[RFC PATCH v2 11/14] xsk: add Tx queue setup and mmap support

["Björn Töpel" <bjorn.topel@gmail.com>]

From: Magnus Karlsson <magnus.karlsson@intel.com>

Another setsockopt (XDP_TX_QUEUE) is added to let the process allocate
a queue, where the user process can pass frames to be transmitted by
the kernel.

The mmapping of the queue is done using the XDP_PGOFF_TX_QUEUE offset.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
---
 include/uapi/linux/if_xdp.h | 2 ++
 net/xdp/xsk.c               | 9 +++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
index aec2eee4e751..6cab56fb8be6 100644
--- a/include/uapi/linux/if_xdp.h
+++ b/include/uapi/linux/if_xdp.h
@@ -33,6 +33,7 @@ struct sockaddr_xdp {
 
 /* XDP socket options */
 #define XDP_RX_QUEUE		  1
+#define XDP_TX_QUEUE		  2
 #define XDP_UMEM_REG		  3
 #define XDP_UMEM_FILL_QUEUE	  4
 #define XDP_UMEM_COMPLETION_QUEUE 5
@@ -46,6 +47,7 @@ struct xdp_umem_reg {
 
 /* Pgoff for mmaping the rings */
 #define XDP_PGOFF_RX_QUEUE			  0
+#define XDP_PGOFF_TX_QUEUE		 0x80000000
 #define XDP_UMEM_PGOFF_FILL_QUEUE	0x100000000
 #define XDP_UMEM_PGOFF_COMPLETION_QUEUE 0x180000000
 
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 2071365c39b1..a9bceb0958d8 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -43,6 +43,7 @@ struct xdp_sock {
 	struct xsk_queue *rx;
 	struct xskq_iter rx_it;
 	u64 rx_dropped;
+	struct xsk_queue *tx;
 	struct net_device *dev;
 	/* Protects multiple processes in the control path */
 	struct mutex mutex;
@@ -218,7 +219,7 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 		goto out_release;
 	}
 
-	if (!xs->rx) {
+	if (!xs->rx && !xs->tx) {
 		err = -EINVAL;
 		goto out_unlock;
 	}
@@ -303,6 +304,7 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
 
 	switch (optname) {
 	case XDP_RX_QUEUE:
+	case XDP_TX_QUEUE:
 	{
 		struct xsk_queue **q;
 		int entries;
@@ -313,7 +315,7 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
 			return -EFAULT;
 
 		mutex_lock(&xs->mutex);
-		q = &xs->rx;
+		q = (optname == XDP_TX_QUEUE) ? &xs->tx : &xs->rx;
 		err = xsk_init_queue(entries, q, false);
 		mutex_unlock(&xs->mutex);
 		return err;
@@ -385,6 +387,8 @@ static int xsk_mmap(struct file *file, struct socket *sock,
 
 	if (offset == XDP_PGOFF_RX_QUEUE) {
 		q = xs->rx;
+	} else if (offset == XDP_PGOFF_TX_QUEUE) {
+		q = xs->tx;
 	} else {
 		if (!xs->umem)
 			return -EINVAL;
@@ -443,6 +447,7 @@ static void xsk_destruct(struct sock *sk)
 		return;
 
 	xskq_destroy(xs->rx);
+	xskq_destroy(xs->tx);
 	xdp_put_umem(xs->umem);
 
 	sk_refcnt_debug_dec(sk);
-- 
2.14.1