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Date: Fri, 25 Oct 2019 00:25:36 -0300
From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To: Xin Long <lucien.xin@...il.com>
Cc: network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
Neil Horman <nhorman@...driver.com>, davem@...emloft.net,
David Laight <david.laight@...lab.com>
Subject: Re: [PATCHv3 net-next 4/5] sctp: add support for Primary Path
Switchover
On Mon, Oct 14, 2019 at 02:14:47PM +0800, Xin Long wrote:
> This is a new feature defined in section 5 of rfc7829: "Primary Path
> Switchover". By introducing a new tunable parameter:
>
> Primary.Switchover.Max.Retrans (PSMR)
>
> The primary path will be changed to another active path when the path
> error counter on the old primary path exceeds PSMR, so that "the SCTP
> sender is allowed to continue data transmission on a new working path
> even when the old primary destination address becomes active again".
>
> This patch is to add this tunable parameter, 'ps_retrans' per netns,
> sock, asoc and transport. It also allows a user to change ps_retrans
> per netns by sysctl, and ps_retrans per sock/asoc/transport will be
> initialized with it.
>
> The check will be done in sctp_do_8_2_transport_strike() when this
> feature is enabled.
>
> Note this feature is disabled by initializing 'ps_retrans' per netns
> as 0xffff by default, and its value can't be less than 'pf_retrans'
> when changing by sysctl.
>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
> include/net/netns/sctp.h | 6 ++++++
> include/net/sctp/structs.h | 11 ++++++++---
> net/sctp/associola.c | 3 +++
> net/sctp/protocol.c | 3 +++
> net/sctp/sm_sideeffect.c | 5 +++++
> net/sctp/socket.c | 1 +
> net/sctp/sysctl.c | 9 +++++++++
> 7 files changed, 35 insertions(+), 3 deletions(-)
>
> diff --git a/include/net/netns/sctp.h b/include/net/netns/sctp.h
> index f97d342..c41ffdf 100644
> --- a/include/net/netns/sctp.h
> +++ b/include/net/netns/sctp.h
> @@ -89,6 +89,12 @@ struct netns_sctp {
> */
> int pf_retrans;
>
> + /* Primary.Switchover.Max.Retrans sysctl value
> + * taken from:
> + * https://tools.ietf.org/html/rfc7829
> + */
> + int ps_retrans;
> +
> /*
> * Disable Potentially-Failed feature, the feature is enabled by default
> * pf_enable - 0 : disable pf
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index 9a43738..3cc913f 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -184,7 +184,8 @@ struct sctp_sock {
> __u32 flowlabel;
> __u8 dscp;
>
> - int pf_retrans;
> + __u16 pf_retrans;
> + __u16 ps_retrans;
>
> /* The initial Path MTU to use for new associations. */
> __u32 pathmtu;
> @@ -897,7 +898,9 @@ struct sctp_transport {
> * and will be initialized from the assocs value. This can be changed
> * using the SCTP_PEER_ADDR_THLDS socket option
> */
> - int pf_retrans;
> + __u16 pf_retrans;
> + /* Used for primary path switchover. */
> + __u16 ps_retrans;
> /* PMTU : The current known path MTU. */
> __u32 pathmtu;
>
> @@ -1773,7 +1776,9 @@ struct sctp_association {
> * and will be initialized from the assocs value. This can be
> * changed using the SCTP_PEER_ADDR_THLDS socket option
> */
> - int pf_retrans;
> + __u16 pf_retrans;
> + /* Used for primary path switchover. */
> + __u16 ps_retrans;
>
> /* Maximum number of times the endpoint will retransmit INIT */
> __u16 max_init_attempts;
> diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> index 46763c5..a839244 100644
> --- a/net/sctp/associola.c
> +++ b/net/sctp/associola.c
> @@ -86,6 +86,7 @@ static struct sctp_association *sctp_association_init(
> */
> asoc->max_retrans = sp->assocparams.sasoc_asocmaxrxt;
> asoc->pf_retrans = sp->pf_retrans;
> + asoc->ps_retrans = sp->ps_retrans;
> asoc->pf_expose = sp->pf_expose;
>
> asoc->rto_initial = msecs_to_jiffies(sp->rtoinfo.srto_initial);
> @@ -628,6 +629,8 @@ struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
>
> /* And the partial failure retrans threshold */
> peer->pf_retrans = asoc->pf_retrans;
> + /* And the primary path switchover retrans threshold */
> + peer->ps_retrans = asoc->ps_retrans;
>
> /* Initialize the peer's SACK delay timeout based on the
> * association configured value.
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index a18c7c4..ea1de9b 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -1217,6 +1217,9 @@ static int __net_init sctp_defaults_init(struct net *net)
> /* Max.Burst - 4 */
> net->sctp.max_burst = SCTP_DEFAULT_MAX_BURST;
>
> + /* Disable of Primary Path Switchover by default */
> + net->sctp.ps_retrans = 0xffff;
> +
> /* Enable pf state by default */
> net->sctp.pf_enable = 1;
>
> diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
> index e52b212..acd737d 100644
> --- a/net/sctp/sm_sideeffect.c
> +++ b/net/sctp/sm_sideeffect.c
> @@ -567,6 +567,11 @@ static void sctp_do_8_2_transport_strike(struct sctp_cmd_seq *commands,
> SCTP_FAILED_THRESHOLD);
> }
>
> + if (transport->error_count > transport->ps_retrans &&
> + asoc->peer.primary_path == transport &&
> + asoc->peer.active_path != transport)
> + sctp_assoc_set_primary(asoc, asoc->peer.active_path);
> +
> /* E2) For the destination address for which the timer
> * expires, set RTO <- RTO * 2 ("back off the timer"). The
> * maximum value discussed in rule C7 above (RTO.max) may be
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index eccd689..38d102b 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -5078,6 +5078,7 @@ static int sctp_init_sock(struct sock *sk)
> sp->hbinterval = net->sctp.hb_interval;
> sp->pathmaxrxt = net->sctp.max_retrans_path;
> sp->pf_retrans = net->sctp.pf_retrans;
> + sp->ps_retrans = net->sctp.ps_retrans;
> sp->pf_expose = net->sctp.pf_expose;
> sp->pathmtu = 0; /* allow default discovery */
> sp->sackdelay = net->sctp.sack_timeout;
> diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
> index 5d1ad44..adf264a 100644
> --- a/net/sctp/sysctl.c
> +++ b/net/sctp/sysctl.c
> @@ -213,6 +213,15 @@ static struct ctl_table sctp_net_table[] = {
> .mode = 0644,
> .proc_handler = proc_dointvec_minmax,
> .extra1 = SYSCTL_ZERO,
> + .extra2 = &init_net.sctp.ps_retrans,
> + },
> + {
> + .procname = "ps_retrans",
> + .data = &init_net.sctp.ps_retrans,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec_minmax,
> + .extra1 = &init_net.sctp.pf_retrans,
> .extra2 = SYSCTL_INT_MAX,
pf_retrans got shrunk to 16 bits on other structs (why? I'm thinking
it was just to keep the structs size in check). INT_MAX doesn't make
sense anymore then and in fact it can lead to unexpected behavior.
Like, setting 0x10000 becoming effectively 0.
(yes, usage of >16bits values are probably unreasoable, but..)
> },
> {
> --
> 2.1.0
>
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