Hi,
On Thu, Mar 03, 2016 at 01:10:47PM +0100, Jiri Slaby wrote:
> From: Hangbin Liu <liuhangbin@xxxxxxxxx>
>
> This patch has been added to the 3.12 stable tree. If you have any
> objections, please let us know.
>
> ===============
>
> [ Upstream commit 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@xxxxxxxxx>
> Acked-by: YOSHIFUJI Hideaki <hideaki.yoshifuji@xxxxxxxxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> ---
> 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 7d8dc93fe2eb..3e5b1b5466e5 100644
> --- a/Documentation/networking/ip-sysctl.txt
> +++ b/Documentation/networking/ip-sysctl.txt
> @@ -1156,6 +1156,14 @@ accept_ra_defrtr - 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_pinfo - BOOLEAN
> Learn Prefix Information in Router Advertisement.
>
> diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
> index 88c0cf0079ad..167c976554fa 100644
> --- a/include/linux/ipv6.h
> +++ b/include/linux/ipv6.h
> @@ -30,6 +30,7 @@ struct ipv6_devconf {
> #endif
> __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 593b0e32d956..25955206757a 100644
> --- a/include/uapi/linux/ipv6.h
> +++ b/include/uapi/linux/ipv6.h
> @@ -163,6 +163,8 @@ enum {
> DEVCONF_MLDV1_UNSOLICITED_REPORT_INTERVAL,
> DEVCONF_MLDV2_UNSOLICITED_REPORT_INTERVAL,
> DEVCONF_SUPPRESS_FRAG_NDISC,
> + DEVCONF_USE_OIF_ADDRS_ONLY,
> + DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT,
As pointed out by Yoshifuji, this will make this uapi header contain
values that are different from upstream. The missing DEVCONF_* values
should be added here so that they become compatible with upstream kernels.
The kernel versions affected seem to be 3.12, 3.13 and 3.19.
Cheers,
--
Luís
> DEVCONF_MAX
> };
>
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 38540a3ed92f..6c629ffb8756 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -192,6 +192,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
> #endif
> .max_addresses = IPV6_MAX_ADDRESSES,
> .accept_ra_defrtr = 1,
> + .accept_ra_min_hop_limit= 1,
> .accept_ra_pinfo = 1,
> #ifdef CONFIG_IPV6_ROUTER_PREF
> .accept_ra_rtr_pref = 1,
> @@ -230,6 +231,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
> #endif
> .max_addresses = IPV6_MAX_ADDRESSES,
> .accept_ra_defrtr = 1,
> + .accept_ra_min_hop_limit= 1,
> .accept_ra_pinfo = 1,
> #ifdef CONFIG_IPV6_ROUTER_PREF
> .accept_ra_rtr_pref = 1,
> @@ -4150,6 +4152,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
> #endif
> 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;
> @@ -4908,6 +4911,13 @@ 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 fda5d95e39f4..e34a6b3520c6 100644
> --- a/net/ipv6/ndisc.c
> +++ b/net/ipv6/ndisc.c
> @@ -1190,18 +1190,16 @@ 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:
> --
> 2.7.2
>
> --
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