automatic renaming and numbering of nics using udev

Question

I'm writing on an udev-rule to automatically rename and number NICs with specific MAC addresses.

The resulting rule should do nearly the same 75-persistent-net-generator.rules does (match first 3 bytes of the MAC address of card, name it 'mycard*' depending on how much cards of this vendor are installed, write the renaming-rule into 70-persistent-net.rules).

This is how far I've come until now:

# udev rules to name rename cards to mycard

ACTION!="add", GOTO="persistent_mycard_generator_end"
SUBSYSTEM!="net", GOTO="persistent_mycard_generator_end"

# ignore the interface if a name has already been set
NAME=="mycard*", GOTO="persistent_mycard_generator_end"

# device name whitelist
KERNEL!="eth*", GOTO="persistent_mycard_generator_end"

# read MAC address
ENV{MATCHADDR}="$attr{address}"

# match interface type
ENV{MATCHIFTYPE}="$attr{type}"

# ignore non mycard MAC addresses
ENV{MATCHADDR}!="00:11:22:*", GOTO="persistent_mycard_generator_end"

# default comment
ENV{COMMENT}=="", ENV{COMMENT}="mycard connected through ($attr{driver})"

#### THIS IS THE PART I DON'T GET ####

# write rule
DRIVERS=="?*", IMPORT{program}="write_net_rules"

# rename interface if needed
ENV{INTERFACE_NEW}=="?*", NAME="mycard*"

#### THIS IS THE END OF THE PART I DON'T GET ####

LABEL="persistent_mycard_generator_end

The task "THE PART I DON'T GET" should do is to rename a card (lets say it's eth3) to mycard0 or if it's the second card in the system with a matching MAC address mycard1 and so on.

Thanks in advance, flokra

Answer 1

If you set ENV{INTERFACE} to "mycard0" before calling write_net_rules, it will find the first unused mycardN for you, write out the rule for it, and return the name in ENV{INTERFACE_NEW}.

Answer 2

OK, here's my solution (I've tested it with Debian 5.0 and Ubuntu 9.04, so I'm not sure if it works with the udev-implementations of other distributions):

1. 75-persistent-mycard-generator.rules

   ACTION!="add", GOTO="persistent_mycard_generator_end"
   SUBSYSTEM!="net", GOTO="persistent_mycard_generator_end"
   
   
   # ignore the interface if a name has already been set
   NAME=="?*", GOTO="persistent_mycard_generator_end"
   
   
   # device name whitelist
   KERNEL!="eth*", GOTO="persistent_mycard_generator_end"
   
   
   # by default match on the MAC address and interface type
   ENV{MATCHADDR}="$attr{address}"
   ENV{MATCHIFTYPE}="$attr{type}"
   
   
   # match interface dev_id
   ATTR{dev_id}=="?*", ENV{MATCHDEVID}="$attr{dev_id}"
   
   
   # by default match on the MAC address and interface type
   ENV{MATCHADDR}="$attr{address}"
   ENV{MATCHIFTYPE}="$attr{type}"
   
   
   # match interface dev_id
   ATTR{dev_id}=="?*", ENV{MATCHDEVID}="$attr{dev_id}"
   
   
   # terminate processing if card is not a mycard
   ENV{MATCHADDR}!="AA:BB:CC:*", GOTO="persistent_mycard_generator_end"
   
   
   # provide nice comments for the generated rules
   SUBSYSTEMS=="pci", ENV{COMMENT}="PCI device $attr{vendor}:$attr{device}"
   SUBSYSTEMS=="pcmcia", ENV{COMMENT}="PCMCIA device $attr{card_id}:$attr{manf_id}"
   SUBSYSTEMS=="usb", ENV{COMMENT}="USB device 0x$attr{idVendor}:0x$attr{idProduct}"
   ENV{COMMENT}=="", ENV{COMMENT}="Unknown $env{SUBSYSTEM} device($env{DEVPATH})"
   ATTRS{driver}=="?*", ENV{COMMENT}="$env{COMMENT} ($attr{driver})"
   
   
   # add mycard to comment
   ENV{COMMENT}="$env{COMMENT} (mycard)"
   
   
   # set interface name to mycard0 (initially)
   ENV{INTERFACE}="mycard0"
   
   
   # generate and write the rule
   DRIVERS=="?*", IMPORT{program}="write_mycard_rules"
   
   
   # rename the interface if requested
   ENV{INTERFACE_NEW}=="?*",NAME="$env{INTERFACE_NEW}"
   
   
   LABEL="persistent_mycard_generator_end"
   

2. write_mycard_rules

   RULES_FILE='/etc/udev/rules.d/70-persistent-net.rules'
   
   
   . /lib/udev/hotplug.functions
   
   
   interface_name_taken() {
       local value="$(find_all_rules 'NAME=' $INTERFACE)"
       if [ "$value" ]; then
        return 0
       fi
       return 1
   
   
   }
   
   
   find_next_available() {
       raw_find_next_available "$(find_all_rules 'NAME=' "$1")"
   }
   
   
   write_rule() {
       local match="$1"
       local name="$2"
       local comment="$3"
   
   
   {
   if [ "$PRINT_HEADER" ]; then
    PRINT_HEADER=
    echo "# This file was automatically generated by the $0"
    echo "# program run by the persistent-mycard-generator.rules rules file."
    echo "#"
    echo "# You can modify it, as long as you keep each rule on a single line."
   fi
   
   
   echo ""
   [ "$comment" ] && echo "# $comment"
   echo "SUBSYSTEM==\"net\", ACTION==\"add\"$match, NAME=\"$name\""
   } >> $RULES_FILE
   
   
   }
   
   
   if [ -z "$INTERFACE" ]; then
       echo "missing \$INTERFACE" >&2
       exit 1
   fi
   
   
   # Prevent concurrent processes from modifying the file at the same time.
   lock_rules_file
   
   
   # Check if the rules file is writeable.
   choose_rules_file
   
   
   # the DRIVERS key is needed to not match bridges and VLAN sub-interfaces
   if [ "$MATCHADDR" ]; then
       match="$match, DRIVERS==\"?*\", ATTR{address}==\"$MATCHADDR\""
   fi
   
   
   if [ "$MATCHDRV" ]; then
       match="$match, DRIVERS==\"$MATCHDRV\""
   fi
   
   
   if [ "$MATCHDEVID" ]; then
       match="$match, ATTR{dev_id}==\"$MATCHDEVID\""
   fi
   
   
   if [ "$MATCHID" ]; then
       match="$match, KERNELS==\"$MATCHID\""
   fi        
   
   
   if [ "$MATCHIFTYPE" ]; then
       match="$match, ATTR{type}==\"$MATCHIFTYPE\""
   fi
   
   
   if [ -z "$match" ]; then
       echo "missing valid match" >&2
       unlock_rules_file
       exit 1
   fi
   
   
   basename=${INTERFACE%%[0-9]*}
   match="$match, KERNEL==\"eth*\""
   if [ "$INTERFACE_NAME" ]; then
       # external tools may request a custom name
       COMMENT="$COMMENT (custom name provided by external tool)"
   
   
   if [ "$INTERFACE_NAME" != "$INTERFACE" ]; then
    INTERFACE=$INTERFACE_NAME;
    echo "INTERFACE_NEW=$INTERFACE"
   fi
   
   
   else
       # if a rule using the current name already exists, find a new name
       if interface_name_taken; then
        INTERFACE="$basename$(find_next_available "$basename[0-9]*")"
        echo "INTERFACE_NEW=$INTERFACE"
       fi
   fi
   
   
   write_rule "$match" "$INTERFACE" "$COMMENT"
   unlock_rules_file
   exit 0
   

The most important changes are ENV{INTERFACE}="mycard0" in 75-persistent-mycard-generator.rules which sets the name the card should get and match="$match, KERNEL==\"eth*\"" in write_mycard_rules which forces udev to not override the used Kernel Subsystem with the new name.

HTH, flokra