Re: [PATCH v3] lib/net: add MPLS insert and strip functionality

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 24 Feb 2023 16:06:19 +0500
Tanzeel-inline <tanxeel1.ahmed@gmail.com> wrote:

> +static inline int
> +rte_mpls_strip_over_l2(struct rte_mbuf *m)
> +{
> +	struct rte_ether_hdr *eh = rte_pktmbuf_mtod(m, struct rte_ether_hdr *);
> +	struct rte_mpls_hdr *mph;
> +	bool mpls_exist = true;
> +
> +	if (eh->ether_type != rte_cpu_to_be_16(RTE_ETHER_TYPE_MPLS))
> +		return -1;
> +
> +	/* Stripping all MPLS header */
> +	while (mpls_exist) {
> +		mph = rte_pktmbuf_mtod_offset(m, struct rte_mpls_hdr*,
space required (i.e "struct rte_mpls_hdr *")
> +		sizeof(struct rte_ether_hdr));
> +		if (mph->bs & 1)
> +			mpls_exist = false;
> +		memmove(rte_pktmbuf_adj(m, sizeof(struct rte_mpls_hdr)),
> +		eh, sizeof(struct rte_ether_hdr));
> +		eh = rte_pktmbuf_mtod(m, struct rte_ether_hdr *);
> +	}
> +
> +	return 0;
> +}

This function will fail for the case of segmented mbuf.
Also need to handle case where mbuf is corrupted and just has stack of mpls
tags and the last one is incomplete.