Date: Sun, 7 Nov 2021 10:51:30 +0300 From: Rozhuk Ivan <rozhuk.im@gmail.com> To: freebsd-net@freebsd.org, freebsd-hackers@FreeBSD.org Cc: Rozhuk Ivan <Rozhuk.IM@gmail.com> Subject: if_vlan allow to set incorrect mtu Message-ID: <20211107105130.2ccbb253@rimwks.local>
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Hi! Why if_vlan allow to set same MTU size or bigger as on parrent nic? Setup: - workstation with MTU 9000 and IPv4 on h/w nic - server with MTU 9000 on h/w nic and IPv4 on vlan nic with MTU 9000 (set by defauil on iface creation) This setup have issue: - big packets from server->wks - OK - big packets from wks->server - FAIL. Server init sequence: 1. Create vlans 2. Set MTU lower than default on parent nic Result: vlan have bigger or same MTU as parrent nic, but parrent nic reports IFCAP_VLAN_MTU. Probably this is if_em driver issue or iflib. This is rc.conf, vlan77 - where I got MTU 9000 and fail to receive packets: ===================================================================================== vlans_igb0="vlan77 vlan86 vlan87" create_args_vlan87="vlan 87" create_args_vlan86="vlan 86" create_args_vlan77="vlan 77" ifconfig_vlan87="inet 15.44.77.2 netmask 255.255.252.0 mtu 1500 down up" ifconfig_vlan87_alias0="link 00:aa:fa:dd:44:55" ifconfig_vlan86="DHCP mtu 1500" ifconfig_vlan86_alias0="link 00:ff:fa:dd:44:55" ifconfig_vlan77="inet 192.168.0.254 netmask 255.255.255.0" ifconfig_vlan77_alias0="link 00:0f:43:48:67:fe" ifconfig_vlan77_ipv6="inet6 2001:470:2345:555::1/64 prefixlen 64 auto_linklocal" ifconfig_igb0="-lro -tso -vlanhwtso mtu 9000 down up" =====================================================================================
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