[net v2] octeontx2-pf: macsec: Fix incorrect max transmit size in TX secy

[net v2] octeontx2-pf: macsec: Fix incorrect max transmit size in TX secy

[Subbaraya Sundeep]

MASCEC hardware block has a field called maximum transmit size for
TX secy. Max packet size going out of MCS block has be programmed
taking into account full packet size which has L2 header,SecTag
and ICV. MACSEC offload driver is configuring max transmit size as
macsec interface MTU which is incorrect. Say with 1500 MTU of real
device, macsec interface created on top of real device will have MTU of
1468(1500 - (SecTag + ICV)). This is causing packets from macsec
interface of size greater than or equal to 1468 are not getting
transmitted out because driver programmed max transmit size as 1468
instead of 1514(1500 + ETH_HDR_LEN).

Fixes: c54ffc73601c ("octeontx2-pf: mcs: Introduce MACSEC hardware offloading")
Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
---
v2 changes:
 Modified commit description and added subject prefix as net.

 drivers/net/ethernet/marvell/octeontx2/nic/cn10k_macsec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/cn10k_macsec.c b/drivers/net/ethernet/marvell/octeontx2/nic/cn10k_macsec.c
index f3b9daf..4c7e0f3 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/cn10k_macsec.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/cn10k_macsec.c
@@ -531,7 +531,8 @@ static int cn10k_mcs_write_tx_secy(struct otx2_nic *pfvf,
 	if (sw_tx_sc->encrypt)
 		sectag_tci |= (MCS_TCI_E | MCS_TCI_C);
 
-	policy = FIELD_PREP(MCS_TX_SECY_PLCY_MTU, secy->netdev->mtu);
+	policy = FIELD_PREP(MCS_TX_SECY_PLCY_MTU,
+			    pfvf->netdev->mtu + OTX2_ETH_HLEN);
 	/* Write SecTag excluding AN bits(1..0) */
 	policy |= FIELD_PREP(MCS_TX_SECY_PLCY_ST_TCI, sectag_tci >> 2);
 	policy |= FIELD_PREP(MCS_TX_SECY_PLCY_ST_OFFSET, tag_offset);
-- 
2.7.4

Re: [net v2] octeontx2-pf: macsec: Fix incorrect max transmit size in TX secy

[Simon Horman]

On Mon, May 12, 2025 at 06:12:36PM +0530, Subbaraya Sundeep wrote:
> MASCEC hardware block has a field called maximum transmit size for
> TX secy. Max packet size going out of MCS block has be programmed
> taking into account full packet size which has L2 header,SecTag
> and ICV. MACSEC offload driver is configuring max transmit size as
> macsec interface MTU which is incorrect. Say with 1500 MTU of real
> device, macsec interface created on top of real device will have MTU of
> 1468(1500 - (SecTag + ICV)). This is causing packets from macsec
> interface of size greater than or equal to 1468 are not getting
> transmitted out because driver programmed max transmit size as 1468
> instead of 1514(1500 + ETH_HDR_LEN).
> 
> Fixes: c54ffc73601c ("octeontx2-pf: mcs: Introduce MACSEC hardware offloading")
> Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>

Thanks, I see that OTX2_ETH_HLEN is already taken into account in several
places including otx2_hw_set_mtu() and otx2_get_max_mtu(). So I agree with
this change.

Reviewed-by: Simon Horman <horms@kernel.org>

...

Re: [net v2] octeontx2-pf: macsec: Fix incorrect max transmit size in TX secy

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 12 May 2025 18:12:36 +0530 you wrote:
> MASCEC hardware block has a field called maximum transmit size for
> TX secy. Max packet size going out of MCS block has be programmed
> taking into account full packet size which has L2 header,SecTag
> and ICV. MACSEC offload driver is configuring max transmit size as
> macsec interface MTU which is incorrect. Say with 1500 MTU of real
> device, macsec interface created on top of real device will have MTU of
> 1468(1500 - (SecTag + ICV)). This is causing packets from macsec
> interface of size greater than or equal to 1468 are not getting
> transmitted out because driver programmed max transmit size as 1468
> instead of 1514(1500 + ETH_HDR_LEN).
> 
> [...]

Here is the summary with links:
  - [net,v2] octeontx2-pf: macsec: Fix incorrect max transmit size in TX secy
    https://git.kernel.org/netdev/net/c/865ab2461375

You are awesome, thank you!
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