From: David Ahern <dsahern@gmail.com>
To: "Ramamurthy, Harshitha" <harshitha.ramamurthy@intel.com>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"ast@kernel.org" <ast@kernel.org>,
"daniel@iogearbox.net" <daniel@iogearbox.net>,
"davem@davemloft.net" <davem@davemloft.net>,
"kuba@kernel.org" <kuba@kernel.org>
Cc: "Duyck, Alexander H" <alexander.h.duyck@intel.com>,
"Herbert, Tom" <tom.herbert@intel.com>
Subject: Re: [PATCH bpf-next] bpf: add bpf_get_xdp_hash helper function
Date: Tue, 1 Sep 2020 20:09:36 -0600 [thread overview]
Message-ID: <f3fbdb56-6e7e-7b18-e160-3f402bee8083@gmail.com> (raw)
In-Reply-To: <MW3PR11MB45220F94F1E303CEC0F6C19C852F0@MW3PR11MB4522.namprd11.prod.outlook.com>
On 9/1/20 6:52 PM, Ramamurthy, Harshitha wrote:
>> 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.
>
> Not sure what you mean - other xdp related helper functions still use xdp_buff as an argument. Could you point me to an example of what you are referring to?
a patch from Jakub that is apparently not committed yet.
>>
>>> + 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?
>
> I wrote this exactly how skb_get_hash calls skb_flow_dissect - with the same flag STOP_AT_FLOW_LABEL. So it should already cover L3 and L4 hash, right? From what I understand STOP_AT_FLOW_LABEL flag is used to only stop parsing when a flow label is seen in ipv6 packets.
right; missed that. That means this new helper will always do an L4 hash
for tcp/udp. Adding a flags argument now for the uapi allows a later
change to make it an L3 hash.
next prev parent reply other threads:[~2020-09-02 2:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-31 19:25 [PATCH bpf-next] bpf: add bpf_get_xdp_hash helper function Harshitha Ramamurthy
2020-08-31 19:54 ` David Ahern
2020-09-02 0:52 ` Ramamurthy, Harshitha
2020-09-02 2:09 ` David Ahern [this message]
2020-08-31 20:33 ` Daniel Borkmann
2020-09-02 0:54 ` Ramamurthy, Harshitha
2020-09-02 15:56 ` Tom Herbert
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