xsk: Check need wakeup flag in sendmsg() (e3920818) · Commits · 戴 / test

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:

Björn Töpel <bjorn.topel@intel.com> Signed-off-by:

Daniel Borkmann <daniel@iogearbox.net> Acked-by:

Magnus Karlsson <magnus.karlsson@intel.com> Link: https://lore.kernel.org/bpf/20201130185205.196029-5-bjorn.topel@gmail.com

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);

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