mctpd: fix endpoint peer iteration on interface delete

We currently scan through ctx->peers while deleting an interface,
removing pertinent peers.

However, the removal will shift the indices (and possibly realloc
ctx->peers). So, adjust our handling of the loop counter to suit.

Fixes: #97
Reported-by: Faizan Ali <faizana@nvidia.com>
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>

Author: jk-ozlabs

CHANGELOG.md

@@ -6,6 +6,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 
+## Fixed
+
+1. mctpd: fixed an issue where endpoints may persist when their dependent
+   interface is deleted
+
 ## [2.2] - 2025-07-28
 
 ### Fixed

src/mctpd.c

@@ -3388,13 +3388,26 @@ static int del_interface(struct link *link)
 	if (ctx->verbose) {
 		fprintf(stderr, "Deleting interface #%d\n", ifindex);
 	}
-	for (size_t i = 0; i < ctx->num_peers; i++) {
+	for (size_t i = 0; i < ctx->num_peers;) {
 		struct peer *p = ctx->peers[i];
+
 		if (p->state == REMOTE && p->phys.ifindex == ifindex) {
-			// Linux removes routes to deleted links, so no need to request removal.
+			int rc;
+
+			// Linux removes routes to deleted links, so no need
+			// to request removal.
 			p->have_neigh = false;
 			p->have_route = false;
-			remove_peer(p);
+			rc = remove_peer(p);
+			if (rc) {
+				bug_warn("Error removing peer on interface "
+					 "deletion, inconsistent state");
+				break;
+			}
+		} else {
+			// Removal will shift indices down, only increment
+			// while skipping.
+			i++;
 		}
 	}
 

tests/test_mctpd.py

@@ -748,6 +748,44 @@ async def test_del_interface_last(dbus, mctpd):
     with pytest.raises(asyncdbus.errors.DBusError):
         await mctpd_mctp_network_obj(dbus, iface.net)
 
+""" Delete an interface with peers attached, ensure all are gone """
+async def test_del_interface_with_peers(dbus, mctpd):
+    net = mctpd.system.interfaces[0].net
+    iface = mctpd.system.Interface(
+        'mctp1', 2, net,  bytes([0x10]), 68, 254, True,
+    )
+    await mctpd.system.add_interface(iface)
+
+    eps = [
+        Endpoint(iface, bytes([0x11])),
+        Endpoint(iface, bytes([0x12])),
+        Endpoint(iface, bytes([0x13])),
+    ]
+
+    mctp = await mctpd_mctp_iface_obj(dbus, iface)
+
+    paths = []
+    for ep in eps:
+        mctpd.network.add_endpoint(ep)
+        (eid, _, path, _) = await mctp.call_setup_endpoint(ep.lladdr)
+        assert eid == ep.eid
+        paths.append(path)
+
+    await mctpd.system.del_interface(iface)
+
+    # interface should be gone
+    with pytest.raises(asyncdbus.errors.DBusError):
+        await mctpd_mctp_iface_obj(dbus, iface)
+
+    # .. but the network should remain, as the default interface is still
+    # present
+    _ = await mctpd_mctp_network_obj(dbus, net)
+
+    for path in paths:
+        with pytest.raises(asyncdbus.errors.DBusError) as ex:
+            ep = await mctpd_mctp_endpoint_common_obj(dbus, path)
+        assert str(ex.value).startswith("Unknown object")
+
 """ Remove and re-add an interface """
 async def test_add_interface(dbus, mctpd):
     net = 1