mctpd: add bridged endpoint polling mechanism

Implement endpoint periodic polling mechanism to validate bridged
endpoint accessiblity. Begin polling as soon as gateway routes are
created. Stop polling once it's established that endpoint path is
accessible.

Publish peer path once downstream endpoint responds to send poll
command.

Since downstream endpoints are behind the bridge, available
query_get_endpoint_id() won't be able to redirect the
GET_ENDPOINT_ID command packet behind the bridge physical
address of downstream endpoint would be same as bridge's own.

But we can do direct query to endpoint since routes have already
been layed out when bridge was allocated the eid pool space.

Remove all downstream endpoints as well if bridge is being removed.
Also stop endpoint periodic polling.

Signed-off-by: Faizan Ali <faizana@nvidia.com>

Author: faizana-nvidia

src/mctpd.c

@@ -101,6 +101,12 @@ struct role {
 	const char *dbus_val;
 };
 
+// Endpoint poll context for bridged endpoint polling
+struct ep_poll_ctx {
+	struct peer *bridge;
+	mctp_eid_t poll_eid;
+};
+
 static const struct role roles[] = {
 	[ENDPOINT_ROLE_UNKNOWN] = {
 		.role = ENDPOINT_ROLE_UNKNOWN,
@@ -199,6 +205,10 @@ struct peer {
 	// Pool size
 	uint8_t pool_size;
 	uint8_t pool_start;
+
+	struct {
+		sd_event_source **sources;
+	} bridge_ep_poll;
 };
 
 struct msg_type_support {
@@ -284,6 +294,7 @@ static int add_peer_from_addr(struct ctx *ctx,
 			      const struct sockaddr_mctp_ext *addr,
 			      struct peer **ret_peer);
 static int remove_peer(struct peer *peer);
+static int remove_bridged_peers(struct peer *bridge);
 static int query_peer_properties(struct peer *peer);
 static int setup_added_peer(struct peer *peer);
 static void add_peer_route(struct peer *peer);
@@ -1963,6 +1974,57 @@ static int check_peer_struct(const struct peer *peer, const struct net *n)
 	return 0;
 }
 
+/* Stops downstream endpoint polling and removes
+ * peer structure when bridge endpoint is being removed.
+ */
+static int remove_bridged_peers(struct peer *bridge)
+{
+	mctp_eid_t ep, pool_start, pool_end;
+	struct ep_poll_ctx *pctx = NULL;
+	struct peer *peer = NULL;
+	struct net *n = NULL;
+	int rc = 0;
+
+	pool_end = bridge->pool_start + bridge->pool_size - 1;
+	n = lookup_net(bridge->ctx, bridge->net);
+	pool_start = bridge->pool_start;
+	for (ep = pool_start; ep <= pool_end; ep++) {
+		// stop endpoint polling before removing peer
+		// else next trigger will create peer again.
+		int idx = ep - pool_start;
+
+		if (bridge->bridge_ep_poll.sources &&
+		    bridge->bridge_ep_poll.sources[idx]) {
+			pctx = sd_event_source_get_userdata(
+				bridge->bridge_ep_poll.sources[idx]);
+			rc = sd_event_source_set_enabled(
+				bridge->bridge_ep_poll.sources[idx],
+				SD_EVENT_OFF);
+			if (rc < 0) {
+				warnx("Failed to stop polling timer while removing peer %d: %s",
+				      ep, strerror(-rc));
+			}
+
+			sd_event_source_unref(
+				bridge->bridge_ep_poll.sources[idx]);
+			bridge->bridge_ep_poll.sources[idx] = NULL;
+			free(pctx);
+		}
+		peer = n->peers[ep];
+		if (!peer)
+			continue;
+
+		rc = remove_peer(peer);
+		if (rc < 0) {
+			warnx("Failed to remove peer %d from bridge eid %d pool [%d - %d]: %s",
+			      ep, bridge->eid, pool_start, pool_end,
+			      strerror(-rc));
+		}
+	}
+
+	return 0;
+}
+
 static int remove_peer(struct peer *peer)
 {
 	struct ctx *ctx = peer->ctx;
@@ -1997,6 +2059,12 @@ static int remove_peer(struct peer *peer)
 		sd_event_source_unref(peer->recovery.source);
 	}
 
+	if (peer->pool_size) {
+		remove_bridged_peers(peer);
+		free(peer->bridge_ep_poll.sources);
+		peer->bridge_ep_poll.sources = NULL;
+	}
+
 	n->peers[peer->eid] = NULL;
 	free(peer->message_types);
 	free(peer->uuid);
@@ -2043,6 +2111,7 @@ static void free_peers(struct ctx *ctx)
 		free(peer->message_types);
 		free(peer->uuid);
 		free(peer->path);
+		free(peer->bridge_ep_poll.sources);
 		sd_bus_slot_unref(peer->slot_obmc_endpoint);
 		sd_bus_slot_unref(peer->slot_cc_endpoint);
 		sd_bus_slot_unref(peer->slot_bridge);
@@ -2446,6 +2515,52 @@ static int get_endpoint_peer(struct ctx *ctx, sd_bus_error *berr,
 	return 0;
 }
 
+/* DSP0236 section 8.17.6 Reclaiming EIDs from hot-plug devices
+ *
+ * The bus owner/bridge can detect a removed device or devices by
+ * validating the EIDs that are presently allocated to endpoints that
+ * are directly on the bus and identifying which EIDs are missing.
+ * It can do this by attempting to access each endpoint that the bridge
+ * has listed in its routing table as being a device that is directly on
+ * the particular bus. Attempting to access each endpoint can be accomplished
+ * by issuing the Get Endpoint ID command...
+
+
+ * since bridged endpoints are routed from bridge, direct query
+ * to eid should work if gateway routes are in place.
+ */
+static int query_endpoint_poll_commmand(struct peer *peer, mctp_eid_t *resp_eid)
+{
+	struct sockaddr_mctp_ext addr = { 0 };
+	struct mctp_ctrl_cmd_get_eid req = { 0 };
+	struct mctp_ctrl_resp_get_eid *resp = NULL;
+
+	uint8_t *buf = NULL;
+	size_t buf_size;
+	uint8_t iid;
+	int rc;
+
+	iid = mctp_next_iid(peer->ctx);
+	mctp_ctrl_msg_hdr_init_req(&req.ctrl_hdr, iid,
+				   MCTP_CTRL_CMD_GET_ENDPOINT_ID);
+	rc = endpoint_query_peer(peer, MCTP_CTRL_HDR_MSG_TYPE, &req,
+				 sizeof(req), &buf, &buf_size, &addr);
+	if (rc < 0)
+		goto out;
+
+	rc = mctp_ctrl_validate_response(buf, buf_size, sizeof(*resp),
+					 peer_tostr_short(peer), iid,
+					 MCTP_CTRL_CMD_GET_ENDPOINT_ID);
+	if (!rc) {
+		resp = (void *)buf;
+		*resp_eid = resp->eid;
+	}
+
+out:
+	free(buf);
+	return rc;
+}
+
 static int query_get_peer_msgtypes(struct peer *peer)
 {
 	struct sockaddr_mctp_ext addr;
@@ -5213,6 +5328,139 @@ static int endpoint_send_allocate_endpoint_ids(
 	return rc;
 }
 
+static int peer_endpoint_poll(sd_event_source *s, uint64_t usec, void *userdata)
+{
+	struct ep_poll_ctx *pctx = userdata;
+	struct peer *bridge = pctx->bridge;
+	mctp_eid_t ep = pctx->poll_eid;
+	mctp_eid_t pool_start, idx;
+	struct peer *peer = NULL;
+	mctp_eid_t ret_eid = 0;
+	struct net *n;
+	int rc = 0;
+
+	if (!bridge) {
+		free(pctx);
+		return 0;
+	}
+
+	pool_start = bridge->pool_start;
+	idx = ep - pool_start;
+
+	/* Polling policy :
+	 *
+	 * Once bridge eid pool space is allocated and gateway
+	 * routes for downstream endpoints are in place, busowner
+	 * would initiate periodic GET_ENDPOINT_ID command at an
+	 * interval of atleast 1/2 * TRECLAIM.
+
+	 1. The downstream endpoint if present behind the bridge,
+	    responds to send poll command, that endpoint path is
+		considered accessible.
+		The endpoint path would be published as reachable to d-bus and
+		polling will no longer continue.
+
+	 2. If endpoint is not present or doesn't responds to send poll
+	    commmand, then it has not been establed yet that endpoint
+		path from the bridge is accessible or not, thus continue
+		to poll.
+	 */
+
+	n = lookup_net(bridge->ctx, bridge->net);
+	peer = n->peers[ep];
+	if (!peer) {
+		rc = add_peer(bridge->ctx, &(bridge->phys), ep, bridge->net,
+			      &peer, true);
+		if (rc < 0)
+			goto exit;
+	}
+
+	rc = query_endpoint_poll_commmand(peer, &ret_eid);
+	if (rc < 0) {
+		goto reschedule;
+	}
+
+	if (ret_eid != ep) {
+		warnx("Unexpected eid %d abort polling for eid %d", ret_eid,
+		      ep);
+		goto exit;
+	}
+
+	if (bridge->ctx->verbose) {
+		fprintf(stderr, "Endpoint %d is accessible\n", ep);
+	}
+
+	rc = setup_added_peer(peer);
+	if (rc < 0)
+		goto reschedule;
+
+exit:
+	if (bridge) {
+		assert(sd_event_source_get_enabled(
+			       bridge->bridge_ep_poll.sources[idx], NULL) == 0);
+		sd_event_source_unref(bridge->bridge_ep_poll.sources[idx]);
+		bridge->bridge_ep_poll.sources[idx] = NULL;
+	}
+	free(pctx);
+	return rc < 0 ? rc : 0;
+
+reschedule:
+	rc = mctp_ops.sd_event.source_set_time_relative(
+		bridge->bridge_ep_poll.sources[idx],
+		bridge->ctx->endpoint_poll);
+	if (rc >= 0) {
+		rc = sd_event_source_set_enabled(
+			bridge->bridge_ep_poll.sources[idx], SD_EVENT_ONESHOT);
+	}
+	return 0;
+}
+
+static int bridge_poll_start(struct peer *bridge)
+{
+	mctp_eid_t pool_start = bridge->pool_start;
+	mctp_eid_t pool_size = bridge->pool_size;
+	sd_event_source **sources = NULL;
+	struct ctx *ctx;
+	int rc;
+	int i;
+
+	sources = calloc(pool_size, sizeof(sd_event_source *));
+	ctx = bridge->ctx;
+
+	if (!sources) {
+		rc = -ENOMEM;
+		warnx("Failed to setup periodic polling for bridge (eid %d)",
+		      bridge->eid);
+		return rc;
+	}
+
+	bridge->bridge_ep_poll.sources = sources;
+	for (i = 0; i < pool_size; i++) {
+		struct ep_poll_ctx *pctx =
+			calloc(1, sizeof(struct ep_poll_ctx));
+		if (!pctx) {
+			warnx("Failed to memory, skip polling for eid %d",
+			      pool_start + i);
+			continue;
+		}
+
+		pctx->bridge = bridge;
+		pctx->poll_eid = pool_start + i;
+		rc = mctp_ops.sd_event.add_time_relative(
+			ctx->event, &bridge->bridge_ep_poll.sources[i],
+			CLOCK_MONOTONIC, ctx->endpoint_poll, 0,
+			peer_endpoint_poll, pctx);
+		if (rc < 0) {
+			warnx("Failed to setup poll event source for eid %d",
+			      (pool_start + i));
+			free(pctx);
+			continue;
+		}
+	}
+
+	return 0;
+}
+
 static int endpoint_allocate_eids(struct peer *peer)
 {
 	uint8_t allocated_pool_size = 0;
@@ -5281,7 +5529,10 @@ static int endpoint_allocate_eids(struct peer *peer)
 			peer->pool_size);
 	}
 
-	// TODO: Polling logic for downstream EID
+	// Poll for downstream endpoint accessibility
+	if (peer->ctx->endpoint_poll) {
+		bridge_poll_start(peer);
+	}
 
 	return 0;
 }