nl-pktloc-lookup man page
nl-pktloc-lookup — Lookup packet location definitions
nl-pktloc-lookup searches the packet location database for a matching entry. It is used to resolve packet location aliases to their definition, i.e. alignment, layer, offset, and mask.
- -h or --help
Print help text to console and exit.
- -v or --version
Print versioning information to console and exit.
- -l or --list
List all packet location definitions.
Prints the packet location definition in a special format that is understood by iproute2's u32 selector parser. It will output a u32 selector which will compare the provided value with the value specified by the packet location.
Please note that due to the limitation of u32, it is not possible to use packet locations based on the link layer. nl-pktloc-lookup will print an error message in this case.
selector=$(nl-pktloc-lookup --u32 22 tcp.sport)
tc filter add [...] u32 match $(selector) flowid 1:2
Thomas Graf is the original author and current maintainer of libnl and libnl tools. Many people have contributed to it since.