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Daniel Hilst 008f83d2e4 test(xCAT-test): add dhcptest, a wire-level DHCP client test tool

xCAT's DHCP behaviour is tested from two directions today, neither of which
touches the wire: xCAT-test/unit/dhcp_*.t assert on generated config text, and
xCAT-test/integration/dhcp_{isc,kea}_config_validation.t feed that config to a
real daemon and check it parses. Both stop at "the server accepted our
config". Nothing verifies that a client sending option 93 = 0x000b actually
gets an aarch64 loader back.

The one existing wire tool, xCAT-probe/subcmds/detect_dhcpd, hand-packs a
fixed DISCOVER carrying no option 60, 77 or 93 (so it never reaches any arch
branch), parses replies by regexing tcpdump output, and binds an
IO::Socket::INET to a local address, so it cannot run on a provisioning NIC
that has no address yet.

dhcptest fills that gap. It is a Python 3 tool using only the standard library
plus Scapy, speaking raw Layer 2, driving DHCP transactions declared in INI
files and asserting on what came back:

  dhcptest run      -i eth1 --set net=10.0.0.0/24 conf/full-lease.conf
  dhcptest validate conf/*.conf      # no root, no network, no scapy
  dhcptest list     conf/*.conf
  dhcptest discover -i eth1          # ad-hoc, no conf file

Scenarios cover DISCOVER/OFFER, the full lease, renew and rebind, reserved
versus pooled addresses, deliberate silence, the PXE architecture matrix and
the iPXE user-class split. Assertions are a small DSL -- target, operator,
value -- over message type, BOOTP header fields, options by number or name,
subnet membership, and the boot file a client would actually use (option 67
or the header, since servers differ on which they fill).

Two boundaries are enforced by unit test rather than by convention:

  - The tool is implementation-agnostic. It exchanges packets and checks
    fields; it never reads the xCAT database, never runs an xCAT command, and
    names no DHCP implementation. Anything that differs between servers is
    expressed by whoever writes the .conf.
  - Only runner.py imports scapy, so validate and list stay usable in CI on a
    host with neither scapy nor root.

Host networking is never modified. The client MAC defaults to a synthetic
locally-administered address, everything goes over a raw L2 socket, no leased
address is ever configured, and the ARP responder answers only for addresses
the session was actually granted.

Variables in .conf files are configparser's own BasicInterpolation, %(name)s,
fed from [vars] and --set. $offer.address and friends are resolved separately
at step-execution time, because they name a reply that has not arrived when
the file is read; BasicInterpolation gives $ no meaning, so the two coexist
without escaping.

Packaging and CI:

  - xCAT-test.spec installs dhcptest alongside unit/ and integration/, and
    only recommends python3-scapy: it lives in EPEL on EL, and a hard Requires
    would make xCAT-test uninstallable on a management node without EPEL.
    The deb depends on it outright.
  - github_action_xcat_test.pl runs the unit tests and `dhcptest validate`
    last, after the fast regression.
  - autotest/testcase/dhcptest/cases0 carries the two offline cases plus a
    wire case that stands down with an explanation when no provisioning NIC
    is available.

Verified against a real DHCP server in a network namespace: 34 lease, renew,
rebind, reservation and silence assertions and 22 PXE/iPXE assertions all
pass, and host networking is untouched before and after.

Signed-off-by: Daniel Hilst <392820+dhilst@users.noreply.github.com>

2026-09-10 08:19:41 -03:00

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xCAT-test

Unit tests that run from the source checkout are split by implementation language:

Test type	Location	Runner
Perl unit tests	`xCAT-test/unit/*.t`	`prove -r xCAT-test/unit`
Shell unit tests	`xCAT-test/bats/*.bats`	`bats -r xCAT-test/bats`
DHCP wire tests	`xCAT-test/dhcptest/`	`python3 -m unittest discover -s tests`, then `dhcptest run -i <nic> <conf>`
CLI functional tests	`xCAT-test/autotest/testcase/` and `xCAT-test/autotest/bundle/`	`xcattest -f <cluster.conf> -t <case>` or `xcattest -f <cluster.conf> -b <bundle>`

Use Perl .t tests for Perl modules, Perl scripts, templates, and repository artifacts. Use BATS tests for shell-script behavior that can be exercised from the checkout by sourcing a shell library or script and shadowing external commands.

Shell behavior should not be tested by Perl tests that grep shell source. Put those tests under xCAT-test/bats instead.

dhcptest is the odd one out: its Python unit tests and dhcptest validate run offline like the others, but its point is the third column -- driving real DHCP transactions on a provisioning NIC and asserting on what came back. It talks to the server only over the wire, so it is agnostic to which DHCP implementation is answering and to xCAT itself.

See unit/README.md, bats/README.md and dhcptest/README.md for the detailed rules for each suite.

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