FW: [PATCH] mbuf: fix packet copy

[Morten Brørup]

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@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