[PATCH net] net: mana: report RX checksum offload for IPv6

[PATCH net] net: mana: report RX checksum offload for IPv6

[Hamza Mahfooz]

The hardware validates TCP and UDP checksums for both IPv4 and IPv6 and
reports the result in rx_tcp_csum_succeed and rx_udp_csum_succeed.
However, mana_rx_skb() also requires rx_iphdr_csum_succeed before it
sets CHECKSUM_UNNECESSARY. That bit is only set for IPv4 (since IPv6
has no header checksum), so IPv6 TCP and UDP traffic is always
checksummed again in software.

So, only look at the L4 result. For IPv4 this makes no material
difference since CHECKSUM_UNNECESSARY only covers the L4 checksum, and
ip_rcv_core() always verifies the IPv4 header checksum in software.

Between two Azure Standard_E16s_v6 VMs (VF enabled), IPv6 TCP and UDP
packets (including VXLAN over IPv6), now arrive with
CHECKSUM_UNNECESSARY instead of CHECKSUM_NONE, so GRO no longer
checksums them in software. Calls to __skb_gro_checksum_complete() on
the receiver during an 8 second iperf3 run:

                               before    after
  TCP/IPv4, 12.2 Gbps              23       28
  TCP/IPv6, 12.1 Gbps         8728419       25
  UDP/IPv6, 1.5 Gbps          1071380       20
  TCP/VXLAN/IPv6, 10.9 Gbps   7934373       18

Cc: stable@vger.kernel.org
Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index e6d494df22e4..05bd4b4b8349 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -2179,10 +2179,9 @@ static void mana_rx_skb(void *buf_va, bool from_pool,
 	skb_checksum_none_assert(skb);
 	skb_record_rx_queue(skb, rxq_idx);
 
-	if ((ndev->features & NETIF_F_RXCSUM) && cqe->rx_iphdr_csum_succeed) {
-		if (cqe->rx_tcp_csum_succeed || cqe->rx_udp_csum_succeed)
-			skb->ip_summed = CHECKSUM_UNNECESSARY;
-	}
+	if ((ndev->features & NETIF_F_RXCSUM) &&
+	    (cqe->rx_tcp_csum_succeed || cqe->rx_udp_csum_succeed))
+		skb->ip_summed = CHECKSUM_UNNECESSARY;
 
 	if (cqe->rx_hashtype != 0 && (ndev->features & NETIF_F_RXHASH)) {
 		if (cqe->rx_hashtype & MANA_HASH_L4)
-- 
2.56.0

Re: [PATCH net] net: mana: report RX checksum offload for IPv6

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found no new issues
in this patch, but noticed 1 related pre-existing issue it does not
introduce:
- [High] net: mana: memory leak on XDP drop path in mana_rx_skb() [1]
--

commit 44321b6481b9b9f9a70166beb9fc63a817e238f6
Author: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>

net: mana: report RX checksum offload for IPv6

This commit removes the rx_iphdr_csum_succeed check in mana_rx_skb() so
that IPv6 TCP and UDP packets with validated L4 checksums receive
CHECKSUM_UNNECESSARY.

> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> index e6d494df22e4d..05bd4b4b8349e 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -2179,10 +2179,9 @@ static void mana_rx_skb(void *buf_va, bool from_pool,
>  	skb_checksum_none_assert(skb);
>  	skb_record_rx_queue(skb, rxq_idx);
>  
> -	if ((ndev->features & NETIF_F_RXCSUM) && cqe->rx_iphdr_csum_succeed) {
> -		if (cqe->rx_tcp_csum_succeed || cqe->rx_udp_csum_succeed)
> -			skb->ip_summed = CHECKSUM_UNNECESSARY;
> -	}
> +	if ((ndev->features & NETIF_F_RXCSUM) &&
> +	    (cqe->rx_tcp_csum_succeed || cqe->rx_udp_csum_succeed))
> +		skb->ip_summed = CHECKSUM_UNNECESSARY;

[Severity: High]
This problem wasn't introduced by this patch, but can mana_rx_skb() leak
rxq->xdp_save_va [1] on its drop path when rxq->frag_count > 1?

When a pre-allocated buffer (from_pool == false) is dropped, mana_rx_skb()
stores buf_va in rxq->xdp_save_va for reuse:

drivers/net/ethernet/microsoft/mana/mana_en.c:mana_rx_skb() {
	...
drop:
	if (from_pool) {
		...
	} else {
		WARN_ON_ONCE(rxq->xdp_save_va);
		/* Save for reuse */
		rxq->xdp_save_va = buf_va;
	}
}

However, mana_get_rxfrag() only checks and reclaims rxq->xdp_save_va when
rxq->frag_count == 1:

drivers/net/ethernet/microsoft/mana/mana_en.c:mana_get_rxfrag() {
	...
	if (rxq->frag_count == 1) {
		/* Reuse XDP dropped page if available */
		if (rxq->xdp_save_va) {
			va = rxq->xdp_save_va;
			page = virt_to_head_page(va);
			rxq->xdp_save_va = NULL;
		...
		return va;
	}

	page =  page_pool_dev_alloc_frag(rxq->page_pool, &offset,
					 rxq->alloc_size);
}

When rxq->frag_count > 1, mana_get_rxfrag() ignores rxq->xdp_save_va and
allocates a new fragment from the page pool, so a subsequent drop of a
pre-allocated buffer triggers the WARN_ON_ONCE() and overwrites
rxq->xdp_save_va, leaking the saved page.

[1] https://sashiko.dev/#/bug/linux-2ba39e78-7dc4-4027-a76e-f2d315147bad

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261109142856.779955-1-hamzamahfooz@linux.microsoft.com?part=1

Re: [PATCH net] net: mana: report RX checksum offload for IPv6

[Hamza Mahfooz]

On Tue, Nov 10, 2026 at 02:29:17PM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found no new issues
> in this patch, but noticed 1 related pre-existing issue it does not
> introduce:
> - [High] net: mana: memory leak on XDP drop path in mana_rx_skb() [1]
> --
> 
> commit 44321b6481b9b9f9a70166beb9fc63a817e238f6
> Author: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
> 
> net: mana: report RX checksum offload for IPv6
> 
> This commit removes the rx_iphdr_csum_succeed check in mana_rx_skb() so
> that IPv6 TCP and UDP packets with validated L4 checksums receive
> CHECKSUM_UNNECESSARY.
> 
> > diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> > index e6d494df22e4d..05bd4b4b8349e 100644
> > --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> > +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> > @@ -2179,10 +2179,9 @@ static void mana_rx_skb(void *buf_va, bool from_pool,
> >  	skb_checksum_none_assert(skb);
> >  	skb_record_rx_queue(skb, rxq_idx);
> >  
> > -	if ((ndev->features & NETIF_F_RXCSUM) && cqe->rx_iphdr_csum_succeed) {
> > -		if (cqe->rx_tcp_csum_succeed || cqe->rx_udp_csum_succeed)
> > -			skb->ip_summed = CHECKSUM_UNNECESSARY;
> > -	}
> > +	if ((ndev->features & NETIF_F_RXCSUM) &&
> > +	    (cqe->rx_tcp_csum_succeed || cqe->rx_udp_csum_succeed))
> > +		skb->ip_summed = CHECKSUM_UNNECESSARY;
> 
> [Severity: High]
> This problem wasn't introduced by this patch, but can mana_rx_skb() leak
> rxq->xdp_save_va [1] on its drop path when rxq->frag_count > 1?
> 
> When a pre-allocated buffer (from_pool == false) is dropped, mana_rx_skb()
> stores buf_va in rxq->xdp_save_va for reuse:
> 
> drivers/net/ethernet/microsoft/mana/mana_en.c:mana_rx_skb() {
> 	...
> drop:
> 	if (from_pool) {
> 		...
> 	} else {
> 		WARN_ON_ONCE(rxq->xdp_save_va);
> 		/* Save for reuse */
> 		rxq->xdp_save_va = buf_va;
> 	}
> }
> 
> However, mana_get_rxfrag() only checks and reclaims rxq->xdp_save_va when
> rxq->frag_count == 1:
> 
> drivers/net/ethernet/microsoft/mana/mana_en.c:mana_get_rxfrag() {
> 	...
> 	if (rxq->frag_count == 1) {
> 		/* Reuse XDP dropped page if available */
> 		if (rxq->xdp_save_va) {
> 			va = rxq->xdp_save_va;
> 			page = virt_to_head_page(va);
> 			rxq->xdp_save_va = NULL;
> 		...
> 		return va;
> 	}
> 
> 	page =  page_pool_dev_alloc_frag(rxq->page_pool, &offset,
> 					 rxq->alloc_size);
> }
> 
> When rxq->frag_count > 1, mana_get_rxfrag() ignores rxq->xdp_save_va and
> allocates a new fragment from the page pool, so a subsequent drop of a
> pre-allocated buffer triggers the WARN_ON_ONCE() and overwrites
> rxq->xdp_save_va, leaking the saved page.
> 

Since, this is an existing issue, I will fix it in it's own patch.

> [1] https://sashiko.dev/#/bug/linux-2ba39e78-7dc4-4027-a76e-f2d315147bad
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20261109142856.779955-1-hamzamahfooz@linux.microsoft.com?part=1

Re: [PATCH net] net: mana: report RX checksum offload for IPv6

[patchwork-bot+netdevbpf]

Hello:

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

On Mon,  9 Nov 2026 09:28:56 -0500 you wrote:
> The hardware validates TCP and UDP checksums for both IPv4 and IPv6 and
> reports the result in rx_tcp_csum_succeed and rx_udp_csum_succeed.
> However, mana_rx_skb() also requires rx_iphdr_csum_succeed before it
> sets CHECKSUM_UNNECESSARY. That bit is only set for IPv4 (since IPv6
> has no header checksum), so IPv6 TCP and UDP traffic is always
> checksummed again in software.
> 
> [...]

Here is the summary with links:
  - [net] net: mana: report RX checksum offload for IPv6
    https://git.kernel.org/netdev/net/c/bbcd02741c4c

You are awesome, thank you!
-- 
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