mctp: Add retry for one-time peer property queries on timeout

The function `query_peer_properties()` is called once during peer initialization
to query basic information after the EID becomes routable.
To improve reliability, this change adds a retry mechanism when the query
fails with `-ETIMEDOUT`. Since these queries are one-time initialization steps,
a single successful attempt is sufficient, and retrying enhances stability
under transient MCTP bus contention or multi-master timing issues.

Testing:
add stress test for peer initialization under multi-master
```
while true; do
    echo "Restarting mctpd.service..."
    systemctl restart mctpd.service

    # Wait a few seconds to allow service to initialize
    sleep 20
done
```
After the 30 loops, the script checks mctpd.service journal for expected
retry messages to verify robustness under transient MCTP bus contention.
```
root@bmc:~# journalctl -xeu mctpd.service | grep Retrying
Oct 29 00:35:21 bmc mctpd[31801]: mctpd: Retrying to get endpoint types for peer eid 10 net 1 phys physaddr if 4 hw len 1 0x20 state 1. Attempt 1
Oct 29 00:39:00 bmc mctpd[32065]: mctpd: Retrying to get endpoint types for peer eid 10 net 1 phys physaddr if 4 hw len 1 0x20 state 1. Attempt 1
Oct 29 00:39:01 bmc mctpd[32065]: mctpd: Retrying to get endpoint types for peer eid 10 net 1 phys physaddr if 4 hw len 1 0x20 state 1. Attempt 2
Oct 29 00:45:08 bmc mctpd[32360]: mctpd: Retrying to get endpoint types for peer eid 10 net 1 phys physaddr if 4 hw len 1 0x20 state 1. Attempt 1
```

Signed-off-by: Daniel Hsu <[email protected]>

Author: JunYe1993

src/mctpd.c

@@ -2835,23 +2835,57 @@ static int method_learn_endpoint(sd_bus_message *call, void *data,
 // and routable.
 static int query_peer_properties(struct peer *peer)
 {
+	const unsigned int max_retries = 4;
 	int rc;
 
-	rc = query_get_peer_msgtypes(peer);
-	if (rc < 0) {
-		// Warn here, it's a mandatory command code.
-		// It might be too noisy if some devices don't implement it.
-		warnx("Error getting endpoint types for %s. Ignoring error %d %s",
-		      peer_tostr(peer), rc, strerror(-rc));
-		rc = 0;
+	for (unsigned int i = 0; i < max_retries; i++) {
+		rc = query_get_peer_msgtypes(peer);
+
+		// Success
+		if (rc == 0)
+			break;
+
+		// On timeout, retry
+		if (rc == -ETIMEDOUT) {
+			if (peer->ctx->verbose)
+				warnx("Retrying to get endpoint types for %s. Attempt %u",
+				      peer_tostr(peer), i + 1);
+			continue;
+		}
+
+		// On other errors, warn and ignore
+		if (rc < 0) {
+			if (peer->ctx->verbose)
+				warnx("Error getting endpoint types for %s. Ignoring error %d %s",
+				      peer_tostr(peer), -rc, strerror(-rc));
+			rc = 0;
+			break;
+		}
 	}
 
-	rc = query_get_peer_uuid(peer);
-	if (rc < 0) {
-		if (peer->ctx->verbose)
-			warnx("Error getting UUID for %s. Ignoring error %d %s",
-			      peer_tostr(peer), rc, strerror(-rc));
-		rc = 0;
+	for (unsigned int i = 0; i < max_retries; i++) {
+		rc = query_get_peer_uuid(peer);
+
+		// Success
+		if (rc == 0)
+			break;
+
+		// On timeout, retry
+		if (rc == -ETIMEDOUT) {
+			if (peer->ctx->verbose)
+				warnx("Retrying to get peer UUID for %s. Attempt %u",
+				      peer_tostr(peer), i + 1);
+			continue;
+		}
+
+		// On other errors, warn and ignore
+		if (rc < 0) {
+			if (peer->ctx->verbose)
+				warnx("Error getting UUID for %s. Ignoring error %d %s",
+				      peer_tostr(peer), -rc, strerror(-rc));
+			rc = 0;
+			break;
+		}
 	}
 
 	// TODO: emit property changed? Though currently they are all const.