Date: Mon, 8 Apr 2024 19:35:42 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: Jamal Hadi Salim <jhs@...atatu.com>, netdev@...r.kernel.org
Cc: deb.chatterjee@...el.com, anjali.singhai@...el.com,
 namrata.limaye@...el.com, tom@...anda.io, mleitner@...hat.com,
 Mahesh.Shirshyad@....com, Vipin.Jain@....com, tomasz.osinski@...el.com,
 jiri@...nulli.us, xiyou.wangcong@...il.com, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, vladbu@...dia.com,
 horms@...nel.org, khalidm@...dia.com, toke@...hat.com, martin.lau@...ux.dev,
 victor@...atatu.com, pctammela@...atatu.com, alexei.starovoitov@...il.com,
 bpf@...r.kernel.org
Subject: Re: [PATCH net-next v15 14/15] p4tc: add set of P4TC table kfuncs

On 4/8/24 2:19 PM, Jamal Hadi Salim wrote:
> We add an initial set of kfuncs to allow interactions from eBPF programs
> to the P4TC domain.
> 
> - bpf_p4tc_tbl_read: Used to lookup a table entry from a BPF
> program installed in TC. To find the table entry we take in an skb, the
> pipeline ID, the table ID, a key and a key size.
> We use the skb to get the network namespace structure where all the
> pipelines are stored. After that we use the pipeline ID and the table
> ID, to find the table. We then use the key to search for the entry.
> We return an entry on success and NULL on failure.
> 
> - xdp_p4tc_tbl_read: Used to lookup a table entry from a BPF
> program installed in XDP. To find the table entry we take in an xdp_md,
> the pipeline ID, the table ID, a key and a key size.
> We use struct xdp_md to get the network namespace structure where all
> the pipelines are stored. After that we use the pipeline ID and the table
> ID, to find the table. We then use the key to search for the entry.
> We return an entry on success and NULL on failure.
> 
> - bpf_p4tc_entry_create: Used to create a table entry from a BPF
> program installed in TC. To create the table entry we take an skb, the
> pipeline ID, the table ID, a key and its size, and an action which will
> be associated with the new entry.
> We return 0 on success and a negative errno on failure
> 
> - xdp_p4tc_entry_create: Used to create a table entry from a BPF
> program installed in XDP. To create the table entry we take an xdp_md, the
> pipeline ID, the table ID, a key and its size, and an action which will
> be associated with the new entry.
> We return 0 on success and a negative errno on failure
> 
> - bpf_p4tc_entry_create_on_miss: conforms to PNA "add on miss".
> First does a lookup using the passed key and upon a miss will add the entry
> to the table.
> We return 0 on success and a negative errno on failure
> 
> - xdp_p4tc_entry_create_on_miss: conforms to PNA "add on miss".
> First does a lookup using the passed key and upon a miss will add the entry
> to the table.
> We return 0 on success and a negative errno on failure
> 
> - bpf_p4tc_entry_update: Used to update a table entry from a BPF
> program installed in TC. To update the table entry we take an skb, the
> pipeline ID, the table ID, a key and its size, and an action which will
> be associated with the new entry.
> We return 0 on success and a negative errno on failure
> 
> - xdp_p4tc_entry_update: Used to update a table entry from a BPF
> program installed in XDP. To update the table entry we take an xdp_md, the
> pipeline ID, the table ID, a key and its size, and an action which will
> be associated with the new entry.
> We return 0 on success and a negative errno on failure
> 
> - bpf_p4tc_entry_delete: Used to delete a table entry from a BPF
> program installed in TC. To delete the table entry we take an skb, the
> pipeline ID, the table ID, a key and a key size.
> We return 0 on success and a negative errno on failure
> 
> - xdp_p4tc_entry_delete: Used to delete a table entry from a BPF
> program installed in XDP. To delete the table entry we take an xdp_md, the
> pipeline ID, the table ID, a key and a key size.
> We return 0 on success and a negative errno on failure
> 
> Note:
> All P4 objects are owned and reside on the P4TC side. IOW, they are
> controlled via TC netlink interfaces and their resources are managed
> (created, updated, freed, etc) by the TC side. As an example, the structure
> p4tc_table_entry_act is returned to the ebpf side on table lookup. On the
> TC side that struct is wrapped around p4tc_table_entry_act_bpf_kern.
> A multitude of these structure p4tc_table_entry_act_bpf_kern are
> preallocated (to match the P4 architecture, patch #9 describes some of
> the subtleties involved) by the P4TC control plane and put in a kernel
> pool. Their purpose is to hold the action parameters for either a table
> entry, a global per-table "miss" and "hit" action, etc - which are
> instantiated and updated via netlink per runtime requests. An instance of
> the p4tc_table_entry_act_bpf_kern.p4tc_table_entry_act is returned
> to ebpf when there is a un/successful table lookup depending on how the
> P4 program is written. When the table entry is deleted the instance of
> the struct p4tc_table_entry_act_bpf_kern is recycled to the pool to be
> reused for a future table entry. The only time the pool memory is released
> is when the pipeline is deleted.
> 
> Co-developed-by: Victor Nogueira <victor@...atatu.com>
> Signed-off-by: Victor Nogueira <victor@...atatu.com>
> Co-developed-by: Pedro Tammela <pctammela@...atatu.com>
> Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
> Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
> Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> Nacked-by: Alexei Starovoitov <alexei.starovoitov@...il.com>
> Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>

Given the many reasons stated earlier & for the record:

Nacked-by: Daniel Borkmann <daniel@...earbox.net>

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