Commit e3920818 authored by Björn Töpel's avatar Björn Töpel Committed by Daniel Borkmann
Browse files

xsk: Check need wakeup flag in sendmsg() 



Add a check for need wake up in sendmsg(), so that if a user calls
sendmsg() when no wakeup is needed, do not trigger a wakeup.

To simplify the need wakeup check in the syscall, unconditionally
enable the need wakeup flag for Tx. This has a side-effect for poll();
If poll() is called for a socket without enabled need wakeup, a Tx
wakeup is unconditionally performed.

The wakeup matrix for AF_XDP now looks like:

need wakeup | poll()       | sendmsg()   | recvmsg()
------------+--------------+-------------+------------
disabled    | wake Tx      | wake Tx     | nop
enabled     | check flag;  | check flag; | check flag;
            |   wake Tx/Rx |   wake Tx   |   wake Rx

Signed-off-by: default avatarBjörn Töpel <bjorn.topel@intel.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarMagnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20201130185205.196029-5-bjorn.topel@gmail.com
parent 45a86681

net/xdp/xsk.c

+5 −1
Original line number Diff line number Diff line
@@ -522,13 +522,17 @@ static int xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len) 
	bool need_wait = !(m->msg_flags & MSG_DONTWAIT);

	struct sock *sk = sock->sk;

	struct xdp_sock *xs = xdp_sk(sk);

	struct xsk_buff_pool *pool;



	if (unlikely(!xsk_is_bound(xs)))

		return -ENXIO;

	if (unlikely(need_wait))

		return -EOPNOTSUPP;



	pool = xs->pool;

	if (pool->cached_need_wakeup & XDP_WAKEUP_TX)

		return __xsk_sendmsg(sk);

	return 0;

}



static int xsk_recvmsg(struct socket *sock, struct msghdr *m, size_t len, int flags)

net/xdp/xsk_buff_pool.c

+6 −7
Original line number Diff line number Diff line
@@ -144,14 +144,13 @@ static int __xp_assign_dev(struct xsk_buff_pool *pool, 
	if (err)

		return err;



	if (flags & XDP_USE_NEED_WAKEUP) {

	if (flags & XDP_USE_NEED_WAKEUP)

		pool->uses_need_wakeup = true;

		/* Tx needs to be explicitly woken up the first time.

		 * Also for supporting drivers that do not implement this

		 * feature. They will always have to call sendto().

	/* Tx needs to be explicitly woken up the first time.  Also

	 * for supporting drivers that do not implement this

	 * feature. They will always have to call sendto() or poll().

	 */

	pool->cached_need_wakeup = XDP_WAKEUP_TX;

	}



	dev_hold(netdev);