From: "D. Wythe" <alibuda@xxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxx>
---
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
