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([2620:10d:c090:400::5:1af8]) by smtp.gmail.com with ESMTPSA id ix17-20020a170902f81100b0019a91895cdfsm7671821plb.50.2023.02.15.10.15.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Feb 2023 10:15:54 -0800 (PST) Message-ID: <91c8b5e3-ac55-3b01-9904-43587bedd319@gmail.com> Date: Wed, 15 Feb 2023 10:15:52 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH bpf-next 2/7] net: Update an existing TCP congestion control algorithm. Content-Language: en-US To: Stanislav Fomichev , Kui-Feng Lee Cc: bpf@vger.kernel.org, ast@kernel.org, martin.lau@linux.dev, song@kernel.org, kernel-team@meta.com, andrii@kernel.org References: <20230214221718.503964-1-kuifeng@meta.com> <20230214221718.503964-3-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: bpf@vger.kernel.org On 2/14/23 18:43, Stanislav Fomichev wrote: > On 02/14, 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. > >> 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            | 39 ++++++++++++++++++++++++++++++++++ >>   5 files changed, 54 insertions(+) > >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >> index 13683584b071..5fe39f56a760 100644 >> --- a/include/linux/bpf.h >> +++ b/include/linux/bpf.h >> @@ -1450,6 +1450,7 @@ 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, >>       .check_member = bpf_tcp_ca_check_member, >>       .init_member = bpf_tcp_ca_init_member, >>       .init = bpf_tcp_ca_init, >> diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c >> index db8b4b488c31..22fd7c12360e 100644 >> --- a/net/ipv4/tcp_cong.c >> +++ b/net/ipv4/tcp_cong.c >> @@ -130,6 +130,45 @@ void tcp_unregister_congestion_control(struct >> tcp_congestion_ops *ca) >>   } >>   EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control); > >> +/* Replace a registered old ca with a new one. >> + * >> + * The new ca must have the same name as the old one, that has been >> + * registered. >> + */ >> +int tcp_update_congestion_control(struct tcp_congestion_ops *ca, >> struct tcp_congestion_ops *old_ca) >> +{ >> +    struct tcp_congestion_ops *existing; >> +    int ret = 0; >> + > > [..] > >> +    /* all algorithms must implement these */ >> +    if (!ca->ssthresh || !ca->undo_cwnd || >> +        !(ca->cong_avoid || ca->cong_control)) { >> +        pr_err("%s does not implement required ops\n", old_ca->name); >> +        return -EINVAL; >> +    } >> + >> +    ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name)); > > Can we have this as some common _validate method to avoid copy-paste > from tcp_register_congestion_control. Sure! > > Or, even better, can we can since function handle both cases? > > tcp_register_congestion_control(ca, old_ca); >     - when old_ca == NULL -> register >     - when old_ca != NULL -> try to update We use this function in a lot of different places. To make it easier, I added a new function instead of changing the old one. > >> + >> +    spin_lock(&tcp_cong_list_lock); >> +    existing = tcp_ca_find_key(ca->key); >> +    if (ca->key == TCP_CA_UNSPEC || !existing || >> strcmp(existing->name, ca->name)) { >> +        pr_notice("%s not registered or non-unique key\n", >> +              ca->name); >> +        ret = -EINVAL; >> +    } else if (existing != old_ca) { >> +        pr_notice("invalid old congestion control algorithm to >> replace\n"); >> +        ret = -EINVAL; >> +    } else { >> +        list_del_rcu(&existing->list); >> +        list_add_tail_rcu(&ca->list, &tcp_cong_list); >> +        pr_debug("%s updated\n", ca->name); >> +    } >> +    spin_unlock(&tcp_cong_list_lock); >> + >> +    return ret; >> +} >> +EXPORT_SYMBOL_GPL(tcp_update_congestion_control); >> + >>   u32 tcp_ca_get_key_by_name(struct net *net, const char *name, bool >> *ecn_ca) >>   { >>       const struct tcp_congestion_ops *ca; >> -- >> 2.30.2 >