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Date: Mon, 1 Sep 2014 21:05:54 -0300
From: Flavio Leitner <fbl@...hat.com>
To: Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc: netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] ipv6: add sysctl_mld_qrv to configure query
robustness variable
Hi Hannes,
On Mon, Sep 01, 2014 at 09:55:34PM +0200, Hannes Frederic Sowa wrote:
> This patch adds a new sysctl_mld_qrv knob to configure the mldv1/v2 query
> robustness variable. It specifies how many retransmit of unsolicited mld
> retransmit should happen. Admins might want to tune this on lossy links.
>
> Also reset mld state on interface down/up, so we pick up new sysctl
> settings during interface up event.
>
> IPv6 certification requests this knob to be available.
>
> I didn't make this knob netns specific, as it is mostly a setting in a
> physical environment and should be per host.
>
> Cc: Flavio Leitner <fbl@...hat.com>
> Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
> ---
> v2) no changes to original version
>
> Documentation/networking/ip-sysctl.txt | 3 +++
> include/net/ipv6.h | 1 +
> net/ipv6/mcast.c | 20 ++++++++++++--------
> net/ipv6/sysctl_net_ipv6.c | 10 ++++++++++
> 4 files changed, 26 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
> index 3cce8ea..b7fe844 100644
> --- a/Documentation/networking/ip-sysctl.txt
> +++ b/Documentation/networking/ip-sysctl.txt
> @@ -1152,6 +1152,9 @@ anycast_src_echo_reply - BOOLEAN
> FALSE: disabled
> Default: FALSE
>
> +mld_qrv - INTEGER
> + Controls the MLD query robustness variable (see RFC3810 9.1).
> +
> IPv6 Fragmentation:
>
> ip6frag_high_thresh - INTEGER
> diff --git a/include/net/ipv6.h b/include/net/ipv6.h
> index a2db816..7e247e9 100644
> --- a/include/net/ipv6.h
> +++ b/include/net/ipv6.h
> @@ -121,6 +121,7 @@ struct frag_hdr {
>
> /* sysctls */
> extern int sysctl_mld_max_msf;
> +extern int sysctl_mld_qrv;
>
> #define _DEVINC(net, statname, modifier, idev, field) \
> ({ \
> diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
> index 7088179..6efb0e5 100644
> --- a/net/ipv6/mcast.c
> +++ b/net/ipv6/mcast.c
> @@ -121,6 +121,7 @@ static int ip6_mc_leave_src(struct sock *sk, struct ipv6_mc_socklist *iml,
> #define IPV6_MLD_MAX_MSF 64
>
> int sysctl_mld_max_msf __read_mostly = IPV6_MLD_MAX_MSF;
> +int sysctl_mld_qrv __read_mostly = MLD_QRV_DEFAULT;
>
> /*
> * socket join on multicast group
> @@ -1196,7 +1197,7 @@ static void mld_update_qrv(struct inet6_dev *idev,
> if (mlh2->mld2q_qrv > 0)
> idev->mc_qrv = mlh2->mld2q_qrv;
>
> - if (unlikely(idev->mc_qrv < 2)) {
> + if (unlikely(idev->mc_qrv < MLD_QRV_DEFAULT)) {
> net_warn_ratelimited("IPv6: MLD: clamping QRV from %u to %u!\n",
> idev->mc_qrv, MLD_QRV_DEFAULT);
> idev->mc_qrv = MLD_QRV_DEFAULT;
You allow the sysctl to be 1, but here it is limited to 2?
> @@ -2478,6 +2479,14 @@ void ipv6_mc_down(struct inet6_dev *idev)
> mld_clear_delrec(idev);
> }
>
> +static void ipv6_mc_reset(struct inet6_dev *idev)
> +{
> + idev->mc_qrv = sysctl_mld_qrv;
> + idev->mc_qi = MLD_QI_DEFAULT;
> + idev->mc_qri = MLD_QRI_DEFAULT;
> + idev->mc_v1_seen = 0;
> + idev->mc_maxdelay = unsolicited_report_interval(idev);
> +}
>
> /* Device going up */
>
> @@ -2488,6 +2497,7 @@ void ipv6_mc_up(struct inet6_dev *idev)
> /* Install multicast list, except for all-nodes (already installed) */
>
> read_lock_bh(&idev->lock);
> + ipv6_mc_reset(idev);
ok, up and down the interface to get the sysctl value applied.
> for (i = idev->mc_list; i; i = i->next)
> igmp6_group_added(i);
> read_unlock_bh(&idev->lock);
> @@ -2508,13 +2518,7 @@ void ipv6_mc_init_dev(struct inet6_dev *idev)
> (unsigned long)idev);
> setup_timer(&idev->mc_dad_timer, mld_dad_timer_expire,
> (unsigned long)idev);
> -
> - idev->mc_qrv = MLD_QRV_DEFAULT;
> - idev->mc_qi = MLD_QI_DEFAULT;
> - idev->mc_qri = MLD_QRI_DEFAULT;
> -
> - idev->mc_maxdelay = unsolicited_report_interval(idev);
> - idev->mc_v1_seen = 0;
> + ipv6_mc_reset(idev);
looks good to me.
> write_unlock_bh(&idev->lock);
> }
>
> diff --git a/net/ipv6/sysctl_net_ipv6.c b/net/ipv6/sysctl_net_ipv6.c
> index 0c56c93..c5c10fa 100644
> --- a/net/ipv6/sysctl_net_ipv6.c
> +++ b/net/ipv6/sysctl_net_ipv6.c
> @@ -16,6 +16,8 @@
> #include <net/addrconf.h>
> #include <net/inet_frag.h>
>
> +static int one = 1;
> +
Although that can be reused later for other purposes, it's nice to
have a comment telling where that value came from. Since you have
defined MLD_QRV_DEFAULT, it helps. Still I didn't know about
rfc6636#section-4.5, so I'd appreciate if you include that info
either in ip-sysctl.txt or close to MLD_QRV_DEFAULT.
E.g.:
/* See RFC3810 9.1 and rfc6636 4.5 */
+int sysctl_mld_qrv __read_mostly = MLD_QRV_DEFAULT;
Actually, maybe that int could be something not specific to ipv6
because I believe there are more users of the same thing. That's ok,
just a comment and it's not part of this patch.
> static struct ctl_table ipv6_table_template[] = {
> {
> .procname = "bindv6only",
> @@ -63,6 +65,14 @@ static struct ctl_table ipv6_rotable[] = {
> .mode = 0644,
> .proc_handler = proc_dointvec
> },
> + {
> + .procname = "mld_qrv",
> + .data = &sysctl_mld_qrv,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec_minmax,
> + .extra1 = &one
> + },
> { }
> };
>
> --
> 1.9.3
>
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