net: datagram: introduce datagram_poll_queue for custom receive queues
Some protocols using TCP encapsulation (e.g., espintcp, openvpn) deliver
userspace-bound packets through a custom skb queue rather than the
standard sk_receive_queue.
Introduce datagram_poll_queue that accepts an explicit receive queue,
and convert datagram_poll into a wrapper around datagram_poll_queue.
This allows protocols with custom skb queues to reuse the core polling
logic without relying on sk_receive_queue.
Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: Antonio Quartulli <antonio@openvpn.net>
Signed-off-by: Ralf Lici <ralf@mandelbit.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Antonio Quartulli <antonio@openvpn.net>
Link: https://patch.msgid.link/20251021100942.195010-2-ralf@mandelbit.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index fb3fec9..a7cc3d1 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -4204,6 +4204,9 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk,
struct sk_buff_head *sk_queue,
unsigned int flags, int *off, int *err);
struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags, int *err);
+__poll_t datagram_poll_queue(struct file *file, struct socket *sock,
+ struct poll_table_struct *wait,
+ struct sk_buff_head *rcv_queue);
__poll_t datagram_poll(struct file *file, struct socket *sock,
struct poll_table_struct *wait);
int skb_copy_datagram_iter(const struct sk_buff *from, int offset,
diff --git a/net/core/datagram.c b/net/core/datagram.c
index cb4b9ef..c285c64 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -920,21 +920,22 @@ int skb_copy_and_csum_datagram_msg(struct sk_buff *skb,
EXPORT_SYMBOL(skb_copy_and_csum_datagram_msg);
/**
- * datagram_poll - generic datagram poll
+ * datagram_poll_queue - same as datagram_poll, but on a specific receive
+ * queue
* @file: file struct
* @sock: socket
* @wait: poll table
+ * @rcv_queue: receive queue to poll
*
- * Datagram poll: Again totally generic. This also handles
- * sequenced packet sockets providing the socket receive queue
- * is only ever holding data ready to receive.
+ * Performs polling on the given receive queue, handling shutdown, error,
+ * and connection state. This is useful for protocols that deliver
+ * userspace-bound packets through a custom queue instead of
+ * sk->sk_receive_queue.
*
- * Note: when you *don't* use this routine for this protocol,
- * and you use a different write policy from sock_writeable()
- * then please supply your own write_space callback.
+ * Return: poll bitmask indicating the socket's current state
*/
-__poll_t datagram_poll(struct file *file, struct socket *sock,
- poll_table *wait)
+__poll_t datagram_poll_queue(struct file *file, struct socket *sock,
+ poll_table *wait, struct sk_buff_head *rcv_queue)
{
struct sock *sk = sock->sk;
__poll_t mask;
@@ -956,7 +957,7 @@ __poll_t datagram_poll(struct file *file, struct socket *sock,
mask |= EPOLLHUP;
/* readable? */
- if (!skb_queue_empty_lockless(&sk->sk_receive_queue))
+ if (!skb_queue_empty_lockless(rcv_queue))
mask |= EPOLLIN | EPOLLRDNORM;
/* Connection-based need to check for termination and startup */
@@ -978,4 +979,27 @@ __poll_t datagram_poll(struct file *file, struct socket *sock,
return mask;
}
+EXPORT_SYMBOL(datagram_poll_queue);
+
+/**
+ * datagram_poll - generic datagram poll
+ * @file: file struct
+ * @sock: socket
+ * @wait: poll table
+ *
+ * Datagram poll: Again totally generic. This also handles
+ * sequenced packet sockets providing the socket receive queue
+ * is only ever holding data ready to receive.
+ *
+ * Note: when you *don't* use this routine for this protocol,
+ * and you use a different write policy from sock_writeable()
+ * then please supply your own write_space callback.
+ *
+ * Return: poll bitmask indicating the socket's current state
+ */
+__poll_t datagram_poll(struct file *file, struct socket *sock, poll_table *wait)
+{
+ return datagram_poll_queue(file, sock, wait,
+ &sock->sk->sk_receive_queue);
+}
EXPORT_SYMBOL(datagram_poll);
