On 3/25/15, Roman Gushchin <kl...@yandex-team.ru> wrote:
> This patch introduces new ipv6 sysctl: ra_default_route_mtu.
> If it's set (> 0), it defines per-route MTU for any new default route
> received by RA.
>
> This sysctl will help in the following configuration: we want to use
> jumbo-frames for internal networks and default ethernet frames for
> default route. Per-route MTU can only lower per-link MTU, so link MTU
> should be set to ~9000 (statically or via RA).
>
> Due to dynamic nature of RA, setting MTU for default route will require
> userspace agent, that will monitor changes of default route
> and (re)configure it. Not simple. The suggested sysctl solves this
> problem.
>
> Signed-off-by: Roman Gushchin <kl...@yandex-team.ru>
It's net-next material
> ---
>
> Changes from v1: add forgotten brace.
> ---
> Documentation/networking/ip-sysctl.txt | 5 +++++
> include/linux/ipv6.h | 1 +
> include/uapi/linux/ipv6.h | 1 +
> net/ipv6/addrconf.c | 10 ++++++++++
> net/ipv6/ndisc.c | 3 ++-
> net/ipv6/route.c | 8 ++++++++
> 6 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/networking/ip-sysctl.txt
> b/Documentation/networking/ip-sysctl.txt
> index 1b8c964..c013dda 100644
> --- a/Documentation/networking/ip-sysctl.txt
> +++ b/Documentation/networking/ip-sysctl.txt
> @@ -1316,6 +1316,11 @@ accept_ra_mtu - BOOLEAN
> Functional default: enabled if accept_ra is enabled.
> disabled if accept_ra is disabled.
>
> +ra_default_route_mtu - INTEGER
> + Define MTU for any new default route received by RA.
> +
> + Functional default: disabled (0).
> +
> accept_redirects - BOOLEAN
> Accept Redirects.
>
> diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
> index 4d5169f..b310c9f 100644
> --- a/include/linux/ipv6.h
> +++ b/include/linux/ipv6.h
> @@ -40,6 +40,7 @@ struct ipv6_devconf {
> __s32 proxy_ndp;
> __s32 accept_source_route;
> __s32 accept_ra_from_local;
> + __s32 ra_default_route_mtu;
> #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
> __s32 optimistic_dad;
> __s32 use_optimistic;
> diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
> index 437a6a4..4539c31 100644
> --- a/include/uapi/linux/ipv6.h
> +++ b/include/uapi/linux/ipv6.h
> @@ -170,6 +170,7 @@ enum {
> DEVCONF_ACCEPT_RA_FROM_LOCAL,
> DEVCONF_USE_OPTIMISTIC,
> DEVCONF_ACCEPT_RA_MTU,
> + DEVCONF_RA_DEFAULT_ROUTE_MTU,
> DEVCONF_MAX
> };
>
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index b603002..322dd733 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -189,6 +189,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly =
> {
> .accept_ra_defrtr = 1,
> .accept_ra_from_local = 0,
> .accept_ra_pinfo = 1,
> + .ra_default_route_mtu = 0,
> #ifdef CONFIG_IPV6_ROUTER_PREF
> .accept_ra_rtr_pref = 1,
> .rtr_probe_interval = 60 * HZ,
> @@ -240,6 +241,7 @@ static struct ipv6_devconf ipv6_devconf_dflt
> __read_mostly = {
> .accept_dad = 1,
> .suppress_frag_ndisc = 1,
> .accept_ra_mtu = 1,
> + .ra_default_route_mtu = 0,
> };
>
> /* Check if a valid qdisc is available */
> @@ -4398,6 +4400,7 @@ static inline void ipv6_store_devconf(struct
> ipv6_devconf *cnf,
> array[DEVCONF_SUPPRESS_FRAG_NDISC] = cnf->suppress_frag_ndisc;
> array[DEVCONF_ACCEPT_RA_FROM_LOCAL] = cnf->accept_ra_from_local;
> array[DEVCONF_ACCEPT_RA_MTU] = cnf->accept_ra_mtu;
> + array[DEVCONF_RA_DEFAULT_ROUTE_MTU] = cnf->ra_default_route_mtu;
> }
>
> static inline size_t inet6_ifla6_size(void)
> @@ -5315,6 +5318,13 @@ static struct addrconf_sysctl_table
> .proc_handler = proc_dointvec,
> },
> {
> + .procname = "ra_default_route_mtu",
> + .data = &ipv6_devconf.ra_default_route_mtu,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec,
> + },
> + {
> /* sentinel */
> }
> },
> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
> index 471ed24..c70ab44 100644
> --- a/net/ipv6/ndisc.c
> +++ b/net/ipv6/ndisc.c
> @@ -1362,7 +1362,8 @@ skip_routeinfo:
> } else if (in6_dev->cnf.mtu6 != mtu) {
> in6_dev->cnf.mtu6 = mtu;
>
> - if (rt)
> + if (rt && (!in6_dev->cnf.ra_default_route_mtu ||
> + mtu < in6_dev->cnf.ra_default_route_mtu))
> dst_metric_set(&rt->dst, RTAX_MTU, mtu);
>
> rt6_mtu_change(skb->dev, mtu);
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 4688bd4..6394adf 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -1714,6 +1714,14 @@ int ip6_route_add(struct fib6_config *cfg)
>
> rt->rt6i_flags = cfg->fc_flags;
>
> + if ((cfg->fc_flags & (RTF_ADDRCONF | RTF_DEFAULT | RTF_GATEWAY)) ==
> + (RTF_ADDRCONF | RTF_DEFAULT | RTF_GATEWAY)) {
> + u32 mtu = idev->cnf.ra_default_route_mtu;
> +
> + if (mtu && mtu >= IPV6_MIN_MTU && mtu <= idev->cnf.mtu6)
> + dst_metric_set(&rt->dst, RTAX_MTU, mtu);
> + }
> +
> install_route:
> rt->dst.dev = dev;
> rt->rt6i_idev = idev;
> --
> 2.1.0
>
> --
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