diff options
author | Stanislav Fomichev <sdf@fomichev.me> | 2024-07-12 18:52:51 -0700 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2024-07-25 11:57:27 +0200 |
commit | d5e726d9143c5624135f5dc9e4069799adeef734 (patch) | |
tree | d24f61de8cd5af48ecedeecac656669eb4a8019f | |
parent | fa5ef655615a01533035c6139248c5b33aa27028 (diff) |
xsk: Require XDP_UMEM_TX_METADATA_LEN to actuate tx_metadata_len
Julian reports that commit 341ac980eab9 ("xsk: Support tx_metadata_len")
can break existing use cases which don't zero-initialize xdp_umem_reg
padding. Introduce new XDP_UMEM_TX_METADATA_LEN to make sure we
interpret the padding as tx_metadata_len only when being explicitly
asked.
Fixes: 341ac980eab9 ("xsk: Support tx_metadata_len")
Reported-by: Julian Schindel <mail@arctic-alpaca.de>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/bpf/20240713015253.121248-2-sdf@fomichev.me
-rw-r--r-- | Documentation/networking/xsk-tx-metadata.rst | 16 | ||||
-rw-r--r-- | include/uapi/linux/if_xdp.h | 4 | ||||
-rw-r--r-- | net/xdp/xdp_umem.c | 9 |
3 files changed, 20 insertions, 9 deletions
diff --git a/Documentation/networking/xsk-tx-metadata.rst b/Documentation/networking/xsk-tx-metadata.rst index bd033fe95cca..e76b0cfc32f7 100644 --- a/Documentation/networking/xsk-tx-metadata.rst +++ b/Documentation/networking/xsk-tx-metadata.rst @@ -11,12 +11,16 @@ metadata on the receive side. General Design ============== -The headroom for the metadata is reserved via ``tx_metadata_len`` in -``struct xdp_umem_reg``. The metadata length is therefore the same for -every socket that shares the same umem. The metadata layout is a fixed UAPI, -refer to ``union xsk_tx_metadata`` in ``include/uapi/linux/if_xdp.h``. -Thus, generally, the ``tx_metadata_len`` field above should contain -``sizeof(union xsk_tx_metadata)``. +The headroom for the metadata is reserved via ``tx_metadata_len`` and +``XDP_UMEM_TX_METADATA_LEN`` flag in ``struct xdp_umem_reg``. The metadata +length is therefore the same for every socket that shares the same umem. +The metadata layout is a fixed UAPI, refer to ``union xsk_tx_metadata`` in +``include/uapi/linux/if_xdp.h``. Thus, generally, the ``tx_metadata_len`` +field above should contain ``sizeof(union xsk_tx_metadata)``. + +Note that in the original implementation the ``XDP_UMEM_TX_METADATA_LEN`` +flag was not required. Applications might attempt to create a umem +with a flag first and if it fails, do another attempt without a flag. The headroom and the metadata itself should be located right before ``xdp_desc->addr`` in the umem frame. Within a frame, the metadata diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h index d31698410410..42ec5ddaab8d 100644 --- a/include/uapi/linux/if_xdp.h +++ b/include/uapi/linux/if_xdp.h @@ -41,6 +41,10 @@ */ #define XDP_UMEM_TX_SW_CSUM (1 << 1) +/* Request to reserve tx_metadata_len bytes of per-chunk metadata. + */ +#define XDP_UMEM_TX_METADATA_LEN (1 << 2) + struct sockaddr_xdp { __u16 sxdp_family; __u16 sxdp_flags; diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c index caa340134b0e..9f76ca591d54 100644 --- a/net/xdp/xdp_umem.c +++ b/net/xdp/xdp_umem.c @@ -151,6 +151,7 @@ static int xdp_umem_account_pages(struct xdp_umem *umem) #define XDP_UMEM_FLAGS_VALID ( \ XDP_UMEM_UNALIGNED_CHUNK_FLAG | \ XDP_UMEM_TX_SW_CSUM | \ + XDP_UMEM_TX_METADATA_LEN | \ 0) static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) @@ -204,8 +205,11 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) if (headroom >= chunk_size - XDP_PACKET_HEADROOM) return -EINVAL; - if (mr->tx_metadata_len >= 256 || mr->tx_metadata_len % 8) - return -EINVAL; + if (mr->flags & XDP_UMEM_TX_METADATA_LEN) { + if (mr->tx_metadata_len >= 256 || mr->tx_metadata_len % 8) + return -EINVAL; + umem->tx_metadata_len = mr->tx_metadata_len; + } umem->size = size; umem->headroom = headroom; @@ -215,7 +219,6 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) umem->pgs = NULL; umem->user = NULL; umem->flags = mr->flags; - umem->tx_metadata_len = mr->tx_metadata_len; INIT_LIST_HEAD(&umem->xsk_dma_list); refcount_set(&umem->users, 1); |