Re: [PATCH v9 9/9] arp/ndp: send gratuitous ARP / unsolicitated NA when MAC cache entry added

[Jon Maloy <jmaloy@redhat.com>]

On 2025-09-25 02:38, David Gibson wrote:
> On Wed, Sep 24, 2025 at 07:32:43PM -0400, Jon Maloy wrote:
>>
>>
>> On 2025-09-24 18:18, Jon Maloy wrote:
>>>
>>>
>>> On 2025-09-23 23:22, David Gibson wrote:
>>>> On Tue, Sep 23, 2025 at 09:13:30PM -0400, Jon Maloy wrote:
>>
>> [...]
>>
>>>>> --- a/fwd.c
>>>>> +++ b/fwd.c
>>>>> @@ -26,6 +26,8 @@
>>>>>    #include "passt.h"
>>>>>    #include "lineread.h"
>>>>>    #include "flow_table.h"
>>>>> +#include "arp.h"
>>>>> +#include "ndp.h"
>>>>>    /* Empheral port range: values from RFC 6335 */
>>>>>    static in_port_t fwd_ephemeral_min = (1 << 15) + (1 << 14);
>>>>> @@ -129,6 +131,15 @@ void fwd_neigh_mac_cache_alloc(const struct ctx *c,
>>>>>        memcpy(&e->addr, addr, sizeof(*addr));
>>>>>        memcpy(e->mac, mac, ETH_ALEN);
>>>>> +
>>>>> +    /* Send gratuitous ARP / unsolicited NA for the new mapping */
>>>>
>>>> AFAICT this doesn't actually implement what the commit message
>>>> describes - it seems to always send an ARP/NA when the neighbour table
>>>> is updated.
>>
>> No. Check the code again.
> 
> Still not seeing it, I'm going to need a more specific pointer to what
> I've missed.
> 
Look in fwd_neigh_mac_cache_alloc().
If the entry already exists, the function updates the mac address just 
to be on the safe side, but then returns without sending any ARP/NA.
Or do I misunderstand your question?

/jon