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Date: Fri, 19 Feb 2016 17:49:58 +0900
From: Yuki Machida <machida.yuki@...fujitsu.com>
To: netdev@...r.kernel.org, hideaki.yoshifuji@...aclelinux.com,
yoshfuji@...ux-ipv6.org, "David S. Miller" <davem@...emloft.net>
Cc: Hangbin Liu <liuhangbin@...il.com>
Subject: Re: [PATCH stable v2 1/1] net/ipv6: add sysctl option
accept_ra_min_hop_limit
ping? thanks.
On 2016年02月03日 10:56, Yuki Machida wrote:
> Please apply the following patch to v4.1.x.
>
> By commit 6fd99094de2b ("ipv6: Don't reduce hop limit for an interface")
> that have been added in the 4.0-rc7, it no longer comply with RFC4861.
> This problem has been fixed in the commit 8013d1d7eafb
> ("net/ipv6: add sysctl option accept_ra_min_hop_limit")
> in 4.3-rc1, but 4.1.x is still.
>
> [ Upstream 8013d1d7eafb0589ca766db6b74026f76b7f5cb4 ]
>
> Commit 6fd99094de2b ("ipv6: Don't reduce hop limit for an interface")
> disabled accept hop limit from RA if it is smaller than the current hop
> limit for security stuff. But this behavior kind of break the RFC definition.
>
> RFC 4861, 6.3.4. Processing Received Router Advertisements
> A Router Advertisement field (e.g., Cur Hop Limit, Reachable Time,
> and Retrans Timer) may contain a value denoting that it is
> unspecified. In such cases, the parameter should be ignored and the
> host should continue using whatever value it is already using.
>
> If the received Cur Hop Limit value is non-zero, the host SHOULD set
> its CurHopLimit variable to the received value.
>
> So add sysctl option accept_ra_min_hop_limit to let user choose the minimum
> hop limit value they can accept from RA. And set default to 1 to meet RFC
> standards.
>
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> Acked-by: YOSHIFUJI Hideaki <hideaki.yoshifuji@...aclelinux.com>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> ---
> Documentation/networking/ip-sysctl.txt | 8 ++++++++
> include/linux/ipv6.h | 1 +
> include/uapi/linux/ipv6.h | 2 ++
> net/ipv6/addrconf.c | 10 ++++++++++
> net/ipv6/ndisc.c | 16 +++++++---------
> 5 files changed, 28 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
> index 071fb18..07fad3d 100644
> --- a/Documentation/networking/ip-sysctl.txt
> +++ b/Documentation/networking/ip-sysctl.txt
> @@ -1321,6 +1321,14 @@ accept_ra_from_local - BOOLEAN
> disabled if accept_ra_from_local is disabled
> on a specific interface.
>
> +accept_ra_min_hop_limit - INTEGER
> + Minimum hop limit Information in Router Advertisement.
> +
> + Hop limit Information in Router Advertisement less than this
> + variable shall be ignored.
> +
> + Default: 1
> +
> accept_ra_pinfo - BOOLEAN
> Learn Prefix Information in Router Advertisement.
>
> diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
> index e4b4649..01c2592 100644
> --- a/include/linux/ipv6.h
> +++ b/include/linux/ipv6.h
> @@ -29,6 +29,7 @@ struct ipv6_devconf {
> __s32 max_desync_factor;
> __s32 max_addresses;
> __s32 accept_ra_defrtr;
> + __s32 accept_ra_min_hop_limit;
> __s32 accept_ra_pinfo;
> #ifdef CONFIG_IPV6_ROUTER_PREF
> __s32 accept_ra_rtr_pref;
> diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
> index 5efa54a..21cfddf 100644
> --- a/include/uapi/linux/ipv6.h
> +++ b/include/uapi/linux/ipv6.h
> @@ -171,6 +171,8 @@ enum {
> DEVCONF_USE_OPTIMISTIC,
> DEVCONF_ACCEPT_RA_MTU,
> DEVCONF_STABLE_SECRET,
> + __DEVCONF_USE_OIF_ADDRS_ONLY, /* not implemented */
> + DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT,
> DEVCONF_MAX
> };
>
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index f4795b0..28c4bc5 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -195,6 +195,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
> .max_addresses = IPV6_MAX_ADDRESSES,
> .accept_ra_defrtr = 1,
> .accept_ra_from_local = 0,
> + .accept_ra_min_hop_limit= 1,
> .accept_ra_pinfo = 1,
> #ifdef CONFIG_IPV6_ROUTER_PREF
> .accept_ra_rtr_pref = 1,
> @@ -236,6 +237,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
> .max_addresses = IPV6_MAX_ADDRESSES,
> .accept_ra_defrtr = 1,
> .accept_ra_from_local = 0,
> + .accept_ra_min_hop_limit= 1,
> .accept_ra_pinfo = 1,
> #ifdef CONFIG_IPV6_ROUTER_PREF
> .accept_ra_rtr_pref = 1,
> @@ -4565,6 +4567,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
> array[DEVCONF_MAX_DESYNC_FACTOR] = cnf->max_desync_factor;
> array[DEVCONF_MAX_ADDRESSES] = cnf->max_addresses;
> array[DEVCONF_ACCEPT_RA_DEFRTR] = cnf->accept_ra_defrtr;
> + array[DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT] = cnf->accept_ra_min_hop_limit;
> array[DEVCONF_ACCEPT_RA_PINFO] = cnf->accept_ra_pinfo;
> #ifdef CONFIG_IPV6_ROUTER_PREF
> array[DEVCONF_ACCEPT_RA_RTR_PREF] = cnf->accept_ra_rtr_pref;
> @@ -5458,6 +5461,13 @@ static struct addrconf_sysctl_table
> .proc_handler = proc_dointvec,
> },
> {
> + .procname = "accept_ra_min_hop_limit",
> + .data = &ipv6_devconf.accept_ra_min_hop_limit,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec,
> + },
> + {
> .procname = "accept_ra_pinfo",
> .data = &ipv6_devconf.accept_ra_pinfo,
> .maxlen = sizeof(int),
> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
> index 96f153c..abb0bdd 100644
> --- a/net/ipv6/ndisc.c
> +++ b/net/ipv6/ndisc.c
> @@ -1225,18 +1225,16 @@ static void ndisc_router_discovery(struct sk_buff *skb)
>
> if (rt)
> rt6_set_expires(rt, jiffies + (HZ * lifetime));
> - if (ra_msg->icmph.icmp6_hop_limit) {
> - /* Only set hop_limit on the interface if it is higher than
> - * the current hop_limit.
> - */
> - if (in6_dev->cnf.hop_limit < ra_msg->icmph.icmp6_hop_limit) {
> + if (in6_dev->cnf.accept_ra_min_hop_limit < 256 &&
> + ra_msg->icmph.icmp6_hop_limit) {
> + if (in6_dev->cnf.accept_ra_min_hop_limit <= ra_msg->icmph.icmp6_hop_limit) {
> in6_dev->cnf.hop_limit = ra_msg->icmph.icmp6_hop_limit;
> + if (rt)
> + dst_metric_set(&rt->dst, RTAX_HOPLIMIT,
> + ra_msg->icmph.icmp6_hop_limit);
> } else {
> - ND_PRINTK(2, warn, "RA: Got route advertisement with lower hop_limit than current\n");
> + ND_PRINTK(2, warn, "RA: Got route advertisement with lower hop_limit than minimum\n");
> }
> - if (rt)
> - dst_metric_set(&rt->dst, RTAX_HOPLIMIT,
> - ra_msg->icmph.icmp6_hop_limit);
> }
>
> skip_defrtr:
>
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