[PATCH net 3/5] net/smc: propagate file from SMC to TCP socket

Ursula Braun
2019-04-11T09:17:32Z

fcntl(fd, F_SETOWN, getpid()) selects the recipient of SIGURG signals
that are delivered when out-of-band data arrives on socket fd.
If an SMC socket program makes use of such an fcntl() call, it fails
in case of fallback to TCP-mode. In case of fallback the traffic is
processed with the internal TCP socket. Propagating field "file" from the
SMC socket to the internal TCP socket fixes the issue.

Reviewed-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
---
include/net/sock.h | 6 ------
net/smc/af_smc.c | 38 ++++++++++++++++++++++++++++----------
2 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 8de5ee258b93..341f8bafa0cf 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2084,12 +2084,6 @@ static inline bool skwq_has_sleeper(struct socket_wq *wq)
* @p: poll_table
*
* See the comments in the wq_has_sleeper function.
- *
- * Do not derive sock from filp->private_data here. An SMC socket establishes
- * an internal TCP socket that is used in the fallback case. All socket
- * operations on the SMC socket are then forwarded to the TCP socket. In case of
- * poll, the filp->private_data pointer references the SMC socket because the
- * TCP socket has no file assigned.
*/
static inline void sock_poll_wait(struct file *filp, struct socket *sock,
poll_table *p)
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 9bdaed2f2e35..d2a0d15f809c 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -445,10 +445,19 @@ static void smc_link_save_peer_info(struct smc_link *link,
link->peer_mtu = clc->qp_mtu;
}

+static void smc_switch_to_fallback(struct smc_sock *smc)
+{
+ smc->use_fallback = true;
+ if (smc->sk.sk_socket && smc->sk.sk_socket->file) {
+ smc->clcsock->file = smc->sk.sk_socket->file;
+ smc->clcsock->file->private_data = smc->clcsock;
+ }
+}
+
/* fall back during connect */
static int smc_connect_fallback(struct smc_sock *smc, int reason_code)
{
- smc->use_fallback = true;
+ smc_switch_to_fallback(smc);
smc->fallback_rsn = reason_code;
smc_copy_sock_settings_to_clc(smc);
if (smc->sk.sk_state == SMC_INIT)
@@ -774,10 +783,14 @@ static void smc_connect_work(struct work_struct *work)
smc->sk.sk_err = -rc;

out:
- if (smc->sk.sk_err)
- smc->sk.sk_state_change(&smc->sk);
- else
- smc->sk.sk_write_space(&smc->sk);
+ if (!sock_flag(&smc->sk, SOCK_DEAD)) {
+ if (smc->sk.sk_err) {
+ smc->sk.sk_state_change(&smc->sk);
+ } else { /* allow polling before and after fallback decision */
+ smc->clcsock->sk->sk_write_space(smc->clcsock->sk);
+ smc->sk.sk_write_space(&smc->sk);
+ }
+ }
kfree(smc->connect_info);
smc->connect_info = NULL;
release_sock(&smc->sk);
@@ -934,8 +947,13 @@ struct sock *smc_accept_dequeue(struct sock *parent,
sock_put(new_sk); /* final */
continue;
}
- if (new_sock)
+ if (new_sock) {
sock_graft(new_sk, new_sock);
+ if (isk->use_fallback) {
+ smc_sk(new_sk)->clcsock->file = new_sock->file;
+ isk->clcsock->file->private_data = isk->clcsock;
+ }
+ }
return new_sk;
}
return NULL;
@@ -1086,7 +1104,7 @@ static void smc_listen_decline(struct smc_sock *new_smc, int reason_code,
return;
}
smc_conn_free(&new_smc->conn);
- new_smc->use_fallback = true;
+ smc_switch_to_fallback(new_smc);
new_smc->fallback_rsn = reason_code;
if (reason_code && reason_code != SMC_CLC_DECL_PEERDECL) {
if (smc_clc_send_decline(new_smc, reason_code) < 0) {
@@ -1246,7 +1264,7 @@ static void smc_listen_work(struct work_struct *work)

/* check if peer is smc capable */
if (!tcp_sk(newclcsock->sk)->syn_smc) {
- new_smc->use_fallback = true;
+ smc_switch_to_fallback(new_smc);
new_smc->fallback_rsn = SMC_CLC_DECL_PEERNOSMC;
smc_listen_out_connected(new_smc);
return;
@@ -1503,7 +1521,7 @@ static int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)

if (msg->msg_flags & MSG_FASTOPEN) {
if (sk->sk_state == SMC_INIT) {
- smc->use_fallback = true;
+ smc_switch_to_fallback(smc);
smc->fallback_rsn = SMC_CLC_DECL_OPTUNSUPP;
} else {
rc = -EINVAL;
@@ -1705,7 +1723,7 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
case TCP_FASTOPEN_NO_COOKIE:
/* option not supported by SMC */
if (sk->sk_state == SMC_INIT) {
- smc->use_fallback = true;
+ smc_switch_to_fallback(smc);
smc->fallback_rsn = SMC_CLC_DECL_OPTUNSUPP;
} else {
if (!smc->use_fallback)
--
2.16.4