Re: [PATCH v8 20/30] tap: Convert tap6_handler() to iov_tail

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

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On Tue, Aug 05, 2025 at 05:46:18PM +0200, Laurent Vivier wrote:
> Use packet_data() and extract headers using IOV_REMOVE_HEADER()
> and IOV_PEEK_HEADER() rather than packet_get().
> 
> Remove packet_get() as it is not used anymore.

[snip]
> @@ -896,21 +896,28 @@ resume:
>  	for (seq_count = 0, seq = NULL; i < in->count; i++) {
>  		size_t l4len, plen, check;
>  		struct in6_addr *saddr, *daddr;
> +		struct ipv6hdr ip6h_storage;
> +		struct ethhdr eh_storage;
> +		struct udphdr uh_storage;
>  		const struct ethhdr *eh;
>  		const struct udphdr *uh;
>  		struct iov_tail data;
>  		struct ipv6hdr *ip6h;
>  		uint8_t proto;
> -		char *l4h;
>  
> -		eh =   packet_get(in, i, 0,		sizeof(*eh), NULL);
> +		if (!packet_data(in, i, &data))
> +			return -1;
> +
> +		eh = IOV_REMOVE_HEADER(&data, eh_storage);
>  		if (!eh)
>  			continue;
>  
> -		ip6h = packet_get(in, i, sizeof(*eh),	sizeof(*ip6h), &check);
> +		ip6h = IOV_PEEK_HEADER(&data, ip6h_storage);
>  		if (!ip6h)
>  			continue;

You peek the IPv6 header here, but I haven't spotted where you remove
/ drop it before...

> +		check = iov_tail_size(&data) - sizeof(*ip6h);
> +
>  		saddr = &ip6h->saddr;
>  		daddr = &ip6h->daddr;
>  
> @@ -918,10 +925,8 @@ 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];
> @@ -946,6 +951,8 @@ resume:
>  		}
>  
>  		if (proto == IPPROTO_ICMPV6) {
> +			struct icmp6hdr l4h_storage;
> +			const struct icmp6hdr *l4h;
>  			PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
>  
>  			if (c->no_icmp)
> @@ -954,9 +961,9 @@ resume:
>  			if (l4len < sizeof(struct icmp6hdr))
>  				continue;
>  
> -			data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
>  			packet_add(pkt, &data);
>  
> +			l4h = IOV_PEEK_HEADER(&data, l4h_storage);

... peeking the next header here.

>  			if (ndp(c, (struct icmp6hdr *)l4h, saddr, pkt))
>  				continue;
>  
> @@ -969,12 +976,13 @@ resume:
>  
>  		if (l4len < sizeof(*uh))
>  			continue;
> -		uh = (struct udphdr *)l4h;
> +		uh = IOV_PEEK_HEADER(&data, uh_storage);

And here.

> +		if (!uh)
> +			continue;
>  
>  		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))
> @@ -1031,7 +1039,6 @@ 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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