What VLAN configurations are supported for kdump?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • kdump configured to dump vmcores to a remote target on a VLAN

Issue

  • What VLAN network configurations work with kdump?

Resolution

Red Hat Enterprise Linux 8

  • Supported VLAN configurations for kdump on the local system

    • Single device
    • Bonds
    • Teams
  • Unsupported VLAN configurations for kdump on the local system

    • Bridges

Red Hat Enterprise Linux 7

  • Supported VLAN configurations for kdump on the local system

    • Single device
    • Bonds
  • Unsupported VLAN configurations for kdump on the local system

    • Bridges
    • Teams

Root Cause

Red Hat Enterprise Linux 8

  • The source code for kdump (kexec-tools-2.0.20-46.el8_4.2.x86_64 at the time of writing) which checks the VLAN configuration on the local system is listed below, wherein kdump explicitly reports to the console that VLAN over a bridged device is unsupported:

    kdump_setup_vlan() {
        local _netdev=$1
        local _phydev="$(awk '/^Device:/{print $2}' /proc/net/vlan/"$_netdev")"
        local _netmac="$(kdump_get_mac_addr $_phydev)"
        local _kdumpdev
    
        #Just support vlan over bond and team
        if kdump_is_bridge "$_phydev"; then
            derror "Vlan over bridge is not supported!"            <-----
            exit 1
        elif kdump_is_bond "$_phydev"; then
            kdump_setup_bond "$_phydev"
            echo " vlan=$(kdump_setup_ifname $_netdev):$_phydev" > ${initdir}/etc/cmdline.d/43vlan.conf
        else
            _kdumpdev="$(kdump_setup_ifname $_phydev)"
            echo " vlan=$(kdump_setup_ifname $_netdev):$_kdumpdev ifname=$_kdumpdev:$_netmac" > ${initdir}/etc/cmdline.d/43vlan.conf
        fi
    }
    

Red Hat Enterprise Linux 7

  • The source code for kdump (kexec-tools-2.0.15-21.el7_6.3.x86_64 at the time of writing) which checks the VLAN configuration on the local system is listed below, wherein kdump explicitly reports to the console that VLAN over a bridged device or over a team is unsupported:

    kdump_setup_vlan() {
        local _netdev=$1
        local _phydev="$(awk '/^Device:/{print $2}' /proc/net/vlan/"$_netdev")"
        local _netmac="$(kdump_get_mac_addr $_phydev)"
        local _kdumpdev
    
        #Just support vlan over bond, it is not easy
        #to support all other complex setup
        if kdump_is_bridge "$_phydev"; then
            derror "Vlan over bridge is not supported!"        <---
            exit 1
        elif kdump_is_team "$_phydev"; then
            derror "Vlan over team is not supported!"           <---
            exit 1
        elif kdump_is_bond "$_phydev"; then
            kdump_setup_bond "$_phydev"
            echo " vlan=$_netdev:$_phydev" > ${initdir}/etc/cmdline.d/43vlan.conf
        else
            _kdumpdev="$(kdump_setup_ifname $_phydev)"
            echo " vlan=$_netdev:$_kdumpdev ifname=$_kdumpdev:$_netmac" > ${initdir}/etc/cmdline.d/43vlan.conf
        fi
    }
    

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