test & fix: add DHCPv4 client hostname resend regression test, fix hostname resend

doc/ChangeLog.md

@@ -23,6 +23,7 @@ All notable changes to the project are documented in this file.
   `92.2` instead of `92.246.137.39`
 - Fix #1466: `show container` showing no output for containers whose command
   line includes environment variables
+- Fix #1439: changing hostname does not regenerate DHCP client conf until restart
 
 [BPI-R4]: https://docs.banana-pi.org/en/BPI-R4/BananaPi_BPI-R4
 

src/confd/src/dhcp-client.c

@@ -180,6 +180,20 @@ int dhcp_client_change(sr_session_ctx_t *session, struct lyd_node *config, struc
 	ifaces  = lydx_get_descendant(config, "interfaces", "interface", NULL);
 	difaces = lydx_get_descendant(diff, "interfaces", "interface", NULL);
 
+	if (diff && lydx_get_xpathf(diff, "/ietf-system:system/hostname")) {
+		LYX_LIST_FOR_EACH(ifaces, iface, "interface") {
+			const char *ifname = lydx_get_cattr(iface, "name");
+
+			ipv4 = lydx_get_descendant(lyd_child(iface), "ipv4", NULL);
+			if (!ipv4)
+				continue;
+
+			dhcp = lydx_get_descendant(lyd_child(ipv4), "dhcp", NULL);
+			if (dhcp)
+				add(ifname, dhcp);
+		}
+	}
+
 	/* find the modified interfaces */
 	LYX_LIST_FOR_EACH(difaces, diface, "interface") {
 		const char *ifname = lydx_get_cattr(diface, "name");

test/case/dhcp/Readme.adoc

@@ -7,6 +7,7 @@ Tests verifying DHCPv4/DHCPv6 client and server functionality:
  - DHCPv4 client with default gateway assignment
  - DHCPv4 client with static route configuration
  - DHCPv4 client hostname management and priority
+ - DHCPv4 client hostname option is resent after system hostname changes
  - Basic DHCPv6 client operation with address assignment
  - DHCPv6 client with prefix delegation (IA_PD)
  - DHCPv6 SLAAC/RA (Stateless)
@@ -30,6 +31,10 @@ include::client_hostname/Readme.adoc[]
 
 <<<
 
+include::client_hostname_resend/Readme.adoc[]
+
+<<<
+
 include::client6_basic/Readme.adoc[]
 
 <<<

test/case/dhcp/client_hostname_resend/Readme.adoc

@@ -0,0 +1 @@
+test.adoc

test/case/dhcp/client_hostname_resend/test.adoc

@@ -0,0 +1,29 @@
+=== DHCP Hostname Resend
+
+ifdef::topdoc[:imagesdir: {topdoc}../../test/case/dhcp/client_hostname_resend]
+
+==== Description
+
+Verify that updating the system hostname restarts the DHCP client so
+subsequent DHCP requests advertise the current hostname (option 12,
+RFC 2132).
+
+Regression test for a bug where the DHCP client callback only reacts
+on diffs in infix-dhcp-client, so a standalone change of
+ietf-system:system/hostname leaves the running udhcpc untouched with
+the old '-x hostname:' argument from when it was first started.
+
+==== Topology
+
+image::topology.svg[DHCP Hostname Resend topology, align=center, scaledwidth=75%]
+
+==== Sequence
+
+. Set up topology and attach to target DUT
+. Configure initial hostname '{HOSTNM_A}'
+. Enable DHCP client sending hostname option
+. Verify running udhcpc announces hostname '{HOSTNM_A}'
+. Update system hostname to '{HOSTNM_B}'
+. Verify running udhcpc announces hostname '{HOSTNM_B}'
+
+

test/case/dhcp/client_hostname_resend/test.py

@@ -0,0 +1,96 @@
+#!/usr/bin/env python3
+"""DHCP Hostname Resend
+
+Verify that updating the system hostname restarts the DHCP client so
+subsequent DHCP requests advertise the current hostname (option 12,
+RFC 2132).
+
+Regression test for a bug where the DHCP client callback only reacts
+on diffs in infix-dhcp-client, so a standalone change of
+ietf-system:system/hostname leaves the running udhcpc untouched with
+the old '-x hostname:' argument from when it was first started.
+
+"""
+
+import infamy
+from infamy.util import until
+
+
+def udhcpc_cmdline(ssh, ifname):
+    """Return the NUL-separated argv of the running udhcpc for ifname."""
+    pidfile = f"/run/dhcp-client-{ifname}.pid"
+    cmd = ssh.runsh(
+        f"p=$(cat {pidfile} 2>/dev/null); "
+        f"[ -n \"$p\" ] && tr '\\0' ' ' < /proc/$p/cmdline"
+    )
+    return cmd.stdout
+
+
+def running_hostname(ssh, ifname):
+    """Extract the hostname udhcpc is currently announcing (-x hostname:<name>)."""
+    for tok in udhcpc_cmdline(ssh, ifname).split():
+        if tok.startswith("hostname:"):
+            return tok.split(":", 1)[1]
+    return None
+
+
+with infamy.Test() as test:
+    HOSTNM_A = "infix-resend-a"
+    HOSTNM_B = "infix-resend-b"
+
+    with test.step("Set up topology and attach to target DUT"):
+        env = infamy.Env()
+        client = env.attach("client", "mgmt")
+        clissh = env.attach("client", "mgmt", "ssh")
+        _, port = env.ltop.xlate("client", "mgmt")
+
+    with test.step(f"Configure initial hostname '{HOSTNM_A}'"):
+        client.put_config_dict("ietf-system", {
+            "system": {
+                "hostname": HOSTNM_A
+            }
+        })
+        until(lambda: client.get_data("/ietf-system:system")
+              .get("system", {}).get("hostname") == HOSTNM_A)
+
+    with test.step("Enable DHCP client sending hostname option"):
+        client.put_config_dict("ietf-interfaces", {
+            "interfaces": {
+                "interface": [{
+                    "name": port,
+                    "ipv4": {
+                        "infix-dhcp-client:dhcp": {
+                            "option": [
+                                {"id": "vendor-class", "value": "infamy"},
+                                {"id": "hostname", "value": "auto"},
+                                {"id": "netmask"},
+                                {"id": "router"}
+                            ]
+                        }
+                    }
+                }]
+            }
+        })
+
+    with test.step(f"Verify running udhcpc announces hostname '{HOSTNM_A}'"):
+        until(lambda: running_hostname(clissh, port) == HOSTNM_A)
+
+    with test.step(f"Update system hostname to '{HOSTNM_B}'"):
+        client.put_config_dict("ietf-system", {
+            "system": {
+                "hostname": HOSTNM_B
+            }
+        })
+        until(lambda: client.get_data("/ietf-system:system")
+              .get("system", {}).get("hostname") == HOSTNM_B)
+
+    with test.step(f"Verify running udhcpc announces hostname '{HOSTNM_B}'"):
+        try:
+            until(lambda: running_hostname(clissh, port) == HOSTNM_B,
+                  attempts=15)
+        except Exception:
+            cur = running_hostname(clissh, port)
+            print(f"udhcpc still announcing hostname '{cur}', expected '{HOSTNM_B}'")
+            test.fail()
+
+    test.succeed()

test/case/dhcp/client_hostname_resend/topology.dot

@@ -0,0 +1,22 @@
+graph "1x1" {
+	layout="neato";
+	overlap="false";
+	esep="+100";
+
+        node [shape=record, fontname="DejaVu Sans Mono, Book"];
+	edge [color="cornflowerblue", penwidth="2", fontname="DejaVu Serif, Book"];
+
+	host [
+	    label="host | { <mgmt> mgmt }",
+	    pos="0,20!",
+	    requires="controller",
+	];
+
+        client [
+	    label="{ <mgmt> mgmt } | client",
+	    pos="200,20!",
+	    requires="infix",
+	];
+
+	host:mgmt -- client:mgmt [requires="mgmt", color=lightgrey]
+}

test/case/dhcp/dhcp_client.yaml

@@ -14,6 +14,9 @@
 - name: DHCP Hostname Priority
   case: client_hostname/test.py
 
+- name: DHCP Hostname Resend
+  case: client_hostname_resend/test.py
+
 - name: DHCPv6 Basic
   case: client6_basic/test.py