While running the latest version of Raspbian Stretch Lite, I've noticed that the ss command does not show any information for processes listening on UDP even though the netstat does report these details.

Has anyone else noticed this behavior?

pi@titan:~ $ ss -anu
State       Recv-Q Send-Q    Local Address:Port     Peer Address:Port

pi@titan:~ $ netstat -anu
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
udp        0      0  *
udp        0      0 *
udp        0      0    *
udp        0      0    *
udp        0      0 *
udp6       0      0 :::5353                 :::*
udp6       0      0 :::48642                :::*
udp6       0      0 :::49253                :::*
  • Yes I've noticed that too and no I can't explain it other than I suspect it's a bug. – John Hawthorne Apr 16 '18 at 19:50

I'm surely too late, but this can be useful for others since I had the same problem myself.

ss (which resides in iproute2 package) indeed has a bug which is fixed in iproute2 4.20.0.

The current installed version on debian stretch is 4.9.0, but since 4.20.0 is not available yet in main repo, you can use the backports repo (this will not affect anything else when updating or installing packages).

sudo touch /etc/apt/sources.list.d/backports.list
sudo echo "deb http://deb.debian.org/debian stretch-backports main" > /etc/apt/sources.list.d/backports.list
sudo apt update
sudo apt -t stretch-backports install "iproute2"

Now you will have iproute2 4.20.0 package instead of 4.9.0.

To see current version and available versions use:

user@box:~$ apt-cache policy iproute2
  Installed: 4.20.0-2~bpo9+1
  Candidate: 4.20.0-2~bpo9+1
  Version table:
 *** 4.20.0-2~bpo9+1 100
        100 http://deb.debian.org/debian stretch-backports/main armhf Packages
        100 /var/lib/dpkg/status
     4.9.0-1+deb9u1 500
        500 http://ftp.debian.org/debian stretch/main armhf Packages
  • The second line should be echo "deb http://deb.debian.org/debian stretch-backports main" | sudo tee -a /etc/apt/sources.list.d/backports.list in order to write to the file, but appreciate the solution all this time later! – Clinton Campbell Mar 31 at 22:25
  • For anybody attempting this on a Raspbian installation, you will also need to add the Debian signing keys: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys E0B11894F66AEC98 sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 7638D0442B90D010 sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 8B48AD6246925553 – Clinton Campbell Apr 1 at 1:02

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