[PATCH dpdk v5 4/5] net: parse L3 protocol after MPLS labels

[Stephen Hemminger]

On Mon, 18 May 2026 15:27:18 +0200
Robin Jarry <rjarry at redhat.com> wrote:

> rte_net_get_ptype stops at the MPLS layer and never identifies the L3
> protocol of the payload. Also, the label parsing uses a fixed maximum of
> 5 headers instead of checking the bottom of stack bit.
> 
> Use the bottom of stack bit to consume all labels and inspect the first
> nibble of the payload to determine if it is IPv4 or IPv6.
> 
> Add test cases to verify this works. Ensure that an unknown protocol
> after MPLS (e.g. ARP) does not produce a bogus L3 type.
> 
> Signed-off-by: Robin Jarry <rjarry at redhat.com>
> ---
Re: [PATCH dpdk v5 4/5] net: parse L3 protocol after MPLS labels

Info:

The local variable name `nimble` (and its companion `nimble_copy`) appears
to be a typo for `nibble`. A nibble is the standard term for 4 bits, which
is what the code reads and masks against `0xf0`. The commit message itself
uses the correct spelling ("inspect the first nibble of the payload"), so
only the code is affected.

	const uint8_t *nimble;
	uint8_t nimble_copy;
	...
	nimble = rte_pktmbuf_read(m, off, sizeof(*nimble), &nimble_copy);
	if (nimble == NULL)
		return pkt_type;
	switch (*nimble & 0xf0) {

Suggest renaming to `nibble`/`nibble_copy` for clarity.