[PATCH] mbuf: fix packet copy

[Morten Brørup]

Forwarding an email is apparently a bad idea; patchwork picked it up as a new patch.

Venlig hilsen / Kind regards,
-Morten Brørup


> -----Original Message-----
> From: Morten Brørup [mailto:mb at smartsharesystems.com]
> Sent: Thursday, 15 January 2026 11.53
> To: Stephen Hemminger
> Cc: dev at dpdk.org; stable at dpdk.org
> Subject: FW: [PATCH] mbuf: fix packet copy
> 
> Stephen,
> 
> As the author of rte_pktmbuf_copy(), can you please review this patch?
> 
> You might find my answers to Konstantin's review informative:
> https://patchwork.dpdk.org/project/dpdk/patch/20251119120403.907511-1-
> mb at smartsharesystems.com/#181914
> 
> 
> Venlig hilsen / Kind regards,
> -Morten Brørup
> 
> 
> From: Morten Brørup [mailto:mb at smartsharesystems.com]
> Sent: Wednesday, 19 November 2025 13.04
> 
> Requests for copying the at the end of a packet incorrectly returned
> NULL,
> as if copying past the end of a packet.
> 
> When allocating copies from a mempool using pinned external buffers,
> the
> external flag was not preserved in these mbufs.
> 
> Fixes: c3a90c381daa ("mbuf: add a copy routine")
> 
> Signed-off-by: Morten Brørup <mb at smartsharesystems.com>
> ---
>  lib/mbuf/rte_mbuf.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/mbuf/rte_mbuf.c b/lib/mbuf/rte_mbuf.c
> index 0d931c7a15..e639aff03e 100644
> --- a/lib/mbuf/rte_mbuf.c
> +++ b/lib/mbuf/rte_mbuf.c
> @@ -675,7 +675,7 @@ rte_pktmbuf_copy(const struct rte_mbuf *m, struct
> rte_mempool *mp,
>  	__rte_mbuf_sanity_check(m, 1);
> 
>  	/* check for request to copy at offset past end of mbuf */
> -	if (unlikely(off >= m->pkt_len))
> +	if (unlikely(off > m->pkt_len))
>  		return NULL;
> 
>  	mc = rte_pktmbuf_alloc(mp);
> @@ -688,8 +688,8 @@ rte_pktmbuf_copy(const struct rte_mbuf *m, struct
> rte_mempool *mp,
> 
>  	__rte_pktmbuf_copy_hdr(mc, m);
> 
> -	/* copied mbuf is not indirect or external */
> -	mc->ol_flags = m->ol_flags &
> ~(RTE_MBUF_F_INDIRECT|RTE_MBUF_F_EXTERNAL);
> +	/* copy flags except indirect and external, and preserve flags of
> newly allocated mbuf */
> +	mc->ol_flags |= m->ol_flags &
> ~(RTE_MBUF_F_INDIRECT|RTE_MBUF_F_EXTERNAL);
> 
>  	prev = &mc->next;
>  	m_last = mc;
> --
> 2.43.0