Re: [PATCH 18/18] tap: Convert to iov_tail

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

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On Wed, Apr 02, 2025 at 07:23:43PM +0200, Laurent Vivier wrote:
> Use packet_base() and extract headers using IOV_REMOVE_HEADER()
> and IOV_PEEK_HEADER() rather than packet_get().

Patch description is a duplicate of 16/18, which is kind of confusing.

> 
> Remove packet_get() as it is not used anymore.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>  packet.c | 53 -----------------------------------------------------
>  packet.h | 10 ----------
>  tap.c    | 23 ++++++++++++++---------
>  3 files changed, 14 insertions(+), 72 deletions(-)
> 
> diff --git a/packet.c b/packet.c
> index 8066ac12502b..e917b0daad2a 100644
> --- a/packet.c
> +++ b/packet.c
> @@ -103,59 +103,6 @@ void packet_add_do(struct pool *p, struct iov_tail *data,
>  	p->count++;
>  }
>  
> -/**
> - * packet_get_do() - Get data range from packet descriptor from given pool
> - * @p:		Packet pool
> - * @idx:	Index of packet descriptor in pool
> - * @offset:	Offset of data range in packet descriptor
> - * @len:	Length of desired data range
> - * @left:	Length of available data after range, set on return, can be NULL
> - * @func:	For tracing: name of calling function, NULL means no trace()
> - * @line:	For tracing: caller line of function call
> - *
> - * Return: pointer to start of data range, NULL on invalid range or descriptor
> - */
> -void *packet_get_do(const struct pool *p, size_t idx, size_t offset,
> -		    size_t len, size_t *left, const char *func, int line)
> -{
> -	char *ptr;
> -
> -	if (idx >= p->size || idx >= p->count) {
> -		if (func) {
> -			trace("packet %zu from pool size: %zu, count: %zu, "
> -			      "%s:%i", idx, p->size, p->count, func, line);
> -		}
> -		return NULL;
> -	}
> -
> -	if (len > PACKET_MAX_LEN) {
> -		if (func) {
> -			trace("packet data length %zu, %s:%i",
> -			      len, func, line);
> -		}
> -		return NULL;
> -	}
> -
> -	if (len + offset > p->pkt[idx].iov_len) {
> -		if (func) {
> -			trace("data length %zu, offset %zu from length %zu, "
> -			      "%s:%i", len, offset, p->pkt[idx].iov_len,
> -			      func, line);
> -		}
> -		return NULL;
> -	}
> -
> -	ptr = (char *)p->pkt[idx].iov_base + offset;
> -
> -	if (packet_check_range(p, ptr, len, func, line))
> -		return NULL;
> -
> -	if (left)
> -		*left = p->pkt[idx].iov_len - offset - len;
> -
> -	return ptr;
> -}
> -
>  /**
>   * packet_base_do() - Get data range from packet descriptor from given pool
>   * @p:		Packet pool
> diff --git a/packet.h b/packet.h
> index 35058e747a43..787535a228a5 100644
> --- a/packet.h
> +++ b/packet.h
> @@ -32,9 +32,6 @@ struct pool {
>  int vu_packet_check_range(void *buf, const char *ptr, size_t len);
>  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);
>  bool packet_base_do(const struct pool *p, const size_t idx,
>  		    struct iov_tail *data,
>  		    const char *func, int line);
> @@ -43,13 +40,6 @@ void pool_flush(struct pool *p);
>  #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__)
> -
> -
> -#define packet_get_try(p, idx, offset, len, left)			\
> -	packet_get_do(p, idx, offset, len, left, NULL, 0)
> -
>  #define packet_base(p, idx, data)					\
>  	packet_base_do(p, idx, data, __func__, __LINE__)
>  
> diff --git a/tap.c b/tap.c
> index 280a04981954..d6a1da8481a2 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -870,17 +870,24 @@ resume:
>  		const struct udphdr *uh;
>  		struct iov_tail data;
>  		struct ipv6hdr *ip6h;
> +		struct ipv6hdr ip6hc;
> +		struct ethhdr ehc;
> +		struct udphdr uhc;
>  		uint8_t proto;
> -		char *l4h;
>  
> -		eh =   packet_get(in, i, 0,		sizeof(*eh), NULL);
> +		if (!packet_base(in, i, &data))
> +			return -1;
> +
> +		eh = IOV_REMOVE_HEADER(&data, ehc);
>  		if (!eh)
>  			continue;
>  
> -		ip6h = packet_get(in, i, sizeof(*eh),	sizeof(*ip6h), &check);
> +		ip6h = IOV_PEEK_HEADER(&data, ip6hc);
>  		if (!ip6h)
>  			continue;
>  
> +		check = iov_tail_size(&data) - sizeof(*ip6h);
> +
>  		saddr = &ip6h->saddr;
>  		daddr = &ip6h->daddr;
>  
> @@ -888,10 +895,8 @@ resume:
>  		if (plen != check)
>  			continue;
>  
> -		data = IOV_TAIL_FROM_BUF(ip6h, sizeof(*ip6h) + check, 0);
>  		if (!ipv6_l4hdr(&data, &proto, &l4len))
>  			continue;
> -		l4h = (char *)data.iov[0].iov_base + data.off;
>  
>  		if (IN6_IS_ADDR_LOOPBACK(saddr) || IN6_IS_ADDR_LOOPBACK(daddr)) {
>  			char sstr[INET6_ADDRSTRLEN], dstr[INET6_ADDRSTRLEN];
> @@ -916,6 +921,8 @@ resume:
>  		}
>  
>  		if (proto == IPPROTO_ICMPV6) {
> +			const struct icmp6hdr *l4h;
> +			struct icmp6hdr l4hc;
>  			PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
>  
>  			if (c->no_icmp)
> @@ -924,9 +931,9 @@ resume:
>  			if (l4len < sizeof(struct icmp6hdr))
>  				continue;
>  
> -			data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
>  			packet_add(pkt, &data);
>  
> +			l4h = IOV_PEEK_HEADER(&data, l4hc);
>  			if (ndp(c, (struct icmp6hdr *)l4h, saddr, pkt))
>  				continue;
>  
> @@ -939,12 +946,11 @@ resume:
>  
>  		if (l4len < sizeof(*uh))
>  			continue;

Shouldn't need this explicit check - peek_header will do it for you.

> -		uh = (struct udphdr *)l4h;
> +		uh = IOV_PEEK_HEADER(&data, uhc);
>  
>  		if (proto == IPPROTO_UDP) {
>  			PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
>  
> -			data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
>  			packet_add(pkt, &data);
>  
>  			if (dhcpv6(c, pkt, saddr, daddr))
> @@ -999,7 +1005,6 @@ resume:
>  #undef L4_SET
>  
>  append:
> -		data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
>  		packet_add((struct pool *)&seq->p, &data);
>  	}
>  

-- 
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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