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([2620:10d:c090:400::5:541e]) by smtp.gmail.com with ESMTPSA id v8-20020a170902b7c800b001994fc55998sm618727plz.217.2023.03.13.21.31.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Mar 2023 21:31:22 -0700 (PDT) Message-ID: <31abe375-d844-8776-6fd5-7b9ab5348a4c@gmail.com> Date: Mon, 13 Mar 2023 21:31:20 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH bpf-next v6 2/8] net: Update an existing TCP congestion control algorithm. Content-Language: en-US, en-ZW To: Martin KaFai Lau , Kui-Feng Lee Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, ast@kernel.org, song@kernel.org, kernel-team@meta.com, andrii@kernel.org, sdf@google.com References: <20230310043812.3087672-1-kuifeng@meta.com> <20230310043812.3087672-3-kuifeng@meta.com> From: Kui-Feng Lee In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 3/13/23 17:28, Martin KaFai Lau wrote: > On 3/9/23 8:38 PM, Kui-Feng Lee wrote: >> This feature lets you immediately transition to another congestion >> control algorithm or implementation with the same name.  Once a name >> is updated, new connections will apply this new algorithm. > > The commit message needs to explain why the change is needed and some > major details on how the patch is doing it. In this case, why a later > bpf patch needs it and what major changes are made to tcp_cong.c. > > For example, > > A later bpf patch will allow attaching a bpf_struct_ops (TCP Congestion > Control implemented in bpf) to bpf_link. The later bpf patch will also > use the existing bpf_link API to replace a bpf_struct_ops (ie. to > replace an old tcp-cc with a new tcp-cc under the same name). This > requires a helper function to replace a tcp-cc under a > tcp_cong_list_lock. Thus, this patch adds a > tcp_update_congestion_control() to replace the "old_ca" with a new "ca". > > This patch also takes this chance to refactor the ca validation into the > new tcp_validate_congestion_control() function. Sure! > >> >> Signed-off-by: Kui-Feng Lee >> --- >>   include/linux/bpf.h            |  1 + >>   include/net/tcp.h              |  2 ++ >>   net/bpf/bpf_dummy_struct_ops.c |  6 ++++ >>   net/ipv4/bpf_tcp_ca.c          |  6 ++++ >>   net/ipv4/tcp_cong.c            | 60 ++++++++++++++++++++++++++++++---- >>   5 files changed, 68 insertions(+), 7 deletions(-) >> >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >> index 00ca92ea6f2e..0f84925d66db 100644 >> --- a/include/linux/bpf.h >> +++ b/include/linux/bpf.h >> @@ -1511,6 +1511,7 @@ struct bpf_struct_ops { >>                  void *kdata, const void *udata); >>       int (*reg)(void *kdata); >>       void (*unreg)(void *kdata); >> +    int (*update)(void *kdata, void *old_kdata); >>       const struct btf_type *type; >>       const struct btf_type *value_type; >>       const char *name; >> diff --git a/include/net/tcp.h b/include/net/tcp.h >> index db9f828e9d1e..239cc0e2639c 100644 >> --- a/include/net/tcp.h >> +++ b/include/net/tcp.h >> @@ -1117,6 +1117,8 @@ struct tcp_congestion_ops { >>   int tcp_register_congestion_control(struct tcp_congestion_ops *type); >>   void tcp_unregister_congestion_control(struct tcp_congestion_ops >> *type); >> +int tcp_update_congestion_control(struct tcp_congestion_ops *type, >> +                  struct tcp_congestion_ops *old_type); >>   void tcp_assign_congestion_control(struct sock *sk); >>   void tcp_init_congestion_control(struct sock *sk); >> diff --git a/net/bpf/bpf_dummy_struct_ops.c >> b/net/bpf/bpf_dummy_struct_ops.c >> index ff4f89a2b02a..158f14e240d0 100644 >> --- a/net/bpf/bpf_dummy_struct_ops.c >> +++ b/net/bpf/bpf_dummy_struct_ops.c >> @@ -222,12 +222,18 @@ static void bpf_dummy_unreg(void *kdata) >>   { >>   } >> +static int bpf_dummy_update(void *kdata, void *old_kdata) >> +{ >> +    return -EOPNOTSUPP; >> +} >> + >>   struct bpf_struct_ops bpf_bpf_dummy_ops = { >>       .verifier_ops = &bpf_dummy_verifier_ops, >>       .init = bpf_dummy_init, >>       .check_member = bpf_dummy_ops_check_member, >>       .init_member = bpf_dummy_init_member, >>       .reg = bpf_dummy_reg, >> +    .update = bpf_dummy_update, >>       .unreg = bpf_dummy_unreg, >>       .name = "bpf_dummy_ops", >>   }; >> diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c >> index 13fc0c185cd9..66ce5fadfe42 100644 >> --- a/net/ipv4/bpf_tcp_ca.c >> +++ b/net/ipv4/bpf_tcp_ca.c >> @@ -266,10 +266,16 @@ static void bpf_tcp_ca_unreg(void *kdata) >>       tcp_unregister_congestion_control(kdata); >>   } >> +static int bpf_tcp_ca_update(void *kdata, void *old_kdata) >> +{ >> +    return tcp_update_congestion_control(kdata, old_kdata); >> +} >> + >>   struct bpf_struct_ops bpf_tcp_congestion_ops = { >>       .verifier_ops = &bpf_tcp_ca_verifier_ops, >>       .reg = bpf_tcp_ca_reg, >>       .unreg = bpf_tcp_ca_unreg, >> +    .update = bpf_tcp_ca_update, > > In v5, a comment was given to move the ".update" related changes to > patch 5 such that patch 2 will only have netdev change in tcp_cong.c for > review purpose. > > Please ensure the earlier review comment is addressed in the next > revision or reply if the earlier review comment does not make sense. > This will save time for the reviewer not to have to repeat the same > comment again. Sorry about this. I only addressed .validate and missed .update. Will fix this. > >>       .check_member = bpf_tcp_ca_check_member, >>       .init_member = bpf_tcp_ca_init_member, >>       .init = bpf_tcp_ca_init, > >