Commit 11614723 authored by Stanislav Fomichev's avatar Stanislav Fomichev Committed by Alexei Starovoitov
Browse files

xsk: Add option to calculate TX checksum in SW 



For XDP_COPY mode, add a UMEM option XDP_UMEM_TX_SW_CSUM
to call skb_checksum_help in transmit path. Might be useful
to debugging issues with real hardware. I also use this mode
in the selftests.

Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20231127190319.1190813-9-sdf@google.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent ce59f968

Documentation/networking/xsk-tx-metadata.rst

+9 −0
Original line number Diff line number Diff line
@@ -50,6 +50,15 @@ packet's ``struct xdp_desc`` descriptor should set ``XDP_TX_METADATA`` 
bit in the ``options`` field. Also note that in a multi-buffer packet

only the first chunk should carry the metadata.



Software TX Checksum

====================



For development and testing purposes its possible to pass

``XDP_UMEM_TX_SW_CSUM`` flag to ``XDP_UMEM_REG`` UMEM registration call.

In this case, when running in ``XDK_COPY`` mode, the TX checksum

is calculated on the CPU. Do not enable this option in production because

it will negatively affect performance.



Querying Device Capabilities

============================

include/net/xsk_buff_pool.h

+1 −0
Original line number Diff line number Diff line
@@ -83,6 +83,7 @@ struct xsk_buff_pool { 
	bool uses_need_wakeup;

	bool dma_need_sync;

	bool unaligned;

	bool tx_sw_csum;

	void *addrs;

	/* Mutual exclusion of the completion ring in the SKB mode. Two cases to protect:

	 * NAPI TX thread and sendmsg error paths in the SKB destructor callback and when

include/uapi/linux/if_xdp.h

+7 −1
Original line number Diff line number Diff line
@@ -35,6 +35,12 @@ 
/* Flags for xsk_umem_config flags */

#define XDP_UMEM_UNALIGNED_CHUNK_FLAG	(1 << 0)



/* Force checksum calculation in software. Can be used for testing or

 * working around potential HW issues. This option causes performance

 * degradation and only works in XDP_COPY mode.

 */

#define XDP_UMEM_TX_SW_CSUM		(1 << 1)



struct sockaddr_xdp {

	__u16 sxdp_family;

	__u16 sxdp_flags;

net/xdp/xdp_umem.c

+6 −1
Original line number Diff line number Diff line
@@ -148,6 +148,11 @@ static int xdp_umem_account_pages(struct xdp_umem *umem) 
	return 0;

}



#define XDP_UMEM_FLAGS_VALID ( \

		XDP_UMEM_UNALIGNED_CHUNK_FLAG | \

		XDP_UMEM_TX_SW_CSUM | \

	0)



static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)

{

	bool unaligned_chunks = mr->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;
@@ -167,7 +172,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) 
		return -EINVAL;

	}



	if (mr->flags & ~XDP_UMEM_UNALIGNED_CHUNK_FLAG)

	if (mr->flags & ~XDP_UMEM_FLAGS_VALID)

		return -EINVAL;



	if (!unaligned_chunks && !is_power_of_2(chunk_size))

net/xdp/xsk.c

+6 −0
Original line number Diff line number Diff line
@@ -744,6 +744,12 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, 
				skb->csum_start = hr + meta->request.csum_start;

				skb->csum_offset = meta->request.csum_offset;

				skb->ip_summed = CHECKSUM_PARTIAL;



				if (unlikely(xs->pool->tx_sw_csum)) {

					err = skb_checksum_help(skb);

					if (err)

						goto free_err;

				}

			}

		}

	}