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

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

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On Fri, Aug 08, 2025 at 03:57:04PM +0200, Laurent Vivier wrote:
> On 06/08/2025 08:21, David Gibson wrote:
> > 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...
> > 
> 
> In fact, data offset is modified by ipv6_l4hdr() that scans the headers and
> the data provided to ipv6_l4hdr() must point to an ipv6hdr (it provides also
> the proto that is alloed to do the correct IOV_PEEK_HEADER()).

Ah, right.

-- 
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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