[PATCH] common/mlx5: fix mac deletion on Linux

[PATCH] common/mlx5: fix mac deletion on Linux

[David Marchand]

Re-enable debug logs unconditionally, this helps understanding why mac
deletions were silently failing (while a bridge fdb del command was
working fine).

testpmd> mac_addr add 0 FA:35:44:3F:58:31
testpmd> mac_addr remove 0 FA:35:44:3F:58:31
mlx5_common: Interface 35 cannot remove MAC address FA:35:44:3F:58:31
	Operation not supported

Then, fix mac deletion as the NLM_F_CREATE == 0x200 flag is relevant
with a RTM_NEWNEIGH op.
For a RTM_DELNEIGH op, 0x200 == NLM_F_BULK and passing this flag
makes the deletion fail miserably for a single mac.

Fixes: ccdcba53a3f4 ("net/mlx5: use Netlink to add/remove MAC addresses")
Cc: stable@dpdk.org

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
 drivers/common/mlx5/linux/mlx5_nl.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/common/mlx5/linux/mlx5_nl.c b/drivers/common/mlx5/linux/mlx5_nl.c
index eceb3d796f..b50431fb61 100644
--- a/drivers/common/mlx5/linux/mlx5_nl.c
+++ b/drivers/common/mlx5/linux/mlx5_nl.c
@@ -581,8 +581,8 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
 	} req = {
 		.hdr = {
 			.nlmsg_len = NLMSG_LENGTH(sizeof(struct ndmsg)),
-			.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE |
-				NLM_F_EXCL | NLM_F_ACK,
+			.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK |
+				add ? NLM_F_CREATE | NLM_F_EXCL : 0,
 			.nlmsg_type = add ? RTM_NEWNEIGH : RTM_DELNEIGH,
 		},
 		.ndm = {
@@ -612,7 +612,6 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
 		goto error;
 	return 0;
 error:
-#ifdef RTE_PMD_MLX5_DEBUG
 	{
 		char m[RTE_ETHER_ADDR_FMT_SIZE];
 
@@ -622,7 +621,6 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
 			iface_idx,
 			add ? "add" : "remove", m, strerror(rte_errno));
 	}
-#endif
 	return -rte_errno;
 }
 
-- 
2.53.0

Re: [PATCH] common/mlx5: fix mac deletion on Linux

[David Marchand]

On Wed, 18 Mar 2026 at 17:37, David Marchand <david.marchand@redhat.com> wrote:
>
> Re-enable debug logs unconditionally, this helps understanding why mac
> deletions were silently failing (while a bridge fdb del command was
> working fine).
>
> testpmd> mac_addr add 0 FA:35:44:3F:58:31
> testpmd> mac_addr remove 0 FA:35:44:3F:58:31
> mlx5_common: Interface 35 cannot remove MAC address FA:35:44:3F:58:31
>         Operation not supported
>
> Then, fix mac deletion as the NLM_F_CREATE == 0x200 flag is relevant
> with a RTM_NEWNEIGH op.
> For a RTM_DELNEIGH op, 0x200 == NLM_F_BULK and passing this flag
> makes the deletion fail miserably for a single mac.

This issue is actually triggered after a change in the kernel uapi.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=545528d788556

So the DPDK bug can be seen with kernels >= 5.19 (and in my case, RHEL9).

Probably worth adding in the commitlog.


> Fixes: ccdcba53a3f4 ("net/mlx5: use Netlink to add/remove MAC addresses")
> Cc: stable@dpdk.org
>
> Signed-off-by: David Marchand <david.marchand@redhat.com>


-- 
David Marchand

Re: [PATCH] common/mlx5: fix mac deletion on Linux

[Dariusz Sosnowski]

On Wed, Mar 18, 2026 at 05:36:28PM +0100, David Marchand wrote:
> Re-enable debug logs unconditionally, this helps understanding why mac
> deletions were silently failing (while a bridge fdb del command was
> working fine).
> 
> testpmd> mac_addr add 0 FA:35:44:3F:58:31
> testpmd> mac_addr remove 0 FA:35:44:3F:58:31
> mlx5_common: Interface 35 cannot remove MAC address FA:35:44:3F:58:31
> 	Operation not supported
> 
> Then, fix mac deletion as the NLM_F_CREATE == 0x200 flag is relevant
> with a RTM_NEWNEIGH op.
> For a RTM_DELNEIGH op, 0x200 == NLM_F_BULK and passing this flag
> makes the deletion fail miserably for a single mac.
> 
> Fixes: ccdcba53a3f4 ("net/mlx5: use Netlink to add/remove MAC addresses")
> Cc: stable@dpdk.org
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
>  drivers/common/mlx5/linux/mlx5_nl.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/common/mlx5/linux/mlx5_nl.c b/drivers/common/mlx5/linux/mlx5_nl.c
> index eceb3d796f..b50431fb61 100644
> --- a/drivers/common/mlx5/linux/mlx5_nl.c
> +++ b/drivers/common/mlx5/linux/mlx5_nl.c
> @@ -581,8 +581,8 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
>  	} req = {
>  		.hdr = {
>  			.nlmsg_len = NLMSG_LENGTH(sizeof(struct ndmsg)),
> -			.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE |
> -				NLM_F_EXCL | NLM_F_ACK,
> +			.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK |
> +				add ? NLM_F_CREATE | NLM_F_EXCL : 0,

It seems that this expression is constructed incorrectly.
IIUC this will be "parenthesised" as follows:

	((NLM_F_REQUEST | NLM_F_ACK) | add) ? (NLM_F_CREATE | NLM_F_EXCL) : 0

Since bitwise OR has higher precendence.
So "add" value will be ignored and only "NLM_F_CREATE | NLM_F_EXCL"
will be returned.

Could you please add parenthesis around the ternary?

>  			.nlmsg_type = add ? RTM_NEWNEIGH : RTM_DELNEIGH,
>  		},
>  		.ndm = {
> @@ -612,7 +612,6 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
>  		goto error;
>  	return 0;
>  error:
> -#ifdef RTE_PMD_MLX5_DEBUG
>  	{
>  		char m[RTE_ETHER_ADDR_FMT_SIZE];
>  
> @@ -622,7 +621,6 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
>  			iface_idx,
>  			add ? "add" : "remove", m, strerror(rte_errno));
>  	}
> -#endif
>  	return -rte_errno;
>  }
>  

Best regards,
Dariusz Sosnowski

Re: [PATCH] common/mlx5: fix mac deletion on Linux

[David Marchand]

On Thu, 19 Mar 2026 at 17:06, Dariusz Sosnowski <dsosnowski@nvidia.com> wrote:
>
> On Wed, Mar 18, 2026 at 05:36:28PM +0100, David Marchand wrote:
> > Re-enable debug logs unconditionally, this helps understanding why mac
> > deletions were silently failing (while a bridge fdb del command was
> > working fine).
> >
> > testpmd> mac_addr add 0 FA:35:44:3F:58:31
> > testpmd> mac_addr remove 0 FA:35:44:3F:58:31
> > mlx5_common: Interface 35 cannot remove MAC address FA:35:44:3F:58:31
> >       Operation not supported
> >
> > Then, fix mac deletion as the NLM_F_CREATE == 0x200 flag is relevant
> > with a RTM_NEWNEIGH op.
> > For a RTM_DELNEIGH op, 0x200 == NLM_F_BULK and passing this flag
> > makes the deletion fail miserably for a single mac.
> >
> > Fixes: ccdcba53a3f4 ("net/mlx5: use Netlink to add/remove MAC addresses")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > ---
> >  drivers/common/mlx5/linux/mlx5_nl.c | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/common/mlx5/linux/mlx5_nl.c b/drivers/common/mlx5/linux/mlx5_nl.c
> > index eceb3d796f..b50431fb61 100644
> > --- a/drivers/common/mlx5/linux/mlx5_nl.c
> > +++ b/drivers/common/mlx5/linux/mlx5_nl.c
> > @@ -581,8 +581,8 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
> >       } req = {
> >               .hdr = {
> >                       .nlmsg_len = NLMSG_LENGTH(sizeof(struct ndmsg)),
> > -                     .nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE |
> > -                             NLM_F_EXCL | NLM_F_ACK,
> > +                     .nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK |
> > +                             add ? NLM_F_CREATE | NLM_F_EXCL : 0,
>
> It seems that this expression is constructed incorrectly.
> IIUC this will be "parenthesised" as follows:
>
>         ((NLM_F_REQUEST | NLM_F_ACK) | add) ? (NLM_F_CREATE | NLM_F_EXCL) : 0
>
> Since bitwise OR has higher precendence.
> So "add" value will be ignored and only "NLM_F_CREATE | NLM_F_EXCL"
> will be returned.
>
> Could you please add parenthesis around the ternary?

Ugh.
That's what happens when doing a last minute change with a ternary and
not testing the new patch...
I will send the right fix.


-- 
David Marchand

[PATCH v2] common/mlx5: fix mac deletion on Linux

[David Marchand]

Re-enable debug logs unconditionally, this helps understanding why mac
deletions were silently failing (while a bridge fdb del command was
working fine).

testpmd> mac_addr add 0 FA:35:44:3F:58:31
testpmd> mac_addr remove 0 FA:35:44:3F:58:31
mlx5_common: Interface 35 cannot remove MAC address FA:35:44:3F:58:31
	Operation not supported

Then, fix mac deletion as the NLM_F_CREATE == 0x200 flag is relevant
with a RTM_NEWNEIGH op.

Since kernel v5.19 though, for a RTM_DELNEIGH op, 0x200 == NLM_F_BULK
and passing this flag makes the deletion fail miserably for a single mac.

Fixes: ccdcba53a3f4 ("net/mlx5: use Netlink to add/remove MAC addresses")
Cc: stable@dpdk.org

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
Changes since v1:
- fixed ternary usage... (thanks Dariusz),
- updated commitlog with a mention of Linux version when it got broken,

---
 drivers/common/mlx5/linux/mlx5_nl.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/common/mlx5/linux/mlx5_nl.c b/drivers/common/mlx5/linux/mlx5_nl.c
index eceb3d796f..8b19838a7e 100644
--- a/drivers/common/mlx5/linux/mlx5_nl.c
+++ b/drivers/common/mlx5/linux/mlx5_nl.c
@@ -581,8 +581,8 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
 	} req = {
 		.hdr = {
 			.nlmsg_len = NLMSG_LENGTH(sizeof(struct ndmsg)),
-			.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE |
-				NLM_F_EXCL | NLM_F_ACK,
+			.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK |
+				(add ? NLM_F_CREATE | NLM_F_EXCL : 0),
 			.nlmsg_type = add ? RTM_NEWNEIGH : RTM_DELNEIGH,
 		},
 		.ndm = {
@@ -612,7 +612,6 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
 		goto error;
 	return 0;
 error:
-#ifdef RTE_PMD_MLX5_DEBUG
 	{
 		char m[RTE_ETHER_ADDR_FMT_SIZE];
 
@@ -622,7 +621,6 @@ mlx5_nl_mac_addr_modify(int nlsk_fd, unsigned int iface_idx,
 			iface_idx,
 			add ? "add" : "remove", m, strerror(rte_errno));
 	}
-#endif
 	return -rte_errno;
 }
 
-- 
2.53.0

Re: [PATCH v2] common/mlx5: fix mac deletion on Linux

[Dariusz Sosnowski]

On Fri, Mar 20, 2026 at 03:14:17PM +0100, David Marchand wrote:
> Re-enable debug logs unconditionally, this helps understanding why mac
> deletions were silently failing (while a bridge fdb del command was
> working fine).
> 
> testpmd> mac_addr add 0 FA:35:44:3F:58:31
> testpmd> mac_addr remove 0 FA:35:44:3F:58:31
> mlx5_common: Interface 35 cannot remove MAC address FA:35:44:3F:58:31
> 	Operation not supported
> 
> Then, fix mac deletion as the NLM_F_CREATE == 0x200 flag is relevant
> with a RTM_NEWNEIGH op.
> 
> Since kernel v5.19 though, for a RTM_DELNEIGH op, 0x200 == NLM_F_BULK
> and passing this flag makes the deletion fail miserably for a single mac.
> 
> Fixes: ccdcba53a3f4 ("net/mlx5: use Netlink to add/remove MAC addresses")
> Cc: stable@dpdk.org
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>

Acked-by: Dariusz Sosnowski <dsosnowski@nvidia.com>

Best regards,
Dariusz Sosnowski

Re: [PATCH v2] common/mlx5: fix mac deletion on Linux

[Raslan Darawsheh]

Hi,


On 20/03/2026 4:14 PM, David Marchand wrote:
> Re-enable debug logs unconditionally, this helps understanding why mac
> deletions were silently failing (while a bridge fdb del command was
> working fine).
> 
> testpmd> mac_addr add 0 FA:35:44:3F:58:31
> testpmd> mac_addr remove 0 FA:35:44:3F:58:31
> mlx5_common: Interface 35 cannot remove MAC address FA:35:44:3F:58:31
> 	Operation not supported
> 
> Then, fix mac deletion as the NLM_F_CREATE == 0x200 flag is relevant
> with a RTM_NEWNEIGH op.
> 
> Since kernel v5.19 though, for a RTM_DELNEIGH op, 0x200 == NLM_F_BULK
> and passing this flag makes the deletion fail miserably for a single mac.
> 
> Fixes: ccdcba53a3f4 ("net/mlx5: use Netlink to add/remove MAC addresses")
> Cc: stable@dpdk.org
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>

Patch applied to next-net-mlx,

Kindest regards
Raslan Darawsheh