net/memif: fix overwriting of head segment

[ upstream commit 10c4c4d ]

The 'dst_off' was reset in multi segment case.
This caused memif buffer segment to write to
beginning of mbuf, overwriting previous data.
Fix it with this patch.

Fixes: 09c7e63 ("net/memif: introduce memory interface PMD")

Reported-by: Ferruh Yigit <ferruh.yigit@xilinx.com>
Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>

drivers/net/memif/rte_eth_memif.c

@@ -349,13 +349,13 @@ eth_memif_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 			goto no_free_bufs;
 		mbuf = mbuf_head;
 		mbuf->port = mq->in_port;
+		dst_off = 0;
 
 next_slot:
 		s0 = cur_slot & mask;
 		d0 = &ring->desc[s0];
 
 		src_len = d0->length;
-		dst_off = 0;
 		src_off = 0;
 
 		do {