* [PATCH net-next] net/smc: Introduce a hook to modify syn_smc at runtime
@ 2024-10-10 3:58 D. Wythe
2024-10-10 16:21 ` Alexei Starovoitov
0 siblings, 1 reply; 5+ messages in thread
From: D. Wythe @ 2024-10-10 3:58 UTC (permalink / raw)
To: kgraul, wenjia, jaka, wintera, guwen, ast
Cc: kuba, davem, netdev, linux-s390, linux-rdma, tonylu, pabeni,
edumazet, bpf
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>
---
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 cc05ec1..15fe8b9 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..550799c 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 = {};
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
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH net-next] net/smc: Introduce a hook to modify syn_smc at runtime
2024-10-10 3:58 [PATCH net-next] net/smc: Introduce a hook to modify syn_smc at runtime D. Wythe
@ 2024-10-10 16:21 ` Alexei Starovoitov
2024-10-11 6:43 ` D. Wythe
0 siblings, 1 reply; 5+ messages in thread
From: Alexei Starovoitov @ 2024-10-10 16:21 UTC (permalink / raw)
To: D. Wythe
Cc: kgraul, wenjia, jaka, wintera, guwen, Alexei Starovoitov,
Jakub Kicinski, David S. Miller, Network Development, linux-s390,
linux-rdma, Tony Lu, Paolo Abeni, Eric Dumazet, bpf
On Wed, Oct 9, 2024 at 8:58 PM D. Wythe <alibuda@linux.alibaba.com> wrote:
>
>
> +__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 = {};
> 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);
> +}
fmodret was an approach that hid-bpf took initially,
but eventually they removed it all and switched to struct-ops approach.
Please learn that lesson.
Use struct_ops from the beginning.
I did a presentation recently explaining the motivation behind
struct_ops and tips on how to extend the kernel.
TLDR: the step one is to design the extension _without_ bpf.
The interface should be usable for kernel modules.
And then when you have *_ops style api in place
the bpf progs will plug-in without extra work.
Slides:
https://github.com/4ast/docs/blob/main/BPF%20struct-ops.pdf
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH net-next] net/smc: Introduce a hook to modify syn_smc at runtime
2024-10-10 16:21 ` Alexei Starovoitov
@ 2024-10-11 6:43 ` D. Wythe
2024-10-11 15:37 ` Alexei Starovoitov
0 siblings, 1 reply; 5+ messages in thread
From: D. Wythe @ 2024-10-11 6:43 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: kgraul, wenjia, jaka, wintera, guwen, Alexei Starovoitov,
Jakub Kicinski, David S. Miller, Network Development, linux-s390,
linux-rdma, Tony Lu, Paolo Abeni, Eric Dumazet, bpf
On 10/11/24 12:21 AM, Alexei Starovoitov wrote:
> On Wed, Oct 9, 2024 at 8:58 PM D. Wythe <alibuda@linux.alibaba.com> wrote:
>>
>>
>> +__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 = {};
>> 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);
>> +}
>
> fmodret was an approach that hid-bpf took initially,
> but eventually they removed it all and switched to struct-ops approach.
> Please learn that lesson.
> Use struct_ops from the beginning.
>
> I did a presentation recently explaining the motivation behind
> struct_ops and tips on how to extend the kernel.
> TLDR: the step one is to design the extension _without_ bpf.
> The interface should be usable for kernel modules.
> And then when you have *_ops style api in place
> the bpf progs will plug-in without extra work.
>
> Slides:
> https://github.com/4ast/docs/blob/main/BPF%20struct-ops.pdf
Hi Alexei,
Thanks very much for your suggestion.
In fact, I tried struct_ops in SMC about a year ago. Unfortunately, at that time struct_ops did not
support registration from modules, and I had to move some smc dependencies into bpf, which met with
community opposition. However, I noticed that this feature is now supported, so perhaps this is an
opportunity.
But on the other hand, given the current functionality, I wonder if struct_ops might be an overkill.
I haven't been able to come up with a suitable abstraction to define this ops, and in the future,
this ops might only contain the very one callback (select_syn_smc).
Looking forward for your advises.
Thanks,
D. Wythe
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH net-next] net/smc: Introduce a hook to modify syn_smc at runtime
2024-10-11 6:43 ` D. Wythe
@ 2024-10-11 15:37 ` Alexei Starovoitov
2024-10-14 5:49 ` D. Wythe
0 siblings, 1 reply; 5+ messages in thread
From: Alexei Starovoitov @ 2024-10-11 15:37 UTC (permalink / raw)
To: D. Wythe
Cc: kgraul, wenjia, jaka, wintera, guwen, Alexei Starovoitov,
Jakub Kicinski, David S. Miller, Network Development, linux-s390,
linux-rdma, Tony Lu, Paolo Abeni, Eric Dumazet, bpf
On Thu, Oct 10, 2024 at 11:44 PM D. Wythe <alibuda@linux.alibaba.com> wrote:
>
>
>
> On 10/11/24 12:21 AM, Alexei Starovoitov wrote:
> > On Wed, Oct 9, 2024 at 8:58 PM D. Wythe <alibuda@linux.alibaba.com> wrote:
> >>
> >>
> >> +__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 = {};
> >> 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);
> >> +}
> >
> > fmodret was an approach that hid-bpf took initially,
> > but eventually they removed it all and switched to struct-ops approach.
> > Please learn that lesson.
> > Use struct_ops from the beginning.
> >
> > I did a presentation recently explaining the motivation behind
> > struct_ops and tips on how to extend the kernel.
> > TLDR: the step one is to design the extension _without_ bpf.
> > The interface should be usable for kernel modules.
> > And then when you have *_ops style api in place
> > the bpf progs will plug-in without extra work.
> >
> > Slides:
> > https://github.com/4ast/docs/blob/main/BPF%20struct-ops.pdf
>
>
> Hi Alexei,
>
> Thanks very much for your suggestion.
>
> In fact, I tried struct_ops in SMC about a year ago. Unfortunately, at that time struct_ops did not
> support registration from modules, and I had to move some smc dependencies into bpf, which met with
> community opposition. However, I noticed that this feature is now supported, so perhaps this is an
> opportunity.
>
> But on the other hand, given the current functionality, I wonder if struct_ops might be an overkill.
> I haven't been able to come up with a suitable abstraction to define this ops, and in the future,
> this ops might only contain the very one callback (select_syn_smc).
>
> Looking forward for your advises.
I guess I wasn't clear. It's a Nack to the current fmodret approach.
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH net-next] net/smc: Introduce a hook to modify syn_smc at runtime
2024-10-11 15:37 ` Alexei Starovoitov
@ 2024-10-14 5:49 ` D. Wythe
0 siblings, 0 replies; 5+ messages in thread
From: D. Wythe @ 2024-10-14 5:49 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: kgraul, wenjia, jaka, wintera, guwen, Alexei Starovoitov,
Jakub Kicinski, David S. Miller, Network Development, linux-s390,
linux-rdma, Tony Lu, Paolo Abeni, Eric Dumazet, bpf
On 10/11/24 11:37 PM, Alexei Starovoitov wrote:
> On Thu, Oct 10, 2024 at 11:44 PM D. Wythe <alibuda@linux.alibaba.com> wrote:
>>
>>
>>
>> On 10/11/24 12:21 AM, Alexei Starovoitov wrote:
>>> On Wed, Oct 9, 2024 at 8:58 PM D. Wythe <alibuda@linux.alibaba.com> wrote:
>>>>
>>>>
>>>> +__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 = {};
>>>> 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);
>>>> +}
>>>
>>> fmodret was an approach that hid-bpf took initially,
>>> but eventually they removed it all and switched to struct-ops approach.
>>> Please learn that lesson.
>>> Use struct_ops from the beginning.
>>>
>>> I did a presentation recently explaining the motivation behind
>>> struct_ops and tips on how to extend the kernel.
>>> TLDR: the step one is to design the extension _without_ bpf.
>>> The interface should be usable for kernel modules.
>>> And then when you have *_ops style api in place
>>> the bpf progs will plug-in without extra work.
>>>
>>> Slides:
>>> https://github.com/4ast/docs/blob/main/BPF%20struct-ops.pdf
>>
>>
>> Hi Alexei,
>>
>> Thanks very much for your suggestion.
>>
>> In fact, I tried struct_ops in SMC about a year ago. Unfortunately, at that time struct_ops did not
>> support registration from modules, and I had to move some smc dependencies into bpf, which met with
>> community opposition. However, I noticed that this feature is now supported, so perhaps this is an
>> opportunity.
>>
>> But on the other hand, given the current functionality, I wonder if struct_ops might be an overkill.
>> I haven't been able to come up with a suitable abstraction to define this ops, and in the future,
>> this ops might only contain the very one callback (select_syn_smc).
>>
>> Looking forward for your advises.
>
> I guess I wasn't clear. It's a Nack to the current fmodret approach.
Understood, we do not oppose the use of struct_ops, especially when modules registration
was already supported.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-10-14 5:49 UTC | newest]
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2024-10-10 3:58 [PATCH net-next] net/smc: Introduce a hook to modify syn_smc at runtime D. Wythe
2024-10-10 16:21 ` Alexei Starovoitov
2024-10-11 6:43 ` D. Wythe
2024-10-11 15:37 ` Alexei Starovoitov
2024-10-14 5:49 ` D. Wythe
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