On 5/11/23 11:24 PM, D. Wythe wrote:
From: "D. Wythe" <alibuda@xxxxxxxxxxxxxxxxx>
As we all know, the SMC protocol is not suitable for all scenarios,
especially for short-lived. However, for most applications, they cannot
guarantee that there are no such scenarios at all. Therefore, apps
may need some specific strategies to decide shall we need to use SMC
or not.
Just like the congestion control implementation in TCP, this patch
provides a generic negotiator implementation. If necessary,
we can provide different protocol negotiation strategies for
apps based on this implementation.
But most importantly, this patch provides the possibility of
eBPF injection, allowing users to implement their own protocol
negotiation policy in userspace.
Signed-off-by: D. Wythe <alibuda@xxxxxxxxxxxxxxxxx>
---
include/net/smc.h | 32 +++++++++++
net/Makefile | 1 +
net/smc/Kconfig | 11 ++++
net/smc/af_smc.c | 134 ++++++++++++++++++++++++++++++++++++++++++++++-
net/smc/smc_negotiator.c | 119 +++++++++++++++++++++++++++++++++++++++++
net/smc/smc_negotiator.h | 116 ++++++++++++++++++++++++++++++++++++++++
6 files changed, 412 insertions(+), 1 deletion(-)
create mode 100644 net/smc/smc_negotiator.c
create mode 100644 net/smc/smc_negotiator.h
diff --git a/include/net/smc.h b/include/net/smc.h
index 6d076f5..191061c 100644
--- a/include/net/smc.h
+++ b/include/net/smc.h
@@ -296,6 +296,8 @@ struct smc_sock { /* smc sock container */
atomic_t queued_smc_hs; /* queued smc handshakes */
struct inet_connection_sock_af_ops af_ops;
const struct inet_connection_sock_af_ops *ori_af_ops;
+ /* protocol negotiator ops */
+ const struct smc_sock_negotiator_ops *negotiator_ops;
/* original af ops */
int sockopt_defer_accept;
/* sockopt TCP_DEFER_ACCEPT
@@ -316,4 +318,34 @@ struct smc_sock { /* smc sock container */
*/
};
+#ifdef CONFIG_SMC_BPF
+/* BPF struct ops for smc protocol negotiator */
+struct smc_sock_negotiator_ops {
+
+ struct list_head list;
+
+ /* ops name */
+ char name[16];
+ /* key for name */
+ u32 key;
+
+ /* init with sk */
+ void (*init)(struct sock *sk);
+
+ /* release with sk */
+ void (*release)(struct sock *sk);
+
+ /* advice for negotiate */
+ int (*negotiate)(struct sock *sk);
+
+ /* info gathering timing */
+ void (*collect_info)(struct sock *sk, int timing);
+
+ /* module owner */
+ struct module *owner;
+};
+#else
+struct smc_sock_negotiator_ops {};
+#endif
+
#endif /* _SMC_H */
diff --git a/net/Makefile b/net/Makefile
index 4c4dc53..222916a 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_TIPC) += tipc/
obj-$(CONFIG_NETLABEL) += netlabel/
obj-$(CONFIG_IUCV) += iucv/
obj-$(CONFIG_SMC) += smc/
+obj-$(CONFIG_SMC_BPF) += smc/smc_negotiator.o > obj-$(CONFIG_RFKILL) += rfkill/
obj-$(CONFIG_NET_9P) += 9p/
obj-$(CONFIG_CAIF) += caif/
diff --git a/net/smc/Kconfig b/net/smc/Kconfig
index 1ab3c5a..bdcc9f1 100644
--- a/net/smc/Kconfig
+++ b/net/smc/Kconfig
@@ -19,3 +19,14 @@ config SMC_DIAG
smcss.
if unsure, say Y.
+
+config SMC_BPF
+ bool "SMC: support eBPF" if SMC
so smc_negotiator will always be in the kernel image even af_smc is compiled as
a module? If the SMC_BPF needs to support af_smc as a module, proper
implementation needs to be added to bpf_struct_ops to support module first. It
is work-in-progress.
+ depends on BPF_SYSCALL
+ default n
+ help
+ Supports eBPF to allows user mode participation in SMC's protocol process
+ via ebpf programs. Alternatively, obtain information about the SMC socks
+ through the ebpf program.
+
+ If unsure, say N.
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 50c38b6..7406fd4 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -52,6 +52,7 @@
#include "smc_close.h"
#include "smc_stats.h"
#include "smc_tracepoint.h"
+#include "smc_negotiator.h"
#include "smc_sysctl.h"
static DEFINE_MUTEX(smc_server_lgr_pending); /* serialize link group
@@ -68,6 +69,119 @@
static void smc_tcp_listen_work(struct work_struct *);
static void smc_connect_work(struct work_struct *);
+#ifdef CONFIG_SMC_BPF
+
+/* Check if sock should use smc */
+int smc_sock_should_select_smc(const struct smc_sock *smc)
+{
+ const struct smc_sock_negotiator_ops *ops;
+ int ret;
+
+ rcu_read_lock();
+ ops = READ_ONCE(smc->negotiator_ops);
+
+ /* No negotiator_ops supply or no negotiate func set,
+ * always pass it.
+ */
+ if (!ops || !ops->negotiate) {
A smc_sock_negotiator_ops without ->negotiate? Is it useful at all to allow the
register in the first place?
+ rcu_read_unlock();
+ return SK_PASS;
+ }
+
+ ret = ops->negotiate((struct sock *)&smc->sk);
+ rcu_read_unlock();
+ return ret;
+}
+
+void smc_sock_perform_collecting_info(const struct smc_sock *smc, int timing)
+{
+ const struct smc_sock_negotiator_ops *ops;
+
+ rcu_read_lock();
+ ops = READ_ONCE(smc->negotiator_ops);
+
+ if (!ops || !ops->collect_info) {
+ rcu_read_unlock();
+ return;
+ }
+
+ ops->collect_info((struct sock *)&smc->sk, timing);
+ rcu_read_unlock();
+}
+
+int smc_sock_assign_negotiator_ops(struct smc_sock *smc, const char *name)
+{
+ struct smc_sock_negotiator_ops *ops;
+ int ret = -EINVAL;
+
+ /* already set */
+ if (READ_ONCE(smc->negotiator_ops))
+ smc_sock_cleanup_negotiator_ops(smc, /* might be still referenced */ false);
+
+ /* Just for clear negotiator_ops */
+ if (!name || !strlen(name))
+ return 0;
+
+ rcu_read_lock();
+ ops = smc_negotiator_ops_get_by_name(name);
+ if (likely(ops)) {
+ if (unlikely(!bpf_try_module_get(ops, ops->owner))) {
+ ret = -EACCES;
+ } else {
+ WRITE_ONCE(smc->negotiator_ops, ops);
+ /* make sure ops can be seen */
+ smp_wmb();
This rcu_read_lock(), WRITE_ONCE, and smp_wmb() combo looks very suspicious.
smc->negotiator_ops is protected by rcu (+refcnt) or lock_sock()?
I am going to stop reviewing here.
+ if (ops->init)
+ ops->init(&smc->sk);
+ ret = 0;
+ }
+ }
+ rcu_read_unlock();
+ return ret;
+}
+
+void smc_sock_cleanup_negotiator_ops(struct smc_sock *smc, bool no_more)
+{
+ const struct smc_sock_negotiator_ops *ops;
+
+ ops = READ_ONCE(smc->negotiator_ops);
+
+ /* not all smc sock has negotiator_ops */
+ if (!ops)
+ return;
+
+ might_sleep();
+
+ /* Just ensure data integrity */
+ WRITE_ONCE(smc->negotiator_ops, NULL);
+ /* make sure NULL can be seen */
+ smp_wmb();
+ /* if the socks may have references to the negotiator ops to be removed.
+ * it means that we might need to wait for the readers of ops
+ * to complete. It's slow though.
+ */
+ if (unlikely(!no_more))
+ synchronize_rcu();
+ if (ops->release)
+ ops->release(&smc->sk);
+ bpf_module_put(ops, ops->owner);
+}
+
+void smc_sock_clone_negotiator_ops(struct sock *parent, struct sock *child)
+{
+ const struct smc_sock_negotiator_ops *ops;
+
+ rcu_read_lock();
+ ops = READ_ONCE(smc_sk(parent)->negotiator_ops);
+ if (ops && bpf_try_module_get(ops, ops->owner)) {
+ smc_sk(child)->negotiator_ops = ops;
+ if (ops->init)
+ ops->init(child);
+ }
+ rcu_read_unlock();
+}
+#endif
+
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);
@@ -166,6 +280,9 @@ static bool smc_hs_congested(const struct sock *sk)
if (workqueue_congested(WORK_CPU_UNBOUND, smc_hs_wq))
return true;
+ if (!smc_sock_should_select_smc(smc))
+ return true;
+
return false;
}
@@ -320,6 +437,9 @@ static int smc_release(struct socket *sock)
sock_hold(sk); /* sock_put below */
smc = smc_sk(sk);
+ /* trigger info gathering if needed.*/
+ smc_sock_perform_collecting_info(smc, SMC_SOCK_CLOSED_TIMING);
+
old_state = sk->sk_state;
/* cleanup for a dangling non-blocking connect */
@@ -356,6 +476,9 @@ static int smc_release(struct socket *sock)
static void smc_destruct(struct sock *sk)
{
+ /* cleanup negotiator_ops if set */
+ smc_sock_cleanup_negotiator_ops(smc_sk(sk), /* no longer used */ true);
+
if (sk->sk_state != SMC_CLOSED)
return;
if (!sock_flag(sk, SOCK_DEAD))
@@ -1627,7 +1750,14 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr,
}
smc_copy_sock_settings_to_clc(smc);
- tcp_sk(smc->clcsock->sk)->syn_smc = 1;
+ /* accept out connection as SMC connection */
+ if (smc_sock_should_select_smc(smc) == SK_PASS) {
+ tcp_sk(smc->clcsock->sk)->syn_smc = 1;
+ } else {
+ tcp_sk(smc->clcsock->sk)->syn_smc = 0;
+ smc_switch_to_fallback(smc, /* active fallback */ 0);
+ }
+
if (smc->connect_nonblock) {
rc = -EALREADY;
goto out;
@@ -1679,6 +1809,8 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc)
}
*new_smc = smc_sk(new_sk);
+ smc_sock_clone_negotiator_ops(lsk, new_sk);
+
mutex_lock(&lsmc->clcsock_release_lock);
if (lsmc->clcsock)
rc = kernel_accept(lsmc->clcsock, &new_clcsock, SOCK_NONBLOCK);
