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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D17278F4B@AcuExch.aculab.com>
Date: Fri, 18 Jul 2014 17:36:34 +0000
From: David Laight <David.Laight@...LAB.COM>
To: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"'linux-sctp@...r.kernel.org'" <linux-sctp@...r.kernel.org>
CC: 'David Miller' <davem@...emloft.net>
Subject: [PATCH net-next v3 3/3] Add support for MSG_MORE on SCTP
If MSG_MORE is set then the data chunk will be buffered until either
a full packet would be generated, or something causes a chunk to be
sent (eg data without MSG_MORE or a heartbeat).
The MSG_MORE flag is saved 'per association' along with a copy
of the SCTP_NODELAY/Nagle flag.
It is expected that an application will only set MSG_MORE when it
has an additional data chunk ready to send. The sends could be done
with a single sendmmsg() system call.
Signed-off-by: David Laight <david.laight@...lab.com>
---
Changes from v2:
- MSG_MORE is now saved per association (not per socket)
- The first data chunk is also not sent
include/net/sctp/structs.h | 9 ++++++++-
net/sctp/endpointola.c | 3 +++
net/sctp/output.c | 16 ++++++++++++----
net/sctp/socket.c | 24 +++++++++++++++++++++---
4 files changed, 44 insertions(+), 8 deletions(-)
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 0dfcc92..441320a 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -209,7 +209,11 @@ struct sctp_sock {
struct sctp_assocparams assocparams;
int user_frag;
__u32 autoclose;
- __u8 nodelay;
+
+#define SCTP_F_TX_NODELAY 0
+#define SCTP_F_TX_NAGLE 1 /* SCTP_NODELAY not set */
+#define SCTP_F_TX_MSG_MORE 2 /* MSG_MORE set on last send */
+ __u8 tx_delay;
__u8 disable_fragments;
__u8 v4mapped;
__u8 frag_interleave;
@@ -1581,6 +1585,9 @@ struct sctp_association {
/* Flag that path mtu update is pending */
__u8 pmtu_pending;
+ /* SCTP_F_TX_xxx, Nagle copied from socket */
+ __u8 tx_delay;
+
/* Association : The smallest PMTU discovered for all of the
* PMTU : peer's transport addresses.
*/
diff --git a/net/sctp/endpointola.c b/net/sctp/endpointola.c
index 3d9f429..077220f 100644
--- a/net/sctp/endpointola.c
+++ b/net/sctp/endpointola.c
@@ -221,6 +221,9 @@ void sctp_endpoint_add_asoc(struct sctp_endpoint *ep,
/* Increment the backlog value for a TCP-style listening socket. */
if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING))
sk->sk_ack_backlog++;
+
+ /* Cache SCTP_NODELAY (aka Nagle) state */
+ asoc->tx_delay = sctp_sk(sk)->tx_delay;
}
/* Free the endpoint structure. Delay cleanup until
diff --git a/net/sctp/output.c b/net/sctp/output.c
index 7f28a8e..275a1ab 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -679,22 +679,30 @@ static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
flight_size >= transport->cwnd)
return SCTP_XMIT_RWND_FULL;
+ /* If MSG_MORE is set we probably shouldn't create a new message.
+ * However unless we also implement a timeout (preferable settable
+ * as a socket option) then data could easily be left unsent.
+ * Instead we ignore MSG_MORE on the first data chunk.
+ * This makes the implementation of MSG_MORE the same as the
+ * implementation of Nagle.
+ */
+
/* Nagle's algorithm to solve small-packet problem:
* Inhibit the sending of new chunks when new outgoing data arrives
* if any previously transmitted data on the connection remains
* unacknowledged.
*/
- if (sctp_sk(asoc->base.sk)->nodelay)
- /* Nagle disabled */
+ if (asoc->tx_delay == SCTP_F_TX_NODELAY)
+ /* Nagle disabled and MSG_MORE unset */
return SCTP_XMIT_OK;
if (!sctp_packet_empty(packet))
/* Append to packet */
return SCTP_XMIT_OK;
- if (inflight == 0)
- /* Nothing unacked */
+ if (inflight == 0 && !(asoc->tx_delay & SCTP_F_TX_MSG_MORE))
+ /* Nothing unacked and application isn't going to send more */
return SCTP_XMIT_OK;
if (!sctp_state(asoc, ESTABLISHED))
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index fee06b9..73a421d 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1927,6 +1927,18 @@ static int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
pr_debug("%s: we associated primitively\n", __func__);
}
+ /* Setting MSG_MORE currently has the same effect as enabling Nagle.
+ * This means that the user can't force bundling of the first two data
+ * chunks. It does mean that all the data chunks will be sent
+ * without an extra timer.
+ * It is enough to save the last value since any data sent with
+ * MSG_MORE clear will already have been sent (subject to flow control).
+ */
+ if (msg->msg_flags & MSG_MORE)
+ asoc->tx_delay |= SCTP_F_TX_MSG_MORE;
+ else
+ asoc->tx_delay &= ~SCTP_F_TX_MSG_MORE;
+
/* Break the message into multiple chunks of maximum size. */
datamsg = sctp_datamsg_from_user(asoc, sinfo, msg, msg_len);
if (IS_ERR(datamsg)) {
@@ -2814,6 +2826,7 @@ static int sctp_setsockopt_primary_addr(struct sock *sk, char __user *optval,
static int sctp_setsockopt_nodelay(struct sock *sk, char __user *optval,
unsigned int optlen)
{
+ struct sctp_association *asoc;
int val;
if (optlen < sizeof(int))
@@ -2821,7 +2834,12 @@ static int sctp_setsockopt_nodelay(struct sock *sk, char __user *optval,
if (get_user(val, (int __user *)optval))
return -EFAULT;
- sctp_sk(sk)->nodelay = (val == 0) ? 0 : 1;
+ val = val == 0 ? SCTP_F_TX_NAGLE : SCTP_F_TX_NODELAY;
+ sctp_sk(sk)->tx_delay = val;
+
+ /* Update cached value on each asoc (clears SCTP_F_TX_MSG_MORE) */
+ list_for_each_entry(asoc, &sctp_sk(sk)->ep->asocs, asocs)
+ asoc->tx_delay = val;
return 0;
}
@@ -3968,7 +3986,7 @@ static int sctp_init_sock(struct sock *sk)
sp->disable_fragments = 0;
/* Enable Nagle algorithm by default. */
- sp->nodelay = 0;
+ sp->tx_delay = SCTP_F_TX_NAGLE;
/* Enable by default. */
sp->v4mapped = 1;
@@ -5020,7 +5038,7 @@ static int sctp_getsockopt_nodelay(struct sock *sk, int len,
return -EINVAL;
len = sizeof(int);
- val = (sctp_sk(sk)->nodelay == 1);
+ val = sctp_sk(sk)->tx_delay & SCTP_F_TX_NAGLE ? 0 : 1;
if (put_user(len, optlen))
return -EFAULT;
if (copy_to_user(optval, &val, len))
--
1.8.1.2
--
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