[PATCH v5 07/11] net: qrtr: Allow sendmsg to target an endpoint

[Mihai Moldovan <ionic@ionic.de>]

From: Denis Kenzior <denkenz@gmail.com>

Allow QIPCRTR family sockets to include QRTR_ENDPOINT auxiliary data
as part of the sendmsg system call.  By including this parameter, the
client can ask the kernel to route the message to a given endpoint, in
situations where multiple endpoints with conflicting node identifier
sets exist in the system.

For legacy clients, or clients that do not include QRTR_ENDPOINT data,
the endpoint is looked up, as before, by only using the node identifier
of the destination qrtr socket address.

Signed-off-by: Denis Kenzior <denkenz@gmail.com>
Reviewed-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Andy Gross <agross@kernel.org>
Signed-off-by: Mihai Moldovan <ionic@ionic.de>

---
v5:
  - no changes
  - Link to v4: https://msgid.link/a30dffc70b84ef33009ac3cd2e5a941fd3cff48f.1753720935.git.ionic@ionic.de

v4:
  - no changes
  - Link to v3: https://msgid.link/4b812aeb566819045dfca401bd06656ea612a4ec.1753312999.git.ionic@ionic.de

v3:
  - rebase against current master
  - port [endpoint ID|node ID] key usage in qrtr_node_lookup() to the generic
    solution already established for the [node ID|port number] usage
  - Link to v2: https://msgid.link/fc510e5f0bae7e2d2cc5c0349ee7c166840b9154.1752947108.git.ionic@ionic.de

v2:
  - rebase against current master
  - no action on review comment regarding initializing out_endpoint_id,
    since that's rightfully already being done
  - Link to v1: https://msgid.link/20241018181842.1368394-7-denkenz@gmail.com
---
 net/qrtr/af_qrtr.c | 89 ++++++++++++++++++++++++++++++++++------------
 net/qrtr/qrtr.h    |  2 ++
 2 files changed, 68 insertions(+), 23 deletions(-)

diff --git a/net/qrtr/af_qrtr.c b/net/qrtr/af_qrtr.c
index 8ddaebbd76d2..fa88a8ed4d8c 100644
--- a/net/qrtr/af_qrtr.c
+++ b/net/qrtr/af_qrtr.c
@@ -106,6 +106,36 @@ static inline struct qrtr_sock *qrtr_sk(struct sock *sk)
 	return container_of(sk, struct qrtr_sock, sk);
 }
 
+int qrtr_msg_get_endpoint(struct msghdr *msg, u32 *out_endpoint_id)
+{
+	struct cmsghdr *cmsg;
+	u32 endpoint_id = 0;
+
+	for_each_cmsghdr(cmsg, msg) {
+		if (!CMSG_OK(msg, cmsg))
+			return -EINVAL;
+
+		if (cmsg->cmsg_level != SOL_QRTR)
+			continue;
+
+		if (cmsg->cmsg_type != QRTR_ENDPOINT)
+			return -EINVAL;
+
+		if (cmsg->cmsg_len < CMSG_LEN(sizeof(u32)))
+			return -EINVAL;
+
+		/* Endpoint ids start at 1 */
+		endpoint_id = *(u32 *)CMSG_DATA(cmsg);
+		if (!endpoint_id)
+			return -EINVAL;
+	}
+
+	if (out_endpoint_id)
+		*out_endpoint_id = endpoint_id;
+
+	return 0;
+}
+
 static unsigned int qrtr_local_nid = 1;
 
 /* for node ids */
@@ -456,14 +486,23 @@ static int qrtr_node_enqueue(struct qrtr_node *node, struct sk_buff *skb,
  *
  * callers must release with qrtr_node_release()
  */
-static struct qrtr_node *qrtr_node_lookup(unsigned int nid)
+static struct qrtr_node *qrtr_node_lookup(unsigned int endpoint_id,
+					  unsigned int nid)
 {
-	struct qrtr_node *node;
+	struct qrtr_node *node = NULL;
 	unsigned long flags;
+	unsigned long key = 0;
+
+	if (endpoint_id > QRTR_INDEX_HALF_UNSIGNED_MAX ||
+	    nid > QRTR_INDEX_HALF_UNSIGNED_MAX)
+		return node;
+
+	key = ((unsigned long)(endpoint_id) << QRTR_INDEX_HALF_BITS) |
+	      ((unsigned long)(nid) & QRTR_INDEX_HALF_UNSIGNED_MAX);
 
 	mutex_lock(&qrtr_node_lock);
 	spin_lock_irqsave(&qrtr_nodes_lock, flags);
-	node = radix_tree_lookup(&qrtr_nodes, nid);
+	node = radix_tree_lookup(&qrtr_nodes, key);
 	node = qrtr_node_acquire(node);
 	spin_unlock_irqrestore(&qrtr_nodes_lock, flags);
 	mutex_unlock(&qrtr_node_lock);
@@ -1028,6 +1067,7 @@ static int qrtr_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 	struct qrtr_sock *ipc = qrtr_sk(sock->sk);
 	struct sock *sk = sock->sk;
 	struct qrtr_node *node;
+	u32 msg_endpoint_id;
 	u32 endpoint_id = qrtr_local_nid;
 	struct sk_buff *skb;
 	size_t plen;
@@ -1040,46 +1080,48 @@ static int qrtr_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 	if (len > 65535)
 		return -EMSGSIZE;
 
+	rc = qrtr_msg_get_endpoint(msg, &msg_endpoint_id);
+	if (rc < 0)
+		return rc;
+
 	lock_sock(sk);
 
 	if (addr) {
-		if (msg->msg_namelen < sizeof(*addr)) {
-			release_sock(sk);
-			return -EINVAL;
-		}
+		rc = -EINVAL;
 
-		if (addr->sq_family != AF_QIPCRTR) {
-			release_sock(sk);
-			return -EINVAL;
-		}
+		if (msg->msg_namelen < sizeof(*addr))
+			goto release_sock;
+
+		if (addr->sq_family != AF_QIPCRTR)
+			goto release_sock;
 
 		rc = qrtr_autobind(sock);
-		if (rc) {
-			release_sock(sk);
-			return rc;
-		}
+		if (rc)
+			goto release_sock;
 	} else if (sk->sk_state == TCP_ESTABLISHED) {
 		addr = &ipc->peer;
 	} else {
-		release_sock(sk);
-		return -ENOTCONN;
+		rc = -ENOTCONN;
+		goto release_sock;
 	}
 
 	node = NULL;
 	if (addr->sq_node == QRTR_NODE_BCAST) {
 		if (addr->sq_port != QRTR_PORT_CTRL &&
 		    qrtr_local_nid != QRTR_NODE_BCAST) {
-			release_sock(sk);
-			return -ENOTCONN;
+			rc = -ENOTCONN;
+			goto release_sock;
 		}
 		enqueue_fn = qrtr_bcast_enqueue;
 	} else if (addr->sq_node == ipc->us.sq_node) {
 		enqueue_fn = qrtr_local_enqueue;
 	} else {
-		node = qrtr_node_lookup(addr->sq_node);
+		endpoint_id = msg_endpoint_id;
+
+		node = qrtr_node_lookup(endpoint_id, addr->sq_node);
 		if (!node) {
-			release_sock(sk);
-			return -ECONNRESET;
+			rc = endpoint_id ? -ENXIO : -ECONNRESET;
+			goto release_sock;
 		}
 		enqueue_fn = qrtr_node_enqueue;
 	}
@@ -1118,6 +1160,7 @@ static int qrtr_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 
 out_node:
 	qrtr_node_release(node);
+release_sock:
 	release_sock(sk);
 
 	return rc;
@@ -1132,7 +1175,7 @@ static int qrtr_send_resume_tx(struct qrtr_cb *cb)
 	struct sk_buff *skb;
 	int ret;
 
-	node = qrtr_node_lookup(remote.sq_node);
+	node = qrtr_node_lookup(cb->endpoint_id, remote.sq_node);
 	if (!node)
 		return -EINVAL;
 
diff --git a/net/qrtr/qrtr.h b/net/qrtr/qrtr.h
index 11b897af05e6..22fcecbf8de2 100644
--- a/net/qrtr/qrtr.h
+++ b/net/qrtr/qrtr.h
@@ -34,4 +34,6 @@ int qrtr_ns_init(void);
 
 void qrtr_ns_remove(void);
 
+int qrtr_msg_get_endpoint(struct msghdr *msg, u32 *out_endpoint_id);
+
 #endif
-- 
2.50.0