InstallICMPIDFilter skip ip header

https://github.com/prometheus-community/pro-bing/blob/c9b2c133ccf6c6212f29ca33c6258f7400ea76f6/utils_linux.go#L144C22-L144C41

bpf.LoadMemShift{Off: 0},          // Skip IP header 
if want to skip ip header, should set Off 20 
bpf.LoadMemShift{Off: 20},

the explain for LoadMemShift  : https://cs.opensource.google/go/x/net/+/v0.37.0:bpf/instructions.go;l=294

