udev

装了OFED，会安装下面的文件:

# cat /etc/udev/rules.d/82-net-setup-link.rules
SUBSYSTEM=="net", ACTION=="add", ATTR{phys_switch_id}!="", ATTR{phys_port_name}!="", \
        IMPORT{program}="/etc/infiniband/vf-net-link-name.sh $attr{phys_port_name} $attr{phys_switch_id}" \
        NAME="$env{NAME}", RUN+="/sbin/ethtool -L $env{NAME} combined 4", GOTO="net_setup_skip_link_name"


SUBSYSTEM=="net", ACTION=="add", ATTR{phys_port_name}!="", \
        IMPORT{program}="/etc/infiniband/vf-net-link-name.sh $attr{phys_port_name}" \
        NAME="$env{NAME}", RUN+="/sbin/ethtool -L $env{NAME} combined 4"

LABEL="net_setup_skip_link_name"

上面的ATTR可以通过udevadm查看：

#  udevadm info -a /sys/class/net/enp4s0f0

Udevadm info starts with the device specified by the devpath and then
walks up the chain of parent devices. It prints for every device
found, all possible attributes in the udev rules key format.
A rule to match, can be composed by the attributes of the device
and the attributes from one single parent device.

  looking at device '/devices/pci0000:00/0000:00:02.0/0000:04:00.0/net/enp4s0f0':
    KERNEL=="enp4s0f0"
    SUBSYSTEM=="net"
    DRIVER==""
    ATTR{dormant}=="0"
    ATTR{testing}=="0"
    ATTR{gro_flush_timeout}=="0"
    ATTR{addr_assign_type}=="0"
    ATTR{num_prio_hp}=="0"
    ATTR{carrier_down_count}=="10"
    ATTR{link_mode}=="0"
    ATTR{duplex}=="full"
    ATTR{netdev_group}=="0"
    ATTR{addr_len}=="6"
    ATTR{iflink}=="47"
    ATTR{broadcast}=="ff:ff:ff:ff:ff:ff"
    ATTR{carrier}=="1"
    ATTR{napi_defer_hard_irqs}=="0"
    ATTR{speed}=="25000"
    ATTR{mtu}=="1500"
    ATTR{dev_id}=="0x0"
    ATTR{ifalias}==""
    ATTR{type}=="1"
    ATTR{address}=="b8:59:9f:bb:31:82"
    ATTR{dev_port}=="0"
    ATTR{tx_queue_len}=="1000"
    ATTR{flags}=="0x1003"
    ATTR{ifindex}=="47"
    ATTR{name_assign_type}=="4"
    ATTR{operstate}=="up"
    ATTR{phys_port_name}=="p0"
    ATTR{carrier_up_count}=="11"
    ATTR{carrier_changes}=="21"
    ATTR{hp_pp_burst_size}=="0"
    ATTR{proto_down}=="0"

比如ATTR{phys_port_name}就是p0，也可以通过sysfs直接查看：

# cat /sys/class/net/enp4s0f0/phys_port_name
p0

/etc/infiniband/vf-net-link-name.sh文件里面出现的变量也可以用udevadm查看：

# udevadm info /sys/class/net/enp4s0f0
P: /devices/pci0000:00/0000:00:02.0/0000:04:00.0/net/enp4s0f0
L: 0
E: DEVPATH=/devices/pci0000:00/0000:00:02.0/0000:04:00.0/net/enp4s0f0
E: INTERFACE=enp4s0f0
E: IFINDEX=47
E: SUBSYSTEM=net
E: USEC_INITIALIZED=319791501875
E: ID_NET_NAMING_SCHEME=v240
E: ID_NET_NAME_MAC=enxb8599fbb3182
E: ID_OUI_FROM_DATABASE=Mellanox Technologies, Inc.
E: ID_NET_NAME_PATH=enp4s0f0np0
E: ID_BUS=pci
E: ID_VENDOR_ID=0x15b3
E: ID_MODEL_ID=0x1017
E: ID_PCI_CLASS_FROM_DATABASE=Network controller
E: ID_PCI_SUBCLASS_FROM_DATABASE=Ethernet controller
E: ID_VENDOR_FROM_DATABASE=Mellanox Technologies
E: ID_MODEL_FROM_DATABASE=MT27800 Family [ConnectX-5]
E: ID_PATH=pci-0000:04:00.0
E: ID_PATH_TAG=pci-0000_04_00_0
E: ID_NET_DRIVER=mlx5_core
E: ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
E: ID_NET_NAME=enp4s0f0np0
E: NAME=enp4s0f0
E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/enp4s0f0 /sys/subsystem/net/devices/enp4s0f0
E: TAGS=:systemd:

比如ID_NET_DRIVER=mlx5_core。

至于ID_NET_NAME是从那里生成的，我觉得是通过systemd生成的。代码可以通 git clone git@github.com:systemd/systemd.git 下载。

调用函数如下：

builtin_net_id
        name_pci
                dev_pci_slot

如果link name是eno1，o代表onboard。如果是enp4s0f0，p代表pci。后面是slot，function。