Re: [PATCH v8 24/30] dhcpv6: use iov_tail rather than pool

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

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On Tue, Aug 05, 2025 at 05:46:22PM +0200, Laurent Vivier wrote:
> This patch refactors the dhcpv6() function to accept `struct iov_tail *data`
> directly as its packet input, replacing the `const struct pool *p` parameter.
> Consequently, dhcpv6() no longer fetches packet data internally using
> packet_data().
> 
> This change simplifies callers, such as tap6_handler(), which now pass
> the iov_tail representing the L4 UDP segment (DHCPv6 message) directly.
> This removes the need for intermediate packet pool handling.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

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

> ---
>  dhcpv6.c | 29 +++++++++++++----------------
>  dhcpv6.h |  2 +-
>  tap.c    |  6 ++----
>  3 files changed, 16 insertions(+), 21 deletions(-)
> 
> diff --git a/dhcpv6.c b/dhcpv6.c
> index f54a75c642df..52611d742b0b 100644
> --- a/dhcpv6.c
> +++ b/dhcpv6.c
> @@ -539,19 +539,19 @@ 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
> - * @p:		Packet pool, single packet starting from UDP header
> + * @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, const struct pool *p,
> +int dhcpv6(struct ctx *c, struct iov_tail *data,
>  	   const struct in6_addr *saddr, const struct in6_addr *daddr)
>  {
>  	const struct opt_server_id *server_id = NULL;
> -	struct iov_tail data, opt, client_id_base;
>  	const struct opt_hdr *client_id = NULL;
>  	struct opt_server_id server_id_storage;
> +	struct iov_tail opt, client_id_base;
>  	const struct opt_ia_na *ia = NULL;
>  	struct opt_hdr client_id_storage;
>  	struct opt_ia_na ia_storage;
> @@ -562,10 +562,7 @@ int dhcpv6(struct ctx *c, const struct pool *p,
>  	const struct udphdr *uh;
>  	size_t mlen, n;
>  
> -	if (!packet_get(p, 0, &data))
> -		return -1;
> -
> -	uh = IOV_REMOVE_HEADER(&data, uh_storage);
> +	uh = IOV_REMOVE_HEADER(data, uh_storage);
>  	if (!uh)
>  		return -1;
>  
> @@ -578,7 +575,7 @@ int dhcpv6(struct ctx *c, const struct pool *p,
>  	if (!IN6_IS_ADDR_MULTICAST(daddr))
>  		return -1;
>  
> -	mlen = iov_tail_size(&data);
> +	mlen = iov_tail_size(data);
>  	if (mlen + sizeof(*uh) != ntohs(uh->len) || mlen < sizeof(*mh))
>  		return -1;
>  
> @@ -586,23 +583,23 @@ int dhcpv6(struct ctx *c, const struct pool *p,
>  
>  	src = &c->ip6.our_tap_ll;
>  
> -	mh = IOV_REMOVE_HEADER(&data, mh_storage);
> +	mh = IOV_REMOVE_HEADER(data, mh_storage);
>  	if (!mh)
>  		return -1;
>  
> -	client_id_base = data;
> +	client_id_base = *data;
>  	if (dhcpv6_opt(&client_id_base, OPT_CLIENTID))
>  		client_id = IOV_PEEK_HEADER(&client_id_base, client_id_storage);
>  	if (!client_id || ntohs(client_id->l) > OPT_VSIZE(client_id))
>  		return -1;
>  
> -	opt = data;
> +	opt = *data;
>  	if (dhcpv6_opt(&opt, OPT_SERVERID))
>  		server_id = IOV_PEEK_HEADER(&opt, server_id_storage);
>  	if (server_id && ntohs(server_id->hdr.l) != OPT_VSIZE(server_id))
>  		return -1;
>  
> -	opt = data;
> +	opt = *data;
>  	if (dhcpv6_opt(&opt, OPT_IA_NA))
>  		ia = IOV_PEEK_HEADER(&opt, ia_storage);
>  	if (ia && ntohs(ia->hdr.l) < MIN(OPT_VSIZE(ia_na), OPT_VSIZE(ia_ta)))
> @@ -620,9 +617,9 @@ int dhcpv6(struct ctx *c, const struct pool *p,
>  		if (mh->type == TYPE_CONFIRM && server_id)
>  			return -1;
>  
> -		if (dhcpv6_ia_notonlink(&data, &c->ip6.addr)) {
> +		if (dhcpv6_ia_notonlink(data, &c->ip6.addr)) {
>  
> -			dhcpv6_send_ia_notonlink(c, &data, &client_id_base,
> +			dhcpv6_send_ia_notonlink(c, data, &client_id_base,
>  						 ntohs(client_id->l), mh->xid);
>  
>  			return 1;
> @@ -635,7 +632,7 @@ int dhcpv6(struct ctx *c, const struct pool *p,
>  		    memcmp(&resp.server_id, server_id, sizeof(resp.server_id)))
>  			return -1;
>  
> -		if (ia || dhcpv6_opt(&data, OPT_IA_TA))
> +		if (ia || dhcpv6_opt(data, OPT_IA_TA))
>  			return -1;
>  
>  		info("DHCPv6: received INFORMATION_REQUEST, sending REPLY");
> @@ -668,7 +665,7 @@ int dhcpv6(struct ctx *c, const struct pool *p,
>  	n = offsetof(struct resp_t, client_id) +
>  	    sizeof(struct opt_hdr) + ntohs(client_id->l);
>  	n = dhcpv6_dns_fill(c, (char *)&resp, n);
> -	n = dhcpv6_client_fqdn_fill(&data, c, (char *)&resp, n);
> +	n = dhcpv6_client_fqdn_fill(data, c, (char *)&resp, n);
>  
>  	resp.hdr.xid = mh->xid;
>  
> diff --git a/dhcpv6.h b/dhcpv6.h
> index 580998862227..c706dfdbb2ac 100644
> --- a/dhcpv6.h
> +++ b/dhcpv6.h
> @@ -6,7 +6,7 @@
>  #ifndef DHCPV6_H
>  #define DHCPV6_H
>  
> -int dhcpv6(struct ctx *c, const struct pool *p,
> +int dhcpv6(struct ctx *c, 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 7d7e89304723..3262b44c4287 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -975,11 +975,9 @@ resume:
>  			continue;
>  
>  		if (proto == IPPROTO_UDP) {
> -			PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
> -
> -			packet_add(pkt, &data);
> +			struct iov_tail uh_data = data;
>  
> -			if (dhcpv6(c, pkt, saddr, daddr))
> +			if (dhcpv6(c, &uh_data, saddr, daddr))
>  				continue;
>  		}
>  

-- 
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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