Update xdp_adjst_tail_shrnk_data to use bpf_dynptr_slice to read the data at the end of the packet, instead of bpf_xdp_load_bytes.
This may avoid a copy by returning a direct pointer to the dynptr data.
Note: since bpf_dynptr_slice() does not support variable lengths, we use MAX_ADJST_OFFSET as the slice size, and update both the size check and the UDP checksum calculation accordingly.
Signed-off-by: Nimrod Oren noren@nvidia.com Reviewed-by: Carolina Jubran cjubran@nvidia.com Reviewed-by: Dragos Tatulea dtatulea@nvidia.com --- .../selftests/net/lib/xdp_native.bpf.c | 20 ++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/tools/testing/selftests/net/lib/xdp_native.bpf.c b/tools/testing/selftests/net/lib/xdp_native.bpf.c index 346cbba9afec..ff768fbc8606 100644 --- a/tools/testing/selftests/net/lib/xdp_native.bpf.c +++ b/tools/testing/selftests/net/lib/xdp_native.bpf.c @@ -272,10 +272,11 @@ static __u16 csum_fold_helper(__u32 csum) static int xdp_adjst_tail_shrnk_data(struct xdp_md *ctx, __u16 offset, __u32 hdr_len) { - char tmp_buff[MAX_ADJST_OFFSET]; - __u32 buff_pos, udp_csum = 0; + char tmp_buff[MAX_ADJST_OFFSET] = {0}; + __u32 buff_len, udp_csum = 0; struct udphdr *udph = NULL; - __u32 buff_len; + struct bpf_dynptr ptr; + void *data = NULL;
udph = update_pkt(ctx, 0 - offset, &udp_csum); if (!udph) @@ -285,18 +286,19 @@ static int xdp_adjst_tail_shrnk_data(struct xdp_md *ctx, __u16 offset,
offset = (offset & 0x1ff) >= MAX_ADJST_OFFSET ? MAX_ADJST_OFFSET : offset & 0xff; - if (offset == 0) - return -1;
/* Make sure we have enough data to avoid eating the header */ - if (buff_len - offset < hdr_len) + if (buff_len - sizeof(tmp_buff) < hdr_len) return -1;
- buff_pos = buff_len - offset; - if (bpf_xdp_load_bytes(ctx, buff_pos, tmp_buff, offset) < 0) + bpf_dynptr_from_xdp(ctx, 0, &ptr); + data = bpf_dynptr_slice(&ptr, buff_len - sizeof(tmp_buff), tmp_buff, + sizeof(tmp_buff)); + if (!data) return -1;
- udp_csum = bpf_csum_diff((__be32 *)tmp_buff, offset, 0, 0, udp_csum); + udp_csum = bpf_csum_diff(data, sizeof(tmp_buff), data, + sizeof(tmp_buff) - offset, udp_csum); udph->check = (__u16)csum_fold_helper(udp_csum);
if (bpf_xdp_adjust_tail(ctx, 0 - offset) < 0)