From: Andrew Lunn <andrew@lunn.ch>
To: Aldo Ariel <qwe.aldo@gmail.com>
Cc: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>,
maxime.chevallier@bootlin.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org,
sashiko-bot@kernel.org
Subject: Re: [PATCH] net: stmmac: guard FCS stripping against runt frames
Date: Thu, 24 Sep 2026 16:10:24 +0200 [thread overview]
Message-ID: <64d3ca1a-7218-4c90-a110-6ff7defb56ac@lunn.ch> (raw)
In-Reply-To: <CAP48HfvkCNb2_UnpvTvn_O3K+vgtDK55JjXPBF0cbBrmb_6oCA@mail.gmail.com>
On Thu, Sep 24, 2026 at 10:51:11AM -0300, Aldo Ariel wrote:
> Hi Andrew, Lorenzo,
>
> Fair point on the subject — the trigger is not limited to runt frames.
>
> The FCS stripping in stmmac_rx() at lines 5810-5817 runs on every
> last-segment descriptor regardless of total frame size:
>
> if (likely(!(status & rx_not_ls))) {
> if (buf2_len) {
> buf2_len -= ETH_FCS_LEN;
> } else if (buf1_len) {
> buf1_len -= ETH_FCS_LEN;
> }
> }
>
> For a multi-descriptor frame, the last descriptor's buf2_len or
> buf1_len carries only the tail of the frame. With the default
> dma_buf_sz = BUF_SIZE_2KiB for MTU 1500, a 4097-byte frame splits as:
Is the MTU programmed into the hardware? Will it even try to transfer
an 4097 octet frame when the MTU is configured to 1500?
Andrew
next prev parent reply other threads:[~2026-09-24 14:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-23 16:23 Aldo Ariel Panzardo
2026-09-23 19:03 ` Andrew Lunn
2026-09-23 19:33 ` Aldo Ariel Panzardo
2026-09-23 20:53 ` Andrew Lunn
2026-09-23 20:37 ` Lorenzo Bianconi
2026-09-24 2:16 ` Andrew Lunn
2026-09-24 7:57 ` Lorenzo Bianconi
2026-09-24 12:51 ` Andrew Lunn
2026-09-24 13:10 ` Lorenzo Bianconi
[not found] ` <CAP48HfvkCNb2_UnpvTvn_O3K+vgtDK55JjXPBF0cbBrmb_6oCA@mail.gmail.com>
2026-09-24 14:10 ` Andrew Lunn [this message]
2026-09-27 16:38 ` netdev-bot+sashiko
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