Re: [RFC] ip_frag: support IPv6 reassembly with extensions

[Thomas Monjalon <thomas@monjalon.net>]

14/02/2024 04:51, Stephen Hemminger:
> On Tue, 13 Feb 2024 12:47:27 +0100
> <vignesh.purushotham.srinivas@ericsson.com> wrote:
> 
> > +/*
> > + * Function to crawl through the extension header stack.
> > + * This function breaks as soon a the fragment header is
> > + * found and returns the total length the traversed exts
> > + * and the last extension before the fragment header
> > + */
> > +static inline uint32_t
> > +ip_frag_get_last_exthdr(struct rte_ipv6_hdr *ip_hdr, uint8_t **last_ext)
> > +{
> > +	uint32_t total_len = 0;
> > +	size_t ext_len = 0;
> > +	*last_ext = (uint8_t *)(ip_hdr + 1);
> > +	int next_proto = ip_hdr->proto;
> > +
> > +	while (next_proto != IPPROTO_FRAGMENT &&
> > +		(next_proto = rte_ipv6_get_next_ext(
> > +		*last_ext, next_proto, &ext_len)) >= 0) {
> > +
> > +		total_len += ext_len;
> > +
> > +		if (next_proto == IPPROTO_FRAGMENT)
> > +			return total_len;
> > +
> > +		*last_ext += ext_len;
> > +	}
> > +
> > +	return total_len;
> > +}
> 
> Doing endless loop like this opens up DoS attacks.
> Better to use rte_next_skip_ip6_ext() or do similar limited loop.

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