On 8/31/20 1:25 PM, Harshitha Ramamurthy wrote:
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index a613750d5515..bffe93b526e7 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3576,6 +3576,14 @@ union bpf_attr {
> * the data in *dst*. This is a wrapper of copy_from_user().
> * Return
> * 0 on success, or a negative error in case of failure.
> + *
> + * u32 bpf_get_xdp_hash(struct xdp_buff *xdp_md)
I thought there was a change recently making the uapi reference xdp_md;
xdp_buff is not exported as part of the uapi.
> + * Description
> + * Return the hash for the xdp context passed. This function
> + * calls skb_flow_dissect in non-skb mode to calculate the
> + * hash for the packet.
> + * Return
> + * The 32-bit hash.
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -3727,6 +3735,7 @@ union bpf_attr {
> FN(inode_storage_delete), \
> FN(d_path), \
> FN(copy_from_user), \
> + FN(get_xdp_hash), \
> /* */
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 47eef9a0be6a..cfb5a6aea6c3 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -3765,6 +3765,33 @@ static const struct bpf_func_proto
> bpf_xdp_redirect_map_proto = {
> .arg3_type = ARG_ANYTHING,
> };
>
> +BPF_CALL_1(bpf_get_xdp_hash, struct xdp_buff *, xdp)
> +{
> + void *data_end = xdp->data_end;
> + struct ethhdr *eth = xdp->data;
> + void *data = xdp->data;
> + struct flow_keys keys;
> + u32 ret = 0;
> + int len;
> +
> + len = data_end - data;
> + if (len <= 0)
> + return ret;
you should verify len covers the ethernet header. Looking at
__skb_flow_dissect use of hlen presumes it exists.
> + memset(&keys, 0, sizeof(keys));
> + __skb_flow_dissect(dev_net(xdp->rxq->dev), NULL, &flow_keys_dissector,
> + &keys, data, eth->h_proto, sizeof(*eth), len,
> + FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
By STOP_AT_FLOW_LABEL I take it you want this to be an L3 hash. Why not
add a flags argument to the helper and let the hash be L3 or L4?
you should add test cases and have them cover the permutations - e.g.,
vlan, Q-in-Q, ipv4, ipv6, non-IP packet for L3 hash and then udp, tcp
for L4 hash.
