/lib/udev/rules.d/90-iphone-tether.rules is in ipheth-utils 1.0+git20111206-0ubuntu4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | # udev rules for setting correct configuration and pairing on tethered iPhones
ATTR{idVendor}!="05ac", GOTO="ipheth_rules_end"
# Execute pairing program when appropriate
ACTION=="add", SUBSYSTEM=="net", ENV{ID_USB_DRIVER}=="ipheth", SYMLINK+="iphone", RUN+="ipheth-pair"
LABEL="ipheth_rules_end"
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