e1000e: fix flow control denial of service possibility
this patch avoids a denial of service from an evildoer sending a continuous stream of flow control at our adapter that is plugged into a non-flow control enabled switch. Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com> Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com> Signed-off-by: Jeff Garzik <jeff@garzik.org>
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@ -1104,34 +1104,13 @@ s32 e1000e_config_fc_after_link_up(struct e1000_hw *hw)
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(mii_nway_lp_ability_reg & NWAY_LPAR_ASM_DIR)) {
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mac->fc = e1000_fc_rx_pause;
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hw_dbg(hw, "Flow Control = RX PAUSE frames only.\r\n");
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}
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/* Per the IEEE spec, at this point flow control should be
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* disabled. However, we want to consider that we could
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* be connected to a legacy switch that doesn't advertise
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* desired flow control, but can be forced on the link
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* partner. So if we advertised no flow control, that is
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* what we will resolve to. If we advertised some kind of
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* receive capability (Rx Pause Only or Full Flow Control)
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* and the link partner advertised none, we will configure
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* ourselves to enable Rx Flow Control only. We can do
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* this safely for two reasons: If the link partner really
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* didn't want flow control enabled, and we enable Rx, no
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* harm done since we won't be receiving any PAUSE frames
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* anyway. If the intent on the link partner was to have
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* flow control enabled, then by us enabling RX only, we
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* can at least receive pause frames and process them.
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* This is a good idea because in most cases, since we are
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* predominantly a server NIC, more times than not we will
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* be asked to delay transmission of packets than asking
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* our link partner to pause transmission of frames.
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*/
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else if ((mac->original_fc == e1000_fc_none) ||
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(mac->original_fc == e1000_fc_tx_pause)) {
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} else {
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/*
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* Per the IEEE spec, at this point flow control
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* should be disabled.
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*/
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mac->fc = e1000_fc_none;
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hw_dbg(hw, "Flow Control = NONE.\r\n");
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} else {
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mac->fc = e1000_fc_rx_pause;
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hw_dbg(hw, "Flow Control = RX PAUSE frames only.\r\n");
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}
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/* Now we need to do one last check... If we auto-
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