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Date: Thu, 19 Jul 2012 06:46:31 -0400
From: Neil Horman <nhorman@...driver.com>
To: Vlad Yasevich <vyasevich@...il.com>
Cc: netdev@...r.kernel.org, Sridhar Samudrala <sri@...ibm.com>,
"David S. Miller" <davem@...emloft.net>, linux-sctp@...r.kernel.org
Subject: 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:
> >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@...driver.com>
> >CC: Vlad Yasevich <vyasevich@...il.com>
> >CC: Sridhar Samudrala <sri@...ibm.com>
> >CC: "David S. Miller" <davem@...emloft.net>
> >CC: linux-sctp@...r.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 ]
>
> >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.
>
> >+
> >+ 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.
>
> >+ }
> >+
> >+ asoc->pf_retrans = val.spt_pathpfthld;
> >+ asoc->pathmaxrxt = val.spt_pathmaxrxt;
>
> Ditto.
>
> >+ } 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.
>
> >+ }
> >+
> >+ 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
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