Hello list, I have VPP running as my home gateway, and found PMTUD broken. Did some captures and discovered that ICMP type 3 code 4 packets, generated by ISP router and forwarded by VPP, has a bad ICMP checksum. The packet, as it enters VPP, is correct; VPP then modifies the destination IP and original packet by looking at its NAT44 session table, and assign a new checksum, then TX; but the new checksum calculated by VPP is wrong.
My setup is VPP 22.06 from fdio ubuntu repositories, running on ubuntu 20.04 kernel 5.14.0-1051-oem; it has two physical interfaces running kernel driver r8169 (which drives a model not supported by DPDK) and connected into VPP by AF_XDP socket. Configuration is like: --- start --- create interface af_xdp host-if enp1s0 name ax-ext num-rx-queues all set interface rx-mode ax-ext adaptive set interface mtu packet 1500 ax-ext set interface ip address ax-ext 192.168.1.8/24 ip route add 0.0.0.0/0 via 192.168.1.1 set interface tcp-mss-clamp ax-ext ip4 enable ip4-mss 1450 ip6 disable set interface state ax-ext up create loopback interface instance 10 set interface l2 bridge loop10 1 bvi set interface ip address loop10 192.168.2.1/24 set interface state loop10 up nat44 plugin enable sessions 65535 set interface nat44 in loop10 out ax-ext nat44 add interface address ax-ext create interface af_xdp host-if enp2s0 name ax-int num-rx-queues all set interface rx-mode ax-int adaptive set interface mtu packet 1500 ax-int set interface l2 bridge ax-int 1 set interface state ax-int up --- end --- I would appreciate any hints on where to continue from here.
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