Scope and purpose

Fixes #2373. Another PR intends to add documentation and release notes.

This pull request

• Adds DHCP stats graphs to VLAN and Prefix pages in NAV where recent-enough stats for that VLAN/Prefix are found in the Carbon/Graphite database:
  

• Changes how paths are stored under "nav.dhcp" in the Carbon/Graphite database:

  • previously, paths followed this pattern:

    nav.dhcp.4.pools.<server-name>.<pool-name>.<first-ip>.<last-ip>.{assigned,total,declined}
    

  • now, paths follow this pattern:

    nav.dhcp.4.<server-name>.{range,pool,subnet}.{special_groups,custom_groups}.<group-name>.<first-ip>.<last-ip>.{assigned,total,declined}
    

    Basically, we
    • Rename <pool-name> to <group-name> in all pieces of documentation.
    • Differentiate between a range, a pool, and a subnet, because different DHCP servers have different semantics and data-coarseness. A range is the set of all IPs between a first-ip and a last-ip (inclusive), whereas a pool is an arbitrary set of IPs greater than or equal to a first-ip and less than or equal to a last-ip. Further, all IPs in a range and a pool are available for lease, whereas this is not necessarily the case for a subnet.
    • Add an additional segment {special_groups,custom_groups} to differentiate between group-names that NAV must create and manage itself and group-names that NAV is able to infer from some piece of externally sourced information such as DHCP server config files.

• Expects [server_<server-name>] sections in dhcpstats.conf instead of [endpoint_<server-name>] for consistency

  • The new code has backwards-compability with the old naming-scheme

• Changes the name of the user_context_poolname_key option in dhcpstats.conf to user_context_groupname_key.

  • The new code does not have backwards-compability with the old naming-scheme here because there is already breaking changes to Graphite paths. Also, NAV works fine when this option is absent.

Contributor Checklist

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• Added a changelog fragment for towncrier
• Added/amended tests for new/changed code
• Added/changed documentation See independent PR
• Linted/formatted the code with ruff, easiest by using pre-commit
• Wrote the commit message so that the first line continues the sentence "If applied, this commit will ...", starts with a capital letter, does not end with punctuation and is 50 characters or less long. See https://cbea.ms/git-commit/
• Based this pull request on the correct upstream branch: For a patch/bugfix affecting the latest stable version, it should be based on that version's branch (<major>.<minor>.x). For a new feature or other additions, it should be based on master.
• If applicable: Created new issues if this PR does not fix the issue completely/there is further work to be done TODO: add a new issue for using Rickshaw graphs instead of PNG images in graph navlets
• If it's not obvious from a linked issue, describe how to interact with NAV in order for a reviewer to observe the effects of this change first-hand (commands, URLs, UI interactions) See screencast below
• If this results in changes in the UI: Added screenshots of the before and after
• If this adds a new Python source code file: Added the boilerplate header to that file

Testing It For Yourself

You can run this script to fill the prefixes 192.0.2.0/24 and 198.51.100.0/24 with DHCP stats (you might need to install socat and gawk, and you might need to change 127.0.0.1 to the address of your Carbon/Graphite database):

#!/bin/sh

cat <<EOF |
kea-trd staff 192.0.2.1 192.0.2.16 16
kea-trd staff 192.0.2.17 192.0.2.64 48
kea-trd staff 192.0.2.65 192.0.2.126 64
kea-trd guest 192.0.2.200 192.0.2.255 56
kea-trd guest 198.51.100.1 198.51.100.255 255
kea-osl staff 198.51.100.1 198.51.100.255 255
EOF

gawk '
BEGIN {
  NOW = systime()
  INTERVAL = 300
  DAYS = 30
}

{
  a = rand()
  b = rand()
  c = rand()
  _ = 1 / (a + b + c)
  a = a * _
  b = b * _
  c = c * _
  d = rand()*3.14*2
  e = 20 + rand()*8
  f = rand()

  server_name = $1
  group_name = $2
  first_ip = $3; gsub(/\./, "_", first_ip)
  last_ip = $4; gsub(/\./, "_", last_ip)
  total_ips = $5
  noise = rand()
  for (offset = 0; offset < 3600*24*DAYS; offset += INTERVAL) {
    sine = (sin((offset*3.14*2)/(3600*e) + d)+1)/2
    noise = noise*f + rand()*(1-f)
    assigned_ips = int(sine*total_ips*a+total_ips*b+noise*total_ips*c)
    printf("nav.dhcp.4.%s.range.custom_groups.%s.%s.%s.assigned %d %d\n", server_name, group_name, first_ip, last_ip, assigned_ips, NOW - offset)
    printf("nav.dhcp.4.%s.range.custom_groups.%s.%s.%s.total %d %d\n", server_name, group_name, first_ip, last_ip, total_ips, NOW - offset)
  }
}' |

socat - tcp:127.0.0.1:2003

Here's a screencast:

At 2:00 in the video, notice that the graph labelled DHCP ranges in 'guest' on server 'kea-trd' has stats from ranges in both 192.0.2.0/24 and 198.51.100.0/24 despite vlan 20 only containing 192.0.2.0/24. This is because whenever a group (here: 'guest' on server 'kea-trd') has at least one range/pool/subnet overlapping with the VLAN/Prefix, the whole group will be displayed on that VLAN/Prefix's page.