Re: [PATCH v5 08/12] dhcp/dhcpv6: Pass queue pair explicitly through DHCP send path

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

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On Tue, Jun 16, 2026 at 02:51:26PM +0200, Laurent Vivier wrote:
> Add a qpair parameter to dhcp(), dhcpv6(), and
> dhcpv6_send_ia_notonlink(), forwarding it to tap_udp4_send() and
> tap_udp6_send() instead of hardcoding QPAIR_DEFAULT.
> 
> No functional change.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

These ones make sense to me since a) there's no associated flow and b)
we're always sending in direct response to a guest message that must
have come on a particular queue.

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

> ---
>  dhcp.c   |  6 +++---
>  dhcp.h   |  2 +-
>  dhcpv6.c | 12 +++++++-----
>  dhcpv6.h |  2 +-
>  tap.c    |  4 ++--
>  5 files changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/dhcp.c b/dhcp.c
> index e652659138b8..6ff094c9179e 100644
> --- a/dhcp.c
> +++ b/dhcp.c
> @@ -296,11 +296,12 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
>  /**
>   * dhcp() - Check if this is a DHCP message, reply as needed
>   * @c:		Execution context
> + * @qpair:	Queue pair on which to send the reply
>   * @data:	Single packet with Ethernet buffer
>   *
>   * Return: 0 if it's not a DHCP message, 1 if handled, -1 on failure
>   */
> -int dhcp(const struct ctx *c, struct iov_tail *data)
> +int dhcp(const struct ctx *c, unsigned int qpair, struct iov_tail *data)
>  {
>  	char macstr[ETH_ADDRSTRLEN];
>  	size_t mlen, dlen, opt_len;
> @@ -473,8 +474,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
>  	else
>  		dst = c->ip4.addr;
>  
> -	tap_udp4_send(c, QPAIR_DEFAULT, c->ip4.our_tap_addr, 67, dst, 68,
> -		      &reply, dlen);
> +	tap_udp4_send(c, qpair, c->ip4.our_tap_addr, 67, dst, 68, &reply, dlen);
>  
>  	return 1;
>  }
> diff --git a/dhcp.h b/dhcp.h
> index cd50c99b8856..6d034f0c58af 100644
> --- a/dhcp.h
> +++ b/dhcp.h
> @@ -6,7 +6,7 @@
>  #ifndef DHCP_H
>  #define DHCP_H
>  
> -int dhcp(const struct ctx *c, struct iov_tail *data);
> +int dhcp(const struct ctx *c, unsigned int qpair, struct iov_tail *data);
>  void dhcp_init(void);
>  
>  #endif /* DHCP_H */
> diff --git a/dhcpv6.c b/dhcpv6.c
> index f4ebeccf912c..3c97c921a849 100644
> --- a/dhcpv6.c
> +++ b/dhcpv6.c
> @@ -370,12 +370,13 @@ notonlink:
>  /**
>   * dhcpv6_send_ia_notonlink() - Send NotOnLink status
>   * @c:			Execution context
> + * @qpair:		Queue pair on which to send the reply
>   * @ia_base:		Non-appropriate IA_NA or IA_TA base
>   * @client_id_base:	Client ID message option base
>   * @len:		Client ID length
>   * @xid:		Transaction ID for message exchange
>   */
> -static void dhcpv6_send_ia_notonlink(struct ctx *c,
> +static void dhcpv6_send_ia_notonlink(struct ctx *c, unsigned int qpair,
>  				     const struct iov_tail *ia_base,
>  				     const struct iov_tail *client_id_base,
>  				     int len, uint32_t xid)
> @@ -405,7 +406,7 @@ static void dhcpv6_send_ia_notonlink(struct ctx *c,
>  
>  	resp_not_on_link.hdr.xid = xid;
>  
> -	tap_udp6_send(c, QPAIR_DEFAULT, src, 547, tap_ip6_daddr(c, src), 546,
> +	tap_udp6_send(c, qpair, src, 547, tap_ip6_daddr(c, src), 546,
>  		      xid, &resp_not_on_link, n);
>  }
>  
> @@ -542,13 +543,14 @@ static size_t dhcpv6_client_fqdn_fill(const struct iov_tail *data,
>  /**
>   * dhcpv6() - Check if this is a DHCPv6 message, reply as needed
>   * @c:		Execution context
> + * @qpair:	Queue pair on which to send the reply
>   * @data:	Single packet starting from UDP header
>   * @saddr:	Source IPv6 address of original message
>   * @daddr:	Destination IPv6 address of original message
>   *
>   * Return: 0 if it's not a DHCPv6 message, 1 if handled, -1 on failure
>   */
> -int dhcpv6(struct ctx *c, struct iov_tail *data,
> +int dhcpv6(struct ctx *c, unsigned int qpair, struct iov_tail *data,
>  	   const struct in6_addr *saddr, const struct in6_addr *daddr)
>  {
>  	const struct opt_server_id *server_id = NULL;
> @@ -630,7 +632,7 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
>  
>  		if (dhcpv6_ia_notonlink(data, &c->ip6.addr)) {
>  
> -			dhcpv6_send_ia_notonlink(c, data, &client_id_base,
> +			dhcpv6_send_ia_notonlink(c, qpair, data, &client_id_base,
>  						 ntohs(client_id->l), mh->xid);
>  
>  			return 1;
> @@ -680,7 +682,7 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
>  
>  	resp.hdr.xid = mh->xid;
>  
> -	tap_udp6_send(c, QPAIR_DEFAULT, src, 547, tap_ip6_daddr(c, src), 546,
> +	tap_udp6_send(c, qpair, src, 547, tap_ip6_daddr(c, src), 546,
>  		      mh->xid, &resp, n);
>  	c->ip6.addr_seen = c->ip6.addr;
>  
> diff --git a/dhcpv6.h b/dhcpv6.h
> index c706dfdbb2ac..3a249b39e6c7 100644
> --- a/dhcpv6.h
> +++ b/dhcpv6.h
> @@ -6,7 +6,7 @@
>  #ifndef DHCPV6_H
>  #define DHCPV6_H
>  
> -int dhcpv6(struct ctx *c, struct iov_tail *data,
> +int dhcpv6(struct ctx *c, unsigned int qpair, struct iov_tail *data,
>  	   struct in6_addr *saddr, struct in6_addr *daddr);
>  void dhcpv6_init(const struct ctx *c);
>  
> diff --git a/tap.c b/tap.c
> index e8fd3661ebb5..8e19390f7273 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -805,7 +805,7 @@ resume:
>  			struct iov_tail eh_data;
>  
>  			packet_get(pool_tap4, i, &eh_data);
> -			if (dhcp(c, &eh_data))
> +			if (dhcp(c, qpair, &eh_data))
>  				continue;
>  		}
>  
> @@ -1049,7 +1049,7 @@ resume:
>  		if (proto == IPPROTO_UDP) {
>  			struct iov_tail uh_data = data;
>  
> -			if (dhcpv6(c, &uh_data, saddr, daddr))
> +			if (dhcpv6(c, qpair, &uh_data, saddr, daddr))
>  				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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