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Date: Wed, 29 Jul 2015 19:39:30 +0900
From: YOSHIFUJI Hideaki <hideaki.yoshifuji@...aclelinux.com>
To: Hangbin Liu <liuhangbin@...il.com>, netdev@...r.kernel.org
CC: hideaki.yoshifuji@...aclelinux.com,
Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCHv3] net/ipv6: add sysctl option accept_ra_min_hop_limit
Hi,
Thank you for you updated patch.
Hangbin Liu wrote:
> Commit 6fd99094de2b ("ipv6: Don't reduce hop limit for an interface")
> disabled accept hop limit from RA if it is higher 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>
> ---
> Documentation/networking/ip-sysctl.txt | 8 ++++++++
> include/linux/ipv6.h | 1 +
> include/uapi/linux/ipv6.h | 1 +
> net/ipv6/addrconf.c | 10 ++++++++++
> net/ipv6/ndisc.c | 8 +++-----
> 5 files changed, 23 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
> index 5fae770..ced0a38 100644
> --- a/Documentation/networking/ip-sysctl.txt
> +++ b/Documentation/networking/ip-sysctl.txt
> @@ -1346,6 +1346,14 @@ accept_ra_pinfo - BOOLEAN
> Functional default: enabled if accept_ra is enabled.
> disabled if accept_ra is disabled.
>
> +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_rt_info_max_plen - INTEGER
> Maximum prefix length of Route Information in RA.
>
> diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
> index 82806c6..ac01ab4 100644
> --- a/include/linux/ipv6.h
> +++ b/include/linux/ipv6.h
> @@ -30,6 +30,7 @@ struct ipv6_devconf {
> __s32 max_addresses;
> __s32 accept_ra_defrtr;
> __s32 accept_ra_pinfo;
> + __s32 accept_ra_min_hop_limit;
accept_ra_defrtr
accept_ra_min_hop_limit
accept_ra_pinfo
(matter of taste)
> #ifdef CONFIG_IPV6_ROUTER_PREF
> __s32 accept_ra_rtr_pref;
> __s32 rtr_probe_interval;
> diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
> index 5efa54a..68094e33 100644
> --- a/include/uapi/linux/ipv6.h
> +++ b/include/uapi/linux/ipv6.h
> @@ -171,6 +171,7 @@ enum {
> DEVCONF_USE_OPTIMISTIC,
> DEVCONF_ACCEPT_RA_MTU,
> DEVCONF_STABLE_SECRET,
> + DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT,
> DEVCONF_MAX
> };
>
This patch cannot apply to current net-next. Please rebase your patch.
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 21c2c81..77df8f2 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -196,6 +196,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
> .accept_ra_defrtr = 1,
> .accept_ra_from_local = 0,
> .accept_ra_pinfo = 1,
> + .accept_ra_min_hop_limit= 1,
> #ifdef CONFIG_IPV6_ROUTER_PREF
> .accept_ra_rtr_pref = 1,
> .rtr_probe_interval = 60 * HZ,
> @@ -237,6 +238,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
> .accept_ra_defrtr = 1,
> .accept_ra_from_local = 0,
> .accept_ra_pinfo = 1,
> + .accept_ra_min_hop_limit= 1,
> #ifdef CONFIG_IPV6_ROUTER_PREF
> .accept_ra_rtr_pref = 1,
> .rtr_probe_interval = 60 * HZ,
> @@ -4561,6 +4563,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
> array[DEVCONF_MAX_ADDRESSES] = cnf->max_addresses;
> array[DEVCONF_ACCEPT_RA_DEFRTR] = cnf->accept_ra_defrtr;
> array[DEVCONF_ACCEPT_RA_PINFO] = cnf->accept_ra_pinfo;
> + array[DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT] = cnf->accept_ra_min_hop_limit;
DEFRTR, MIN_HOP_LIMIT then PINFO
(matter of taste)
> #ifdef CONFIG_IPV6_ROUTER_PREF
> array[DEVCONF_ACCEPT_RA_RTR_PREF] = cnf->accept_ra_rtr_pref;
> array[DEVCONF_RTR_PROBE_INTERVAL] =
> @@ -5462,6 +5465,13 @@ static struct addrconf_sysctl_table
> .mode = 0644,
> .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,
> + },
> #ifdef CONFIG_IPV6_ROUTER_PREF
> {
> .procname = "accept_ra_rtr_pref",
> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
> index 0a05b35..acda056 100644
> --- a/net/ipv6/ndisc.c
> +++ b/net/ipv6/ndisc.c
> @@ -1226,13 +1226,11 @@ 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 <= ra_msg->icmph.icmp6_hop_limit &&
> + ra_msg->icmph.icmp6_hop_limit != 0) {
> in6_dev->cnf.hop_limit = 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,
>
Please see my comments against your previous patch.
--
Hideaki Yoshifuji <hideaki.yoshifuji@...aclelinux.com>
Technical Division, MIRACLE LINUX CORPORATION
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