[RFC PATCH net-next v2] net/smc: Introduce a hook to modify syn_smc at runtime

[RFC PATCH net-next v2] net/smc: Introduce a hook to modify syn_smc at runtime

[D. Wythe]

From: "D. Wythe" <alibuda@linux.alibaba.com>

The introduction of IPPROTO_SMC enables eBPF programs to determine
whether to use SMC based on the context of socket creation, such as
network namespaces, PID and comm name, etc.

As a subsequent enhancement, this patch introduces a new hook for eBPF
programs that allows decisions on whether to use SMC or not at runtime,
including but not limited to local/remote IP address or ports. In
simpler words, this feature allows modifications to syn_smc through eBPF
programs before the TCP three-way handshake got established.

Thanks to kfunc for making it easier for us to implement this feature in
SMC.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>

---
v1 -> v2:
1. Fix wrong use of ireq->smc_ok, should be rx_opt->smc_ok.
2. Fix compile error when CONFIG_IPV6 or CONFIG_BPF_SYSCALL was not set.

---
 include/linux/tcp.h  |  4 ++-
 net/ipv4/tcp_input.c |  4 +--
 net/smc/af_smc.c     | 75 ++++++++++++++++++++++++++++++++++++++++++++++------
 3 files changed, 72 insertions(+), 11 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 6a5e08b..d028d76 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -478,7 +478,9 @@ struct tcp_sock {
 #endif
 #if IS_ENABLED(CONFIG_SMC)
 	bool	syn_smc;	/* SYN includes SMC */
-	bool	(*smc_hs_congested)(const struct sock *sk);
+	void	(*smc_openreq_init)(struct request_sock *req,
+			     const struct tcp_options_received *rx_opt,
+			     struct sk_buff *skb, const struct sock *sk);
 #endif
 
 #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9f314df..99f34f5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -7036,8 +7036,8 @@ static void tcp_openreq_init(struct request_sock *req,
 	ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
 	ireq->ir_mark = inet_request_mark(sk, skb);
 #if IS_ENABLED(CONFIG_SMC)
-	ireq->smc_ok = rx_opt->smc_ok && !(tcp_sk(sk)->smc_hs_congested &&
-			tcp_sk(sk)->smc_hs_congested(sk));
+	if (rx_opt->smc_ok && tcp_sk(sk)->smc_openreq_init)
+		tcp_sk(sk)->smc_openreq_init(req, rx_opt, skb, sk);
 #endif
 }
 
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 0316217..fdac7e2b 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -70,6 +70,15 @@
 static void smc_tcp_listen_work(struct work_struct *);
 static void smc_connect_work(struct work_struct *);
 
+__bpf_hook_start();
+
+__weak noinline int select_syn_smc(const struct sock *sk, struct sockaddr *peer)
+{
+	return 1;
+}
+
+__bpf_hook_end();
+
 int smc_nl_dump_hs_limitation(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	struct smc_nl_dmp_ctx *cb_ctx = smc_nl_dmp_ctx(cb);
@@ -156,19 +165,43 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
 	return NULL;
 }
 
-static bool smc_hs_congested(const struct sock *sk)
+static void smc_openreq_init(struct request_sock *req,
+			     const struct tcp_options_received *rx_opt,
+			     struct sk_buff *skb, const struct sock *sk)
 {
+	struct inet_request_sock *ireq = inet_rsk(req);
+	struct sockaddr_storage rmt_sockaddr = {0};
 	const struct smc_sock *smc;
 
 	smc = smc_clcsock_user_data(sk);
 
 	if (!smc)
-		return true;
+		return;
 
-	if (workqueue_congested(WORK_CPU_UNBOUND, smc_hs_wq))
-		return true;
+	if (smc->limit_smc_hs && workqueue_congested(WORK_CPU_UNBOUND, smc_hs_wq))
+		goto out_no_smc;
 
-	return false;
+	rmt_sockaddr.ss_family = sk->sk_family;
+
+	if (rmt_sockaddr.ss_family == AF_INET) {
+		struct sockaddr_in *rmt4_sockaddr =  (struct sockaddr_in *)&rmt_sockaddr;
+
+		rmt4_sockaddr->sin_addr.s_addr = ireq->ir_rmt_addr;
+		rmt4_sockaddr->sin_port	= ireq->ir_rmt_port;
+#if IS_ENABLED(CONFIG_IPV6)
+	} else {
+		struct sockaddr_in6 *rmt6_sockaddr =  (struct sockaddr_in6 *)&rmt_sockaddr;
+
+		rmt6_sockaddr->sin6_addr = ireq->ir_v6_rmt_addr;
+		rmt6_sockaddr->sin6_port = ireq->ir_rmt_port;
+#endif /* CONFIG_IPV6 */
+	}
+
+	ireq->smc_ok = select_syn_smc(sk, (struct sockaddr *)&rmt_sockaddr);
+	return;
+out_no_smc:
+	ireq->smc_ok = 0;
+	return;
 }
 
 struct smc_hashinfo smc_v4_hashinfo = {
@@ -1671,7 +1704,7 @@ int smc_connect(struct socket *sock, struct sockaddr *addr,
 	}
 
 	smc_copy_sock_settings_to_clc(smc);
-	tcp_sk(smc->clcsock->sk)->syn_smc = 1;
+	tcp_sk(smc->clcsock->sk)->syn_smc = select_syn_smc(sk, addr);
 	if (smc->connect_nonblock) {
 		rc = -EALREADY;
 		goto out;
@@ -2650,8 +2683,7 @@ int smc_listen(struct socket *sock, int backlog)
 
 	inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops;
 
-	if (smc->limit_smc_hs)
-		tcp_sk(smc->clcsock->sk)->smc_hs_congested = smc_hs_congested;
+	tcp_sk(smc->clcsock->sk)->smc_openreq_init = smc_openreq_init;
 
 	rc = kernel_listen(smc->clcsock, backlog);
 	if (rc) {
@@ -3475,6 +3507,24 @@ static void __net_exit smc_net_stat_exit(struct net *net)
 	.exit = smc_net_stat_exit,
 };
 
+#if IS_ENABLED(CONFIG_BPF_SYSCALL)
+BTF_SET8_START(bpf_smc_fmodret_ids)
+BTF_ID_FLAGS(func, select_syn_smc)
+BTF_SET8_END(bpf_smc_fmodret_ids)
+
+static const struct btf_kfunc_id_set bpf_smc_fmodret_set = {
+	.owner = THIS_MODULE,
+	.set   = &bpf_smc_fmodret_ids,
+};
+
+static int bpf_smc_kfunc_init(void)
+{
+	return register_btf_fmodret_id_set(&bpf_smc_fmodret_set);
+}
+#else
+static inline int bpf_smc_kfunc_init(void) { return 0; }
+#endif /* CONFIG_BPF_SYSCALL */
+
 static int __init smc_init(void)
 {
 	int rc;
@@ -3574,8 +3624,17 @@ static int __init smc_init(void)
 		pr_err("%s: smc_inet_init fails with %d\n", __func__, rc);
 		goto out_ulp;
 	}
+
+	rc = bpf_smc_kfunc_init();
+	if (rc) {
+		pr_err("%s: bpf_smc_kfunc_init fails with %d\n", __func__, rc);
+		goto out_inet;
+	}
+
 	static_branch_enable(&tcp_have_smc);
 	return 0;
+out_inet:
+	smc_inet_exit();
 out_ulp:
 	tcp_unregister_ulp(&smc_ulp_ops);
 out_lo:
-- 
1.8.3.1

Re: [RFC PATCH net-next v2] net/smc: Introduce a hook to modify syn_smc at runtime

[Zhu Yanjun]

在 2024/9/27 11:42, D. Wythe 写道:
> From: "D. Wythe" <alibuda@linux.alibaba.com>
> 
> The introduction of IPPROTO_SMC enables eBPF programs to determine
> whether to use SMC based on the context of socket creation, such as
> network namespaces, PID and comm name, etc.
> 
> As a subsequent enhancement, this patch introduces a new hook for eBPF
> programs that allows decisions on whether to use SMC or not at runtime,
> including but not limited to local/remote IP address or ports. In
> simpler words, this feature allows modifications to syn_smc through eBPF
> programs before the TCP three-way handshake got established.
> 
> Thanks to kfunc for making it easier for us to implement this feature in
> SMC.
> 
> Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
> 
> ---
> v1 -> v2:
> 1. Fix wrong use of ireq->smc_ok, should be rx_opt->smc_ok.
> 2. Fix compile error when CONFIG_IPV6 or CONFIG_BPF_SYSCALL was not set.
> 
> ---
>   include/linux/tcp.h  |  4 ++-
>   net/ipv4/tcp_input.c |  4 +--
>   net/smc/af_smc.c     | 75 ++++++++++++++++++++++++++++++++++++++++++++++------
>   3 files changed, 72 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index 6a5e08b..d028d76 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -478,7 +478,9 @@ struct tcp_sock {
>   #endif
>   #if IS_ENABLED(CONFIG_SMC)
>   	bool	syn_smc;	/* SYN includes SMC */
> -	bool	(*smc_hs_congested)(const struct sock *sk);
> +	void	(*smc_openreq_init)(struct request_sock *req,
> +			     const struct tcp_options_received *rx_opt,
> +			     struct sk_buff *skb, const struct sock *sk);
>   #endif
>   
>   #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 9f314df..99f34f5 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -7036,8 +7036,8 @@ static void tcp_openreq_init(struct request_sock *req,
>   	ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
>   	ireq->ir_mark = inet_request_mark(sk, skb);
>   #if IS_ENABLED(CONFIG_SMC)
> -	ireq->smc_ok = rx_opt->smc_ok && !(tcp_sk(sk)->smc_hs_congested &&
> -			tcp_sk(sk)->smc_hs_congested(sk));
> +	if (rx_opt->smc_ok && tcp_sk(sk)->smc_openreq_init)
> +		tcp_sk(sk)->smc_openreq_init(req, rx_opt, skb, sk);
>   #endif
>   }
>   
> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
> index 0316217..fdac7e2b 100644
> --- a/net/smc/af_smc.c
> +++ b/net/smc/af_smc.c
> @@ -70,6 +70,15 @@
>   static void smc_tcp_listen_work(struct work_struct *);
>   static void smc_connect_work(struct work_struct *);
>   
> +__bpf_hook_start();
> +
> +__weak noinline int select_syn_smc(const struct sock *sk, struct sockaddr *peer)
> +{
> +	return 1;
> +}
> +
> +__bpf_hook_end();
> +
>   int smc_nl_dump_hs_limitation(struct sk_buff *skb, struct netlink_callback *cb)
>   {
>   	struct smc_nl_dmp_ctx *cb_ctx = smc_nl_dmp_ctx(cb);
> @@ -156,19 +165,43 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
>   	return NULL;
>   }
>   
> -static bool smc_hs_congested(const struct sock *sk)
> +static void smc_openreq_init(struct request_sock *req,
> +			     const struct tcp_options_received *rx_opt,
> +			     struct sk_buff *skb, const struct sock *sk)
>   {
> +	struct inet_request_sock *ireq = inet_rsk(req);
> +	struct sockaddr_storage rmt_sockaddr = {0};

A trivial problem.

The following should be better?

struct sockaddr_storage rmt_sockaddr = {};

I think, we have discussed this problem in RDMA maillist for several times.

Zhu Yanjun

>   	const struct smc_sock *smc;
>   
>   	smc = smc_clcsock_user_data(sk);
>   
>   	if (!smc)
> -		return true;
> +		return;
>   
> -	if (workqueue_congested(WORK_CPU_UNBOUND, smc_hs_wq))
> -		return true;
> +	if (smc->limit_smc_hs && workqueue_congested(WORK_CPU_UNBOUND, smc_hs_wq))
> +		goto out_no_smc;
>   
> -	return false;
> +	rmt_sockaddr.ss_family = sk->sk_family;
> +
> +	if (rmt_sockaddr.ss_family == AF_INET) {
> +		struct sockaddr_in *rmt4_sockaddr =  (struct sockaddr_in *)&rmt_sockaddr;
> +
> +		rmt4_sockaddr->sin_addr.s_addr = ireq->ir_rmt_addr;
> +		rmt4_sockaddr->sin_port	= ireq->ir_rmt_port;
> +#if IS_ENABLED(CONFIG_IPV6)
> +	} else {
> +		struct sockaddr_in6 *rmt6_sockaddr =  (struct sockaddr_in6 *)&rmt_sockaddr;
> +
> +		rmt6_sockaddr->sin6_addr = ireq->ir_v6_rmt_addr;
> +		rmt6_sockaddr->sin6_port = ireq->ir_rmt_port;
> +#endif /* CONFIG_IPV6 */
> +	}
> +
> +	ireq->smc_ok = select_syn_smc(sk, (struct sockaddr *)&rmt_sockaddr);
> +	return;
> +out_no_smc:
> +	ireq->smc_ok = 0;
> +	return;
>   }
>   
>   struct smc_hashinfo smc_v4_hashinfo = {
> @@ -1671,7 +1704,7 @@ int smc_connect(struct socket *sock, struct sockaddr *addr,
>   	}
>   
>   	smc_copy_sock_settings_to_clc(smc);
> -	tcp_sk(smc->clcsock->sk)->syn_smc = 1;
> +	tcp_sk(smc->clcsock->sk)->syn_smc = select_syn_smc(sk, addr);
>   	if (smc->connect_nonblock) {
>   		rc = -EALREADY;
>   		goto out;
> @@ -2650,8 +2683,7 @@ int smc_listen(struct socket *sock, int backlog)
>   
>   	inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops;
>   
> -	if (smc->limit_smc_hs)
> -		tcp_sk(smc->clcsock->sk)->smc_hs_congested = smc_hs_congested;
> +	tcp_sk(smc->clcsock->sk)->smc_openreq_init = smc_openreq_init;
>   
>   	rc = kernel_listen(smc->clcsock, backlog);
>   	if (rc) {
> @@ -3475,6 +3507,24 @@ static void __net_exit smc_net_stat_exit(struct net *net)
>   	.exit = smc_net_stat_exit,
>   };
>   
> +#if IS_ENABLED(CONFIG_BPF_SYSCALL)
> +BTF_SET8_START(bpf_smc_fmodret_ids)
> +BTF_ID_FLAGS(func, select_syn_smc)
> +BTF_SET8_END(bpf_smc_fmodret_ids)
> +
> +static const struct btf_kfunc_id_set bpf_smc_fmodret_set = {
> +	.owner = THIS_MODULE,
> +	.set   = &bpf_smc_fmodret_ids,
> +};
> +
> +static int bpf_smc_kfunc_init(void)
> +{
> +	return register_btf_fmodret_id_set(&bpf_smc_fmodret_set);
> +}
> +#else
> +static inline int bpf_smc_kfunc_init(void) { return 0; }
> +#endif /* CONFIG_BPF_SYSCALL */
> +
>   static int __init smc_init(void)
>   {
>   	int rc;
> @@ -3574,8 +3624,17 @@ static int __init smc_init(void)
>   		pr_err("%s: smc_inet_init fails with %d\n", __func__, rc);
>   		goto out_ulp;
>   	}
> +
> +	rc = bpf_smc_kfunc_init();
> +	if (rc) {
> +		pr_err("%s: bpf_smc_kfunc_init fails with %d\n", __func__, rc);
> +		goto out_inet;
> +	}
> +
>   	static_branch_enable(&tcp_have_smc);
>   	return 0;
> +out_inet:
> +	smc_inet_exit();
>   out_ulp:
>   	tcp_unregister_ulp(&smc_ulp_ops);
>   out_lo:

Re: [RFC PATCH net-next v2] net/smc: Introduce a hook to modify syn_smc at runtime

[D. Wythe]

On 9/29/24 7:56 PM, Zhu Yanjun wrote:
> 在 2024/9/27 11:42, D. Wythe 写道:
>> From: "D. Wythe" <alibuda@linux.alibaba.com>
>>
>> The introduction of IPPROTO_SMC enables eBPF programs to determine
>> whether to use SMC based on the context of socket creation, such as
>> network namespaces, PID and comm name, etc.
>>
>> As a subsequent enhancement, this patch introduces a new hook for eBPF
>> programs that allows decisions on whether to use SMC or not at runtime,
>> including but not limited to local/remote IP address or ports. In
>> simpler words, this feature allows modifications to syn_smc through eBPF
>> programs before the TCP three-way handshake got established.
>>
>> Thanks to kfunc for making it easier for us to implement this feature in
>> SMC.
>>
>> Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
>>
>> ---
>> v1 -> v2:
>> 1. Fix wrong use of ireq->smc_ok, should be rx_opt->smc_ok.
>> 2. Fix compile error when CONFIG_IPV6 or CONFIG_BPF_SYSCALL was not set.
>>
>> ---
>>   include/linux/tcp.h  |  4 ++-
>>   net/ipv4/tcp_input.c |  4 +--
>>   net/smc/af_smc.c     | 75 ++++++++++++++++++++++++++++++++++++++++++++++------
>>   3 files changed, 72 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
>> index 6a5e08b..d028d76 100644
>> --- a/include/linux/tcp.h
>> +++ b/include/linux/tcp.h
>> @@ -478,7 +478,9 @@ struct tcp_sock {
>>   #endif
>>   #if IS_ENABLED(CONFIG_SMC)
>>       bool    syn_smc;    /* SYN includes SMC */
>> -    bool    (*smc_hs_congested)(const struct sock *sk);
>> +    void    (*smc_openreq_init)(struct request_sock *req,
>> +                 const struct tcp_options_received *rx_opt,
>> +                 struct sk_buff *skb, const struct sock *sk);
>>   #endif
>>   #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
>> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
>> index 9f314df..99f34f5 100644
>> --- a/net/ipv4/tcp_input.c
>> +++ b/net/ipv4/tcp_input.c
>> @@ -7036,8 +7036,8 @@ static void tcp_openreq_init(struct request_sock *req,
>>       ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
>>       ireq->ir_mark = inet_request_mark(sk, skb);
>>   #if IS_ENABLED(CONFIG_SMC)
>> -    ireq->smc_ok = rx_opt->smc_ok && !(tcp_sk(sk)->smc_hs_congested &&
>> -            tcp_sk(sk)->smc_hs_congested(sk));
>> +    if (rx_opt->smc_ok && tcp_sk(sk)->smc_openreq_init)
>> +        tcp_sk(sk)->smc_openreq_init(req, rx_opt, skb, sk);
>>   #endif
>>   }
>> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
>> index 0316217..fdac7e2b 100644
>> --- a/net/smc/af_smc.c
>> +++ b/net/smc/af_smc.c
>> @@ -70,6 +70,15 @@
>>   static void smc_tcp_listen_work(struct work_struct *);
>>   static void smc_connect_work(struct work_struct *);
>> +__bpf_hook_start();
>> +
>> +__weak noinline int select_syn_smc(const struct sock *sk, struct sockaddr *peer)
>> +{
>> +    return 1;
>> +}
>> +
>> +__bpf_hook_end();
>> +
>>   int smc_nl_dump_hs_limitation(struct sk_buff *skb, struct netlink_callback *cb)
>>   {
>>       struct smc_nl_dmp_ctx *cb_ctx = smc_nl_dmp_ctx(cb);
>> @@ -156,19 +165,43 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
>>       return NULL;
>>   }
>> -static bool smc_hs_congested(const struct sock *sk)
>> +static void smc_openreq_init(struct request_sock *req,
>> +                 const struct tcp_options_received *rx_opt,
>> +                 struct sk_buff *skb, const struct sock *sk)
>>   {
>> +    struct inet_request_sock *ireq = inet_rsk(req);
>> +    struct sockaddr_storage rmt_sockaddr = {0};
> 
> A trivial problem.
> 
> The following should be better?
> 
> struct sockaddr_storage rmt_sockaddr = {};
> 
> I think, we have discussed this problem in RDMA maillist for several times.
> 
> Zhu Yanjun


This is truly new information to me. Can you provide me with some discussion links?
Thanks.

D. Wythe


> 
>>       const struct smc_sock *smc;
>>       smc = smc_clcsock_user_data(sk);
>>       if (!smc)
>> -        return true;
>> +        return;
>> -    if (workqueue_congested(WORK_CPU_UNBOUND, smc_hs_wq))
>> -        return true;
>> +    if (smc->limit_smc_hs && workqueue_congested(WORK_CPU_UNBOUND, smc_hs_wq))
>> +        goto out_no_smc;
>> -    return false;
>> +    rmt_sockaddr.ss_family = sk->sk_family;
>> +
>> +    if (rmt_sockaddr.ss_family == AF_INET) {
>> +        struct sockaddr_in *rmt4_sockaddr =  (struct sockaddr_in *)&rmt_sockaddr;
>> +
>> +        rmt4_sockaddr->sin_addr.s_addr = ireq->ir_rmt_addr;
>> +        rmt4_sockaddr->sin_port    = ireq->ir_rmt_port;
>> +#if IS_ENABLED(CONFIG_IPV6)
>> +    } else {
>> +        struct sockaddr_in6 *rmt6_sockaddr =  (struct sockaddr_in6 *)&rmt_sockaddr;
>> +
>> +        rmt6_sockaddr->sin6_addr = ireq->ir_v6_rmt_addr;
>> +        rmt6_sockaddr->sin6_port = ireq->ir_rmt_port;
>> +#endif /* CONFIG_IPV6 */
>> +    }
>> +
>> +    ireq->smc_ok = select_syn_smc(sk, (struct sockaddr *)&rmt_sockaddr);
>> +    return;
>> +out_no_smc:
>> +    ireq->smc_ok = 0;
>> +    return;
>>   }
>>   struct smc_hashinfo smc_v4_hashinfo = {
>> @@ -1671,7 +1704,7 @@ int smc_connect(struct socket *sock, struct sockaddr *addr,
>>       }
>>       smc_copy_sock_settings_to_clc(smc);
>> -    tcp_sk(smc->clcsock->sk)->syn_smc = 1;
>> +    tcp_sk(smc->clcsock->sk)->syn_smc = select_syn_smc(sk, addr);
>>       if (smc->connect_nonblock) {
>>           rc = -EALREADY;
>>           goto out;
>> @@ -2650,8 +2683,7 @@ int smc_listen(struct socket *sock, int backlog)
>>       inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops;
>> -    if (smc->limit_smc_hs)
>> -        tcp_sk(smc->clcsock->sk)->smc_hs_congested = smc_hs_congested;
>> +    tcp_sk(smc->clcsock->sk)->smc_openreq_init = smc_openreq_init;
>>       rc = kernel_listen(smc->clcsock, backlog);
>>       if (rc) {
>> @@ -3475,6 +3507,24 @@ static void __net_exit smc_net_stat_exit(struct net *net)
>>       .exit = smc_net_stat_exit,
>>   };
>> +#if IS_ENABLED(CONFIG_BPF_SYSCALL)
>> +BTF_SET8_START(bpf_smc_fmodret_ids)
>> +BTF_ID_FLAGS(func, select_syn_smc)
>> +BTF_SET8_END(bpf_smc_fmodret_ids)
>> +
>> +static const struct btf_kfunc_id_set bpf_smc_fmodret_set = {
>> +    .owner = THIS_MODULE,
>> +    .set   = &bpf_smc_fmodret_ids,
>> +};
>> +
>> +static int bpf_smc_kfunc_init(void)
>> +{
>> +    return register_btf_fmodret_id_set(&bpf_smc_fmodret_set);
>> +}
>> +#else
>> +static inline int bpf_smc_kfunc_init(void) { return 0; }
>> +#endif /* CONFIG_BPF_SYSCALL */
>> +
>>   static int __init smc_init(void)
>>   {
>>       int rc;
>> @@ -3574,8 +3624,17 @@ static int __init smc_init(void)
>>           pr_err("%s: smc_inet_init fails with %d\n", __func__, rc);
>>           goto out_ulp;
>>       }
>> +
>> +    rc = bpf_smc_kfunc_init();
>> +    if (rc) {
>> +        pr_err("%s: bpf_smc_kfunc_init fails with %d\n", __func__, rc);
>> +        goto out_inet;
>> +    }
>> +
>>       static_branch_enable(&tcp_have_smc);
>>       return 0;
>> +out_inet:
>> +    smc_inet_exit();
>>   out_ulp:
>>       tcp_unregister_ulp(&smc_ulp_ops);
>>   out_lo:

Re: [RFC PATCH net-next v2] net/smc: Introduce a hook to modify syn_smc at runtime

[Zhu Yanjun]

在 2024/9/30 15:15, D. Wythe 写道:
> 
> 
> On 9/29/24 7:56 PM, Zhu Yanjun wrote:
>> 在 2024/9/27 11:42, D. Wythe 写道:
>>> From: "D. Wythe" <alibuda@linux.alibaba.com>
>>>
>>> The introduction of IPPROTO_SMC enables eBPF programs to determine
>>> whether to use SMC based on the context of socket creation, such as
>>> network namespaces, PID and comm name, etc.
>>>
>>> As a subsequent enhancement, this patch introduces a new hook for eBPF
>>> programs that allows decisions on whether to use SMC or not at runtime,
>>> including but not limited to local/remote IP address or ports. In
>>> simpler words, this feature allows modifications to syn_smc through eBPF
>>> programs before the TCP three-way handshake got established.
>>>
>>> Thanks to kfunc for making it easier for us to implement this feature in
>>> SMC.
>>>
>>> Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
>>>
>>> ---
>>> v1 -> v2:
>>> 1. Fix wrong use of ireq->smc_ok, should be rx_opt->smc_ok.
>>> 2. Fix compile error when CONFIG_IPV6 or CONFIG_BPF_SYSCALL was not set.
>>>
>>> ---
>>>   include/linux/tcp.h  |  4 ++-
>>>   net/ipv4/tcp_input.c |  4 +--
>>>   net/smc/af_smc.c     | 75 +++++++++++++++++++++++++++++++++++++++++ 
>>> +++++------
>>>   3 files changed, 72 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
>>> index 6a5e08b..d028d76 100644
>>> --- a/include/linux/tcp.h
>>> +++ b/include/linux/tcp.h
>>> @@ -478,7 +478,9 @@ struct tcp_sock {
>>>   #endif
>>>   #if IS_ENABLED(CONFIG_SMC)
>>>       bool    syn_smc;    /* SYN includes SMC */
>>> -    bool    (*smc_hs_congested)(const struct sock *sk);
>>> +    void    (*smc_openreq_init)(struct request_sock *req,
>>> +                 const struct tcp_options_received *rx_opt,
>>> +                 struct sk_buff *skb, const struct sock *sk);
>>>   #endif
>>>   #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
>>> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
>>> index 9f314df..99f34f5 100644
>>> --- a/net/ipv4/tcp_input.c
>>> +++ b/net/ipv4/tcp_input.c
>>> @@ -7036,8 +7036,8 @@ static void tcp_openreq_init(struct 
>>> request_sock *req,
>>>       ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
>>>       ireq->ir_mark = inet_request_mark(sk, skb);
>>>   #if IS_ENABLED(CONFIG_SMC)
>>> -    ireq->smc_ok = rx_opt->smc_ok && !(tcp_sk(sk)->smc_hs_congested &&
>>> -            tcp_sk(sk)->smc_hs_congested(sk));
>>> +    if (rx_opt->smc_ok && tcp_sk(sk)->smc_openreq_init)
>>> +        tcp_sk(sk)->smc_openreq_init(req, rx_opt, skb, sk);
>>>   #endif
>>>   }
>>> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
>>> index 0316217..fdac7e2b 100644
>>> --- a/net/smc/af_smc.c
>>> +++ b/net/smc/af_smc.c
>>> @@ -70,6 +70,15 @@
>>>   static void smc_tcp_listen_work(struct work_struct *);
>>>   static void smc_connect_work(struct work_struct *);
>>> +__bpf_hook_start();
>>> +
>>> +__weak noinline int select_syn_smc(const struct sock *sk, struct 
>>> sockaddr *peer)
>>> +{
>>> +    return 1;
>>> +}
>>> +
>>> +__bpf_hook_end();
>>> +
>>>   int smc_nl_dump_hs_limitation(struct sk_buff *skb, struct 
>>> netlink_callback *cb)
>>>   {
>>>       struct smc_nl_dmp_ctx *cb_ctx = smc_nl_dmp_ctx(cb);
>>> @@ -156,19 +165,43 @@ static struct sock *smc_tcp_syn_recv_sock(const 
>>> struct sock *sk,
>>>       return NULL;
>>>   }
>>> -static bool smc_hs_congested(const struct sock *sk)
>>> +static void smc_openreq_init(struct request_sock *req,
>>> +                 const struct tcp_options_received *rx_opt,
>>> +                 struct sk_buff *skb, const struct sock *sk)
>>>   {
>>> +    struct inet_request_sock *ireq = inet_rsk(req);
>>> +    struct sockaddr_storage rmt_sockaddr = {0};
>>
>> A trivial problem.
>>
>> The following should be better?
>>
>> struct sockaddr_storage rmt_sockaddr = {};
>>
>> I think, we have discussed this problem in RDMA maillist for several 
>> times.
>>
>> Zhu Yanjun
> 
> 
> This is truly new information to me. Can you provide me with some 
> discussion links?
> Thanks.

It is a trivial problem. This is the link
https://www.spinics.net/lists/linux-rdma/msg119815.html

Zhu Yanjun

> 
> D. Wythe
> 
> 
>>
>>>       const struct smc_sock *smc;
>>>       smc = smc_clcsock_user_data(sk);
>>>       if (!smc)
>>> -        return true;
>>> +        return;
>>> -    if (workqueue_congested(WORK_CPU_UNBOUND, smc_hs_wq))
>>> -        return true;
>>> +    if (smc->limit_smc_hs && workqueue_congested(WORK_CPU_UNBOUND, 
>>> smc_hs_wq))
>>> +        goto out_no_smc;
>>> -    return false;
>>> +    rmt_sockaddr.ss_family = sk->sk_family;
>>> +
>>> +    if (rmt_sockaddr.ss_family == AF_INET) {
>>> +        struct sockaddr_in *rmt4_sockaddr =  (struct sockaddr_in 
>>> *)&rmt_sockaddr;
>>> +
>>> +        rmt4_sockaddr->sin_addr.s_addr = ireq->ir_rmt_addr;
>>> +        rmt4_sockaddr->sin_port    = ireq->ir_rmt_port;
>>> +#if IS_ENABLED(CONFIG_IPV6)
>>> +    } else {
>>> +        struct sockaddr_in6 *rmt6_sockaddr =  (struct sockaddr_in6 
>>> *)&rmt_sockaddr;
>>> +
>>> +        rmt6_sockaddr->sin6_addr = ireq->ir_v6_rmt_addr;
>>> +        rmt6_sockaddr->sin6_port = ireq->ir_rmt_port;
>>> +#endif /* CONFIG_IPV6 */
>>> +    }
>>> +
>>> +    ireq->smc_ok = select_syn_smc(sk, (struct sockaddr 
>>> *)&rmt_sockaddr);
>>> +    return;
>>> +out_no_smc:
>>> +    ireq->smc_ok = 0;
>>> +    return;
>>>   }
>>>   struct smc_hashinfo smc_v4_hashinfo = {
>>> @@ -1671,7 +1704,7 @@ int smc_connect(struct socket *sock, struct 
>>> sockaddr *addr,
>>>       }
>>>       smc_copy_sock_settings_to_clc(smc);
>>> -    tcp_sk(smc->clcsock->sk)->syn_smc = 1;
>>> +    tcp_sk(smc->clcsock->sk)->syn_smc = select_syn_smc(sk, addr);
>>>       if (smc->connect_nonblock) {
>>>           rc = -EALREADY;
>>>           goto out;
>>> @@ -2650,8 +2683,7 @@ int smc_listen(struct socket *sock, int backlog)
>>>       inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops;
>>> -    if (smc->limit_smc_hs)
>>> -        tcp_sk(smc->clcsock->sk)->smc_hs_congested = smc_hs_congested;
>>> +    tcp_sk(smc->clcsock->sk)->smc_openreq_init = smc_openreq_init;
>>>       rc = kernel_listen(smc->clcsock, backlog);
>>>       if (rc) {
>>> @@ -3475,6 +3507,24 @@ static void __net_exit 
>>> smc_net_stat_exit(struct net *net)
>>>       .exit = smc_net_stat_exit,
>>>   };
>>> +#if IS_ENABLED(CONFIG_BPF_SYSCALL)
>>> +BTF_SET8_START(bpf_smc_fmodret_ids)
>>> +BTF_ID_FLAGS(func, select_syn_smc)
>>> +BTF_SET8_END(bpf_smc_fmodret_ids)
>>> +
>>> +static const struct btf_kfunc_id_set bpf_smc_fmodret_set = {
>>> +    .owner = THIS_MODULE,
>>> +    .set   = &bpf_smc_fmodret_ids,
>>> +};
>>> +
>>> +static int bpf_smc_kfunc_init(void)
>>> +{
>>> +    return register_btf_fmodret_id_set(&bpf_smc_fmodret_set);
>>> +}
>>> +#else
>>> +static inline int bpf_smc_kfunc_init(void) { return 0; }
>>> +#endif /* CONFIG_BPF_SYSCALL */
>>> +
>>>   static int __init smc_init(void)
>>>   {
>>>       int rc;
>>> @@ -3574,8 +3624,17 @@ static int __init smc_init(void)
>>>           pr_err("%s: smc_inet_init fails with %d\n", __func__, rc);
>>>           goto out_ulp;
>>>       }
>>> +
>>> +    rc = bpf_smc_kfunc_init();
>>> +    if (rc) {
>>> +        pr_err("%s: bpf_smc_kfunc_init fails with %d\n", __func__, rc);
>>> +        goto out_inet;
>>> +    }
>>> +
>>>       static_branch_enable(&tcp_have_smc);
>>>       return 0;
>>> +out_inet:
>>> +    smc_inet_exit();
>>>   out_ulp:
>>>       tcp_unregister_ulp(&smc_ulp_ops);
>>>   out_lo: