[ovs-dev] [PATCH v3 02/14] dp-packet: Init specific mbuf fields.

Tiago Lam tiago.lam at intel.com
Thu Jul 5 16:29:17 UTC 2018

From: Mark Kavanagh <mark.b.kavanagh at intel.com>

dp_packets are created using xmalloc(); in the case of OvS-DPDK, it's
possible the the resultant mbuf portion of the dp_packet contains
random data. For some mbuf fields, specifically those related to
multi-segment mbufs and/or offload features, random values may cause
unexpected behaviour, should the dp_packet's contents be later copied
to a DPDK mbuf. It is critical therefore, that these fields should be
initialized to 0.

This patch ensures that the following mbuf fields are initialized to
appropriate values on creation of a new dp_packet:
   - ol_flags=0
   - nb_segs=1
   - tx_offload=0
   - packet_type=0
   - next=NULL

Adapted from an idea by Michael Qiu <qiudayu at chinac.com>:

Co-authored-by: Tiago Lam <tiago.lam at intel.com>

Signed-off-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
Signed-off-by: Tiago Lam <tiago.lam at intel.com>
Acked-by: Eelco Chaudron <echaudro at redhat.com>
 lib/dp-packet.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/dp-packet.h b/lib/dp-packet.h
index 596cfe6..cfe0824 100644
--- a/lib/dp-packet.h
+++ b/lib/dp-packet.h
@@ -625,14 +625,15 @@ dp_packet_mbuf_rss_flag_reset(struct dp_packet *p OVS_UNUSED)
 /* This initialization is needed for packets that do not come
- * from DPDK interfaces, when vswitchd is built with --with-dpdk.
- * The DPDK rte library will still otherwise manage the mbuf.
- * We only need to initialize the mbuf ol_flags. */
+ * from DPDK interfaces, when vswitchd is built with --with-dpdk. */
 static inline void
 dp_packet_mbuf_init(struct dp_packet *p OVS_UNUSED)
-    p->mbuf.ol_flags = 0;
+    struct rte_mbuf *mbuf = &(p->mbuf);
+    mbuf->ol_flags = mbuf->tx_offload = mbuf->packet_type = 0;
+    mbuf->nb_segs = 1;
+    mbuf->next = NULL;

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