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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>
This commit is contained in:
Ralf Lici 2025-10-21 12:09:40 +02:00 committed by Paolo Abeni
parent 10843e1492
commit f6ceec6434
2 changed files with 37 additions and 10 deletions
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3
include/linux/skbuff.h
View File

@ -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,

44
net/core/datagram.c
View File

@ -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);