Netdev Archive on lore.kernel.org
help / color / mirror / Atom feed
From: David Ahern <dsahern@gmail.com>
To: Harshitha Ramamurthy <harshitha.ramamurthy@intel.com>,
	bpf@vger.kernel.org, netdev@vger.kernel.org, ast@kernel.org,
	daniel@iogearbox.net, davem@davemloft.net, kuba@kernel.org
Cc: alexander.h.duyck@intel.com, tom.herbert@intel.com
Subject: Re: [PATCH bpf-next] bpf: add bpf_get_xdp_hash helper function
Date: Mon, 31 Aug 2020 13:54:15 -0600	[thread overview]
Message-ID: <04856bca-0952-4dd7-3313-a13be6b2e95a@gmail.com> (raw)
In-Reply-To: <20200831192506.28896-1-harshitha.ramamurthy@intel.com>

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.


  reply	other threads:[~2020-08-31 19:54 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-31 19:25 Harshitha Ramamurthy
2020-08-31 19:54 ` David Ahern [this message]
2020-09-02  0:52   ` Ramamurthy, Harshitha
2020-09-02  2:09     ` David Ahern
2020-08-31 20:33 ` Daniel Borkmann
2020-09-02  0:54   ` Ramamurthy, Harshitha
2020-09-02 15:56   ` Tom Herbert

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=04856bca-0952-4dd7-3313-a13be6b2e95a@gmail.com \
    --to=dsahern@gmail.com \
    --cc=alexander.h.duyck@intel.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=davem@davemloft.net \
    --cc=harshitha.ramamurthy@intel.com \
    --cc=kuba@kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=tom.herbert@intel.com \
    --subject='Re: [PATCH bpf-next] bpf: add bpf_get_xdp_hash helper function' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).