Merge branch 'lsfd-more-inet-1' of https://github.com/masatake/util-linux

* 'lsfd-more-inet-1' of https://github.com/masatake/util-linux: (26 commits)
  tests: (lsfd) skip if the platform doesn't permit to use ioctl(fd, SIOCGSKNS)
  tests: (lsfd) skip if the platform doesn't permit to use unshare(2)
  tests: (lsfd) skip if the platform doesn't attach a buffer to a packet socket
  tests: (lsfd) skip if the platform doesn't provide pidfd_open(2)
  tests: (mkfds) introduce constants representing the limitation of the test environment
  tests: (lsfd) send a signal only if the target PID is know
  tests: (lsfd) add comments about the reason using ts_skip_qemu_user()
  tests: (mkfds) fix minor typo in comment
  tests: (lsfd) add a case for PING and PINGv6 sockets
  lsfd: use extra information loaded from /proc/net/icmp6
  lsfd: use extra information loaded from /proc/net/icmp
  tests: (mkfds) add ping and ping6 factories
  tests: (lsfd) add a case for UDPLITEv6 sockets
  tests: (lsfd) add a case for UDP-Lite sockets
  lsfd: use extra information loaded from /proc/net/udplite6
  lsfd: use extra information loaded from /proc/net/udplite
  tests: (mkfds) add "lite" parameter to udp and udp6 factories
  tests: (lsfd) add a case for RAWv6 sockets
  tests: (mkfds) add raw6 factory
  lsfd: use extra information loaded from /proc/net/raw6
  ...