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author | Sowmini Varadhan <sowmini.varadhan@oracle.com> | 2016-05-02 11:24:52 -0700 |
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committer | David S. Miller <davem@davemloft.net> | 2016-05-03 16:03:44 -0400 |
commit | bd7c5f983f3185b75cc23bdd5dbc3a676aef3d1e (patch) | |
tree | 42b348d05eaf5e948bd694bdbe390ebb6a9c354f /net/rds/tcp_listen.c | |
parent | eb192840266fab3e3da644018121eed30153355d (diff) | |
download | op-kernel-dev-bd7c5f983f3185b75cc23bdd5dbc3a676aef3d1e.zip op-kernel-dev-bd7c5f983f3185b75cc23bdd5dbc3a676aef3d1e.tar.gz |
RDS: TCP: Synchronize accept() and connect() paths on t_conn_lock.
An arbitration scheme for duelling SYNs is implemented as part of
commit 241b271952eb ("RDS-TCP: Reset tcp callbacks if re-using an
outgoing socket in rds_tcp_accept_one()") which ensures that both nodes
involved will arrive at the same arbitration decision. However, this
needs to be synchronized with an outgoing SYN to be generated by
rds_tcp_conn_connect(). This commit achieves the synchronization
through the t_conn_lock mutex in struct rds_tcp_connection.
The rds_conn_state is checked in rds_tcp_conn_connect() after acquiring
the t_conn_lock mutex. A SYN is sent out only if the RDS connection is
not already UP (an UP would indicate that rds_tcp_accept_one() has
completed 3WH, so no SYN needs to be generated).
Similarly, the rds_conn_state is checked in rds_tcp_accept_one() after
acquiring the t_conn_lock mutex. The only acceptable states (to
allow continuation of the arbitration logic) are UP (i.e., outgoing SYN
was SYN-ACKed by peer after it sent us the SYN) or CONNECTING (we sent
outgoing SYN before we saw incoming SYN).
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/rds/tcp_listen.c')
-rw-r--r-- | net/rds/tcp_listen.c | 30 |
1 files changed, 20 insertions, 10 deletions
diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c index 0896187..be263cd 100644 --- a/net/rds/tcp_listen.c +++ b/net/rds/tcp_listen.c @@ -76,7 +76,9 @@ int rds_tcp_accept_one(struct socket *sock) struct rds_connection *conn; int ret; struct inet_sock *inet; - struct rds_tcp_connection *rs_tcp; + struct rds_tcp_connection *rs_tcp = NULL; + int conn_state; + struct sock *nsk; ret = sock_create_kern(sock_net(sock->sk), sock->sk->sk_family, sock->sk->sk_type, sock->sk->sk_protocol, @@ -116,6 +118,10 @@ int rds_tcp_accept_one(struct socket *sock) */ rs_tcp = (struct rds_tcp_connection *)conn->c_transport_data; rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING); + mutex_lock(&rs_tcp->t_conn_lock); + conn_state = rds_conn_state(conn); + if (conn_state != RDS_CONN_CONNECTING && conn_state != RDS_CONN_UP) + goto rst_nsk; if (rs_tcp->t_sock) { /* Need to resolve a duelling SYN between peers. * We have an outstanding SYN to this peer, which may @@ -126,14 +132,7 @@ int rds_tcp_accept_one(struct socket *sock) wait_event(conn->c_waitq, !test_bit(RDS_IN_XMIT, &conn->c_flags)); if (ntohl(inet->inet_saddr) < ntohl(inet->inet_daddr)) { - struct sock *nsk = new_sock->sk; - - nsk->sk_user_data = NULL; - nsk->sk_prot->disconnect(nsk, 0); - tcp_done(nsk); - new_sock = NULL; - ret = 0; - goto out; + goto rst_nsk; } else if (rs_tcp->t_sock) { rds_tcp_restore_callbacks(rs_tcp->t_sock, rs_tcp); conn->c_outgoing = 0; @@ -143,8 +142,19 @@ int rds_tcp_accept_one(struct socket *sock) rds_connect_complete(conn); /* marks RDS_CONN_UP */ new_sock = NULL; ret = 0; - + goto out; +rst_nsk: + /* reset the newly returned accept sock and bail */ + nsk = new_sock->sk; + rds_tcp_stats_inc(s_tcp_listen_closed_stale); + nsk->sk_user_data = NULL; + nsk->sk_prot->disconnect(nsk, 0); + tcp_done(nsk); + new_sock = NULL; + ret = 0; out: + if (rs_tcp) + mutex_unlock(&rs_tcp->t_conn_lock); if (new_sock) sock_release(new_sock); return ret; |