From: Tirthendu Sarkar <tirthendu.sarkar@xxxxxxxxx>
As of now xsk core drops any xdp_buff with data size greater than the
xsk frame_size as set by the af_xdp application. With multi-buffer
support introduced in the next patch xsk core can now split those
buffers into multiple descriptors provided the af_xdp application can
handle them. Such capability of the application needs to be independent
of the xdp_prog's frag support capability since there are cases where
even a single xdp_buffer may need to be split into multiple descriptors
owing to a smaller xsk frame size.
For e.g., with NIC rx_buffer size set to 4kB, a 3kB packet will
constitute of a single buffer and so will be sent as such to AF_XDP layer
irrespective of 'xdp.frags' capability of the XDP program. Now if the xsk
frame size is set to 2kB by the AF_XDP application, then the packet will
need to be split into 2 descriptors if AF_XDP application can handle
multi-buffer, else it needs to be dropped.
Applications can now advertise their frag handling capability to xsk core
so that xsk core can decide if it should drop or split xdp_buffs that
exceed xsk frame size. This is done using a new 'XSK_USE_SG' bind flag
for the xdp socket.
Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@xxxxxxxxx>
---
include/net/xdp_sock.h | 1 +
include/uapi/linux/if_xdp.h | 6 ++++++
net/xdp/xsk.c | 5 +++--
3 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index e96a1151ec75..36b0411a0d1b 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -52,6 +52,7 @@ struct xdp_sock {
struct xsk_buff_pool *pool;
u16 queue_id;
bool zc;
+ bool sg;
enum {
XSK_READY = 0,
XSK_BOUND,
diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
index 434f313dc26c..8d48863472b9 100644
--- a/include/uapi/linux/if_xdp.h
+++ b/include/uapi/linux/if_xdp.h
@@ -25,6 +25,12 @@
* application.
*/
#define XDP_USE_NEED_WAKEUP (1 << 3)
+/* By setting this option, userspace application indicates that it can
+ * handle multiple descriptors per packet thus enabling AF_XDP to split
+ * multi-buffer XDP frames into multiple Rx descriptors. Without this set
+ * such frames will be dropped.
+ */
+#define XDP_USE_SG (1 << 4)
/* Flags for xsk_umem_config flags */
#define XDP_UMEM_UNALIGNED_CHUNK_FLAG (1 << 0)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 914a80cd55d3..7b709e4e7ec4 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -897,7 +897,7 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
flags = sxdp->sxdp_flags;
if (flags & ~(XDP_SHARED_UMEM | XDP_COPY | XDP_ZEROCOPY |
- XDP_USE_NEED_WAKEUP))
+ XDP_USE_NEED_WAKEUP | XDP_USE_SG))
return -EINVAL;
bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
@@ -929,7 +929,7 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
struct socket *sock;
if ((flags & XDP_COPY) || (flags & XDP_ZEROCOPY) ||
- (flags & XDP_USE_NEED_WAKEUP)) {
+ (flags & XDP_USE_NEED_WAKEUP) || (flags & XDP_USE_SG)) {
/* Cannot specify flags for shared sockets. */
err = -EINVAL;
goto out_unlock;
@@ -1028,6 +1028,7 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
xs->dev = dev;
xs->zc = xs->umem->zc;
+ xs->sg = !!(flags & XDP_USE_SG);
xs->queue_id = qid;
xp_add_xsk(xs->pool, xs);
--
2.34.1
