When using OVS-DPDK and setting MTU to 1500 for an Interface of type 'dpdkvhostuserclient', the maximum packet size that can be transmitted is 1522, as DPDK seems to have stripped off 4 bytes of CRC by default. However, in OVS the maximum packet size is 'MTU+RTE_ETHER_HDR_LEN + RTE_ETHER_CRC_LEN', and the actual maximum packet size that can be transmitted for IP packets is 1504. Is this reasonable?
In netdev-dpdk.c: #define MTU_TO_FRAME_LEN(mtu) ((mtu) + RTE_ETHER_HDR_LEN + RTE_ETHER_CRC_LEN) ...... dev->max_packet_len = MTU_TO_FRAME_LEN(dev->mtu) The Figure 1 shows the packets that are captured on the Test Master, which include CRC. The Figure 2 shows the packets captured on the OVS dpdkvhostuserclient interface, where the CRC has been stripped. Figure 1 [cid:image002.jpg@01DA5534.772C4020] Figure 2 [cid:image004.jpg@01DA5534.772C4020] ------------------------------------------------------------------------------------------------------------------------------------- ????????????????????????????????? ???????????????????????????????????????? ???????????????????????????????????????? ??? This e-mail and its attachments contain confidential information from New H3C, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it!
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