OsmoUPF> list
...
  gtp1u-echo send to (A.B.C.D|X:X::X:X)
  gtp1u-echo send to (A.B.C.D|X:X::X:X) local-ip (A.B.C.D|X:X::X:X)
  gtp1u-echo send to (A.B.C.D|X:X::X:X) local-dev DEV_NAME
...
OsmoUPF> enable
OsmoUPF# list
...
  gtp1u-echo send to (A.B.C.D|X:X::X:X)
  gtp1u-echo send to (A.B.C.D|X:X::X:X) local-ip (A.B.C.D|X:X::X:X)
  gtp1u-echo send to (A.B.C.D|X:X::X:X) local-dev DEV_NAME
...
OsmoUPF# configure terminal
OsmoUPF(config)# list
... !gtp1u-echo
OsmoUPF(config)# end

OsmoUPF# gtp1u-echo?
  gtp1u-echo  GTP1-U Echo probing
OsmoUPF# gtp1u-echo ?
  send  Send a GTP1-U Echo Request to a remote peer
OsmoUPF# gtp1u-echo send ?
  to  Send to remote peer's GTP address
OsmoUPF# gtp1u-echo send to ?
  A.B.C.D   IPv4 address
  X:X::X:X  IPv6 address
OsmoUPF# gtp1u-echo send to 1.2.3.4 ?
  local-ip   Send from local GTP device, chosen by IP address
  local-dev  Send from local GTP device, chosen by name as configured in 'dev create' or 'dev use'.
  <cr>       
OsmoUPF# gtp1u-echo send to 1.2.3.4 local-ip ?
  A.B.C.D   IPv4 address
  X:X::X:X  IPv6 address
OsmoUPF# gtp1u-echo send to 1.2.3.4 local-dev ?
  DEV_NAME  A GTP device name as it appears in the cfg
OsmoUPF# gtp1u-echo send to 1.2.3.4
% Error: cannot send Echo: there is no GTP device
OsmoUPF# gtp1u-echo send to 1.2.3.4 local-ip 1.2.3.4
% Error: cannot send Echo: this does not seem to be a locally bound GTP address: 1.2.3.4:2152
OsmoUPF# gtp1u-echo send to 1.2.3.4 local-dev apn0
% Error: cannot send Echo: there is no GTP device by the name of 'apn0'