mctpd: add AssignEndpointPreferred for preferred EID

README.md

@@ -85,6 +85,7 @@ configuring remote endpoints on that bus:
     au.com.codeconstruct.MCTP.Interface1 interface -          -             -
     .AssignEndpoint                      method    ay         yisb          -
     .AssignEndpointStatic                method    ayy        yisb          -
+    .AssignEndpointPreferred             method    ayy        yisb          -
     .LearnEndpoint                       method    ay         yisb          -
     .SetupEndpoint                       method    ay         yisb          -
 

docs/endpoint-recovery.md

@@ -180,6 +180,8 @@ root@cc-nvme-mi:~# busctl introspect au.com.codeconstruct.MCTP1 /au/com/codecons
 NAME                                TYPE      SIGNATURE  RESULT/VALUE  FLAGS
 au.com.codeconstruct.Interface1     interface -          -             -
 .AssignEndpoint                     method    ay         yisb          -
+.AssignEndpointStatic               method    ayy        yisb          -
+.AssignEndpointPreferred            method    ayy        yisb          -
 .LearnEndpoint                      method    ay         yisb          -
 .SetupEndpoint                      method    ay         yisb          -
 org.freedesktop.DBus.Introspectable interface -          -             -

docs/mctpd.md

@@ -138,6 +138,7 @@ au.com.codeconstruct.MCTP.Interface1 interface -         -            -
 au.com.codeconstruct.MCTP.BusOwner1  interface -         -            -
 .AssignEndpoint                      method    ay        yisb         -
 .AssignEndpointStatic                method    ayy       yisb         -
+.AssignEndpointPreferred             method    ayy       yisb         -
 .LearnEndpoint                       method    ay        yisb         -
 .SetupEndpoint                       method    ay        yisb         -
 ```
@@ -203,6 +204,20 @@ This call will fail if the endpoint already has an EID, and that EID is
 different from `static-EID`, or if `static-EID` is already assigned to another
 endpoint.
 
+#### `.AssignEndpointPreferred`: `ayy` → `yisb`
+
+Similar to AssignEndpointStatic, but takes the additional EID argument as a
+preferred EID rather than a strict static assignment:
+
+```
+AssignEndpointPreferred <hwaddr> <preferred-EID>
+```
+
+If `<preferred-EID>` is available, it will be assigned to the endpoint. If that
+EID is already assigned to another endpoint, `mctpd` falls back to dynamic EID
+allocation. If the endpoint is already known to `mctpd`, the existing endpoint
+record is returned.
+
 #### `.LearnEndpoint`: `ay` → `yisb`
 
 Like SetupEndpoint but will not assign EIDs, will only query endpoints for a

src/mctpd.c

@@ -3126,6 +3126,84 @@ static int method_assign_endpoint_static(sd_bus_message *call, void *data,
 	return rc;
 }
 
+static int method_assign_endpoint_preferred(sd_bus_message *call, void *data,
+					    sd_bus_error *berr)
+{
+	dest_phys desti, *dest = &desti;
+	const char *peer_path = NULL;
+	struct peer *peer = NULL;
+	struct link *link = data;
+	struct ctx *ctx = link->ctx;
+	uint8_t eid;
+	int rc;
+
+	dest->ifindex = link->ifindex;
+	if (dest->ifindex <= 0)
+		return sd_bus_error_setf(berr, SD_BUS_ERROR_INVALID_ARGS,
+					 "Unknown MCTP interface");
+
+	rc = message_read_hwaddr(call, dest);
+	if (rc < 0)
+		goto err;
+
+	rc = sd_bus_message_read(call, "y", &eid);
+	if (rc < 0)
+		goto err;
+
+	rc = validate_dest_phys(ctx, dest);
+	if (rc < 0)
+		return sd_bus_error_setf(berr, SD_BUS_ERROR_INVALID_ARGS,
+					 "Bad physaddr");
+
+	peer = find_peer_by_phys(ctx, dest);
+	if (peer) {
+		// Return existing record, even if it differs from the preferred EID.
+		peer_path = path_from_peer(peer);
+		if (!peer_path)
+			goto err;
+
+		return sd_bus_reply_method_return(call, "yisb", peer->eid,
+						  peer->net, peer_path, 0);
+	} else {
+		uint32_t netid;
+		struct net *net;
+
+		netid = mctp_nl_net_byindex(ctx->nl, dest->ifindex);
+		net = lookup_net(ctx, netid);
+		peer = find_peer_by_addr(ctx, eid, netid);
+		if (peer || (net && is_eid_in_bridge_pool(net, ctx, eid))) {
+			if (peer) {
+				warnx("Preferred EID %d already in use by %s, using dynamic EID for %s",
+				      eid, peer_tostr(peer),
+				      dest_phys_tostr(dest));
+			} else {
+				warnx("Preferred EID %d is in a bridge pool, using dynamic EID for %s",
+				      eid, dest_phys_tostr(dest));
+			}
+			rc = endpoint_assign_eid(ctx, berr, dest, &peer, 0,
+						 true);
+		} else {
+			rc = endpoint_assign_eid(ctx, berr, dest, &peer, eid,
+						 false);
+		}
+		if (rc < 0)
+			goto err;
+	}
+
+	if (peer->pool_size > 0)
+		endpoint_allocate_eids(peer);
+
+	peer_path = path_from_peer(peer);
+	if (!peer_path)
+		goto err;
+
+	return sd_bus_reply_method_return(call, "yisb", peer->eid, peer->net,
+					  peer_path, 1);
+err:
+	set_berr(ctx, rc, berr);
+	return rc;
+}
+
 static int method_learn_endpoint(sd_bus_message *call, void *data,
 				 sd_bus_error *berr)
 {
@@ -4055,6 +4133,18 @@ static const sd_bus_vtable bus_link_owner_vtable[] = {
 		method_assign_endpoint_static,
 		0),
 
+	SD_BUS_METHOD_WITH_NAMES("AssignEndpointPreferred",
+		"ayy",
+		SD_BUS_PARAM(physaddr)
+		SD_BUS_PARAM(eid),
+		"yisb",
+		SD_BUS_PARAM(eid)
+		SD_BUS_PARAM(net)
+		SD_BUS_PARAM(path)
+		SD_BUS_PARAM(new),
+		method_assign_endpoint_preferred,
+		0),
+
 	SD_BUS_METHOD_WITH_NAMES("LearnEndpoint",
 		"ay",
 		SD_BUS_PARAM(physaddr),

tests/test_mctpd.py

@@ -409,6 +409,47 @@ async def test_assign_endpoint_static_conflict(dbus, mctpd):
     assert str(ex.value) == "Address in use"
 
 
+async def test_assign_endpoint_preferred_static(dbus, mctpd):
+    """Test that preferred assignment uses the requested EID when available"""
+    iface = mctpd.system.interfaces[0]
+    mctp = await mctpd_mctp_iface_obj(dbus, iface)
+    dev = mctpd.network.endpoints[0]
+    preferred_eid = 12
+
+    (eid, _, _, new) = await mctp.call_assign_endpoint_preferred(
+        dev.lladdr, preferred_eid
+    )
+
+    assert eid == preferred_eid
+    assert dev.eid == preferred_eid
+    assert new
+
+
+async def test_assign_endpoint_preferred_conflict_falls_back(dbus, mctpd):
+    """Test that preferred assignment falls back to dynamic EID on conflict"""
+    iface = mctpd.system.interfaces[0]
+    mctp = await mctpd_mctp_iface_obj(dbus, iface)
+    dev1 = mctpd.network.endpoints[0]
+    dev2 = Endpoint(iface, bytes([0x1E]))
+    preferred_eid = 12
+
+    mctpd.network.add_endpoint(dev2)
+
+    (eid1, _, _, new1) = await mctp.call_assign_endpoint_static(
+        dev1.lladdr, preferred_eid
+    )
+    assert eid1 == preferred_eid
+    assert new1
+
+    (eid2, _, _, new2) = await mctp.call_assign_endpoint_preferred(
+        dev2.lladdr, preferred_eid
+    )
+
+    assert eid2 != preferred_eid
+    assert dev2.eid == eid2
+    assert new2
+
+
 async def test_assign_endpoint_static_varies(dbus, mctpd):
     """Test that we cannot re-assign a static EID to an endpoint that already
     has a different EID allocated