netdev(dev);
if (rc)
goto err_out_iomap;
--
2.4.3
--
David Woodhouse Open Source Technology Centre
david.woodho...@intel.com Intel Corporation
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