[PATCH] mbuf: fix packet copy

Morten Brørup
2025-11-19T12:04:07Z

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@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