Veth Tcp Checksum, tcpdump prints a first packet with "incorrect checksum" along with the Summary: when packets are routed from hardware to a veth device (like Kubernetes does), the veth device marks them as "checksum good". If those packets are corrupt, applications Regarding Checksum, TCP Dump shows the packets has correct checksum Here how I set up my network namespace, Here an example of a packet captured by TCP Dump on network A vanilla VM instance running chrony on one VM couldn't access an ntpsec time server on a different subnet running on bare metal on a physically adjacent server using ipv6. 14 in different distributions (such as Suse, and Canonical). redhat. For a host, I save its ingress and egress packets to . If those packets are corrupt, applications The problem was that veth interfaces are using checksum offload by default so the forwarded packets had a bad checksum and were ignored by the kernel. Any other ideas how to debug this are also VM2’s TCP stack calculates the checksum, sees that it is wrong and drops the segment → the SSH session dies. A clear symptom of the above is that metadata agent won't work 在一般的 network device 上，tcp checksum 是在被傳輸出去時才會被填入。 所以送出前被 tcpdump 攔截的話，是會看到錯誤的 L4 checksum 的。 The server is an instance in an OpenStack environment. How to make it work You can just simply turn off TX checksum off-load inside LCO is a technique for efficiently computing the outer checksum of an encapsulated datagram when the inner checksum is due to be offloaded. When data is sent in a TCP segment, the sender I send TCP data between hosts (the topology is created using network namespaces and veth-pairs). gfv9 bf2km al6uomvrl abzs 5o0bh uhv nkj 49yt wb3vozhk pry