examples/ip_fragmentation: fix fail to start on i40e
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Commit Message
Previous commit sets mtu to the same value as max_rx_pkt_len.
Though PMDs (at least Intel ones) consider MTU as
max_rx_pkt_len minus ether header, crc bytes, vlan tags.
Fixes: 73d2c1d3f33c ("examples/ip_fragmentation: support big packets")
Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
---
examples/ip_fragmentation/main.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
Comments
16/01/2019 13:55, Konstantin Ananyev:
> Previous commit sets mtu to the same value as max_rx_pkt_len.
> Though PMDs (at least Intel ones) consider MTU as
> max_rx_pkt_len minus ether header, crc bytes, vlan tags.
>
> Fixes: 73d2c1d3f33c ("examples/ip_fragmentation: support big packets")
> Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Applied, thanks
@@ -55,6 +55,13 @@
#define IPV4_MTU_DEFAULT ETHER_MTU
#define IPV6_MTU_DEFAULT ETHER_MTU
+/*
+ * The overhead from max frame size to MTU.
+ * We have to consider the max possible overhead.
+ */
+#define MTU_OVERHEAD \
+ (ETHER_HDR_LEN + ETHER_CRC_LEN + 2 * sizeof(struct vlan_hdr))
+
/*
* Default payload in bytes for the IPv6 packet.
*/
@@ -938,7 +945,7 @@ main(int argc, char **argv)
/* set the mtu to the maximum received packet size */
ret = rte_eth_dev_set_mtu(portid,
- local_port_conf.rxmode.max_rx_pkt_len);
+ local_port_conf.rxmode.max_rx_pkt_len - MTU_OVERHEAD);
if (ret < 0) {
printf("\n");
rte_exit(EXIT_FAILURE, "Set MTU failed: "