Re: [PATCH v6 05/12] arp: Pass queue pair explicitly through ARP send path

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Jul 31, 2026 at 06:16:10PM +0200, Laurent Vivier wrote:
> Add a qpair parameter to arp(), forwarding it to tap_send_single()
> instead of hardcoding QPAIR_DEFAULT, so replies go out on the same
> queue pair the request arrived on.
> 
> arp_send_init_req() and arp_announce() are unsolicited, low-volume
> messages with no meaningful queue pair context, so they hardcode
> QPAIR_DEFAULT internally.
> 
> No functional change.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  arp.c | 5 +++--
>  arp.h | 2 +-
>  tap.c | 2 +-
>  3 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/arp.c b/arp.c
> index e97c4de86a99..a12b50ff8439 100644
> --- a/arp.c
> +++ b/arp.c
> @@ -63,11 +63,12 @@ static bool ignore_arp(const struct ctx *c,
>  /**
>   * arp() - Check if this is a supported ARP message, reply as needed
>   * @c:		Execution context
> + * @qpair:	Queue pair on which to send the reply
>   * @data:	Single packet with Ethernet buffer
>   *
>   * Return: 1 if handled, -1 on failure
>   */
> -int arp(const struct ctx *c, struct iov_tail *data)
> +int arp(const struct ctx *c, unsigned int qpair, struct iov_tail *data)
>  {
>  	union inany_addr tgt;
>  	struct {
> @@ -112,7 +113,7 @@ int arp(const struct ctx *c, struct iov_tail *data)
>  	memcpy(resp.am.tha,		am->sha,	sizeof(resp.am.tha));
>  	memcpy(resp.am.tip,		am->sip,	sizeof(resp.am.tip));
>  
> -	tap_send_single(c, QPAIR_DEFAULT, &resp, sizeof(resp));
> +	tap_send_single(c, qpair, &resp, sizeof(resp));
>  
>  	return 1;
>  }
> diff --git a/arp.h b/arp.h
> index 4b1f38bcec9b..5872b535635a 100644
> --- a/arp.h
> +++ b/arp.h
> @@ -22,7 +22,7 @@ struct arpmsg {
>  	unsigned char tip[4];
>  } __attribute__((__packed__));
>  
> -int arp(const struct ctx *c, struct iov_tail *data);
> +int arp(const struct ctx *c, unsigned int qpair, struct iov_tail *data);
>  void arp_send_init_req(const struct ctx *c);
>  void arp_announce(const struct ctx *c, struct in_addr *ip,
>  		  const unsigned char *mac);
> diff --git a/tap.c b/tap.c
> index 206a1c36b779..928cf5c086ee 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -727,7 +727,7 @@ resume:
>  		if (!eh)
>  			continue;
>  		if (ntohs(eh->h_proto) == ETH_P_ARP) {
> -			arp(c, &data);
> +			arp(c, qpair, &data);
>  			continue;
>  		}
>  
> -- 
> 2.54.0
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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