On Wed, Oct 9, 2024 at 8:58 PM D. Wythe <alibuda@xxxxxxxxxxxxxxxxx> 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
