Re: [PATCH 04/18] packet: Use iov_tail with packet_add()

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

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On Wed, Apr 02, 2025 at 07:23:29PM +0200, Laurent Vivier wrote:

Needs at least some sort of commit message.

> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

But otherwise,

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

> ---
>  iov.h    |  1 +
>  packet.c | 15 ++++++++++++---
>  packet.h |  8 +++++---
>  tap.c    | 32 ++++++++++++++++++--------------
>  4 files changed, 36 insertions(+), 20 deletions(-)
> 
> diff --git a/iov.h b/iov.h
> index f9b5fdf0803e..99442d031549 100644
> --- a/iov.h
> +++ b/iov.h
> @@ -17,6 +17,7 @@
>  
>  #include <unistd.h>
>  #include <string.h>
> +#include <stdbool.h>
>  
>  #define IOV_OF_LVALUE(lval) \
>  	(struct iovec){ .iov_base = &(lval), .iov_len = sizeof(lval) }
> diff --git a/packet.c b/packet.c
> index bcac03750dc0..8b11e0850ff6 100644
> --- a/packet.c
> +++ b/packet.c
> @@ -64,15 +64,16 @@ static int packet_check_range(const struct pool *p, const char *ptr, size_t len,
>  /**
>   * packet_add_do() - Add data as packet descriptor to given pool
>   * @p:		Existing pool
> - * @len:	Length of new descriptor
> - * @start:	Start of data
> + * @data:	Data to add
>   * @func:	For tracing: name of calling function, NULL means no trace()
>   * @line:	For tracing: caller line of function call
>   */
> -void packet_add_do(struct pool *p, size_t len, const char *start,
> +void packet_add_do(struct pool *p, struct iov_tail *data,
>  		   const char *func, int line)
>  {
>  	size_t idx = p->count;
> +	const char *start;
> +	size_t len;
>  
>  	if (idx >= p->size) {
>  		trace("add packet index %zu to pool with size %zu, %s:%i",
> @@ -80,6 +81,14 @@ void packet_add_do(struct pool *p, size_t len, const char *start,
>  		return;
>  	}
>  
> +	if (!iov_tail_prune(data))
> +		return;
> +
> +	ASSERT(data->cnt == 1); /* we don't support iovec */
> +
> +	len = data->iov[0].iov_len - data->off;
> +	start = (char *)data->iov[0].iov_base + data->off;
> +
>  	if (packet_check_range(p, start, len, func, line))
>  		return;
>  
> diff --git a/packet.h b/packet.h
> index d099f026631b..f386295da203 100644
> --- a/packet.h
> +++ b/packet.h
> @@ -6,6 +6,8 @@
>  #ifndef PACKET_H
>  #define PACKET_H
>  
> +#include "iov.h"
> +
>  /* Maximum size of a single packet stored in pool, including headers */
>  #define PACKET_MAX_LEN	UINT16_MAX
>  
> @@ -28,15 +30,15 @@ struct pool {
>  };
>  
>  int vu_packet_check_range(void *buf, const char *ptr, size_t len);
> -void packet_add_do(struct pool *p, size_t len, const char *start,
> +void packet_add_do(struct pool *p, struct iov_tail *data,
>  		   const char *func, int line);
>  void *packet_get_do(const struct pool *p, const size_t idx,
>  		    size_t offset, size_t len, size_t *left,
>  		    const char *func, int line);
>  void pool_flush(struct pool *p);
>  
> -#define packet_add(p, len, start)					\
> -	packet_add_do(p, len, start, __func__, __LINE__)
> +#define packet_add(p, data)					\
> +	packet_add_do(p, data, __func__, __LINE__)
>  
>  #define packet_get(p, idx, offset, len, left)				\
>  	packet_get_do(p, idx, offset, len, left, __func__, __LINE__)
> diff --git a/tap.c b/tap.c
> index ab3effe80f89..4b54807c4101 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -683,6 +683,7 @@ resume:
>  		size_t l2len, l3len, hlen, l4len;
>  		const struct ethhdr *eh;
>  		const struct udphdr *uh;
> +		struct iov_tail data;
>  		struct iphdr *iph;
>  		const char *l4h;
>  
> @@ -694,7 +695,8 @@ resume:
>  		if (ntohs(eh->h_proto) == ETH_P_ARP) {
>  			PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
>  
> -			packet_add(pkt, l2len, (char *)eh);
> +			data = IOV_TAIL_FROM_BUF((void *)eh, l2len, 0);
> +			packet_add(pkt, &data);
>  			arp(c, pkt);
>  			continue;
>  		}
> @@ -739,7 +741,8 @@ resume:
>  
>  			tap_packet_debug(iph, NULL, NULL, 0, NULL, 1);
>  
> -			packet_add(pkt, l4len, l4h);
> +			data = IOV_TAIL_FROM_BUF((void *)l4h, l4len, 0);
> +			packet_add(pkt, &data);
>  			icmp_tap_handler(c, PIF_TAP, AF_INET,
>  					 &iph->saddr, &iph->daddr,
>  					 pkt, now);
> @@ -753,7 +756,8 @@ resume:
>  		if (iph->protocol == IPPROTO_UDP) {
>  			PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
>  
> -			packet_add(pkt, l2len, (char *)eh);
> +			data = IOV_TAIL_FROM_BUF((void *)eh, l2len, 0);
> +			packet_add(pkt, &data);
>  			if (dhcp(c, pkt))
>  				continue;
>  		}
> @@ -802,7 +806,8 @@ resume:
>  #undef L4_SET
>  
>  append:
> -		packet_add((struct pool *)&seq->p, l4len, l4h);
> +		data = IOV_TAIL_FROM_BUF((void *)l4h, l4len, 0);
> +		packet_add((struct pool *)&seq->p, &data);
>  	}
>  
>  	for (j = 0, seq = tap4_l4; j < seq_count; j++, seq++) {
> @@ -858,6 +863,7 @@ resume:
>  		struct in6_addr *saddr, *daddr;
>  		const struct ethhdr *eh;
>  		const struct udphdr *uh;
> +		struct iov_tail data;
>  		struct ipv6hdr *ip6h;
>  		uint8_t proto;
>  		char *l4h;
> @@ -911,7 +917,8 @@ resume:
>  			if (l4len < sizeof(struct icmp6hdr))
>  				continue;
>  
> -			packet_add(pkt, l4len, l4h);
> +			data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
> +			packet_add(pkt, &data);
>  
>  			if (ndp(c, (struct icmp6hdr *)l4h, saddr, pkt))
>  				continue;
> @@ -930,7 +937,8 @@ resume:
>  		if (proto == IPPROTO_UDP) {
>  			PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
>  
> -			packet_add(pkt, l4len, l4h);
> +			data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
> +			packet_add(pkt, &data);
>  
>  			if (dhcpv6(c, pkt, saddr, daddr))
>  				continue;
> @@ -984,7 +992,8 @@ resume:
>  #undef L4_SET
>  
>  append:
> -		packet_add((struct pool *)&seq->p, l4len, l4h);
> +		data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
> +		packet_add((struct pool *)&seq->p, &data);
>  	}
>  
>  	for (j = 0, seq = tap6_l4; j < seq_count; j++, seq++) {
> @@ -1058,18 +1067,13 @@ void tap_add_packet(struct ctx *c, struct iov_tail *data)
>  		proto_update_l2_buf(c->guest_mac, NULL);
>  	}
>  
> -	iov_tail_prune(data);
> -	ASSERT(data->cnt == 1); /* packet_add() doesn't support iovec */
> -
>  	switch (ntohs(eh->h_proto)) {
>  	case ETH_P_ARP:
>  	case ETH_P_IP:
> -		packet_add(pool_tap4, data->iov[0].iov_len - data->off,
> -			   (char *)data->iov[0].iov_base + data->off);
> +		packet_add(pool_tap4, data);
>  		break;
>  	case ETH_P_IPV6:
> -		packet_add(pool_tap6, data->iov[0].iov_len - data->off,
> -			   (char *)data->iov[0].iov_base + data->off);
> +		packet_add(pool_tap6, data);
>  		break;
>  	default:
>  		break;

-- 
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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