Add a netconsole role

This role sets up a host to report via netconsole.  It is a port of
old devstack-gate functionality from circa
Iebc8e1812d1441aba7c18d3e7c982b620b5198a0.

Change-Id: I37c26fdbcdf61a55fae4cbee3eb61a4bc45ca628

doc/source/general-roles.rst

@@ -13,6 +13,7 @@ General Purpose Roles
 .. zuul:autorole:: download-artifact
 .. zuul:autorole:: dstat-graph
 .. zuul:autorole:: emit-job-header
+.. zuul:autorole:: enable-netconsole
 .. zuul:autorole:: ensure-dstat-graph
 .. zuul:autorole:: git-prepare-nodecache
 .. zuul:autorole:: log-inventory

roles/enable-netconsole/README.rst

@@ -0,0 +1,32 @@
+Enable netconsole for host
+
+This enables the netconsole on a host to send kernel/dmesg logs to a
+remote host.  This can be very useful if a node is experiencing a
+kernel oops or another form of unexpected disconnect where you can not
+retrieve information via standard logging methods.
+
+The ``netconsole_remote_ip`` and ``netconsole_remote_port`` variables
+must be set.  This host can capture the logs with a command like::
+
+  $ nc -v -u -l -p 6666 | tee console-output.log
+
+or::
+
+  $ socat udp-recv:6666 - | tee console-output.log
+
+One further trick is to send interesting data to ``/dev/kmsg``, this
+should make it across the netconsole even if the main interface has
+been disabled, etc.  e.g.::
+
+  $ ip addr | sudo tee /dev/kmsg
+
+
+**Role Variables**
+
+.. zuul:rolevar:: netconsole_remote_ip
+
+   The IP address of the remote host to send to.
+
+.. zuul:rolevar:: netconsole_remote_port
+
+   The port listening on the remote host.

roles/enable-netconsole/tasks/main.yaml

@@ -0,0 +1,82 @@
+- name: Check remote IP set
+  assert:
+    that:
+      - netconsole_remote_ip is defined
+      - netconsole_remote_port is defined
+    fail_msg: "Must set remote host and port"
+
+- name: Register netconsole target var
+  set_fact:
+    nc_target: '/sys/kernel/config/netconsole/target1'
+
+- name: Everything needs root
+  become: yes
+  block:
+
+    # netconsole requires the device to send packtes from and the
+    # destination MAC.  This works for hosts on the same subnet, but the
+    # way to get packets out to the world is to specify the default gw as
+    # the remote destination.
+
+    - name: Get default gateway
+      shell: "ip route | grep default | awk '{print $3}'"
+      register: default_gw_cmd
+
+    - name: Save default gateway
+      set_fact:
+        default_gw: '{{ default_gw_cmd.stdout }}'
+
+    - name: Get default gateway MAC
+      shell: "arp {{ default_gw }} | grep {{ default_gw }} | awk '{print $3}'"
+      register: default_gw_cmd_mac
+
+    - name: Save default gateway MAC
+      set_fact:
+        default_gw_mac: '{{ default_gw_cmd_mac.stdout }}'
+
+    - name: Get default device
+      shell: "ip route | grep default | awk '{print $5}'"
+      register: default_gw_cmd_dev
+
+    - name: Save default device
+      set_fact:
+        default_gw_dev: '{{ default_gw_cmd_dev.stdout }}'
+
+    - name: Install configfs
+      command: modprobe configfs
+
+    - name: Install netconsole
+      command: modprobe netconsole
+
+    - name: Mount configfs
+      mount:
+        path: /sys/kernel/config
+        fstype: configfs
+        src: configfs
+        state: mounted
+
+    - name: Make netconsole target directory
+      file:
+        path: '{{ nc_target }}'
+        state: directory
+
+    - name: Configure gateway
+      shell: 'echo {{ default_gw_dev }} > {{ nc_target }}/dev_name'
+
+    - name: Configure gateway MAC
+      shell: 'echo {{ default_gw_mac }} > {{ nc_target }}/remote_mac'
+
+    - name: Configure remote IP
+      shell: 'echo {{ netconsole_remote_ip }} > {{ nc_target }}/remote_ip'
+
+    - name: Configure remote port
+      shell: 'echo {{ netconsole_remote_port }} > {{ nc_target }}/remote_port'
+
+    - name: Enable netconsole
+      shell: 'echo 1 > {{ nc_target }}/enabled'
+
+    - name: Turn up dmesg
+      command: dmesg -n 8
+
+    - name: Send a test message
+      shell: "echo 'netconsole enabled' > /dev/kmsg"

zuul-tests.d/general-roles-jobs.yaml

@@ -232,6 +232,17 @@
     vars:
       role_name: clear-firewall
 
+- job:
+    name: zuul-jobs-test-netconsole
+    description: Test the netconsole setup role
+    files:
+      - ^roles/enable-netconsole/.*
+    run: test-playbooks/simple-role-test.yaml
+    vars:
+      role_name: enable-netconsole
+      netconsole_remote_ip: 192.0.2.1
+      netconsole_remote_port: 6666
+
 - job:
     name: zuul-jobs-test-dstat-graph
     description: Test the dstat-graph roles
@@ -464,6 +475,7 @@
         - zuul-jobs-test-base-roles-ubuntu-xenial
         - zuul-jobs-test-bindep
         - zuul-jobs-test-clear-firewall
+        - zuul-jobs-test-netconsole
         - zuul-jobs-test-dstat-graph
         - zuul-jobs-test-multinode-roles-centos-7
         - zuul-jobs-test-multinode-roles-debian-stretch