[ovs-dev] [RFC PATCH V4 4/9] dp-packet: Fix data_len issue with multi-seg mbufs

[Mark Kavanagh]

From: Michael Qiu <qiudayu at chinac.com>

When a packet is from DPDK source, and it contains
multiple segments, data_len is not equal to the
packet size. This patch fixes this issue.

Co-authored-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
Co-authored-by: Przemyslaw Lal <przemyslawx.lal at intel.com>
Co-authored-by: Marcin Ksiadz <mksiadz at gmail.com>
Co-authored-by: Yuanhan Liu <yliu at fridaylinux.org>

Signed-off-by: Michael Qiu <qiudayu at chinac.com>
Signed-off-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
Signed-off-by: Przemyslaw Lal <przemyslawx.lal at intel.com>
Signed-off-by: Marcin Ksiadz <mksiadz at gmail.com>
Signed-off-by: Yuanhan Liu <yliu at fridaylinux.org>
---
 lib/dp-packet.h | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/lib/dp-packet.h b/lib/dp-packet.h
index 47502ad..7ac0404 100644
--- a/lib/dp-packet.h
+++ b/lib/dp-packet.h
@@ -23,6 +23,7 @@
 #ifdef DPDK_NETDEV
 #include <rte_config.h>
 #include <rte_mbuf.h>
+#include "rte_ether.h"
 #endif
 
 #include "netdev-dpdk.h"
@@ -429,17 +430,14 @@ dp_packet_size(const struct dp_packet *b)
 static inline void
 dp_packet_set_size(struct dp_packet *b, uint32_t v)
 {
-    /* netdev-dpdk does not currently support segmentation; consequently, for
-     * all intents and purposes, 'data_len' (16 bit) and 'pkt_len' (32 bit) may
-     * be used interchangably.
-     *
-     * On the datapath, it is expected that the size of packets
-     * (and thus 'v') will always be <= UINT16_MAX; this means that there is no
-     * loss of accuracy in assigning 'v' to 'data_len'.
+    /*
+     * Assign current segment length. If total length is greater than
+     * max data length in a segment, additional calculation is needed.
      */
-    b->mbuf.data_len = (uint16_t)v;  /* Current seg length. */
-    b->mbuf.pkt_len = v;             /* Total length of all segments linked to
-                                      * this segment. */
+    b->mbuf.data_len = MIN(v, b->mbuf.buf_len - b->mbuf.data_off);
+
+    /* Total length of all segments linked to this segment. */
+    b->mbuf.pkt_len = v;
 }
 
 static inline uint16_t
-- 
1.9.3