[PATCH net-next v3 2/4] net/smc: handle sockopts forcing fallback

Ursula Braun
2018-04-26T15:18:21Z

Several TCP sockopts do not work for SMC. One example are the
TCP_FASTOPEN sockopts, since SMC-connection setup is based on the TCP
three-way-handshake.
If the SMC socket is still in state SMC_INIT, such sockopts trigger
fallback to TCP. Otherwise an error is returned.

Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
---
net/smc/af_smc.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 50 insertions(+), 4 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 4470501374bf..d274be7265ea 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -391,6 +391,9 @@ static int smc_connect_rdma(struct smc_sock *smc)

sock_hold(&smc->sk); /* sock put in passive closing */

+ if (smc->use_fallback)
+ goto out_connected;
+
if (!tcp_sk(smc->clcsock->sk)->syn_smc) {
/* peer has not signalled SMC-capability */
smc->use_fallback = true;
@@ -790,6 +793,9 @@ static void smc_listen_work(struct work_struct *work)
int rc = 0;
u8 ibport;

+ if (new_smc->use_fallback)
+ goto out_connected;
+
/* check if peer is smc capable */
if (!tcp_sk(newclcsock->sk)->syn_smc) {
new_smc->use_fallback = true;
@@ -968,7 +974,7 @@ static void smc_tcp_listen_work(struct work_struct *work)
continue;

new_smc->listen_smc = lsmc;
- new_smc->use_fallback = false; /* assume rdma capability first*/
+ new_smc->use_fallback = lsmc->use_fallback;
sock_hold(lsk); /* sock_put in smc_listen_work */
INIT_WORK(&new_smc->smc_listen_work, smc_listen_work);
smc_copy_sock_settings_to_smc(new_smc);
@@ -1004,7 +1010,8 @@ static int smc_listen(struct socket *sock, int backlog)
* them to the clc socket -- copy smc socket options to clc socket
*/
smc_copy_sock_settings_to_clc(smc);
- tcp_sk(smc->clcsock->sk)->syn_smc = 1;
+ if (!smc->use_fallback)
+ tcp_sk(smc->clcsock->sk)->syn_smc = 1;

rc = kernel_listen(smc->clcsock, backlog);
if (rc)
@@ -1097,6 +1104,16 @@ static int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
(sk->sk_state != SMC_APPCLOSEWAIT1) &&
(sk->sk_state != SMC_INIT))
goto out;
+
+ if (msg->msg_flags & MSG_FASTOPEN) {
+ if (sk->sk_state == SMC_INIT) {
+ smc->use_fallback = true;
+ } else {
+ rc = -EINVAL;
+ goto out;
+ }
+ }
+
if (smc->use_fallback)
rc = smc->clcsock->ops->sendmsg(smc->clcsock, msg, len);
else
@@ -1274,14 +1291,43 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
{
struct sock *sk = sock->sk;
struct smc_sock *smc;
+ int rc;

smc = smc_sk(sk);

/* generic setsockopts reaching us here always apply to the
* CLC socket
*/
- return smc->clcsock->ops->setsockopt(smc->clcsock, level, optname,
- optval, optlen);
+ rc = smc->clcsock->ops->setsockopt(smc->clcsock, level, optname,
+ optval, optlen);
+ if (smc->clcsock->sk->sk_err) {
+ sk->sk_err = smc->clcsock->sk->sk_err;
+ sk->sk_error_report(sk);
+ }
+ if (rc)
+ return rc;
+
+ lock_sock(sk);
+ switch (optname) {
+ case TCP_ULP:
+ case TCP_FASTOPEN:
+ case TCP_FASTOPEN_CONNECT:
+ case TCP_FASTOPEN_KEY:
+ case TCP_FASTOPEN_NO_COOKIE:
+ /* option not supported by SMC */
+ if (sk->sk_state == SMC_INIT) {
+ smc->use_fallback = true;
+ } else {
+ if (!smc->use_fallback)
+ rc = -EINVAL;
+ }
+ break;
+ default:
+ break;
+ }
+ release_sock(sk);
+
+ return rc;
}

static int smc_getsockopt(struct socket *sock, int level, int optname,
--
2.13.5