On Tue, Feb 09, 2021 at 09:22:41AM +0800, Bin Meng wrote:
> From: Bin Meng <bin.m...@windriver.com>
>
> Per MPC8548ERM [1] chapter 14.5.3.4.1:
>
> When RCTRL.RSF is 1, frames less than 64 bytes are accepted upon
> a DA match. But currently QEMU does the opposite.
>
> When RCTRL.RSF is 0, short frames are silently dropped, however
> we cannot drop such frames in QEMU as of today, due to both slirp
> and tap networking do not pad short frames (e.g.: an ARP packet)
> to the minimum frame size of 60 bytes.
>
> If eTSEC is programmed to reject short frames, ARP requests will be
> dropped, preventing the guest from becoming visible on the network.
>
> The same issue was reported on e1000 and vmxenet3 before, see:
>
> commit 78aeb23eded2 ("e1000: Pad short frames to minimum size (60 bytes)")
> commit 40a87c6c9b11 ("vmxnet3: Pad short frames to minimum size (60 bytes)")
>
> Ideally this should be fixed on the slirp/tap networking side to
> pad short frames to the minimum frame length, but I am not sure
> whether that's doable.
>
> This commit reverses the RCTRL.RSF testing logic to match the spec.
> The log message is updated to mention the reject short frames
> functionality is unimplemented.
>
> [1] https://www.nxp.com/docs/en/reference-manual/MPC8548ERM.pdf
>
> Fixes: eb1e7c3e5146 ("Add Enhanced Three-Speed Ethernet Controller (eTSEC)")
> Signed-off-by: Bin Meng <bin.m...@windriver.com>
Applied to ppc-for-6.0.
Thanks for the excellent commit message with the links to the relevant
documentation.
>
> ---
>
> Changes in v2:
> - rewrite the commit message and reverse the RCTRL.RSF test logic
>
> hw/net/fsl_etsec/rings.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/hw/net/fsl_etsec/rings.c b/hw/net/fsl_etsec/rings.c
> index 121415a..f89aa7f 100644
> --- a/hw/net/fsl_etsec/rings.c
> +++ b/hw/net/fsl_etsec/rings.c
> @@ -502,10 +502,17 @@ ssize_t etsec_rx_ring_write(eTSEC *etsec, const uint8_t
> *buf, size_t size)
> return -1;
> }
>
> - if ((etsec->regs[RCTRL].value & RCTRL_RSF) && (size < 60)) {
> + /*
> + * Both slirp and tap networking do not pad short frames
> + * (e.g.: an ARP packet) to the minimum frame size of 60 bytes.
> + *
> + * If eTSEC is programmed to reject short frames, ARP requests
> + * will be dropped, preventing the guest from becoming visible
> + * on the network.
> + */
> + if (!(etsec->regs[RCTRL].value & RCTRL_RSF) && (size < 60)) {
> /* CRC is not in the packet yet, so short frame is below 60 bytes */
> - RING_DEBUG("%s: Drop short frame\n", __func__);
> - return -1;
> + RING_DEBUG("%s: Drop short frame not implemented\n", __func__);
> }
>
> rx_init_frame(etsec, buf, size);
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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