Re: [PATCH v2] sctp: Implement quick failover draft from tsvwg

On Wed, Jul 18, 2012 at 05:23:05PM -0400, Vlad Yasevich wrote:

On 07/18/2012 02:01 PM, Neil Horman wrote:

quoted

I've seen several attempts recently made to do quick failover of sctp transports
by reducing various retransmit timers and counters.  While its possible to
implement a faster failover on multihomed sctp associations, its not
particularly robust, in that it can lead to unneeded retransmits, as well as
false connection failures due to intermittent latency on a network.

Instead, lets implement the new ietf quick failover draft found here:
http://tools.ietf.org/html/draft-nishida-tsvwg-sctp-failover-05

This will let the sctp stack identify transports that have had a small number of
errors, and avoid using them quickly until their reliability can be
re-established.  I've tested this out on two virt guests connected via multiple
isolated virt networks and believe its in compliance with the above draft and
works well.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Vlad Yasevich <redacted>
CC: Sridhar Samudrala <redacted>
CC: "David S. Miller" <davem@davemloft.net>
CC: linux-sctp@vger.kernel.org

---
Change notes:

V2)
- Added socket option API from section 6.1 of the specification, as per
request from Vlad. Adding this socket option allows us to alter both the path
maximum retransmit value and the path partial failure threshold for each
transport and the association as a whole.

- Added a per transport pf_retrans value, and initialized it from the
association value.  This makes each transport independently configurable as per
the socket option above, and prevents changes in the sysctl from bleeding into
an already created association.
---
 Documentation/networking/ip-sysctl.txt |   14 +++++
 include/net/sctp/constants.h           |    1 +
 include/net/sctp/structs.h             |   11 +++-
 include/net/sctp/user.h                |   11 ++++
 net/sctp/associola.c                   |   36 ++++++++++--
 net/sctp/outqueue.c                    |    6 +-
 net/sctp/sm_sideeffect.c               |   33 ++++++++++-
 net/sctp/socket.c                      |   96 ++++++++++++++++++++++++++++++++
 net/sctp/sysctl.c                      |    9 +++
 net/sctp/transport.c                   |    4 +-
 10 files changed, 206 insertions(+), 15 deletions(-)

[ snip ]

quoted

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index b3b8a8d..dfffece 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c

@@ -3470,6 +3470,52 @@ static int sctp_setsockopt_auto_asconf(struct sock *sk, char __user *optval,
 }


+/*
+ * SCTP_PEER_ADDR_THLDS
+ *
+ * This option allows us to alter the partially failed threshold for one or all
+ * transports in an association.  See Section 6.1 of:
+ * http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt
+ */
+static int sctp_setsockopt_paddr_thresholds(struct sock *sk,
+					    char __user *optval,
+					    unsigned int optlen)
+{
+	struct sctp_paddrthlds val;
+	struct sctp_transport *trans;
+	struct sctp_association *asoc;
+
+	if (optlen < sizeof(struct sctp_paddrthlds))
+		return -EINVAL;
+	if (copy_from_user(&val, (struct sctp_paddrthlds __user *)optval,
+			   optlen))
+		return -EFAULT;

What if optlen is bigger?  You going to trash the stack.

quoted

+
+	if (sctp_is_any(sk, (const union sctp_addr *)&val.spt_address)) {
+		asoc = sctp_id2assoc(sk, val.spt_assoc_id);
+		if (!asoc)
+			return -ENOENT;
+		list_for_each_entry(trans, &asoc->peer.transport_addr_list,
+				    transports) {
+			trans->pathmaxrxt = val.spt_pathmaxrxt;
+			trans->pf_retrans = val.spt_pathpfthld;

You want to make sure that the values aren't 0.  Otherwise, you'll
set the pathmaxrxt to 0 and that would be bad.

quoted

+		}
+
+		asoc->pf_retrans = val.spt_pathpfthld;
+		asoc->pathmaxrxt = val.spt_pathmaxrxt;

Ditto.

quoted

+	} else {
+		trans = sctp_addr_id2transport(sk, &val.spt_address,
+					       val.spt_assoc_id);
+		if (!trans)
+			return -ENOENT;
+
+		trans->pathmaxrxt = val.spt_pathmaxrxt;
+		trans->pf_retrans = val.spt_pathpfthld;

Ditto.

quoted

+	}
+
+	return 0;
+}
+
 /* API 6.2 setsockopt(), getsockopt()
  *
  * Applications use setsockopt() and getsockopt() to set or retrieve

@@ -3619,6 +3665,9 @@ SCTP_STATIC int sctp_setsockopt(struct sock *sk, int level, int optname,
 	case SCTP_AUTO_ASCONF:
 		retval = sctp_setsockopt_auto_asconf(sk, optval, optlen);
 		break;
+	case SCTP_PEER_ADDR_THLDS:
+		retval = sctp_setsockopt_paddr_thresholds(sk, optval, optlen);
+		break;
 	default:
 		retval = -ENOPROTOOPT;
 		break;

@@ -5490,6 +5539,50 @@ static int sctp_getsockopt_assoc_ids(struct sock *sk, int len,
 	return 0;
 }

+/*
+ * SCTP_PEER_ADDR_THLDS
+ *
+ * This option allows us to fetch the partially failed threshold for one or all
+ * transports in an association.  See Section 6.1 of:
+ * http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt
+ */
+static int sctp_getsockopt_paddr_thresholds(struct sock *sk,
+					    char __user *optval,
+					    int optlen)
+{
+	struct sctp_paddrthlds val;
+	struct sctp_transport *trans;
+	struct sctp_association *asoc;
+
+	if (optlen < sizeof(struct sctp_paddrthlds))
+		return -EINVAL;
+	if (copy_from_user(&val, (struct sctp_paddrthlds __user *)optval, optlen))
+		return -EFAULT;

Again, trashing the stack if optlen and optval are bigger.

-vlad

Ack, I'll fix these up and repost.  Thanks!
Neil